Acquired renal cysts are simple cysts that must be distinguished from more serious causes of cystic disease.

Acquired cysts are usually simple, ie, they are round and sharply demarcated with smooth walls. They may be solitary or multiple.

Solitary cysts: Isolated cysts are most often detected incidentally on imaging studies; they are distinguished from other cystic renal disorders and renal masses, such as renal cell carcinoma, which is typically irregular or multiloculated with irregular walls, septae, and areas of unclear demarcation. Their cause is unknown. They are generally clinically insignificant but rarely can cause hematuria or become infected.

Multiple cysts: Multiple cysts are most common in patients with chronic kidney disease, especially patients undergoing dialysis. Cause is unknown, but the cysts may be due to compensatory hyperplasia of residually functioning nephrons. Usual criterion for diagnosis is ≥ 4 cysts in each kidney detected with ultrasonography or CT. Multiple acquired cysts (acquired cystic disease) can usually be differentiated from autosomal dominant polycystic kidney disease by the absence of family history and by small or normal-sized kidneys.

Acquired cysts are usually asymptomatic, but occasional patients develop hematuria, renal or perirenal hemorrhage, infection, or flank pain. Acquired cysts are significant mainly because patients have a higher incidence of renal cell carcinoma; whether the cysts become malignant is unknown. For this reason, some physicians periodically screen patients with acquired cysts for renal carcinoma using ultrasonography or CT. Cysts that cause persistent bleeding or infection may require percutaneous drainage or, rarely, partial or complete nephrectomy.

Last full review/revision July 2009 by Drew C. Cutler, MD

Content last modified February 2012