polycystic kidney

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pol·y·cys·tic kid·ney

a progressive disease characterized by formation of multiple cysts of varying size scattered diffusely throughout both kidneys, resulting in compression and destruction of renal parenchyma, usually with hypertension, gross hematuria, and uremia leading to progressive renal failure. There are two major types: with onset in infancy or early childhood, usually of autosomal recessive inheritance [MIM*263200]; with onset in adulthood, of autosomal dominant inheritance with genetic heterogeneity [MIM*173900, 173910, and 600666]; may be caused by mutation in either polycystin-1 gene on chromosome 16p, polycystin-2 gene on 4q, or gene(s) not identified yet.

polycystic kidney

A nonspecific term for two morphologically similar but clinically and genetically distinct conditions:
(1) Autosomal dominant (“adult") polycystic kidney disease (OMIM:173900);
(2) Autosomal recessive (“infantile") polycystic kidney disease (OMIM:263200).

polycystic kidney

Polycystic renal disease Nephrology An inherited disease characterized by the development of innumerable cysts in the kidneys filled with fluid–urine that replace much of the mass of the kidneys and reduce kidney function leading to kidney failure. See Autosomal dominant polycystic kidney disease, Multilocular cyst of the kidney.
Polycystic disorders of kidneys
Renal dysplasia Relatively common, often acquired, presents in infancy; unilateral or bilateral and segmental, focally irregular cystic kidneys, related to mesenchymal immaturity, accompanied by obstruction
Infantile polycystic kidneys Uncommon, AR, seen in infants with massively enlarged kidneys and aberrant bile ducts.
Adult polycystic kidneys Common (1-2:1000, US), AD, located to a gene on chromosome 16, affects adults, large bumpy kidneys, cysts in liver, lung, pancreas, berry aneurysms in brain
Medullary sponge kidneys Common, bilateral, uncertain pattern of heredity, affects adults, inability to concentrate urine, hypercalcemia, nephrolithiasis, pyelonephritis, distal renal tubular acidosis and cystic dilation of collecting ducts; renal function and life span may be normal
Uremic medullary sponge kidney Rare, inherited, first seen in young adults; bilateral corticomedullary junction cysts and functional tubular defects, Fanconi syndrome and uremia.

pol·y·cys·tic kid·ney

, polycystic disease of kidneys (pol'ē-sis'tik kid'nē, di-zēz' kid'nēz)
A progressive disease characterized by formation of multiple cysts of varying size scattered diffusely throughout both kidneys, resulting in compression and destruction of kidney parenchyma, usually with hypertension, gross hematuria, and uremia.

kidney

(kid'ne)
Enlarge picture
KIDNEY: A. Urinary Structures; B. Cross section of the kidney
Enlarge picture
NEPHRON WITH ITS ASSOCIATED BLOOD VESSELS
One of a pair of purple-brown organs situated at the back (retroperitoneal area) of the abdominal cavity; each is lateral to the spinal column. The kidneys form urine from blood plasma. They are the major regulators of the water, electrolyte, and acid-base content of the blood and, indirectly, all body fluids.

Anatomy

The top of each kidney is opposite the 12th thoracic vertebra; the bottom is opposite the third lumbar vertebra. The right kidney is slightly lower than the left one. Each kidney weighs 113 to 170 g (4 to 6 oz), and each is about 11.4 cm (4 1 2 in) long, 5 to 7.5 cm (2 to 3 in) broad, and 2.5 cm (1 in) thick. The kidneys in the newborn are about three times as large in proportion to body weight as they are in the adult.

Each kidney is surrounded by adipose tissue and by the renal fascia, a fibrous membrane that helps hold the kidney in place. On the medial side of a kidney is an indentation called the hilus or hilum, at which the renal artery enters and the renal vein and ureter emerge. The microscopic nephrons are the structural and functional units of the kidney; each consists of a renal corpuscle and renal tubule with associated blood vessels. In frontal section, the kidney is composed of two areas of tissue and a medial cavity. The outer renal cortex is made of renal corpuscles and convoluted tubules. The renal medulla consists of 8 to 18 wedge-shaped areas called renal pyramids; they are made of loops of Henle and collecting tubules. Adjacent to the hilus is the renal pelvis, the expanded end of the ureter within the kidney. Urine formed in the nephrons is carried by a papillary duct to the tip (papilla) of a pyramid, which projects into a cuplike calyx, an extension of the renal pelvis. See: illustration

Nephron

The nephron consists of a renal corpuscle and renal tubule. The renal corpuscle is made of a capillary network called a glomerulus surrounded by Bowman's capsule. The renal tubule extends from Bowman's capsule. The parts, in order, are as follows: proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting tubule, all of which are surrounded by peritubular capillaries. See: illustration

