Pyelonephritis and Perinephric Abscess

Pyelonephritis is infection affecting the renal pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 "hip" bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy and the renal parenchyma. This condition arises mostly as a complication of bladder infection that ascends to the upper urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy. Pyelonephritis can be acute or chronic (which results from persistent or chronic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease). Typical acute symptoms are flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics with vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia. The chronic type depends on the underlying pathology. The diagnosis is established via clinical presentation, supported by laboratory findings (in blood and urine). Imaging studies are performed if severe illness is noted or there is no response to initial treatment (antibiotics). CT is the study of choice, given its ability to detect renal abnormalities associated with the infection, including the extent of the disease. Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is an infection involving the perinephric space between the kidney and Gerota’s fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis. Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease can be an extension Extension Examination of the Upper Limbs from pyelonephritis or from hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread of a systemic infection. The diagnosis is established via CT scan. The treatment includes antibiotics, with abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease drainage (which is both diagnostic and therapeutic).

Last updated: 27 Jun, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Definitions

  • Pyelonephritis is infection of the kidney ( pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy and parenchyma) or the upper urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy and is considered a complicated urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy infection ( UTI UTI Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Urinary tract infections (UTIs)).
  • Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is an infection characterized by suppurative material (liquefaction) between Gerota’s fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis and the renal capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides.
    • Can extend into the psoas and transversalis muscles
    • Can extend into the peritoneal cavity Peritoneal Cavity The space enclosed by the peritoneum. It is divided into two portions, the greater sac and the lesser sac or omental bursa, which lies behind the stomach. The two sacs are connected by the foramen of winslow, or epiploic foramen. Peritoneum: Anatomy
Uti ascending and hematogenous

Ascending hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy infection

Image by Lecturio. License: CC BY-NC-SA 4.0

Types of pyelonephritis

Acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System is the sudden-onset infectious Infectious Febrile Infant process and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the kidney(s) from ascending infection Ascending Infection Urinary Tract Infections (UTIs) in Children or hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread of systemic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease.

  • Uncomplicated pyelonephritis: infection with typical presentation and without the risk factors listed for the complicated type.
  • Complicated pyelonephritis may manifest as:
    • Bacteremia Bacteremia The presence of viable bacteria circulating in the blood. Fever, chills, tachycardia, and tachypnea are common acute manifestations of bacteremia. The majority of cases are seen in already hospitalized patients, most of whom have underlying diseases or procedures which render their bloodstreams susceptible to invasion. Glycopeptides, sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock, multiple organ system dysfunction, shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
    • Acute renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome
    • Intrarenal corticomedullary abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease
    • Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease
    • Emphysematous pyelonephritis
    • Papillary necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage
    • Pyonephrosis
  • Chronic pyelonephritis: 
    • Emerges from recurrent or continuing urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, often associated with major anatomic abnormalities
    • Xanthogranulomatous pyelonephritis is a variant of chronic pyelonephritis, usually due to obstruction by infected renal calculi Renal calculi Stones in the kidney, usually formed in the urine-collecting area of the kidney (kidney pelvis). Their sizes vary and most contains calcium oxalate. Imaging of the Urinary System.

Epidemiology

  • Acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System:
    • More common in females than in males; increased incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency in pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
    • 15–17 cases per 10,000 females 
    • 3–4 cases per 10,000 males
  • Chronic pyelonephritis: 
    • Common in children
    • Associated with vesicoureteral reflux Vesicoureteral Reflux Vesicoureteral reflux (VUR) is the retrograde flow of urine from the bladder into the upper urinary tract. Primary VUR often results from the incomplete closure of the ureterovesical junction, whereas secondary VUR is due to an anatomic or physiologic obstruction. Vesicoureteral Reflux (VUR) disease, which is noted in 30%–40% of children with UTIs
    • More common in females
  • Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease
    • Rare; accounts for approximately 0.02% of hospital admissions 
    • Approximately 75% due to complications of UTIs
    • 20%–60% associated with renal calculi Renal calculi Stones in the kidney, usually formed in the urine-collecting area of the kidney (kidney pelvis). Their sizes vary and most contains calcium oxalate. Imaging of the Urinary System

