There are two types of kidney cysts. The first type covers a single bag filled with liquid which, for unknown reasons, develops in the kidney. During the years the cyst can grow slowly, and usually does not cause problems if cancer does not develop on its wall (which is rare). The second type of cyst is the consequence of inherited disease – the so-called polycystic kidney disease – i.e., a congenital condition in which many cysts of various sizes develop in both kidneys.
It is unclear why cysts develop rapidly in some people, but slow (or almost none) in others. Many people do not have any problems, although in some cases there may be a gradual injury that leads to one of the forms of kidney failure.
One single cyst does not cause any symptoms until it becomes so large that it begins to cause pain in the lower part of the back. In that case, the bump will be so big that you will be able to feel it with your fingers. Polycystic kidney sometimes causes the appearance of blood in the urine (hematuria) or repeated attacks of chronic pyelonephritis. This disease is often without symptoms, but in some cases cysts may occupy so much space, at the expense of normal kidney tissue, that chronic renal insufficiency will develop and, with it, the symptoms of that disease (such as fatigue and frequent urination) will appear.
It is impossible to estimate the number of people with renal cysts because many people who have them are not even aware of them. The presence of the cyst is often detected only when another condition requires a kidney scan. However, it is well known that the polycystic kidney is very rare. This disease causes about 3% of chronic renal insufficiency cases; in other words, less than 100 new cases of advanced polycystic kidney disease are detected in the average year.
If you have only one cyst, the only danger is the the possible development of malignant neoplasm (tumor), though this is rarely the case. As we have noted, polycystic kidney disease can cause chronic renal insufficiency, although such cases are also rare.
What to do?
If you have only one kidney cyst, you will probably find about it during the examination for some other reason. Considering the possibility (though small) that there may be cancerous cells in the cyst, the doctor will probably refer you to a special search, so-called cyst aspiration, i.e. drilling a cyst with a needle and extracting the fluid for tests. Cysts can usually be painlessly aspirated with local anesthetic. Such cyst can sometimes completely disappear. If the cyst cells are normal, no further measures should be taken.
The doctor may accidentally detect that you have a polycystic kidney when you are being examined for some other discomfort. However, if it is known that you have this disease in your family, be sure to contact your doctor – not just for yourself, but also to find out if the disease will affect your children. In any case, even if your kidneys are not affected by this disease, you should go to medical examinatons more often.
Painless benign cyst does not require any treatment. If it grows and begins to cause pain, or – although it is rare – if it is malignant, it will probably require an operative procedure, i.e. removal of the affected kidney.
No specific therapy for polycystic kidney disease. If the presence of the cyst is detected early, and if you go to the controls regularly after that, your doctor will probably be able to help you, i.e. slow the progression of kidney damage.