Formation of Urine

Urine is formed by filtration, reabsorption, and secretion. As blood passes through the glomerulus, water and dissolved substances are filtered through the capillary membranes and the inner or visceral layer of Bowman's capsule; this fluid is now called glomerular filtrate. Blood cells and large proteins are retained within the capillaries. Filtration is a continuous process; the rate varies with blood flow through the kidneys and daily fluid intake and loss. As the glomerular filtrate passes through the renal tubules, useful materials such as water, glucose, amino acids, vitamins, and minerals are reabsorbed into the peritubular capillaries. Most of these have a renal threshold level, i.e., a limit to how much can be reabsorbed, but this level is usually not exceeded unless the blood level of these materials is above normal. Reabsorption of water is regulated directly by antidiuretic hormone and indirectly by aldosterone. Most waste products remain in the filtrate and become part of the urine. Hydrogen ions, creatinine, and the metabolic products of medications may be actively secreted into the filtrate to become part of the urine. The collecting tubules unite to form papillary ducts that empty urine into the calyces of the renal pelvis, from which it enters the ureter and is transported to the urinary bladder. Periodically the bladder is emptied (a reflex subject to voluntary control) by way of the urethra; this is called micturition, urination, or voiding. If a normally hydrated individual ingests a large volume of aqueous fluids, in about 45 min a sufficient quantity will have been excreted into the bladder to cause the urge to urinate. See:

Urine

Urine is about 95% water and about 5% dissolved substances. The dissolved materials include minerals, esp. sodium, the nitrogenous waste products urea, uric acid, and creatinine, and other metabolic end products. The volume of urine excreted daily varies from 1000 to 2000 ml (averaging 1500 ml). The amount varies with water intake, nature of diet, degree of body activity, environmental and body temperature, age, blood pressure, and many other factors. Pathological conditions may affect the volume and nature of the urine excreted. However, patients with only one kidney have been found to have normal renal function even after half of that kidney was removed because of cancer. There is no evidence that forcing fluids is detrimental to the kidneys.

Nerve Supply

The nerve supply consists of sympathetic fibers to the renal blood vessels. These promote constriction or dilation, esp. of arteries and arterioles.

Disorders

Frequently encountered diseases of the kidney include infection (pyelonephritis), stone formation (nephrolithiasis), dilation (hydronephrosis), protein loss (nephrosis), cancer (hypernephroma), and acute or chronic renal failure. See: dialysis; glomerulonephritis; nephropathy; nephritis; renal failure

Examination

The kidneys are examined by palpation, intravenous pyelography, ultrasonography, computed tomography scan, cystoscopy, retrograde cystoscopy, or magnetic resonance imaging. Kidney function is also frequently examined with blood tests (e.g., for electrolytes, blood urea nitrogen, and creatinine) and by urinalysis or timed collections of urine.

amyloid kidney

An enlarged, firm, smooth kidney usually associated with systemic amyloidosis. Synonym: waxy kidney

Symptoms

Infected persons typically lose large quantities of protein in the urine and may present with edema or symptoms of fluid overload, nephrosis, or renal failure.

artificial kidney

Dialyzer.

cake kidney

Congenitally fused kidneys.

contracted kidney

The abnormally small kidney found in end-stage renal disease.

cystic kidney

A kidney that has undergone cystic degeneration.
See: polycystic kidney disease

embolic contracted kidney

A kidney in which embolic infarction of the renal arterioles produces degeneration of renal tissue and hyperplasia of fibrous tissues produces irregular contraction.

fatty kidney

A kidney with fatty infiltration or degeneration of tubular, glomerular, or capsular epithelium, or of vascular connective tissue.

flea-bitten kidney

A kidney with small petechiae covering the surface, a pathological finding in bacterial endocarditis and some other systemic illnesses.

floating kidney

A kidney that is displaced and movable.

fused kidney

A condition in which the kidneys are joined into one anomalous organ.

Goldblatt kidney

See: Goldblatt, Harry

granular kidney

A slow form of chronic nephritis characterized by diminishing size; by redness; and by a hard, fibrous, and granular texture. Synonym: red contracted kidney

horseshoe kidney

A congenital malformation in which the superior or inferior extremities are united by an isthmus of renal or fibrous tissue, forming a horseshoe shape.

hypermobile kidney

A freely movable kidney. Synonym: wandering kidney

medullary sponge kidney

A congenital condition characterized by the presence—seen best during urography—of spongy or porous appearing renal collecting tubules. The disease may be asymptomatic or may cause urinary bleeding, stone formation with renal colic, or recurrent urinary tract infections.
Synonym: Cacchi-Ricci syndrome

movable kidney

A kidney that is not firmly attached owing to lack of support of fatty tissue and perinephric fascia. Synonym: nephroptosis

myeloma kidney

Cast nephropathy.

polycystic kidney

A kidney bearing many cysts. See: kidney disease, polycystic

red contracted kidney

Granular kidney.

sacculated kidney

A condition in which the kidney has been absorbed and only the distended capsule remains.

small indented calcified kidney

Abbreviation: SICK
The computed tomographic (CT) appearance of the kidneys in patients who develop chronic kidney disease from the overuse of analgesic medications like acetaminophen, aspirin, ibuprofen, or phenacetin.

syphilitic kidney

Kidney with fibrous bands running across it, and caseating gummata, as a result of syphilis.

wandering kidney

Hypermobile kidney.

waxy kidney

Amyloid kidney.

polycystic kidney

A genetically determined condition in which both kidneys are greatly enlarged and contain large numbers of cysts. Kidney function is prejudiced and most affected people suffer kidney failure or other serious complications by middle age. See also AUTOSOMAL POLYCYSTIC KIDNEY DISEASE.
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