What Are Kidney Cysts?
Kidney cysts are essentially fluid-filled bubbles on your kidney. Kidney cysts are very common, especially as people get older. Studies show that about 1 in 2 people over the age of 50 have at least one simple kidney cyst. Most of these cysts are harmless and do not affect kidney function. However, some cysts may be complex, meaning they have irregular shapes, thick walls, or solid areas. These require further evaluation to rule out cancer. Doctors use imaging tests like ultrasound, CT scan, or MRI to check kidney cysts and determine whether they need follow-up or treatment.
Symptoms and When to See a Doctor
Most kidney cysts do not cause symptoms and are found during scans for other medical reasons. However, if a cyst becomes large, it may cause back or side pain, blood in the urine, or high blood pressure. In rare cases, cysts can become infected, rupture, or block urine flow, leading to discomfort and complications. If you experience persistent pain, urinary problems, or unexplained high blood pressure, see a doctor to check if a kidney cyst could be the cause.
Doctors use the Bosniak Classification System to determine the risk of a kidney cyst being cancerous. Below is a simplified version of this scale:
| Bosniak Category | Description | Chance of Cancer | Follow-up Needed? |
|---|---|---|---|
| Bosniak I | Simple cyst, thin walls, no solid areas | 0% (Always benign) | No follow-up needed |
| Bosniak II | Few thin septations (divisions), small calcium deposits | ~0% (Benign) | No follow-up needed |
| Bosniak IIF | More septations, thicker walls, more calcium | ~5% | Periodic imaging recommended |
| Bosniak III | Thickened walls or septations, possible solid areas | 40-60% | Further testing or treatment considered |
| Bosniak IV | Clearly solid areas, irregular walls, high blood flow | 80-90% (High risk of cancer) | Treatment considered |
Treatment and Management
Most simple cysts (Bosniak I and II) do not require treatment and only need monitoring if they cause symptoms. Bosniak IIF cysts may need periodic imaging to ensure they do not change over time. If a Bosniak III or IV cyst is found, doctors may recommend a biopsy, additional imaging, or surgery to remove it and confirm whether it is cancerous. If you have multiple cysts or a condition like polycystic kidney disease (PKD), your doctor may suggest more frequent monitoring.
If you have questions about kidney cysts or your kidney health, talk to a urologist or nephrologist for personalized care.
