Liddle Syndrome

Overview

Definition

Liddle syndrome is a rare autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance genetic disorder associated with abnormal increased function of epithelial sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia channels Channels The Cell: Cell Membrane (ENaC) in the collecting tubules Collecting tubules Straight tubes commencing in the radiate part of the kidney cortex where they receive the curved ends of the distal convoluted tubules. In the medulla the collecting tubules of each pyramid converge to join a central tube (duct of Bellini) which opens on the summit of the papilla. Kidneys: Anatomy. Liddle syndrome is clinically characterized by 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, low plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products renin Renin A highly specific (leu-leu) endopeptidase that generates angiotensin I from its precursor angiotensinogen, leading to a cascade of reactions which elevate blood pressure and increase sodium retention by the kidney in the renin-angiotensin system. Renal Sodium and Water Regulation activity, metabolic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis, hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia, and low aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia levels.

Epidemiology

• Extremely rare disorder reported in < 80 families
• Overall population prevalence Prevalence The total number of cases of a given disease in a specified population at a designated time. It is differentiated from incidence, which refers to the number of new cases in the population at a given time. Measures of Disease Frequency is unknown.
• Individuals may remain asymptomatic for up to 40 years, but Liddle syndrome can also be diagnosed as early as 12 years in a majority of cases.
• Often remains undiagnosed

Etiology

An autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance gain-of-function gene mutation Gene Mutation Myotonic Dystrophies changes the structure of an ENaC subunit and also affects the region of the protein involved in signaling for its breakdown, which is normally controlled by aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia.

• SCNN1A: encodes the alpha subunit of the ENaC
• SCNN1B: encodes the beta subunit of the ENaC
• SCNN1G: encodes the gamma subunit of the ENaC

Pathophysiology

• Mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations occurs in the SCNN1A, SCNN1B, and SCNN1G genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure that encode the alpha, beta, and gamma subunits of the ENaC.
  • Normally located on the epithelial cell surface 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 (collecting tubule)
    • Lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy
    • 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: Anatomy
    • Sweat glands Sweat glands Sweat-producing structures that are embedded in the dermis. Each gland consists of a single tube, a coiled body, and a superficial duct. Soft Tissue Abscess
  • Normal function of the channels Channels The Cell: Cell Membrane: Na reabsorption
• Dysregulation of the ENaC follows due to structural changes in the respective subunits.
• Domain change in the channel → ↓ internalization and degradation of ENaC channels Channels The Cell: Cell Membrane (by the ubiquitin-proteasome pathway)
• Inability to degrade the channels Channels The Cell: Cell Membrane → ↑ presence of the channel in the collecting duct Collecting duct Straight tubes commencing in the radiate part of the kidney cortex where they receive the curved ends of the distal convoluted tubules. In the medulla the collecting tubules of each pyramid converge to join a central tube (duct of bellini) which opens on the summit of the papilla. Renal Cell Carcinoma → ↑ Na reabsorption, resulting in: 
  • ↑ Water reabsorption and 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
  • ↑ Na/K ATPase activity → ↑ cellular K influx and secretion Secretion Coagulation Studies through apical K channels Channels The Cell: Cell Membrane
• Aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia is responsible for controlling the number of Na channels Channels The Cell: Cell Membrane. Loss of this ability in Liddle syndrome → ↓ in channel degradation → hyperaldosteronism-like state

Clinical Presentation and Diagnosis

Clinical presentation

Liddle syndrome is rare and has a presentation similar to many other syndromes associated with mineralocorticoid excess Mineralocorticoid excess A hereditary disease characterized by childhood onset hypertension, hypokalemic alkalosis, and low renin and aldosterone secretion. It results from a defect in the activity of the 11-beta-hydroxysteroid dehydrogenase type 2 enzyme which results in inadequate conversion of cortisol to cortisone. The build up of unprocessed cortisol to levels that stimulate mineralocorticoid receptors creates the appearance of having excessive mineralocorticoids. Metabolic Alkalosis. Thus, Liddle syndrome is often misdiagnosed or remains undetected.

