What Is a Kidney Cyst?

A kidney cyst is a small sac of fluid that develops in the kidneys. This kind of cyst comes in two types: a simple kidney cyst, which is an oval-shaped, liquid-filled sac, and a complex kidney cyst, which is not in the traditional oval form and could possibly be cancerous. These cysts are most often a result of the aging process and are rarely malignant; many people have them without even knowing it. They may also result as a product of polycystic kidney disease, an inherited condition marked by regular kidney infections.

No one is certain what causes a simple cyst on the kidney that is not the result of polycystic kidney disease. It is thought to be a natural by-product of the aging of the organ. Complex cysts can be symptomatic of larger issues with the kidneys, signaling potentially serious health concerns in the kidneys themselves or in other areas of the body.

A simple cyst on the kidney is very small and circular in shape. The wall of the cyst itself is traditionally slight and harbors no irregular markings or indications. The liquid within the cyst is either clear or yellow in color. It is estimated that 50% of adults have these benign cysts by the time they reach 50 years of age.

Complex cysts possess irregularities either in shape or inside the cyst. Walls called septations are frequently seen inside a complex kidney cyst. Cysts of this variety are considered much more serious than the simple type and can be indicative of kidney cancer or other critical health problems.

While a simple cyst will rarely cause any telltale signs, symptoms of a kidney cyst that is complex may give a few indicators. These include a generalized, dull pain in the back or side, pain in the upper region of the stomach, and fever. Although cysts commonly develop as an individual ages, they can strike anyone of any age without discrimination.

Kidney cyst treatment is not usually necessary for simple cysts. Complex cysts are typically punctured, allowing the fluid to drain from the sac. After the fluid has been removed, a solution containing alcohol is injected into the deflated wall; this ensures the cyst does not return. Larger or more serious complex varieties will involve cyst removal through a surgical process. During the surgery, a small video camera is inserted into the kidney region, allowing the surgeon to target the cyst and remove it completely.