Kidney cysts

MANY questions have been asked of me concerning kidney cysts and I thought that it may be appropriate to review the topic today.

What are cysts and are they dangerous?

A kidney cyst is simply a collection of fluid in the kidney. Cysts in the kidneys are in fact quite common and it is estimated that one in four persons under 40 years old has a cyst. Cysts may occur on their own or may be a manifestation of other diseases such as polycystic kidney disease in which there are many cysts along with chronic kidney damage. Simple cysts in the kidney are not cancerous and often cause no symptoms. It is not entirely clear what causes these cysts but they seem to be more common in men and increase as one gets older.

What are the symptoms of simple cysts?

These cysts are often asymptomatic and are commonly discovered during imaging for other conditions like gallstones or kidney stones. Many times, back pain may be falsely blamed on a small kidney cyst and it is often something else causing the pain! Large cysts may cause a dull back or tummy pain and rarely, a cyst may become infected, causing pain and fever. Sometimes bigger cysts can block the flow of urine and this can cause the kidney to swell, leading to kidney damage. Simple cysts which are asymptomatic do not need treatment.

When should I be worried?

A number of imaging tests may be used to look at the kidneys including CT scan, ultrasound and MRI. Ultrasound is the most common test used to look at cysts but the best test to have a good look at the cyst is a CT scan using a dye which is injected in the veins. The cysts are graded by a system called the Bosniak (pronounced Bos -nee-ack) system and this system groups cysts into four types. A qualified radiologist can look at your imaging and tell you what type of cyst you have.

A simple cyst, also known as a type 1 cyst, is the most common type is crisp and thin walled ­– there are no blood vessels or calcium in the wall. This progresses all the way to type 4 cysts which have thick walls and solid, fleshy looking parts. Types 3 and 4 cysts have a high risk of cancer and should be removed; sometimes this may even mean removing the entire kidney.

Type 1 cysts and most type 2 cysts do not even need to be followed up unless they are causing symptoms and you definitely do not need to have your simple cysts drained routinely. If you have multiple cysts in both kidneys and have high blood pressure along with poor kidney function on your blood tests, you should seek the opinion of a qualified nephrologist – this is a specialist kidney doctor.

How are cysts treated?

Simple cysts require no treatment or follow up unless they cause symptoms such as pain. Some type 2 cysts require periodic scans to make sure all is well. For simple cysts which are causing symptoms, a number of treatments exist, the most simple of which involves passing a needle into the cyst and sucking out all of the fluid. This is done under local anaesthetic and the doctor uses an ultrasound machine to see the cyst, following which a small needle is used to remove the fluid. Many cysts will recur after simple drainage and the urologist may inject the cyst with chemicals to prevent it from coming back. This is a day procedure with no hospital stay.

Surgery is an option for large, symptomatic cysts or cysts which have come back after needle drainage. This is most often done through laparoscopic or “keyhole” surgery using a few tiny cuts. A window is cut into the cyst and this allows fluid to drain and not recollect. Limited resources or lack of laparoscopic skill may mean your doctor in rare cases has to make a larger cut to remove the cyst.

If your CT scan shows that the cyst wall is thick, has calcium and has parts which look solid and fleshy, then you likely have a high-grade cyst (type 3 or 4) and your urologist may recommend that you remove all or part of that kidney given the risk of cancer. This may also be done via key hole surgery or via a cut on the tummy.

If you have an ultrasound showing cysts and you are concerned, I urge you to consult a qualified medical practitioner who can look at the tests further and refer you to a urologist as necessary.

Dr Satyendra

Persaud is a consultant urologist at San Fernando General Hospital. He is a lecturer in
u
rology at the University of the West Indies and is responsible for urology training at UWI.