Polycystic Kidney Disease (PKD)



This familial disorder is the most significant of a number of renal cystic disorders . Inherited as an autosomal dominant trait with high penetrance, PKD is a relatively common cause of end-stage renal failure in the fourth and fifth decades of life. Virtually 100 per cent of per­sons inheriting the disorder will have cystic changes, but not necessarily renal failure, by age 80 years. A separate, infantile form of the disease occurs in association with congenital hepatic fi­brosis and causes death from renal failure in the first year of life. In adults, benign multiple renal cysts may present a similar radiographic appear­ance but are not associated with renal dysfunction or failure.

Clinical manifestations of PKD rarely occur be­fore the ages of 20 to 25 years. This accounts for the frequent passage of the genetic trait to off­spring by asymptomatic, yet affected, individuals of child-bearing age. Nonspecific, dull lumbar pain is the most frequent initial symptom and usually occurs when the kidneys are sufficiently enlarged to be palpable on examination of the ab­domen. Sharp, localized pain may result from cyst rupture or infection or from passage of a renal calcuius Microhematuria without RBC casts is fre­quently the initial sign of PKD; gross hematuria mav also occur.

Hypertension occurs commonly in PKD at early stages of the disease. Polycystic disease may thus be discovered in the course of evaluating hyper­tension in a young adult. Nocturia due to a urinary concentrating defect is often present at the time of diagnosis, and most patients are unable to con­serve salt on a salt-restricted intake. Urinary tract infection and pyelonephritis are common com­plications. Up to one third of patients with po­lycystic renal disease have multiple, asympto­matic hepatic cysts, and cerebral aneurysms are more prevalent than in unaffected persons.

The diagnosis of polycystic kidney disease is made on the basis of radiographic evidence of multiple cysts distributed throughout the renal parenchyma. The nephrogram phase of intrave­nous urography (IVP) shows the lucent cysts sur­rounded by attenuated strands of functional renal tissue. Renal ultrasonography is another valuable tool in demonstrating the distribution and size of the cystic lesions. Both studies can be employed to screen younger (>16 years of age) family mem­bers of patients in order to identify the asymp­tomatic lesion at a time when genetic counseling may be useful. Failure to concentrate the urine above 800 mOsm/kg H20 after dehydration is highly predictive of PKD in adolescents at risk for the disorder.

Therapy for polycystic kidney disease is di­rected toward control of hypertension and pre­vention and early treatment of urinary tract in­fections. Nephrectomy is occasionally indicated for persistent gross hematuria or for an infected renal cyst. Decompressing cysts by surgical “un­roofing” is associated with a high incidence of complications, including complete renal failure. End-stage renal failure is managed by either di­alysis or transplantation. Bilateral nephrectomy may be required prior to transplant in patients with inordinately large kidneys or in those with a history of frequent or persistent urinary tract in­fection.