Etiology

Uropathogens

  • Gram-negative bacteria gram-negative bacteria Bacteria which lose crystal violet stain but are stained pink when treated by gram’s method. Bacteriology
    • Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli (most common):
      • Adheres to urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy
      • Has P fimbriae Fimbriae Thin, hairlike appendages, 1 to 20 microns in length and often occurring in large numbers, present on the cells of gram-negative bacteria, particularly enterobacteriaceae and Neisseria. Unlike flagella, they do not possess motility, but being protein (pilin) in nature, they possess antigenic and hemagglutinating properties. They are of medical importance because some fimbriae mediate the attachment of bacteria to cells via adhesins. Bacterial fimbriae refer to common pili, to be distinguished from the preferred use of ‘pili’. Escherichia coli that interacts with the uroepithelial cells
    • Proteus mirabilis Proteus mirabilis A species of gram-negative, facultatively anaerobic, rod-shaped bacteria that is frequently isolated from clinical specimens. Its most common site of infection is the urinary tract. Proteus
    • Klebsiella Klebsiella Klebsiella are encapsulated gram-negative, lactose-fermenting bacilli. They form pink colonies on MacConkey agar due to lactose fermentation. The main virulence factor is a polysaccharide capsule. Klebsiella pneumoniae is the most important pathogenic species. Klebsiella spp.
    • Citrobacter Citrobacter Multidrug-resistant Organisms and Nosocomial Infections spp.
    • Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas aeruginosa (seen in individuals who underwent procedures or had prior healthcare exposure)
  • Gram-positive bacteria gram-positive bacteria Bacteria which retain the crystal violet stain when treated by gram’s method. Bacteriology
    • Staphylococci
    • Enterococci
    • Group B streptococci
  • In some cases, fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology (e.g., Candida Candida Candida is a genus of dimorphic, opportunistic fungi. Candida albicans is part of the normal human flora and is the most common cause of candidiasis. The clinical presentation varies and can include localized mucocutaneous infections (e.g., oropharyngeal, esophageal, intertriginous, and vulvovaginal candidiasis) and invasive disease (e.g., candidemia, intraabdominal abscess, pericarditis, and meningitis). Candida/Candidiasis) and viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology (e.g., adenovirus Adenovirus Adenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis. Adenovirus) cause UTIs.

Risk factors for urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease

Associated with the development of pyelonephritis and perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease:

  • Stasis and obstruction caused by: 
    • Benign Benign Fibroadenoma prostatic hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation ( BPH BPH Benign prostatic hyperplasia (bph) is a condition indicating an increase in the number of stromal and epithelial cells within the prostate gland (transition zone). Benign prostatic hyperplasia is common in men > 50 years of age and may greatly affect their quality of life. Benign Prostatic Hyperplasia
    • VUR
    • Medications that promote incomplete emptying of the bladder
    • Obstructing urinary stones
    • Urethral stricture Stricture Primary Sclerosing Cholangitis
    • Cystocele Cystocele A hernia-like condition in which the weakened pelvic muscles cause the urinary bladder to drop from its normal position. Fallen urinary bladder is more common in females with the bladder dropping into the vagina and less common in males with the bladder dropping into the scrotum. Pelvic Organ Prolapse
    • Neurogenic bladder Neurogenic bladder Dysfunction of the urinary bladder due to disease of the central or peripheral nervous system pathways involved in the control of urination. This is often associated with spinal cord diseases, but may also be caused by brain diseases or peripheral nerve diseases. Urinary Incontinence
  • Foreign body Foreign Body Foreign Body Aspiration (e.g., a catheter, especially a long-term indwelling catheter Indwelling catheter Catheters designed to be left within an organ or passage for an extended period of time. Urinary tract infections (UTIs))
  • Conditions that cause decreased resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing to organisms, such as:
    • Diabetes mellitus Diabetes mellitus Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
    • Malignancy Malignancy Hemothorax
    • Immunosuppression
    • Spermicide use
    • Estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy depletion
    • Antimicrobial use
  • Other:
    • Trauma
    • Anatomic abnormalities
    • Female ( urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy is shorter and the anal and genital regions are near each other)
    • Sexual activity
    • Menopause Menopause Menopause is a physiologic process in women characterized by the permanent cessation of menstruation that occurs after the loss of ovarian activity. Menopause can only be diagnosed retrospectively, after 12 months without menstrual bleeding. Menopause
    • Fecal incontinence Fecal incontinence Failure of voluntary control of the anal sphincters, with involuntary passage of feces and flatus. Pediatric Constipation
    • Chronic constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation in toddlers
    • Kidney transplantation Kidney Transplantation The transference of a kidney from one human or animal to another. Organ Transplantation

