Urinary Tract Obstruction

Urinary tract obstruction (UTO) refers to the blockage of the urinary tract, which can occur anywhere in the urinary tract. Urinary tract obstruction can be acute or chronic, partial or complete, and unilateral or bilateral. Urinary tract obstruction can cause acute or chronic kidney disease Chronic Kidney Disease Chronic kidney disease (CKD) is kidney impairment that lasts for ≥ 3 months, implying that it is irreversible. Hypertension and diabetes are the most common causes; however, there are a multitude of other etiologies. In the early to moderate stages, CKD is usually asymptomatic and is primarily diagnosed by laboratory abnormalities. Chronic Kidney Disease. The etiology of UTO depends on where the UTO occurs in the urinary tract and includes kidney stones, transitional cell carcinoma, blood clots, and external compression. Clinical presentation depends on the location, degree, and acuteness of the obstruction. Symptoms can include pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain, change in urine output, hypertension, hematuria, and increased serum creatinine. Diagnosis is made by imaging, with ultrasound being the preferred initial modality. The mainstay of treatment is to relieve the cause of obstruction with a nephrostomy tube, ureteral stent, or catheterization. Renal function prognosis after the UTO is relieved is dependent on the severity and duration of the obstruction.

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Overview

Epidemiology

  • No specific epidemiological data
  • More common than generally expected
  • Rare cause of 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 ( AKI AKI 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)
  • More common in children than adults, in patients presenting with urinary tract symptoms or kidney failure (due to congenital abnormalities)
  • More common in men than women (especially due to benign prostatic hyperplasia Benign prostatic hyperplasia 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 (BPH) as men age)
  • More common cause of AKI AKI 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 in outpatient setting than in the hospital setting

Etiology

Etiology can be congenital, acquired, or functional. Urinary tract obstruction can occur anywhere along the urinary tract:

  • Obstruction within the kidney causes dilation of specific affected calyces or caliectasis. 
  • Obstruction at or distal to 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 causes diffuse caliectasis or 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.
Table: Etiologies of urinary tract obstruction
Renal Bladder inlet Bladder outlet Urethra
Congenital
  • Polycystic kidney disease
  • Peripelvic cyst
  • Ureteropelvic junction narrowing or obstruction (UPJO)
  • Vesicouterine reflux
  • Ureterocele
  • Retrocaval ureter
  • Bladder neck obstruction
  • Ureterocele
  • Posterior urethral valves
  • Anterior urethral valves
  • Stricture
  • Phimosis
  • Meatal stenosis
Acquired intrinsic defects
  • Calculi
  • 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
  • Infection
  • Trauma
  • Sloughed papillae
  • Tumor
  • Blood clots
  • Benign prostatic hyperplasia
  • Cancer of 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. Prostate and other Male Reproductive Glands or bladder
  • Calculi
  • Diabetic nephropathy
  • Spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord disease
  • Calculi
  • Stricture
  • Tumor
  • Trauma
  • Phimosis
Acquired extrinsic defects
  • Pregnant uterus
  • Retroperitoneal fibrosis
  • Aortic aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Extremity and Visceral Aneurysms
  • Uterine leiomyomata
  • Carcinoma of uterus, 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. Prostate and other Male Reproductive Glands, bladder, colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix, or rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal
  • Lymphoma
  • Pelvic inflammatory disease Pelvic inflammatory disease Pelvic inflammatory disease (PID) is defined as a polymicrobial infection of the upper female reproductive system. The disease can affect the uterus, fallopian tubes, ovaries, and adjacent structures. Pelvic inflammatory disease is closely linked with sexually transmitted diseases, most commonly caused by Chlamydia trachomatis, Neisseria gonorrhoeae, and Gardnerella vaginalis. Pelvic Inflammatory Disease
  • Endometriosis Endometriosis Endometriosis is a common disease in which patients have endometrial tissue implanted outside of the uterus. Endometrial implants can occur anywhere in the pelvis, including the ovaries, the broad and uterosacral ligaments, the pelvic peritoneum, and the urinary and gastrointestinal tracts. Endometriosis
  • Accidental surgical ligation
  • Carcinoma of cervix
  • Carcinoma of colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix
Trauma
Functional defects
  • Neurogenic bladder
  • Anticholinergic drugs Anticholinergic drugs Anticholinergic drugs block the effect of the neurotransmitter acetylcholine at the muscarinic receptors in the central and peripheral nervous systems. Anticholinergic agents inhibit the parasympathetic nervous system, resulting in effects on the smooth muscle in the respiratory tract, vascular system, urinary tract, GI tract, and pupils of the eyes. Anticholinergic Drugs
  • α-adrenergic antagonists
  • Diabetic nephropathy
  • Detrusor-sphincter dyssynergia
  • Dysfunctional voiding
  • External sphincter pseudodyssynergia
  • Multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis
  • Parkinson disease

