The kidneys are two bean-shaped organs located behind the abdominal organs and just under the rib cage.
The kidneys filter the waste from the blood before it is passed out of the body as urine. They are also vital in regulating blood pressure and managing many other important functions in the body.
Finding a cyst on a kidney may sound serious, but there is little need to worry in cases of simple kidney cysts, which are a common occurrence.
Kidney cysts are round fluid-filled sacs that form in the kidneys.
In most cases, simple kidney cysts do not cause complications or affect kidney function in any way. However, they may cause pain, become infected, or cause other symptoms if they grow too large.
Simple kidney cysts are different from the cysts that form due to polycystic kidney disease.
Polycystic kidney disease is a genetic condition that may cause numerous cysts, enlarge the kidneys, and affect kidney function.
In the case of acquired cystic kidney disease, the kidneys develop cysts as a result of long-term damage from kidney disease or dialysis.
Acquired cystic kidney disease is different from polycystic kidney disease because it is not genetic but happens as a result of other kidney problems.
Cysts caused by acquired cystic kidney disease may not require treatment, but the underlying cause will.
Doctors are not sure why simple kidney cysts form. Other than aging, there are no real risk factors for developing simple kidney cysts. Interestingly, diet and lifestyle factors do not seem to impact the risk of developing these cysts.
Simple kidney cysts are fairly common as people age, however. In fact, up to 25 percent of adults over age 40 and half of those over 50 develop simple kidney cysts at some point.
Additionally, men may be slightly more likely to develop simple kidney cysts than women.
Most simple kidney cysts are asymptomatic, meaning they do not cause any symptoms. However, if a kidney cyst grows large enough, it may cause symptoms that do become noticeable.
These symptoms can include:
- dull pain in the back or side
- pain in the upper abdomen or hips
- fever if the cyst becomes infected
- blood in the urine
- need to urinate frequently
Symptoms may intensify if a complication occurs, such as an infection or a rupture.
Most simple kidney cysts do not cause complications or problems, although these can occur in rare cases.
Complications of simple kidney cysts include:
- ruptured cysts
- infected cysts
- swollen kidneys caused by urine obstruction
When complications occur, symptoms may intensify, and a person should seek medical attention immediately.
Most complications, including ruptured cysts, can be managed conservatively. However, they can be life-threatening if they are not treated promptly.
Most of the time, simple kidney cysts are discovered during imaging tests done for other reasons.
Once a kidney cyst is found, other diagnostic tests may be ordered to find out more about the growth. These tests can include:
- CT scans: Computerized imaging that creates a three-dimensional picture of the kidneys to show tumors or cysts.
- MRIs: Imaging using radio waves and magnets to show pictures of the body's soft tissues and organs, including the kidneys.
- Ultrasounds: Imaging that uses sound waves to create a picture of the kidneys.
- Kidney function test: A simple blood test that checks how well the kidneys are working.
- Urinalysis: A procedure that measures the contents of urine from a urine sample.
These can all be performed on an outpatient basis. Most of the time, no preparation is needed beforehand, although a person should always follow a doctor's instructions prior to undergoing the test.
Most simple kidney cysts do not need any treatment beyond periodic monitoring.
Kidney cysts that cause symptoms may require treatment, particularly if they block the flow of urine or blood through the kidneys. In these cases, a doctor may recommend draining the cyst, using a procedure called sclerotherapy.
During sclerotherapy, a doctor uses ultrasound to guide a needle to the cyst. The sac of fluid is then punctured with the needle and drained.
Next, the doctor will inject a saline solution into the area to harden the surrounding tissue and prevent another cyst from forming. The procedure is done using local anesthesia and on an outpatient basis.
In rare cases of a very large cyst, surgery may be required to drain or remove the growth. Normally, this is done with a small tool that has a light and camera on one end that allows the surgeon to keep the incision small.
Kidney cyst removal is usually performed in a hospital under general anesthesia.
In the case of an infected cyst, antibiotic therapy may be started prior to any other treatment.
Simple kidney cysts are normally harmless and do not require any treatment.
In cases where treatment is needed because of a blood or a urine blockage within the kidney, a full recovery is very likely.