Pathophysiology

Acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System

  • Initial process:
    • Starts when the vaginal introitus or urethral meatus is colonized by pathogens, often the fecal flora
    • These microorganisms ascend into the bladder, and acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System develops when the infection reaches the kidney(s).
    • Infection also can come from bacteremia Bacteremia The presence of viable bacteria circulating in the blood. Fever, chills, tachycardia, and tachypnea are common acute manifestations of bacteremia. The majority of cases are seen in already hospitalized patients, most of whom have underlying diseases or procedures which render their bloodstreams susceptible to invasion. Glycopeptides, when seeding Seeding The local implantation of tumor cells by contamination of instruments and surgical equipment during and after surgical resection, resulting in local growth of the cells and tumor formation. Grading, Staging, and Metastasis of the kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy takes place (seen in staphylococci). 
  • Histopathologic findings: 
    • Within the parenchyma, inflammatory neutrophilic exudates collect within the tubules and interstitial areas and can be associated with necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage or abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease formation.
    • After the acute phase Acute phase Short Bowel Syndrome of pyelonephritis, healing starts to occur when the neutrophilic infiltrates are replaced by macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation, plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products cells, and lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology
    • Fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans:
      • The ultimate healed phase, leaving residual irregular (“pyelonephritic”)  scars on the cortical surface, noted as fibrous Fibrous Fibrocystic Change depressions
      • However, the parenchyma will show deformation of the underlying calyx and pelvis Pelvis The pelvis consists of the bony pelvic girdle, the muscular and ligamentous pelvic floor, and the pelvic cavity, which contains viscera, vessels, and multiple nerves and muscles. The pelvic girdle, composed of 2 “hip” bones and the sacrum, is a ring-like bony structure of the axial skeleton that links the vertebral column with the lower extremities. Pelvis: Anatomy, patchy tubular atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation, interstitial fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, and persistent lymphoplasmacytic infiltrates, reflecting the often unabated role of ascending infection Ascending Infection Urinary Tract Infections (UTIs) in Children and vesicoureteral reflux Vesicoureteral Reflux Vesicoureteral reflux (VUR) is the retrograde flow of urine from the bladder into the upper urinary tract. Primary VUR often results from the incomplete closure of the ureterovesical junction, whereas secondary VUR is due to an anatomic or physiologic obstruction. Vesicoureteral Reflux in the pathogenesis of the disease.
  • Complications:
    • Bacteremia Bacteremia The presence of viable bacteria circulating in the blood. Fever, chills, tachycardia, and tachypnea are common acute manifestations of bacteremia. The majority of cases are seen in already hospitalized patients, most of whom have underlying diseases or procedures which render their bloodstreams susceptible to invasion. Glycopeptides, sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock, multiple organ system dysfunction, shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock
    • Acute kidney injury Acute Kidney Injury Acute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine. Acute Kidney Injury (acute renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome)
    • Intrarenal corticomedullary abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease: a walled-off cavity of infection, with large lesions (> 2 cm) seen in those with delayed diagnosis or diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
    • Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease: an infection characterized by suppurative material between Gerota’s fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis and the renal capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides
      • Can extend into the psoas and transversalis muscles
      • Can extend into the peritoneal cavity Peritoneal Cavity The space enclosed by the peritoneum. It is divided into two portions, the greater sac and the lesser sac or omental bursa, which lies behind the stomach. The two sacs are connected by the foramen of winslow, or epiploic foramen. Peritoneum: Anatomy
    • Emphysematous pyelonephritis
    • Papillary necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage
    • Pyonephrosis

Chronic pyelonephritis

  • Chronic pyelonephritis can occur when infection is persistent or recurrent. 
  • Affected kidney marked by inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and scarring Scarring Inflammation:
    • Dilated, blunted calyces
    • Tubular thyroidization (tubules filled with colloid Colloid Colloid solutions include large proteins or cells that do not readily cross capillary membranes. They remain in the ecf and do not distribute into the icf (similar to crystalloids). Intravenous Fluids casts, like thyroid Thyroid The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland: Anatomy tissue)
    • Fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans and inflammatory infiltrates in interstitium
  • Predominant risk factors include:
    • Genitourinary tract anomalies 
    • Urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy obstruction (such as enlarged prostate Prostate The prostate is a gland in the male reproductive system. The gland surrounds the bladder neck and a portion of the urethra. The prostate is an exocrine gland that produces a weakly acidic secretion, which accounts for roughly 20% of the seminal fluid. or renal calculus)
    • VUR:
      • Primary: most common form of reflux, arising from incompetent or inadequate closure of the ureterovesical junction (UVJ)
      • Secondary: abnormally high voiding pressure does not close the UVJ (such as in posterior urethral valves)
  • Xanthogranulomatous pyelonephritis:
    • A variant of chronic pyelonephritis
    • Characterized by renal destruction by granulomatous tissue, which is believed to be from aberrant inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
    • Usual setting is obstruction due to infected renal stones.
    • Commonly associated with Proteus mirabilis Proteus mirabilis A species of gram-negative, facultatively anaerobic, rod-shaped bacteria that is frequently isolated from clinical specimens. Its most common site of infection is the urinary tract. Proteus and E. coli
    • Histopathologic changes show infiltration by lipid-laden macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation.
    • May be confused with renal malignancy Malignancy Hemothorax on imaging and gross appearance

Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease

  • Also begins either from local infection or hematogenous Hematogenous Hepatocellular Carcinoma (HCC) and Liver Metastases spread
    • When the organism initially invades the kidney, there can be outward spread to the perirenal fat (usually by gram-negative organisms). 
    • Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease also can form from a ruptured intrarenal abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease.
    • The organism can come from the circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment (seen in staphylococcal infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease) and seed the peritoneal fat and, in most cases, but in most of these cases, does not affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment the kidney.
  • Risk factors include:
    • Diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
    • Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
    • Urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy abnormalities

Clinical Presentation

Clinical features of pyelonephritis

  • Acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System:
    • Classic triad of symptoms:
      • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
      • Costovertebral tenderness
      • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics/ vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
    • Can be associated with symptoms of cystitis Cystitis Inflammation of the urinary bladder, either from bacterial or non-bacterial causes. Cystitis is usually associated with painful urination (dysuria), increased frequency, urgency, and suprapubic pain. Urinary tract infections (UTIs) (but not always seen): 
    • Pediatric symptoms:
      • Poor feeding 
      • Failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive
    • Geriatric symptoms: 
  • Chronic pyelonephritis is associated with: 
    • History of acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System 
    • Recurrent episodes of fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, lethargy Lethargy A general state of sluggishness, listless, or uninterested, with being tired, and having difficulty concentrating and doing simple tasks. It may be related to depression or drug addiction. Hyponatremia, flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma, and nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics

Clinical features of perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease

  • Insidious onset of:
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Vague lumboabdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia, sweats, and weight loss Weight loss Decrease in existing body weight. Bariatric Surgery
  • Can have a palpable flank mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
  • Symptoms of a lower UTI UTI Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Urinary tract infections (UTIs) are not typical.

Diagnosis

Pyelonephritis

Findings suspicious for pyelonephritis:

  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
  • Flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics/ vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia

Blood tests:

  • Possible ↑ serum creatinine 
  • Leukocytosis Leukocytosis A transient increase in the number of leukocytes in a body fluid. West Nile Virus (CBC)

Urine studies:

  • Urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children:
    • Pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs) 
    • Bacteriuria Bacteriuria The presence of bacteria in the urine which is normally bacteria-free. These bacteria are from the urinary tract and are not contaminants of the surrounding tissues. Bacteriuria can be symptomatic or asymptomatic. Significant bacteriuria is an indicator of urinary tract infection. Urinary Tract Infections (UTIs) in Children
    • WBC casts (suggestive of renal origin of pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs))
    • Dipstick results:
      • Nitrite Nitrite Salts of nitrous acid or compounds containing the group NO2-. The inorganic nitrates of the type mno2 (where m=metal) are all insoluble, except the alkali nitrites. The organic nitrites may be isomeric, but not identical with the corresponding nitro compounds. Kidney Function Tests: may be positive if the pathogen is in sufficient numbers and produces nitrate reductase (e.g.,  E.coli, Proteus mirabilis Proteus mirabilis A species of gram-negative, facultatively anaerobic, rod-shaped bacteria that is frequently isolated from clinical specimens. Its most common site of infection is the urinary tract. Proteus, Klebsiella Klebsiella Klebsiella are encapsulated gram-negative, lactose-fermenting bacilli. They form pink colonies on MacConkey agar due to lactose fermentation. The main virulence factor is a polysaccharide capsule. Klebsiella pneumoniae is the most important pathogenic species. Klebsiella), but  many other bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology do not produce this reductase and the test will be negative (e.g., Staphylococcus Staphylococcus Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus, Pseudomonas Pseudomonas Pseudomonas is a non-lactose-fermenting, gram-negative bacillus that produces pyocyanin, which gives it a characteristic blue-green color. Pseudomonas is found ubiquitously in the environment, as well as in moist reservoirs, such as hospital sinks and respiratory equipment. Pseudomonas, Group B Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus, Acinetobacter Acinetobacter Multidrug-resistant Organisms and Nosocomial Infections, Enterococcus Enterococcus Enterococcus is a genus of oval-shaped gram-positive cocci that are arranged in pairs or short chains. Distinguishing factors include optochin resistance and the presence of pyrrolidonyl arylamidase (PYR) and Lancefield D antigen. Enterococcus is part of the normal flora of the human GI tract. Enterococcus faecalis, and fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology).
      • Nitrite Nitrite Salts of nitrous acid or compounds containing the group NO2-. The inorganic nitrates of the type mno2 (where m=metal) are all insoluble, except the alkali nitrites. The organic nitrites may be isomeric, but not identical with the corresponding nitro compounds. Kidney Function Tests is usually combined with leukocyte esterase Leukocyte esterase Kidney Function Tests (corresponds to pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs)) and the presence of blood on a urine dipstick test.
      • If all 3 tests are positive ( nitrite Nitrite Salts of nitrous acid or compounds containing the group NO2-. The inorganic nitrates of the type mno2 (where m=metal) are all insoluble, except the alkali nitrites. The organic nitrites may be isomeric, but not identical with the corresponding nitro compounds. Kidney Function Tests, leukocyte esterase Leukocyte esterase Kidney Function Tests, blood), then the positive  predictive value is 82%; if all 3 are negative, then the  negative predictive value Negative predictive value The NPV is the percentage of people with a negative test result who are actually disease free, among all people with a negative result regardless of whether or not they have the disease. Epidemiological Values of Diagnostic Tests is 67%
      • Bottom line: Dipstick results can improve the diagnosis of UTI UTI Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Urinary tract infections (UTIs), but cannot adequately rule out infection.
  • Urine culture Urine culture Urinary tract infections (UTIs): growth supports diagnosis of infection and identifies etiologic organism
  • Pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care test: pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care affects management choices

