Many people find out that they have a kidney cyst by chance, during an ultrasound done for another reason – and it often worries them more than it should. Cysts are among the most common findings in urology and in the vast majority of cases they are completely harmless.
They become more common with age – roughly one in three people over 50 has at least one. The urologist’s task is to tell a simple cyst, which needs no treatment, apart from the rare complex lesions that are monitored or operated on.
What is a kidney cyst?
A cyst is a round, thin-walled sac filled with clear fluid within the kidney tissue. It is most often single and can range from a few millimetres to more than ten centimetres in size.
A simple cyst has a smooth, thin wall and clear contents with no solid parts. It does not turn into cancer and does not impair kidney function.
A complex cyst has a thickened wall, septa (internal partitions), calcifications or solid areas. Some of these cysts are benign, others may be malignant. They are assessed with the Bosniak classification, which uses their appearance on computed tomography (CT) or magnetic resonance imaging (MRI) to decide whether the cyst is harmless, needs follow-up or should be operated on.
Polycystic kidney disease is a separate, inherited condition: many cysts form in both kidneys, grow over the years and impair kidney function. It is managed together with a nephrologist, and close relatives should be tested.
Symptoms
Most cysts cause no symptoms; symptoms appear with large cysts or complications:
- a dull ache or heaviness in the back and flank;
- sudden severe back pain and blood in the urine – when the cyst ruptures or bleeds into itself;
- fever, shivering and pain – when the cyst becomes infected.
When it is urgent. Sudden severe back pain after a blow, heavy bleeding in the urine, or a high temperature with shivering and pain in the flank need immediate help – the emergency department or 112 (the European emergency number), not a booked appointment.
Causes and risk factors
The cause is not fully understood – probably, with age, individual kidney tubules become blocked and widen. Those at greater risk are:
- older people – the main factor;
- men and people with high blood pressure;
- patients with chronic kidney disease and those on dialysis – multiple acquired cysts with a higher risk of tumour form in the damaged kidneys;
- families with polycystic kidney disease – the condition is passed from parent to child.
Diagnosis
Ultrasound is the main test and is usually all that is needed: it shows whether the lesion is filled with fluid, what its wall is like and whether there are any solid parts. Dr Penev usually performs it during the consultation itself – at the practice in Plovdiv or at Vita Med Medical Centre in Karlovo – and in most cases you get an answer straight away. The initial consultation is €50 and a follow-up consultation €30.
When the ultrasound shows a complex cyst or cannot distinguish it from a solid kidney tumour, a CT or MRI scan with contrast follows to determine the Bosniak category and the plan.
Treatment
A simple cyst without symptoms is not treated. Depending on the doctor’s judgement, one follow-up ultrasound may be done after 6–12 months; if the finding is unchanged, regular follow-up is usually not necessary.
A large or symptomatic cyst. Treatment is considered when the cyst causes pain, leads to urine backing up (hydronephrosis) or keeps becoming infected. Draining it with a needle is often followed by the cyst filling up again, so it is combined with a sclerosing agent. A more lasting result is achieved by laparoscopic removal of the cyst wall – an operation through several small incisions with a short hospital stay, which, when needed, is performed at the Department of Urology at Kaspela University Hospital (UMBAL Kaspela), Plovdiv.
A complex cyst in a high category. If cancer is suspected, the cyst is removed together with part of the kidney or, less often, the whole kidney. Intermediate categories are monitored with CT or MRI at set intervals.
An infected cyst is treated with antibiotics and, if needed, drainage. In polycystic kidney disease, treatment includes control of blood pressure, enough fluids, treatment of infections and stones, and monitoring of kidney function.
When to see a urologist
- if a cyst has been described in a test report and you want a specialist’s assessment;
- if the cyst has been described as complex – with septa, calcifications or solid parts;
- if you have pain or heaviness in the back, blood in the urine or recurrent infections;
- if you have a relative with polycystic kidney disease or cysts in both kidneys;
- if it has grown quickly between two tests.
Prevention
A simple cyst cannot be prevented. Normal blood pressure, enough fluids and not smoking protect the kidneys, and in polycystic kidney disease early monitoring slows down the damage.
A kidney cyst is rarely a problem, but it deserves to be assessed properly at least once. Book an appointment with Dr Penev and bring your previous test results – comparing them over time is the surest path to peace of mind.
Frequently asked questions
Do I need to give up sport or follow a diet because of a kidney cyst?
With a simple cyst, no restrictions on diet or exercise are needed. With a very large cyst, the doctor may advise caution with contact sports because of the risk of a blow to the back.
The cyst has grown by a few millimetres between two ultrasounds – is that a problem?
Simple cysts slowly grow over the years, and a small difference in size is not worrying in itself, especially as the measurement depends on the machine and the position. What matters is the structure of the cyst and whether there are any symptoms.
Can a cyst burst on its own?
Rupture is rare and usually happens with large cysts or after an injury. It shows up as sudden pain and blood in the urine; in most cases it settles with rest, but it must always be checked by a doctor.
Can a child have a kidney cyst?
Yes, but rarely. In children cysts are assessed more carefully because they are sometimes part of congenital conditions, so a consultation with a urologist who works with children is recommended.
Are kidney cysts linked to cysts in the liver?
In polycystic kidney disease there are often cysts in the liver too. Single simple cysts in the two organs, however, are common with age and are usually not related to each other.
The information on this website is for general education and does not replace an examination and consultation with a doctor. If you have urgent symptoms, seek medical help immediately or call 112.