Kidney Cancer and Cysts Information

photo credit: euthman
Renal masses and cysts are a cause of anxiety for many patients that automatically assume any mass or cyst of the kidney must be due to cancer. However the vast majority of these cysts are benign simple cysts of the kidney. They are predominantly seen in patients over the age of 50 years. They are usually asymptomatic and are an incidental finding in the majority of cases. No one really knows why simple cysts occur but the fact that they are usually seen in older persons may imply that this is one of the effects of normal aging of the kidney.

A simple renal cyst has a characteristic appearance on ultrasound that differentiates it from cysts which may be suspicious for cancer. This method of testing has all but replaced older methods that relied on imaging the blood vessels of the kidney and examining the picture for any disturbance of the normal pattern, which may imply a mass or cyst splaying the blood vessels apart. With the advent of CT and MRI the mass or cyst can be directly visualized and a determination made as to how likely it is to be due to cancer.


There are some genetic conditions that predispose to the formation of cysts in the kidney. The most common such condition is known as Autosomal Dominant Polycystic Kidney Disease or ADPK for short. This disease is associated with development of cysts in the kidney which progressively destroys the substance of the kidney decreasing its ability to filter blood and form urine. MRI, Ultrasound and CT scan are both able to make a possible diagnosis of polycystic kidney disease by examining the distribution of the cysts their number and the individual characteristics of the cysts. True polycystic kidney disease is not associated with transformation to cancer.

A very similar pattern of cysts may be seen in individuals who are on dialysis who do not have ADPK. The cysts in these patients tend to increase in number and volume as the number of years on dialysis increases. These cysts are usually present in small shrunken kidneys unlike ADPK where the kidney is quite massively enlarged in most cases. These cysts have to be monitored very carefully as the have a chance of transforming to cancer. As such patients on dialysis are routinely monitored for the development of cysts with yearly ultrasound after 3 to 4 years on dialysis.

The combination of kidney cysts and stones is seen in medullary cystic disease of the kidney. In this condition the tiny tubes that carry urine from the individual filter in the kidney tissue are supposed to join together like tributaries of a great river ultimately leading into the bladder through the ureter. In this disease the smaller tributaries develop cystic dilations which pool the fluid which will become urine. These pools of fluid have low flow and sediments eventually settle which form concretions and ultimately stones in the tissue of the kidney. Therefore many small stones tend to be present within the kidney. This condition develops due to a problem with formation of the kidney and is not transmitted genetically.

As has been shown the causes of cysts on the kidney are diverse and this was not a complete list. There exists very well established means of determining the danger of cancer in any situation where cysts are found on the kidney. A detailed history and family history as well as a routine examination and blood tests with the required imaging tests will lead to speedy diagnosis with relief of anxiety or rapid and timely treatment should the diagnosis be cancer.