What exactly is a renal cyst?

Fluid filled cavity: Kidney cysts are formed by blockage of a minute kidney tubule called a nephron. We have about a million nephrons in each normal kidney. Simple kidney cysts are very common and present in about one third of people and are benign. Polycystic kidneys have cysts throughout the organ, are usually present on both sides and are an inherited congenital condition. Rare complex cysts can be cancerous.

See details: It is a cyst in the kidney. A cyst is a thin-walled cavity often filled with fluid. Small single cysts are often present at birth and cause no harm. Multiple cysts in both kidneys is often related to polycystic kidney disease and is potentially serious.