Imaging studies:

  • Often pursued if the infection is associated with severe illness or does not improve
  • CT (method of choice):
    • Detects an obstruction (e.g., stones causing hydroureter, hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis)
    • Identifies urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy anomalies 
    • Hypodense renal lesions due to ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage can be seen.
  • Ultrasonography ( acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System):
    • Kidney may be diffusely or focally enlarged
    • Areas with edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema are hypoechoic Hypoechoic A structure that produces a low-amplitude echo (darker grays) Ultrasound (Sonography).
    • If hemorrhage is present, the area affected is hyperechoic Hyperechoic A structure that produces a high-amplitude echo (lighter grays and white) Ultrasound (Sonography).
    • Can be normal
  • Ultrasonography (chronic pyelonephritis):
    • Renal scarring Scarring Inflammation, atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation, and/or cortical thinning
    • Retraction of the papilla from overlying scar Scar Dermatologic Examination leads to calyceal clubbing Clubbing Cardiovascular Examination
    • Thickened and dilated calyceal system
    • Asymmetric kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys: Anatomy
  • CT (method of choice):
    • Detects an obstruction (e.g., stones causing hydroureter, hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis)
    • Identifies urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy anomalies 
    • Hypodense renal lesions due to ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage can be seen.
  • MRI is an option if it is necessary to avoid use of contrast or radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma.
  • Other imaging studies:
    • Voiding cystourethrography: establishes presence and degree of VUR  
    • IV pyelography Pyelography Hydronephrosis/urography: checks for anomalies and obstruction

Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease

  • Findings of:
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, costovertebral tenderness
    • No response to treatment for pyelonephritis
    • Unexplained peritonitis Peritonitis Inflammation of the peritoneum lining the abdominal cavity as the result of infectious, autoimmune, or chemical processes. Primary peritonitis is due to infection of the peritoneal cavity via hematogenous or lymphatic spread and without intra-abdominal source. Secondary peritonitis arises from the abdominal cavity itself through rupture or abscess of intra-abdominal organs. Penetrating Abdominal Injury, pelvic abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease, and pleural empyema Empyema Presence of pus in a hollow organ or body cavity. Pneumonia (rare)
  • Blood tests:
    • ↑ WBC
    • Elevated inflammatory markers
    • ↑ Creatinine and ↓ GFR GFR The volume of water filtered out of plasma through glomerular capillary walls into Bowman’s capsules per unit of time. It is considered to be equivalent to inulin clearance. Kidney Function Tests 
    • Blood culture 
  • Urine studies: 
    • Urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children
      • Pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs)
      • WBC casts
      • Bacteriuria Bacteriuria The presence of bacteria in the urine which is normally bacteria-free. These bacteria are from the urinary tract and are not contaminants of the surrounding tissues. Bacteriuria can be symptomatic or asymptomatic. Significant bacteriuria is an indicator of urinary tract infection. Urinary Tract Infections (UTIs) in Children
      • May be negative if the abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease does not communicate with the collecting system
    • Urine culture Urine culture Urinary tract infections (UTIs): may identify the offending organism
  • Imaging: 
    • Abdominal CT with contrast CT with Contrast Imaging of the Head and Brain:
    • If presentation is nonspecific, plain radiography can be the initial test. Radiography may occasionally reveal suspicious findings.
      • Scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis with the concavity toward the affected kidney
      • Abdominal mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast 
      • Kidney enlargement with indistinct outlines or undefined renal shadow 
      • Loss of psoas margin
      • Radiopaque Radiopaque An object of high density that blocks X-rays (looks white) X-rays calculus/calculi
    • Ultrasonography: can show a thick-walled perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease ( hypoechoic Hypoechoic A structure that produces a low-amplitude echo (darker grays) Ultrasound (Sonography) or mixed echogenicity)
Axial ct image

