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Guideline Current Radiology 2019

Bosniak Classification of Cystic Renal Masses, Version 2019

Version 2019 update to the Bosniak classification for cystic renal masses on CT and MRI. Assigns cysts to five classes (I, II, IIF, III, IV) based on wall/septal thickness, enhancement, and calcification, guiding management from no follow-up to surgical resection.

Structured reportUpdated Jul 5, 2026
Applies to
  • Cystic renal masses
  • Contrast-enhanced CT or MRI
Classification
  • Bosniak class I
  • Bosniak class II
  • Bosniak class IIF
  • Bosniak class III
  • Bosniak class IV
Exclusions
  • Solid renal masses
  • Non-contrast imaging alone
  • Known renal cell carcinoma
Interactive

Decision tree

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Recommendation builder

Select the Bosniak class assigned from the imaging features.

Evidence

References

  1. PrimarySilverman 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.
FAQ

Frequently asked

Does this guideline apply to oncology patients?

No — patients with known malignancy fall outside the scope unless the guideline states otherwise. Follow oncologic surveillance protocols instead.