Pathophysiology

  • Obstruction induces apoptosis of the renal tubular cells: Glomerular cells are resistant to obstruction-related apoptosis. 
  • Renal tubular cell apoptosis is mediated via caspases (generated from cytokine release and inflammatory responses) 
  • Prolonged obstructive processes induce tubulointerstitial fibrosis and inflammation: accumulates extracellular matrix and promotes fibrosis 
  • Postobstructive diuresis: 
    • Physiologic phenomenon seen after acute release of bilateral obstruction 
    • Urine flow increases by about 3–10-fold.
    • Possible mechanisms:
      • Impaired sodium reabsorption due to tubular damage 
      • Impaired urine-concentrating ability
      • Solute diuresis with excretion of retained urea 
      • Increased circulating natriuretic factor (ANP)
Table: Effects of urinary tract obstruction (UTO) on glomerular filtration Glomerular filtration The kidneys are primarily in charge of the maintenance of water and solute homeostasis through the processes of filtration, reabsorption, secretion, and excretion. Glomerular filtration is the process of converting the systemic blood supply into a filtrate, which will ultimately become the urine. Glomerular Filtration and renal blood flow
Hemodynamic effects Tubule effects
Acute obstruction
  • ↑ Renal blood flow
  • ↓ GFR
  • ↓ Medullary blood flow
  • ↑ Vasodilator prostaglandins and nitric oxide
  • ↑ Ureteral and tubule pressures
  • ↑ Reabsorption of urea, water, and sodium
Chronic obstruction
  • ↓ Renal blood flow
  • ↓↓ GFR
  • ↑ Renin-angiotensin production
  • ↑ Vasoconstrictor prostaglandins
  • ↓ Medullary osmolarity
  • ↓ Concentrating ability
  • ↓ Transport functions of sodium, potassium, hydrogen
  • Structural damage
  • Parenchymal atrophy
Release of obstruction Slow ↑ in GFR, which is variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables
  • Natriuretic factors are present.
  • ↓ Tubule pressure
  • ↓ Solute load per nephron (e.g., urea, sodium chloride)

Clinical Presentation

Clinical presentation depends on the location, degree, and how quickly the obstruction develops.

Symptoms can include:

  • Pain:
    • Often absent
    • If present, is usually the result of bladder distention, secondary infection, or obstructing stone/mass
    • Associated with rate at which the distension develops
    • Often affects the flank or suprapubic region
  • Change in urine output:
    • Azotemia
    • Polyuria
    • Nocturia  
  • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
  • Hematuria

Classic laboratory findings:

  • Elevated serum creatinine
  • Urinalysis with red cells or white cells 
  • Hyperkalemic renal tubular acidosis Renal Tubular Acidosis Renal tubular acidosis (RTA) is an imbalance in physiologic pH caused by the kidney's inability to acidify urine to maintain blood pH at physiologic levels. Renal tubular acidosis exist in multiple types, including distal RTA (type 1), proximal RTA (type 2), and hyperkalemic RTA (type 4). Renal Tubular Acidosis
    • Mostly found in patients with chronic obstruction
    • Likely from mineralocorticoid resistance impairing distal sodium reabsorption