The classic triad of the presentation includes:

1. 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:
   • Early onset
   • Long-standing
   • Often severe or resistant
   • Associated features:
     • Intermittent headaches
     • 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
     • Dizziness Dizziness An imprecise term which may refer to a sense of spatial disorientation, motion of the environment, or lightheadedness. Lateral Medullary Syndrome (Wallenberg Syndrome)
     • Changes in vision Vision Ophthalmic Exam
2. Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia symptoms:
   • Weakness
   • 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
   • Palpitations Palpitations Ebstein’s Anomaly
   • Myalgia Myalgia Painful sensation in the muscles. Ion Channel Myopathy
   • 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
   • Exercise intolerance
3. Metabolic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis

Diagnosis

The preliminary diagnosis of Liddle syndrome is based mainly on suspicion resulting from the clinical presentation. It is also important to:

• Consider family history Family History Adult Health Maintenance of early-onset 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 with or without hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia.
• Rule out other causes of 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, hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia, and metabolic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis.

Laboratory findings:

• ↓ Plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products renin Renin A highly specific (leu-leu) endopeptidase that generates angiotensin I from its precursor angiotensinogen, leading to a cascade of reactions which elevate blood pressure and increase sodium retention by the kidney in the renin-angiotensin system. Renal Sodium and Water Regulation
• ↓ Plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia
• ↓ Urine aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia
• ↓ Urine Na
• Serum electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes:
  • ↑ Na
  • ↓ K
  • ↑ HCO3

Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies should be considered in individuals with a family history Family History Adult Health Maintenance of Liddle syndrome and in those in whom this condition is suspected.

Management

Treatment

Early diagnosis of Liddle syndrome leads to resolution or control of the disorder, enabling the affected individual to lead a normal life.

• Potassium-sparing diuretics Potassium-sparing diuretics Potassium-sparing diuretics are medications that act in the principal cells in the collecting ducts to induce diuresis that does not result in excretion of potassium. These diuretics include 2 subclasses: sodium channel blockers and aldosterone antagonists. Potassium-sparing Diuretics:
  • Act by blocking ENaC activity:
    • Amiloride
    • Triamterene Triamterene A pteridinetriamine compound that inhibits sodium reabsorption through sodium channels in renal epithelial cells. Potassium-sparing Diuretics
  • Used to treat 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 while resolving hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia and metabolic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis
• Salt restriction: < 2 g sodium Sodium A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23. Hyponatremia/day
• Conventional hypertensive therapies are ineffective.
• Renal transplantation resolves the disorder completely.

Complications

Owing to its rare occurrence and similarity of symptoms to those of other disorders associated with mineralocorticoid excess Mineralocorticoid excess A hereditary disease characterized by childhood onset hypertension, hypokalemic alkalosis, and low renin and aldosterone secretion. It results from a defect in the activity of the 11-beta-hydroxysteroid dehydrogenase type 2 enzyme which results in inadequate conversion of cortisol to cortisone. The build up of unprocessed cortisol to levels that stimulate mineralocorticoid receptors creates the appearance of having excessive mineralocorticoids. Metabolic Alkalosis, Liddle syndrome is often misdiagnosed, which may cause an increase in the occurrence of complications:

• Resistant hypertension Resistant hypertension Blood pressure that remains uncontrolled despite concurrent use of 3 antihypertensive agents of different classes. Uncontrolled Hypertension
• Left ventricular hypertrophy Left ventricular hypertrophy Enlargement of the left ventricle of the heart. This increase in ventricular mass is attributed to sustained abnormal pressure or volume loads and is a contributor to cardiovascular morbidity and mortality. Hypertension
• Hypertensive retinopathy Retinopathy Degenerative changes to the retina due to hypertension. Alport Syndrome
• Nephrosclerosis
• Cerebral 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 leading to cerebrovascular accidents
• Chronic 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
• Hypertensive encephalopathy Encephalopathy Hyper-IgM Syndrome
• Pulmonary 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

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

• Early diagnosis and treatment are key in the prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas of Liddle syndrome.
• Adequate treatment → good prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas
• Delayed detection → delay in therapy → manifestation as major cardiovascular and renal complications

