Kidney cysts: symptoms, causes, diagnosis and treatment

Most people with a kidney cyst have no symptoms at all. Kidney Research UK says simple kidney cysts usually do not cause any symptoms and are found incidentally when you have tests for another reason. They do not usually change the size of the kidneys or how they look.

In rare cases, larger cysts (typically over 5 cm) can cause symptoms:

• Pain or discomfort from a large cyst pressing on other organs or bones.

• Bursting of a cyst, which can cause loin pain and blood in your urine.

• High blood pressure.

• Blockage of the flow of blood or urine in the kidneys or ureters, the tubes that carry urine away from the kidney.

• Infection of a cyst, which can cause pain and a high temperature.

Kidney Research UK describes kidney cysts as fluid-filled sacs that can develop in one or both kidneys, usually round or oval in shape. Fluid accumulates within a thin wall, forming a cyst. Simple kidney cysts are the most common type and usually develop with age.

There are other kinds, which are different from simple cysts. The charity explains the three groups in the table below.

Kidney Research UK says the causes of simple kidney cysts are not known, but they are more common with increasing age, and you are more likely to have them if you are a biological male and older than 50.

Acquired kidney cysts develop in people who have chronic kidney disease or kidney failure. Polycystic kidney disease is caused by faulty genes; the charity explains that autosomal dominant PKD (ADPKD), the most common form, is caused by mutations in the PKD1 and PKD2 genes, with a one in two (50%) chance that an affected parent will pass it on to a child, although it can occur for the first time in a person with no family history.

Simple kidney cysts do not tend to be harmful, according to Kidney Research UK, and most people with them have a good outcome because they usually do not cause symptoms or need treatment.

In very rare cases kidney cysts can be cancerous. Your doctor uses medical imaging to look at the appearance and size of any cysts and for signs of a cancerous cyst. This is why you may be offered follow-up scans for a cyst with unusual features, and why the separate page on simple versus complex cysts may help you understand your report.

The NHS says blood in your pee must always be checked because it can be a sign of cancer; cancer may be easier to treat if it is found early.

Kidney Research UK says kidney cysts are usually found by a healthcare professional when looking at a medical image, such as an abdominal ultrasound, CT or MRI scan, which you have had for another health reason. The scan lets the doctor assess the appearance and size of the cysts.

If many cysts are seen in both kidneys, the charity says imaging tests (ultrasound, CT or MRI) may be used to confirm polycystic kidney disease, blood and urine tests gauge kidney function and look for protein in the urine, and diagnosis of the particular type of ADPKD usually requires analysis of your DNA. A kidney specialist can give advice about the chances of family members being affected.

Usually simple kidney cysts do not require treatment, says Kidney Research UK. If a cyst becomes infected you will be given antibiotics. For very large simple cysts causing problems because of their size, a procedure to drain or remove the cyst may be needed:

• Sclerotherapy: a healthcare professional uses an ultrasound scan to guide a needle into the cyst and drains the fluid. They usually flush the cyst with alcohol to harden its wall and try to prevent it forming again.

• Laparoscopic (keyhole) surgery: the cyst is drained of fluid and its wall is removed.

Kidney Research UK describes polycystic kidney disease (PKD) as a name for a range of life-threatening inherited disorders that can cause kidney failure and damage to other organs. Fluid-filled cysts develop and grow in the kidneys, which can enlarge to three or four times their normal size. In the UK there are about 70,000 adults and children with PKD.

When the cysts multiply and enlarge they can cause a swollen stomach, pain in the abdomen, side or back, blood in the urine, high blood pressure, fever and urinary infections from cyst infection, and kidney stones. Cystic liver disease is a frequent finding alongside ADPKD, and very rarely ADPKD can cause abnormal blood vessels in the brain which may bleed.

Treatment of ADPKD includes tolvaptan, which has been available across the UK since early 2016 and slows the progression of cyst development, helping to protect kidney function and in most cases likely to significantly delay the need for dialysis or a transplant. Other measures include blood pressure medicines such as ACE inhibitors and ARBs, paracetamol rather than anti-inflammatory painkillers such as ibuprofen (which can reduce blood supply to the kidneys), antibiotics for urinary infections, and treatment of kidney stones. Kidney Research UK also advises regular exercise but avoiding contact sports such as rugby or football that could cause cysts to rupture and bleed, and eating a healthy, balanced, low-salt diet.

For simple kidney cysts the UK sources used for this page do not recommend any specific diet. For people with PKD, Kidney Research UK advises a healthy balanced low-salt diet and regular exercise. Because high blood pressure is a possible effect of larger cysts, the NHS general advice also applies: a healthy, balanced diet, regular exercise, losing weight if you are overweight, and checking your blood pressure. The NHS says you are usually considered to have high blood pressure if readings are 140/90 or higher at a clinic or 135/85 or higher at home.

Simple kidney cysts usually develop with age, so they are uncommon in children. Kidney Research UK says PKD can develop at any point in childhood or adulthood, and notes a rare recessive form (ARPKD) that may present in very young children or later in adulthood. If a child has been found to have cysts on a scan, they should be reviewed by a paediatric kidney specialist.

The UK sources used for this page do not give pregnancy advice for kidney cysts. If you have PKD or a cyst-related blood pressure problem and are planning a pregnancy, discuss it with your kidney team and midwife first.

• Ask for an urgent GP appointment or get help from NHS 111 if you have blood in your pee or think you may have, even if it is a small amount (NHS). It may be bright pink, red or dark brown.

• Ask for an urgent GP appointment or call NHS 111 for a kidney infection with a very high temperature or feeling hot, cold and shivery, pain in your back just under the ribs, vomiting, or if you have not passed urine all day (NHS).

• Call 999 or go to A&E if you are confused, drowsy or have difficulty speaking with a suspected kidney infection (NHS).

• See a GP if you have side or back pain, a swollen tummy, or new high blood pressure, particularly with a family history of kidney disease.

• Do not take anti-inflammatory painkillers regularly if you have PKD without checking with your kidney team (Kidney Research UK).

Most simple cysts are found during scans arranged by a GP or hospital doctor, who will tell you whether any follow-up is needed. Kidney Research UK says you usually do not need treatment. For polycystic kidney disease, care is led by a kidney specialist (nephrologist) team, and the PKD Charity is a patient organisation set up by patients, professionals and family members.

Private scans and consultations are available. If you are told you have a cyst privately, ask for the report and share it with your GP so that any recommended follow-up is arranged on the NHS or privately as agreed.