Renal Cyst

Renal Cyst

Description, Causes and Risk Factors:

A cyst is an enclosed sac or pouch that usually contains liquid or semisolid material. A renal cyst is a small pocket filled with fluid and located in the kidneys. Also known as kidney cysts, many renal cysts are benign, and people can live out their entire lives without any knowledge of a cyst.

ICD-10 N28.

ICD-9 593.2

As people get older, sacs filled with fluid can form in the kidneys. These sacs are called "cysts." They are usually small oval or round thin-walled sacs with watery fluid in them.

Kidney cysts are almost always benign. Usually, the cysts do not cause any problems. In fact, people can go through life without even knowing that they have them.

Some people have kidney cysts caused by an inherited disease called polycystic kidney disease (PKD). This disease can cause symptoms such as high blood pressure, pain in the back and side, blood in the urine or frequent kidney infections. Not all people who have PKD will have these symptoms.

Some people have one or more renal cysts at birth. In other cases, a renal cyst develops as a result of an obstruction somewhere in the kidney. Lymphatic obstructions and vascular disease can both contribute to the development of a renal cyst. Patients can also have a condition called polycystic kidney disease (PKD), a genetic condition in which numerous cysts develop in the kidneys, causing damage to the kidneys and surrounding organs.

Renal cysts are categorizes into five groups:

    Category I: Benign simple cyst with thin wall without septae, calcifications, or solid components. It does not enhance with contrast, and has a density equal to that of water.

  • Category II: Benign cyst with a few thin septae, which may contain fine calcifications or a small segment of mildly thickened calcification. This includes homogenous, high-attenuation lesions less than 3 cm with sharp margins but without enhancement.

  • Category III: Well marginated cysts with a number of thin septae, with or without mild enhancement or thickening of septae. Calcifications may be present; these may be thick and nodular. There are no enhancing soft tissue components. This also includes non-enhancing high-attenuation lesions that are completely contained within the kidney and are 3 cm are larger.

  • Category IV: Indeterminate cystic masses with thickened irregular septae with enhancement.

  • Category V: Malignant cystic masses with all the characteristics of category III lesions but also with enhancing soft tissue components independent of but adjacent to the septae.


There are usually no symptoms. In rare cases, however, if the cyst is unusually large, symptoms may include back pain, abdominal pain or blood in the urine. Occasionally, infections can occur, causing pain when passing urine, or fever, sweats and pain in the back.

Diagnosis & Tests:

Tests and procedures used to diagnose simple renal cysts include:

    Imaging tests: Imaging tests, such as ultrasound, computerized tomography (CT) and magnetic resonance imaging (MRI) are often used to investigate simple kidney cysts. Imaging tests can help your doctor determine whether a kidney mass is a cyst or a tumor.

  • Kidney function tests: Testing a sample of your blood may reveal whether a kidney cyst is impairing your kidney function.

Treatment Options:

Treatment is not usually required. Antibiotics are used, if a cyst becomes infected. Sometimes these are hard to treat, requiring long courses of antibiotics. If the cyst is unusually large it could impair kidney function and lead to kidney failure. A physician may choose to collapse or decompress a large Kidney cyst. This is done by inserting a needle, guided by ultrasound or x-rays, through the skin and into the cyst. This procedure requires some local anaesthetic to dull the pain.

In extreme cases, particularly if severe infection has cause irreversible damage, the whole kidney can be removed.

Surgery to remove the cyst: A large cyst may require surgery to drain and remove it. To access the cyst, the surgeon makes several small incisions in your skin and inserts special tools and a small video camera. While watching a video monitor in the operating room, the surgeon guides the tools to the kidney and uses them to drain the fluid from the cyst. Then the walls of the cyst are cut or burned away.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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