What it is
Most kidney cysts are “simple” — thin-walled, water-filled, and benign. Radiologists sometimes grade cysts with the Bosniak system, where category I and II are considered benign.
How common is it?
Very common, and they become more frequent with age. Simple renal cysts are a routine incidental finding on abdominal imaging.
What's usually next
Simple cysts usually need no follow-up. Cysts with more complex features may be watched with repeat imaging or evaluated further, based on their Bosniak category.
When it usually isn't — and when it might be — worrying
Usually reassuring
- Described as a “simple cyst” (Bosniak I or II)
- Thin walls and clear fluid
- Stable over time
Worth discussing with your doctor
- A “complex” cyst with thick walls, septations, or solid parts
- A higher Bosniak category (III or IV)
- Growth compared with prior imaging
Questions to ask your doctor
- 1Is this a simple cyst or a complex one?
- 2What Bosniak category is it, if graded?
- 3Does it need any follow-up imaging?
- 4Could it be related to my symptoms?
Educational use only. This explanation helps you understand terminology on your report. It is not a diagnosis, is not FDA-cleared, and does not replace your doctor. Bring questions to your care team.