An exophytic kidney cyst is a ball-shaped mass located in the kidney that grows and compresses the area around it, according to the University of Virginia School of Medicine. This type of cyst is different from an infiltrating cyst, which invades the surrounding area and conforms to the shape of the kidney. Exophytic kidney cysts are typically simple cysts or abscesses.
Simple exophytic kidney cysts are benign fluid-filled pouches that form on the kidney, states Mayo Clinic. They rarely cause any complications and usually do not require treatment unless there are symptoms. Generally, patients have only one simple kidney cyst, but multiple cysts can sometimes appear. These cysts can form on one or both kidneys.
As of 2015, physicians do not know the exact cause of simple exophytic kidney cysts, according to WebMD. They are more common in men and people over the age of 50. Physicians typically find the cysts during a computerized tomography (CT) scan or ultrasound performed for another medical reason. In some cases, the cysts do cause symptoms, including abdominal, back or side pain, fever or bleeding. If symptoms occur, patients need to have the cysts drained and filled with an alcohol solution to prevent recurrence. Cysts that continuously recur and cause symptoms typically require surgical removal.