Bosniak Classification (renal cyst, 2019)
Bosniak 2019 renal-cyst classification: wall, septa, enhancing protrusion, and calcification map to class I–IV with a corresponding malignancy estimate.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Wall
- Thick (≥ 4 mm) or irregular, enhancing
- Septa
- 1–3 thin (≤ 2 mm) septa
- Enhancing protrusion / nodule
- None
Result: Bosniak III — malignancy ~50%.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Classes
- Enhancing nodule → IV; thick wall/septa or small obtuse protrusion → III; minimal (3 mm) thickening or ≥4 thin enhancing septa → IIF; 1–3 thin septa or calcification → II; thin smooth wall → I.
- Malignancy
- Approximate: I ~0%, II <1%, IIF ~5%, III ~50%, IV ~90%. Calcification never upgrades class in v2019.
What you enter
- Wall
- Septa
- Enhancing protrusion / nodule
- Calcification present
How this is calculated
Silverman SG, Pedrosa I, Ellis JH, et al. Bosniak classification of cystic renal masses, version 2019: an update proposal and needs assessment. Radiology. 2019;292(2):475-488. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.