What are simple kidney cysts?
Kidney cysts are fluid-filled sacs that can develop in one or both kidneys. You might have one kidney cyst or several. These cysts are usually round or oval shaped.
There are several reasons why kidney cysts can develop. This information page is focused on simple kidney cysts. Simple kidney cysts are the most common type of kidney cyst and usually develop with age.
Often, simple kidney cysts do not cause any symptoms and are found incidentally when having tests for another reason. These cysts do not usually change the size of the kidneys or how they look, and do not tend to be harmful.
Are simple kidney cysts different to acquired kidney cysts?
Simple kidney cysts are different to acquired kidney cysts. Acquired kidney cysts are fluid-filled sacs that can develop in one or both kidneys in patients who have chronic kidney disease (CKD) or kidney failure. They usually don’t cause symptoms and are most common in patients on dialysis.
Both simple and acquired kidney cysts are different to the cysts in cystic diseases of the kidney, such as polycystic kidney disease (PKD), where there are many cysts in both kidneys causing enlargement of the kidneys.
What causes simple kidney cysts?
Kidney cysts are caused by an accumulation of fluid, which forms within a thin wall. This leads to a sac of fluid, called a cyst, developing.
The causes of simple kidney cysts are not known, but they are more common with increasing age. You are more likely to have simple kidney cysts if you are a biological male and older than 50 years old.
What are the symptoms of simple kidney cysts?
Simple kidney cysts usually don’t cause any symptoms.
In rare cases, larger cysts (typically over 5 cm) can cause symptoms including:
- Pain or discomfort from large cysts pressing on other organs or bones
- Bursting of the cysts, 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 the cysts, which can cause pain and a high temperature
How are simple kidney cysts diagnosed?
Kidney cysts are usually found by your 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. Using medical imaging your doctor can look at the appearance and size of any cysts.
In very rare cases, kidney cysts can be cancerous. Your doctor will look at the cyst using medical imaging to look for any signs of a cancerous cyst.
What are the treatments for simple kidney cysts?
Usually, simple kidney cysts don’t require treatment.
In rarer cases, if kidney cysts become infected you will be given antibiotics.
For very large simple kidney cysts, that are causing problems because of their size, you may need a procedure to drain or remove the cyst. This includes:
- Sclerotherapy. This is where a healthcare professional uses an ultrasound scan to look at the cyst and inserts a needle to drain the fluid out. They will usually flush the cyst with alcohol to harden its wall to try and prevent the cyst forming again.
- Laparoscopic surgery. This is a type of surgery where the cyst is drained of fluid and its wall is removed.
What is the prognosis for simple kidney cysts?
Most patients with simple kidney cysts have a good outcome as they usually don’t cause symptoms or require treatment. In rare cases patients may need antibiotics for infected kidney cysts, or procedures to drain or remove larger cysts.
References
Garfield, K. and Leslie, S. W. Simple Renal Cyst [online]. 2023. Treasure Island (FL): StatPearls Publishing. [Accessed 16 March 2026]. Available from: <PMID: 29763075>
National Institute of Diabetes and Digestive and Kidney Diseases. Simple Kidney Cysts [online]. US; Jun 2019 [Accessed 16 March 2026]. Available from: Simple Kidney Cysts - NIDDK
Fung, E. Acquired Kidney Cysts [online]. MSD Manual, Merck & Co, Inc., Rahway, NJ, USA; Mar 2025. [Accessed 25 March 2026]. Available from: Acquired Kidney Cysts - Kidney Disorders - MSD Manual Consumer Version
National Institute of Diabetes and Digestive and Kidney Diseases. Acquired Kidney Cysts [online]. US; Aug 2015 [Accessed 25 March 2026]. Available from: Acquired Cystic Kidney Disease - NIDDK
Cheng, D. Amin, P. and Van Ha, T. Percutaneous Sclerotherapy of Cystic Lesions [online]. 2012. Semin Intervent Radiol. 29(4):295–300. Thieme Medical Publishers. [Accessed 25 March 2026]. Available from: <PMID: 24293802>
Reviewed May 2026: Professor John Sayer, Clin Prof of Renal Medicine at Newcastle University.
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