ESSENTIALS OF DIAGNOSIS
Multiple cysts in both kidneys; number of cysts depends on patient age.
Combination of hypertension and large palpable kidneys suggestive of disease.
Autosomal dominant chromosomal abnormalities present in some patients.
Polycystic kidney disease is among the most common hereditary diseases in the United States, affecting 500,000 individuals, or 1 in 800 live births. ESRD develops by age 60 years in up to 50% of patients. The disease has variable penetrance but accounts for 10% of dialysis patients in the United States. At least two genes account for this disorder: ADPKD1 on the short arm of chromosome 16 (85–90% of patients) and ADPKD2 on chromosome 4 (10–15%). Patients with the PKD2 mutation have slower progression of disease and longer life expectancy than those with PKD1. Other sporadic cases without these mutations are also recognized.
Abdominal or flank pain and microscopic or gross hematuria are present in most patients. A history of urinary tract infections and nephrolithiasis is common. A family history is present in 75% of cases, and more than 50% of patients have hypertension that may precede clinical manifestations of the disease. Patients have large kidneys that may be palpable on abdominal examination. The combination of hypertension and an abdominal mass should suggest the disease. Forty to 50 percent have concurrent hepatic cysts; pancreatic and splenic cysts may occur. Hemoglobin tends to be maintained as a result of erythropoietin production by the cysts. Urinalysis may show hematuria and subnephrotic. In patients with a confirmed family history of PKD1, ultrasonography confirms the diagnosis (eFigure 22–18) (eFigure 22–19)—two or more cysts in patients under age 30 years (sensitivity of 88.5%), two or more cysts in each kidney in patients aged 30–59 years (sensitivity of 100%), and four or more cysts in each kidney in patients aged 60 years or older are diagnostic for autosomal dominant polycystic kidney disease. Importantly, these criteria do not apply to individuals without a known family history; patients without a known family history of polycystic kidney disease require additional diagnostic evaluation including CT scanning, which reveals innumerable cysts in cases of polycystic kidney disease (Figure 22–6); the presence of multiple hepatic cysts can aid in establishing the diagnosis. In some cases, genetic testing for ADPKD1 and ADPKD2 mutations may be required.
Polycystic kidney disease. Transverse prone sonogram shows bilateral enlarged kidneys (K) containing multiple cysts (S). S, spine. (Reproduced, with permission, from Krebs CA. Renal Ultrasound Home Study Course. American Society of Radiologic Technologists, 1990.)
Adult polycystic kidney disease. Longitudinal sonogram from a patient with known adult polycystic kidney disease. The kidney is markedly enlarged and deformed, with multiple cysts (arrows) of varying sizes. (Used, with permission, from Peter W. Callen, MD.)