Axial Axial Computed Tomography (CT) CT image through the upper pole of the right kidney showing perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease reaching posteriorly to the inferior vena cava Inferior vena cava The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy.

Image: “ Axial Axial Computed Tomography (CT) CT image through the upper pole of the right kidney showing perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease reaching posterior to IVC IVC The venous trunk which receives blood from the lower extremities and from the pelvic and abdominal organs. Mediastinum and Great Vessels: Anatomy.” by Wani NA. License: CC BY 2.0

Management

Acute pyelonephritis Acute pyelonephritis Inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. It is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea. Imaging of the Urinary System

Management depends on the severity of the clinical presentation and risk factors for drug resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing:

  • Uncomplicated pyelonephritis (mild course or with hemodynamic stability):
    • Empiric treatment:
      • 1st choice: oral fluoroquinolones Fluoroquinolones Fluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms. Fluoroquinolones such as ciprofloxacin Ciprofloxacin A broad-spectrum antimicrobial carboxyfluoroquinoline. Fluoroquinolones or levofloxacin Levofloxacin The l-isomer of ofloxacin. Fluoroquinolones (not for children)
      • Alternative: cephalosporins Cephalosporins Cephalosporins are a group of bactericidal beta-lactam antibiotics (similar to penicillins) that exert their effects by preventing bacteria from producing their cell walls, ultimately leading to cell death. Cephalosporins are categorized by generation and all drug names begin with “cef-” or “ceph-.” Cephalosporins (such as ceftibuten or cefpodoxime) or trimethoprim–sulfamethoxazole Trimethoprim–sulfamethoxazole A drug combination with broad-spectrum antibacterial activity against both gram-positive and gram-negative organisms. It is effective in the treatment of many infections, including pneumocystis pneumonia in aids. Chronic Granulomatous Disease
    • Most cases can be managed on an outpatient basis.
    • Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium is necessary if an affected individual is unable to maintain hydration or is severely ill.
  •  Complicated pyelonephritis or severe uncomplicated pyelonephritis: 
    • Hospitalization Hospitalization The confinement of a patient in a hospital. Delirium:
      • IV therapy
      • After clinical improvement → oral therapy
    • Empiric therapy Empiric Therapy Meningitis in Children options (no risk of multidrug resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing):
      • Ceftriaxone Ceftriaxone A broad-spectrum cephalosporin antibiotic and cefotaxime derivative with a very long half-life and high penetrability to meninges, eyes and inner ears. Cephalosporins
      • Piperacillin Piperacillin Semisynthetic, broad-spectrum, ampicillin derived ureidopenicillin antibiotic proposed for pseudomonas infections. It is also used in combination with other antibiotics. Penicillins tazobactam Tazobactam A penicillanic acid and sulfone derivative and potent beta-lactamase inhibitor that enhances the activity of other anti-bacterial agents against beta-lactamase producing bacteria. Cephalosporins
      • Ciprofloxacin Ciprofloxacin A broad-spectrum antimicrobial carboxyfluoroquinoline. Fluoroquinolones or levofloxacin Levofloxacin The l-isomer of ofloxacin. Fluoroquinolones
    • Empiric therapy Empiric Therapy Meningitis in Children options (with risk for multidrug resistance Resistance Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow. Ventilation: Mechanics of Breathing):
      • Piperacillin Piperacillin Semisynthetic, broad-spectrum, ampicillin derived ureidopenicillin antibiotic proposed for pseudomonas infections. It is also used in combination with other antibiotics. Penicillins tazobactam Tazobactam A penicillanic acid and sulfone derivative and potent beta-lactamase inhibitor that enhances the activity of other anti-bacterial agents against beta-lactamase producing bacteria. Cephalosporins
      • Meropenem Meropenem A thienamycin derivative antibacterial agent that is more stable to renal dehydropeptidase I than imipenem, but does not need to be given with an enzyme inhibitor such as cilastatin. It is used in the treatment of bacterial infections, including infections in immunocompromised patients. Carbapenems and Aztreonam, imipenem Imipenem Semisynthetic thienamycin that has a wide spectrum of antibacterial activity against gram-negative and gram-positive aerobic and anaerobic bacteria, including many multiresistant strains. It is stable to beta-lactamases. Clinical studies have demonstrated high efficacy in the treatment of infections of various body systems. Its effectiveness is enhanced when it is administered in combination with cilastatin, a renal dipeptidase inhibitor. Carbapenems and Aztreonam, or doripenem Doripenem A carbapenem derivative antibacterial agent that is more stable to renal dehydropeptidase I than imipenem, but does not need to be given with an enzyme inhibitor such as cilastatin. It is used in the treatment of infections such as hospital-acquired pneumonia, and complicated intra-abdominal or urinary-tract infections, including pyelonephritis. Carbapenems and Aztreonam
      • If urine shows gram-positive Gram-Positive Penicillins cocci Cocci Bacteriology: Add vancomycin Vancomycin Antibacterial obtained from streptomyces orientalis. It is a glycopeptide related to ristocetin that inhibits bacterial cell wall assembly and is toxic to kidneys and the inner ear. Glycopeptides, daptomycin Daptomycin A cyclic lipopeptide antibiotic that inhibits gram-positive bacteria. Lipopeptides and Lipoglycopeptides, or linezolid Linezolid An oxazolidinone and acetamide derived anti-bacterial agent and protein synthesis inhibitor that is used in the treatment of gram-positive bacterial infections of the skin and respiratory tract. Oxazolidinones.
    • For critically ill individuals (requiring intensive care): vancomycin Vancomycin Antibacterial obtained from streptomyces orientalis. It is a glycopeptide related to ristocetin that inhibits bacterial cell wall assembly and is toxic to kidneys and the inner ear. Glycopeptides + antipseudomonal carbapenem Carbapenem The carbapenems and aztreonam are both members of the bactericidal beta-lactam family of antibiotics (similar to penicillins). They work by preventing bacteria from producing their cell wall, ultimately leading to bacterial cell death. Carbapenems and Aztreonam

