Malignancy rates and diagnostic performance of the Bosniak classification for the diagnosis of cystic renal lesions in computed tomography - a systematic review and meta-analysis.

OBJECTIVE

To systematically review the literature on the Bosniak classification system in CT to determine its diagnostic performance to diagnose malignant cystic lesions and the prevalence of malignancy in Bosniak categories.

METHODS

A predefined database search was performed from 1 January 1986 to 18 January 2016. Two independent reviewers extracted data on malignancy rates in Bosniak categories and several covariates using predefined criteria. Study quality was assessed using QUADAS-2. Meta-analysis included data pooling, subgroup analyses, meta-regression and investigation of publication bias.

RESULTS

A total of 35 studies, which included 2,578 lesions, were investigated. Data on observer experience, inter-observer variation and technical CT standards were insufficiently reported. The pooled rate of malignancy increased from Bosniak I (3.2 %, 95 % CI 0-6.8, I2 = 5 %) to Bosniak II (6 %, 95 % CI 2.7-9.3, I2 = 32 %), IIF (6.7 %, 95 % CI 5-8.4, I2 = 0 %), III (55.1 %, 95 % CI 45.7-64.5, I2 = 89 %) and IV (91 %, 95 % CI 87.7-94.2, I2 = 36). Several study design-related influences on malignancy rates and subsequent diagnostic performance indices were identified.

CONCLUSION

The Bosniak classification is an accurate tool with which to stratify the risk of malignancy in renal cystic lesions.

KEY POINTS: • The Bosniak classification can accurately rule out malignancy. • Specificity remains moderate at 74 % (95 % CI 64-82). • Follow-up examinations should be considered in Bosniak IIF and Bosniak II cysts. • Data on the influence of reader experience and inter-reader variability are insufficient. • Technical CT standards and publication year did not influence diagnostic performance.