Polycystic kidney disease
Polycystic kidney disease is an inherited disorder characterized by multiple, bilateral, grapelike clusters of fluid-filled cysts that grossly enlarge the kidneys, compressing and eventually replacing functioning renal tissue. (See Polycystic kidney.) The disease appears in two distinct forms: The infantile form typically causes stillbirth or early neonatal death, although some infants may survive for 2 years, then develop fatal renal, cardiac, or respiratory failure. The adult form begins insidiously but usually becomes obvious between ages 30 and 50; rarely, it causes no symptoms until the patient is in his 70s. In the adult form, renal deterioration is more gradual but, as in the infantile form, progresses relentlessly to fatal uremia.
The prognosis in adults is extremely variable. Progression may be slow, even after symptoms of renal insufficiency appear. However, after uremic symptoms develop, polycystic kidney disease is usually fatal within 4 years, unless the patient receives treatment with dialysis, kidney transplantation, or both.
Causes and incidence
While both types of polycystic kidney disease are genetically transmitted, the incidence in two distinct age groups and different inheritance patterns suggest two unrelated disorders. The infantile type appears to be inherited as an autosomal recessive trait, whereas the adult type seems to be an autosomal dominant trait. The gene has been located on chromosome 6, supporting the premise that this is a single genetic disease with variable phenotype presentation.
Polycystic kidney disease reportedly affects 1 in every 1,000 Americans; yet that number may be even higher because some cases from patients who aren’t symptomatic go unreported. Both types of polycystic kidney disease affect males and females equally.
Signs and symptoms
The neonate with infantile polycystic disease often has pronounced epicanthal folds, a pointed nose, a small chin, and floppy, low-set ears (Potter facies). At birth, he has huge bilateral masses on the flanks that are symmetrical, tense, and can’t be transilluminated. He characteristically shows signs of respiratory distress and heart failure. Eventually, he develops uremia and renal failure. Accompanying hepatic fibrosis may cause portal hypertension and bleeding varices to develop, requiring sclerotherapy or portacaval shunting.
Adult polycystic kidney disease is commonly asymptomatic through the patient’s 40s, but may induce nonspecific symptoms, such as hypertension, polyuria, and recurrent urinary tract infections (UTIs). Later, the patient develops overt symptoms related to the enlarging kidney mass, such as lumbar pain, widening girth, and swollen or tender abdomen. Abdominal pain is usually worsened by exertion and relieved by lying down. In advanced stages, this disease may cause recurrent hematuria, life-threatening retroperitoneal bleeding resulting from cyst rupture, proteinuria, and colicky abdominal pain from the ureteral passage of clots or calculi. Generally, about 10 years after symptoms appear, progressive compression of kidney structures by the enlarging mass produces renal failure and uremia. Hypertension is found in about 20% to 30% of children and up to 75% of adults due to intrarenal ischemia, which activates the renin-angiotensin system.
Diagnosis
A family history and a physical examination revealing large bilateral, irregular masses in the flanks strongly suggest polycystic kidney disease. In advanced stages, grossly enlarged and palpable kidneys make the diagnosis obvious. In patients with these findings, the following laboratory results are typical:
❑ Excretory urography reveals enlarged kidneys, with elongation of pelvis, flattening of the calyces, and indentations caused by cysts. Excretory urography of the neonate shows poor excretion of contrast medium.
❑ Ultrasound and computed tomography scan show kidney enlargement and the presence of cysts; tomography demonstrates multiple areas of cystic damage. Ultrasonography is the preferred imaging technique because it’s less expensive, doesn’t require contrast or radiation exposure, and is easily and safely performed on children and pregnant females.
❑ Urinalysis and creatinine clearance tests are nonspecific tests that evaluate renal function and reveal urine protein or blood in the urine.
Diagnosis must rule out the presence of renal tumors.
Treatment
Polycystic kidney disease can’t be cured. The primary goal of treatment is preserving renal parenchyma and preventing infectious complications. Management of secondary hypertension will also help prevent rapid deterioration in function. Progressive renal failure requires treatment similar to that for other types of renal disease, including dialysis or, rarely, kidney transplantation.
When adult polycystic kidney disease is discovered in the asymptomatic stage, careful monitoring is required, including urine cultures and creatinine clearance tests every 6 months. Prompt and vigorous antibiotic treatment is needed when a urine culture reveals infection — even when the patient is asymptomatic. As renal impairment progresses, selected patients may undergo dialysis, transplantation, or both. Cystic abscess or retroperitoneal bleeding may require surgical drainage; intractable pain (a rare symptom) may also require surgery. However, because this disease affects both kidneys, nephrectomy usually isn’t recommended because it increases the risk of infection in the remaining kidney.
Special considerations
Because polycystic kidney disease is usually relentlessly progressive, comprehensive patient teaching and emotional support are essential.
❑ Refer the young adult patient or the parents of infants with polycystic kidney disease for genetic counseling. Parents will probably have many questions about the risk to other offspring.
❑ Provide supportive care to minimize any associated symptoms. Carefully assess the patient’s lifestyle and his physical and mental status; determine how rapidly the disease is progressing. Use this information to plan individualized patient care.
❑ Acquaint yourself with all aspects of end-stage renal disease, including dialysis and transplantation, so you can provide appropriate care and patient teaching as the disease progresses.
❑ Explain all diagnostic procedures to the patient or to his family if the patient is an infant. Before beginning excretory urography or other procedures that use an iodine-based contrast medium, determine whether the patient has ever had an allergic reaction to iodine or shellfish. Even if the patient has no history of allergy, watch for an allergic reaction after performing the procedures.
❑ Administer antibiotics as ordered for UTI. Stress to the patient the need to take the medication exactly as prescribed, even if symptoms are minimal or absent.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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