Differential Diagnosis

• Primary hyperaldosteronism Primary hyperaldosteronism Autonomous (renin-independent) secretion of aldosterone. Hyperaldosteronism: also known as Conn’s syndrome. Primary hyperaldosteronism Primary hyperaldosteronism Autonomous (renin-independent) secretion of aldosterone. Hyperaldosteronism is characterized by the excess production of aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia, which results in low renin Renin A highly specific (leu-leu) endopeptidase that generates angiotensin I from its precursor angiotensinogen, leading to a cascade of reactions which elevate blood pressure and increase sodium retention by the kidney in the renin-angiotensin system. Renal Sodium and Water Regulation levels. Primary hyperaldosteronism Primary hyperaldosteronism Autonomous (renin-independent) secretion of aldosterone. Hyperaldosteronism is caused by primary adrenal 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 or adrenal adenoma Adrenal Adenoma Cushing Syndrome and presents with 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, muscle weakness, muscle spasms Spasms An involuntary contraction of a muscle or group of muscles. Spasms may involve skeletal muscle or smooth muscle. Ion Channel Myopathy, polyuria Polyuria Urination of a large volume of urine with an increase in urinary frequency, commonly seen in diabetes. Renal Potassium Regulation, and headaches. Diagnosis is based on clinical history, examination, and laboratory testing. Management includes adrenalectomy Adrenalectomy Excision of one or both adrenal glands. Cushing Syndrome and therapy with spironolactone Spironolactone A potassium sparing diuretic that acts by antagonism of aldosterone in the distal renal tubules. It is used mainly in the treatment of refractory edema in patients with congestive heart failure, nephrotic syndrome, or hepatic cirrhosis. Its effects on the endocrine system are utilized in the treatments of hirsutism and acne but they can lead to adverse effects. Potassium-sparing Diuretics.
• Apparent mineralocorticoid excess Mineralocorticoid excess A hereditary disease characterized by childhood onset hypertension, hypokalemic alkalosis, and low renin and aldosterone secretion. It results from a defect in the activity of the 11-beta-hydroxysteroid dehydrogenase type 2 enzyme which results in inadequate conversion of cortisol to cortisone. The build up of unprocessed cortisol to levels that stimulate mineralocorticoid receptors creates the appearance of having excessive mineralocorticoids. Metabolic Alkalosis: a rare autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance disorder that presents with 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, hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia, metabolic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis, and low plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products renin Renin A highly specific (leu-leu) endopeptidase that generates angiotensin I from its precursor angiotensinogen, leading to a cascade of reactions which elevate blood pressure and increase sodium retention by the kidney in the renin-angiotensin system. Renal Sodium and Water Regulation. Diagnosis is made by calculating the ratio of free urinary cortisol Cortisol Glucocorticoids to free urinary cortisone Cortisone A naturally occurring glucocorticoid that has been used in replacement therapy for adrenal insufficiency and as an anti-inflammatory agent. Cortisone itself is inactive; it is converted in the liver to the active metabolite hydrocortisone. Glucocorticoids, which is higher in affected individuals. Management includes aldosterone Aldosterone A hormone secreted by the adrenal cortex that regulates electrolyte and water balance by increasing the renal retention of sodium and the excretion of potassium. Hyperkalemia antagonists, such as spironolactone Spironolactone A potassium sparing diuretic that acts by antagonism of aldosterone in the distal renal tubules. It is used mainly in the treatment of refractory edema in patients with congestive heart failure, nephrotic syndrome, or hepatic cirrhosis. Its effects on the endocrine system are utilized in the treatments of hirsutism and acne but they can lead to adverse effects. Potassium-sparing Diuretics.
