Assigns a Bosniak class to a renal cyst from wall/septa, enhancement and septa features, with malignancy risk and management.
The Bosniak classification stratifies cystic renal masses by their likelihood of malignancy using wall and septal thickness, the number of septa, and the presence of measurable or nodular enhancement. The 2019 update sharpened the definitions of each class.
🧮 Interactive Calculator
📐 Formula
Feature mapping → Bosniak I / II / IIF / III / IV
🎯 When to Use
Characterising a cystic renal mass on contrast-enhanced CT or MRI.
Deciding between reassurance, surveillance and surgical referral.
Standardised communication of cyst complexity to urology.
⚙️ How It Works
Assess the thickness and regularity of the wall and any septa.
Count the number of septa and grade any enhancement as none, minimal (thin septa) or measurable/nodular.
Map the worst feature to the corresponding Bosniak class.
Nodular or measurable enhancement upgrades the cyst regardless of other features.
📊 Interpreting the Result
Bosniak I: simple cyst, ~0% malignancy — no follow-up.