Diagnosis

  • Take a thorough history and physical:
    • Elicit any prior GU surgical history. 
    • Palpate for costovertebral angle tenderness. 
    • General abdominal exam assessing for suprapubic tenderness 
  • Urinalysis and culture: 
    • Hematuria: 
      • Gross 
      • Microscopic with > 3 RBCs per high power field 
    • Pyuria: WBCs in urine 
    • Bacteriuria: may reveal gross 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: Overview in urine specimen 
  • Labs: may reveal ↑ creatinine 
  • Gold standard is imaging: 
    • Hallmark finding is dilatation of the collecting system in 1 or both 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.
    • Ultrasound is the preferred imaging modality:
      • Advantage of no ionizing radiation 
      • Inexpensive 
      • Identifies 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, but is not a functional test 
    • CT scan:
      • Provides superior anatomic information 
      • Ability to have contrasted images with both nephrographic and excretory phases 
      • Excretory phases allow for delayed contrast images to identify the level of obstruction 
      • Risks include: contrast nephropathy and ionizing radiation exposure 
    • Can use voiding cystourethrography to diagnose 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 or bladder neck and urethral obstructions
Ultrasound of fetal bladder obstruction

Fetal ultrasound revealing urinary tract obstruction (UTO) with classic keyhole sign (B: bladder, U: urethra)

Image: “Ultrasound of fetal bladder obstruction” by St. David’s Women’s Center of Texas, Austin Maternal-Fetal Medicine, 12200 Renfert Way, G-3, Austin, Austin, TX 78758 USA. License: CC BY 4.0

Management

Treatment

Mainstay of treatment is to relieve the cause of obstruction.

  • UTO complicated by infection requires immediate relief of the obstruction to prevent sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock and renal damage.
  • Drainage may be achieved by nephrostomy tube, ureterostomy, ureteral stent placement, or bladder catheterization.
  • Decompression of the urinary system is combined with antibiosis for sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock-related obstruction. 
  • Benign prostatic hyperplasia can be treated with α-adrenergic blockers or 5α-reductase inhibitors. When associated with severe infection and bladder outlet obstruction, urethral catheterization is indicated.

Prognosis

After relief of obstruction:

  • Renal prognosis depends on:
    • If irreversible renal damage has occurred
    • Severity and duration of obstruction
  • Most functional recovery is seen 7–10 days
  • Some patients with severe renal failure may require dialysis Dialysis Renal replacement therapy refers to dialysis and/or kidney transplantation. Dialysis is a procedure by which toxins and excess water are removed from the circulation. Hemodialysis and peritoneal dialysis (PD) are the two types of dialysis, and their primary difference is the location of the filtration process (external to the body in hemodialysis versus inside the body for PD). Overview and Types of Dialysis.

With unrelieved obstruction:

  • Clinical course depends on whether the obstruction is complete, partial, or bilateral. 
  • Complete obstruction that is complicated by infection can lead to complete renal destruction within days.
  • Partial recovery of renal function can be seen after 1–2 weeks of complete obstruction.
  • After 8 weeks of complete obstruction, recovery is unlikely.

References

  1. Dmochowski R. R. Bladder outlet obstruction: etiology and evaluation. Reviews in Urology. 2005; 7 (Supplement 6): S3–S13.
  2. Kumar V, Abbas AK AK Actinic keratosis (AK) is a precancerous skin lesion that affects sun-exposed areas. The condition presents as small, non-tender macules/papules with a characteristic sandpaper-like texture that can become erythematous scaly plaques. Actinic Keratosis (AK), Aster JC. (2015). Robbins & Cotran Pathologic Basis of Disease. Philadelphia, PA: Elsevier Saunders; 2015.
  3. MedlinePlus. (2020). Hydronephrosis of one kidney. Retrieved April 30, 2021, from https://medlineplus.gov/ency/article/000506.htm 
  4. Preminger GM. (2020). 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 Obstruction. Merck Manual Consumer Version. Retrieved April 30, 2021, from https://www.merckmanuals.com/home/kidney-and-urinary-tract-disorders/obstruction-of-the-urinary-tract/urinary-tract-obstruction 
  5. Seifter JL. (2018). Urinary tract obstruction. Jameson J, & Fauci AS, & Kasper DL, & Hauser SL, & Longo DL, & Loscalzo J (Eds.), Harrison’s Principles of Internal Medicine, 20e. McGraw-Hill. https://accessmedicine-mhmedical-com.aucmed.idm.oclc.org/content.aspx?bookid=2129&sectionid=192281753
  6. Zeidel ML, O’Neill WC. Clinical manifestations and diagnosis of urinary tract obstruction and 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. UpToDate. Retrieved April 30, 2021, from https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-urinary-tract-obstruction-and-hydronephrosis

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