ARRS 2022 Abstracts

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1543. Evaluation of Class II Cystic Renal Masses Proposed in Bosniak Classification Version 2019: A Systematic Review of Supporting Evidence
Authors * Denotes Presenting Author
  1. Trevor McGrath *; The Ottawa Hospital; University of Ottawa
  2. Ahmed Shoeib; University of Ottawa Faculty of Medicine
  3. Matthew Davenport; University of Michigan
  4. Stuart Silverman; Brigham and Women’s Hospital, Harvard University
  5. Matthew McInnes; The Ottawa Hospital; University of Ottawa
  6. Nicola Schieda; The Ottawa Hospital; University of Ottawa
Objective:
The Bosniak classification of cystic renal masses version 2019 (v.2019) includes an expanded number of types of masses in class II; such masses are considered benign in clinical practice. Data supporting these additions have not been well-documented. We aim to determine the proportion of malignant or probably malignant renal masses among the types added to Bosniak v.2019 class II.

Materials and Methods:
Multiple databases were searched for studies evaluating the proportion of malignant or probably malignant renal masses among new Bosniak v.2019 class II types, four for CT and two for MRI. Risk of bias and applicability was assessed using the QUADAS-2 tool.

Results:
Ten studies (2,068 renal masses) met inclusion criteria. Among the four added class II types at CT, the proportion of malignancy among ‘homogeneous hyperattenuating (=70 HU) masses at unenhanced CT’ was 0% (0/32) in three studies; ‘homogeneous masses -9 to 20 HU at unenhanced CT’ was 0% (0/1454) in two studies, and for ‘homogeneous masses 21 to 30 HU at portal-venous phase CT’ was 0% (0/454) in four studies. Masses that are homogeneous, low attenuation, and too small to characterize on CT had no supportive evidence. Among the two added class II types at MRI, the proportion of malignancy among ‘homogeneous masses markedly hyperintense at unenhanced T2-weighted MR imaging (similar to CSF) was 0% (0/72) in one study; and ‘homogeneous masses markedly hyperintense at T1-weighted MR imaging (~2.5x renal parenchyma signal intensity) was 0% (0/32) and 5% (2/37) in two studies. Nine studies were at risk of bias within at least one QUADAS-2 domain.

Conclusion:
The addition of six types of cystic renal masses to class II in the Bosniak v.2019 proposal may be justified but based on limited evidence, with no evidence for ‘homogeneous low-attenuation masses that are too small to characterize’ on CT, and thus considering them benign is, in part, based on expert opinion.