• Glucocorticoid 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: a familial disease characterized by reduced cortisol Cortisol Glucocorticoids effects due to a glucocorticoid receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors defect countered by hyperactivity Hyperactivity Attention Deficit Hyperactivity Disorder of the hypothalamic– pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types–adrenal axis. Affected individuals present with signs of adrenal overproduction of mineralocorticoids Mineralocorticoids Mineralocorticoids are a drug class within the corticosteroid family and fludrocortisone is the primary medication within this class. Fludrocortisone is a fluorinated analog of cortisone. The fluorine moiety protects the drug from isoenzyme inactivation in the kidney, allowing it to exert its mineralocorticoid effect. Mineralocorticoids— 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, hypokalemic alkalosis Alkalosis A pathological condition that removes acid or adds base to the body fluids. Respiratory Alkalosis, hirsutism Hirsutism A condition observed in women and children when there is excess coarse body hair of an adult male distribution pattern, such as facial and chest areas. It is the result of elevated androgens from the ovaries, the adrenal glands, or exogenous sources. The concept does not include hypertrichosis, which is an androgen-independent excessive hair growth. Polycystic Ovarian Syndrome in women, male-pattern baldness Baldness Alopecia is the loss of hair in areas anywhere on the body where hair normally grows. Alopecia may be defined as scarring or non-scarring, localized or diffuse, congenital or acquired, reversible or permanent, or confined to the scalp or universal; however, alopecia is usually classified using the 1st 3 factors. Alopecia, and menstrual irregularities. Diagnosis is based on high cortisol Cortisol Glucocorticoids levels and normal-to-high adrenocorticotrophic hormone (ACTH) levels. Management is using mineralocorticoid-sparing synthetic glucocorticoids Glucocorticoids Glucocorticoids are a class within the corticosteroid family. Glucocorticoids are chemically and functionally similar to endogenous cortisol. There are a wide array of indications, which primarily benefit from the antiinflammatory and immunosuppressive effects of this class of drugs. Glucocorticoids to suppress ACTH secretion Secretion Coagulation Studies.
• Renovascular hypertension Renovascular hypertension Hypertension due to renal artery obstruction or compression. Renal Artery Stenosis: a condition caused by narrowing or occlusion of the renal arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology and/or their branches, often due to atherosclerosis Atherosclerosis Atherosclerosis is a common form of arterial disease in which lipid deposition forms a plaque in the blood vessel walls. Atherosclerosis is an incurable disease, for which there are clearly defined risk factors that often can be reduced through a change in lifestyle and behavior of the patient. Atherosclerosis or fibromuscular dysplasia Fibromuscular dysplasia Fibromuscular dysplasia (FMD) is a nonatherosclerotic, noninflammatory, medium-sized angiopathy due to fibroplasia of the vessel wall. The condition leads to complications related to arterial stenosis, aneurysm, or dissection. Fibromuscular Dysplasia. The clinical presentation of renovascular hypertension Renovascular hypertension Hypertension due to renal artery obstruction or compression. Renal Artery Stenosis includes 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, renal dysfunction, and pulmonary 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 caused by activation of the renin-angiotensin-aldosterone system Renin-angiotensin-aldosterone system A blood pressure regulating system of interacting components that include renin; angiotensinogen; angiotensin converting enzyme; angiotensin i; angiotensin ii; and angiotensinase. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming angiotensin I. Angiotensin-converting enzyme, contained in the lung, acts on angiotensin I in the plasma converting it to angiotensin II, an extremely powerful vasoconstrictor. Angiotensin II causes contraction of the arteriolar and renal vascular smooth muscle, leading to retention of salt and water in the kidney and increased arterial blood pressure. In addition, angiotensin II stimulates the release of aldosterone from the adrenal cortex, which in turn also increases salt and water retention in the kidney. Angiotensin-converting enzyme also breaks down bradykinin, a powerful vasodilator and component of the kallikrein-kinin system. Adrenal Hormones. Diagnosis is based on renal imaging Renal imaging The renal system is composed of 2 kidneys, 2 ureters, a bladder, and a urethra. Varying conditions such as infections, cysts, solid masses, ischemia, and mechanical obstruction can affect the renal system. Evaluation of diseases rely on imaging methods such as radiography, ultrasonography, CT, and MRI. Some of these are also used to guide tissue sampling (e.g., renal biopsy). Imaging of the Urinary System, such as duplex ultrasonography Duplex ultrasonography Ultrasonography applying the doppler effect combined with real-time imaging. The real-time image is created by rapid movement of the ultrasound beam. A powerful advantage of this technique is the ability to estimate the velocity of flow from the doppler shift frequency. Hypercoagulable States. Management is by surgical intervention.