Chronic pyelonephritis

  • Treatment of underlying cause (e.g., urology consult for obstruction)
  • For recurrent infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, long-term antibiotic therapy is an option.
  • Xanthogranulomatous pyelonephritis is treated with nephrectomy Nephrectomy Excision of kidney. Renal Cell Carcinoma (partial or full) after initial antibiotic treatment.

Perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease

  • Antibiotics (choice depends on the suspected pathogenesis):
    • If associated with pyelonephritis, therapy targets Enterobacteriaceae Enterobacteriaceae A family of gram-negative, facultatively anaerobic, rod-shaped bacteria that do not form endospores. Its organisms are distributed worldwide with some being saprophytes and others being plant and animal parasites. Many species are of considerable economic importance due to their pathogenic effects on agriculture and livestock. Cephalosporins.
    • If associated with staphylococcal systemic infection, therapy targets this etiologic agent.
  • Drainage:
    • If abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is small (e.g., < 3 cm):
      • Drainage may not be necessary.
      • The antibiotic may be enough (especially if other specimens provide sufficient information regarding etiology).
    • Percutaneous drainage Percutaneous Drainage Echinococcus/Echinococcosis is done for diagnostic (especially if other specimens are not available) and therapeutic purposes.
    • Larger abscesses and/or failures to resolve with antibiotics require surgical intervention.

