Kidney Cysts
Kidney cysts are very common, fluid-filled sacs that can develop within the kidneys. Most are simple cysts, which are harmless, don’t affect kidney function, and often cause no symptoms at all. They’re frequently found by chance during an ultrasound scan and usually don’t require any treatment.
Overview | Symptoms & Causes | Diagnosis | Treatment Options
What is a Kidney Cyst?
The kidneys are two bean-shaped organs that sit towards the back of the abdomen. Their main role is to filter waste and excess fluid from the blood, producing urine. They also help regulate blood pressure, maintain electrolyte balance, and support healthy red blood cell production.
A kidney cyst is a fluid-filled sac that forms within or on the surface of a kidney. Most kidney cysts are simple cysts, meaning they have thin walls, contain clear fluid, and are harmless. These simple cysts are very common, especially as people get older, and they rarely cause symptoms or affect kidney function. Many are found incidentally during scans for unrelated reasons.
There are also complex cysts, which may have thicker walls, internal structures, or irregular features. Most complex cysts are still benign, but they may require closer monitoring or further imaging to ensure there are no concerning changes.
Kidney cysts can occur in one or both kidneys and vary widely in size. Most do not require treatment unless they cause symptoms or have features that warrant further evaluation.
Understanding Kidney Cysts
Most kidney cysts, especially simple cysts, cause no symptoms at all and are discovered by chance during an ultrasound, CT, or MRI scan for another reason. When symptoms do occur, they are usually related to the cyst becoming large, infected, or causing pressure on nearby structures.
Common symptoms when a kidney cyst does cause problems may include:
- Dull pain or discomfort in the side, lower back, or abdomen
- A feeling of fullness or pressure in the flank (side of the body)
- Pain that worsens with movement or prolonged sitting
- Blood in the urine (haematuria) - may be visible or picked up on a urine test
- Frequent urination or discomfort when passing urine (less common)
- Fever, chills, or general unwellness - this can occur if a cyst becomes infected
- High blood pressure - occasionally linked to large or multiple cysts
Most of these symptoms can be caused by many other conditions, so having symptoms does not necessarily mean a cyst is the cause. Many kidney cysts remain completely harmless and stable for years.
If you develop severe pain, fever, or visible blood in the urine, you should seek medical advice promptly, as this may indicate infection, bleeding into the cyst, or another kidney condition.
Causes & Risk Factors
Most kidney cysts are simple cysts, meaning they have a thin wall and contain clear fluid. Their exact cause isn’t fully understood, but they tend to become more common with age. They are not caused by injury, lifestyle, or diet, and in most cases, they develop without any clear trigger.
You may be more likely to develop kidney cysts if:
| Age | Most common in people over 50; more than half of adults in this age group have at least one simple cyst. |
| Sex | Slightly more common in men than in women. |
| Family history | Simple cysts are not usually inherited, but they can appear more frequently in some families. |
| Kidney health | Chronic kidney disease or dialysis increases the likelihood of developing multiple cysts. |
| Inherited or complex cyst conditions (less common) | Polycystic kidney disease (PKD): A genetic condition causing many cysts throughout the kidneys. |
Diagnosing Kidney Cysts
Kidney cysts are often found incidentally, meaning they are discovered during scans performed for unrelated reasons. When a cyst is suspected, diagnosis focuses on confirming that it is a simple, benign cyst and not something that needs further investigation.
| Urine & Blood Tests | These tests do not diagnose cysts, but help assess overall kidney function and check for issues such as reduced filtration (eGFR), blood or protein in the urine, or possible infections. |
| Ultrasound | An ultrasound is usually the first test used to diagnose kidney cysts. It can: - Confirm the presence of a cyst - Assess its size, location, and overall appearance - Check whether the cyst is simple (thin-walled and fluid-filled) or has complex features |
| Additional Imaging | If an ultrasound shows unclear or complex features, further imaging may be recommended. CT or MRI can provide a more detailed view of the cyst’s structure, helping to distinguish a simple benign cyst from one that may need monitoring or treatment. These scans are mainly used when extra clarity is needed to guide the next steps in management. |
Treatment Options
Most kidney cysts are simple, harmless, and require no treatment at all. They often stay the same size for many years and rarely cause complications. Management focuses on monitoring and addressing symptoms only if they appear.
| Observation | If the cyst is simple and not causing symptoms, no intervention is needed. Your clinician may recommend periodic ultrasound scans to keep an eye on it, especially if it is large or newly found. Many people never need any further action. |
| Treating symptoms (if they occur) | If a cyst causes discomfort, infection, or pressure on nearby structures, treatment may be considered. Options can include: - Pain relief: Simple pain medication may help if the cyst causes mild ache. - Antibiotics: If the cyst becomes infected, antibiotics can manage the infection. |
| Drainage or surgery (rarely required) | In uncommon cases where a cyst is large, painful, or affecting kidney function: - Percutaneous drainage may be performed, using a needle to remove fluid from the cyst. - Surgical removal (usually keyhole surgery) is only considered when other methods are not suitable. |
Most people with kidney cysts never require a procedure and live completely normal lives with them.
How can Lanthorn help?
Kidney Ultrasound - £300
We offer high-resolution ultrasound to assess kidney cysts. This can be used if you’re experiencing kidney-related symptoms, if a cyst was found incidentally and needs follow-up, or if you simply want reassurance. Ultrasound can confirm the cyst’s size, appearance, and whether it has features of a simple, harmless cyst.
Additional Imaging - From £450
If a cyst appears complex or your clinician needs more detail, we can arrange further imaging, such as CT or MRI scans, to give a clearer picture of its structure and guide management.
Kidney & Liver Function Blood Test - £99
If there are concerns about kidney function, we can arrange blood tests (including eGFR and creatinine). These help assess how well the kidneys are working and whether any further steps are needed.
