Bosniak classification v2019
Nephrology and urology
Also known as: Bosniak-Klassifikation (Version 2019) · Bosniak sınıflaması (2019) · Bosniak classification of cystic renal masses, version 2019
What it is for
CT/MRI classification of cystic renal masses (enhancing solid tissue less than about 25% of the mass), excluding infectious, inflammatory and vascular lesions and necrotic solid masses. Thin = ≤2 mm, minimally thickened = 3 mm, thick = ≥4 mm. If features fit several classes, the highest class applies.
Classification
| Category | Description |
|---|---|
| Class I | well-defined, thin (≤2 mm) smooth wall; homogeneous simple fluid (CT −9 to 20 HU; MRI fluid signal like cerebrospinal fluid); no septa or calcification; the wall may enhance. |
| Class II | thin smooth wall with few (1–3) thin enhancing septa, calcification of any type allowed; or, on CT, homogeneous masses that are ≥70 HU unenhanced, >20 HU non-enhancing on renal-mass protocol, −9 to 20 HU unenhanced, 21–30 HU portal venous, or too small to characterise; on MRI, homogeneous masses markedly T2-hyperintense like cerebrospinal fluid or markedly T1-hyperintense (about 2.5 × renal parenchyma) unenhanced. |
| Class IIF | smooth minimally thickened (3 mm) enhancing wall, or smooth minimal (3 mm) thickening of one or more enhancing septa, or many (≥4) smooth thin enhancing septa; on MRI also a cystic mass heterogeneously hyperintense on fat-saturated unenhanced T1. |
| Class III | one or more enhancing thick (≥4 mm) or enhancing irregular walls or septa (irregular = focal or diffuse convex protrusion ≤3 mm with obtuse margins). |
| Class IV | one or more enhancing nodules: a convex protrusion of any size with acute margins, or ≥4 mm with obtuse margins. |
| Enhancement | visibly or measurably enhancing (CT increase ≥20 HU; MRI signal increase ≥15% against unenhanced images). |
Source
Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment
Radiology 2019;292:475–488 (Silverman SG et al.)
DOI: 10.1148/radiol.2019182646
PMID: 31210616
- Edition
- Bosniak 2019 (replaces the 2005 CT-based version; adds MRI)
- Checked on
Summary of the published classification in our own words. Not a substitute for the original publication.
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