Differential Diagnosis

  • Acute appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the vermiform appendix Appendix A worm-like blind tube extension from the cecum. Colon, Cecum, and Appendix: Anatomy. Acute appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis can also present with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs). The pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways of appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis is typically localized in the RLQ, not the costophrenic angle. Diagnosis can be confirmed with imaging (CT scan).  
  • Acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis: like pyelonephritis, acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis is more common in women and may present with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways. However, in acute cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis, the pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is localized in the RUQ, not the costophrenic angle. Also, urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children in the case of pyelonephritis shows bacteriuria Bacteriuria The presence of bacteria in the urine which is normally bacteria-free. These bacteria are from the urinary tract and are not contaminants of the surrounding tissues. Bacteriuria can be symptomatic or asymptomatic. Significant bacteriuria is an indicator of urinary tract infection. Urinary Tract Infections (UTIs) in Children, which can help differentiate it from cholecystitis Cholecystitis Cholecystitis is the inflammation of the gallbladder (GB) usually caused by the obstruction of the cystic duct (acute cholecystitis). Mechanical irritation by gallstones can also produce chronic GB inflammation. Cholecystitis is one of the most common complications of cholelithiasis but inflammation without gallstones can occur in a minority of patients. Cholecystitis
  • Pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis: can present with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and abdominal pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, but the pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is localized in the epigastrium Epigastrium Surgical Anatomy of the Abdomen, not the costophrenic angle. Laboratory studies help distinguish these conditions: the urinalysis Urinalysis Examination of urine by chemical, physical, or microscopic means. Routine urinalysis usually includes performing chemical screening tests, determining specific gravity, observing any unusual color or odor, screening for bacteriuria, and examining the sediment microscopically. Urinary Tract Infections (UTIs) in Children in pyelonephritis shows abnormalities such as bacteriuria Bacteriuria The presence of bacteria in the urine which is normally bacteria-free. These bacteria are from the urinary tract and are not contaminants of the surrounding tissues. Bacteriuria can be symptomatic or asymptomatic. Significant bacteriuria is an indicator of urinary tract infection. Urinary Tract Infections (UTIs) in Children and pyuria Pyuria The presence of white blood cells (leukocytes) in the urine. It is often associated with bacterial infections of the urinary tract. Pyuria without bacteriuria can be caused by tuberculosis, stones, or cancer. Urinary tract infections (UTIs),  and pancreatitis Pancreatitis Inflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis. Acute Pancreatitis is associated with elevated amylase Amylase A group of amylolytic enzymes that cleave starch, glycogen, and related alpha-1, 4-glucans. Digestion and Absorption and lipase Lipase An enzyme of the hydrolase class that catalyzes the reaction of triacylglycerol and water to yield diacylglycerol and a fatty acid anion. It is produced by glands on the tongue and by the pancreas and initiates the digestion of dietary fats. Malabsorption and Maldigestion
  • Lower UTI UTI Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Urinary tract infections (UTIs): can coexist with pyelonephritis. Lower UTIs usually are not associated with flank pain Flank pain Pain emanating from below the ribs and above the ilium. Renal Cell Carcinoma and are generally shorter in duration. Similar organisms lead to lower and upper UTIs; thus, antibiotics targeting these etiologic agents cover both lower UTI UTI Urinary tract infections (UTIs) represent a wide spectrum of diseases, from self-limiting simple cystitis to severe pyelonephritis that can result in sepsis and death. Urinary tract infections are most commonly caused by Escherichia coli, but may also be caused by other bacteria and fungi. Urinary tract infections (UTIs)  and pyelonephritis. 
  • Renal abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease: collection of suppurative material within the renal parenchyma. Renal abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is usually associated with VUR and urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy obstruction from a stone. Differentiation from perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease is achieved with imaging studies (e.g., CT scan).
  • Urinoma: mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast or encapsulated Encapsulated Klebsiella collection of extravasated urine. Urinoma arises from urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy injury or from spontaneous rupture secondary to urinary obstruction.  Urinoma can be differentiated from perinephric abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease by imaging studies, which include ultrasonography, CT, and MRI.

References

  1. Barshak M, Kasper DL. (2018). Intraabdominal infections and abscesses. Chapter 127 of Jameson J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Loscalzo J (Eds.), Harrison’s Principles of Internal Medicine, 20th ed. McGraw-Hill. https://accessmedicine.mhmedical.com/content.aspx?bookid=2129&sectionid=186949739
  2. Belyayeva M, Jeong JM. (2021). Acute pyelonephritis. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK519537/
  3. Hooton T, Gupta K. (2021). Acute complicated urinary tract infection (including pyelonephritis) in adults. UpToDate. Retrieved July 25, 2021, from https://www.uptodate.com/contents/acute-complicated-urinary-tract-infection-including-pyelonephritis-in-adults
  4. Lohr J. (2019). Chronic pyelonephritis. Medscape. Retrieved July 25, 2021, from https://emedicine.medscape.com/article/245464-overview
  5. Meyrier A. (2021). Renal and perinephric abscess. UpToDate. Retrieved July 25, 2021, from https://www.uptodate.com/contents/renal-and-perinephric-abscess?topicRef=16109&source=related_link#H1492726249 
  6. Okafor CN, Onyeaso EE. (2020). Perinephric abscess. StatPearls. Retrieved July 28, 2021, https://www.ncbi.nlm.nih.gov/books/NBK536936/
  7. Gupta K, Hooton T, Naber KG, Wullt B, Colgan R, Miller LG, Moran GJ, Nicolle LE, Raz R, Schaeffer AJ, Soper DE. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases, Clinical Infectious Diseases. 2011;52(5):e103–e120. https://doi.org/10.1093/cid/ciq257
  8. National Institute for Healthcare Excellence; NICE guideline [NG111]. Pyelonephritis (acute): antimicrobial prescribing. https://www.nice.org.uk/guidance/ng111/chapter/Recommendations. Published October 2018. Retrieved April 26, 2022.

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