Image-guided biopsy of small (≤4 cm) renal masses: the effect of size and anatomical location on biopsy success rate and complications

To study the influence of tumour diameter and anatomy on the success and complication rates of small renal mass (SRM, ≤4 cm) core biopsy. Retrospective analysis of SRMs that underwent ultrasound or CT-guided biopsy. Diagnostic and complication rates were compared according to tumour size (subcategorised as axial diameter ≤2 cm, >2 to- ≤3 cm, >3-≤4 cm) and anatomical disposition (exophytic/endophytic, centrality, polar location and anterior/posterior). 94 patients (54 male; age range 21.8-84.3 years) with 95 SRMs underwent biopsy. The first biopsy was diagnostic in 81/95 (85.3%). Seven patients underwent repeat biopsy (6/7 diagnostic), to give an overall diagnostic rate of 91.5%. The primary diagnostic rates in the ≤2, >2-≤3 , >3-≤4 cm groups were 21/25 (84%); 38/44 (86.4%) and 22/26 (84.6%) respectively and were similar (p = 1.00). Anterior and upper pole SRMs were more likely to fail initial biopsy (odds ratio 13.8, p < 0.01; and odds ratio 4.35, p = 0.04) respectively, but other anatomical factors were not relevant. Complications occurred in 14% (all conservatively managed perinephric haematomas; Clavien-Dindo Grade 1) and size or location were not relevant. Image-guided biopsy of SRMs has a high diagnostic rate irrespective of tumour size. Anterior and upper pole location had lower diagnostic rates. Biopsy should be considered for all patients with SRMs, if the result will impact on management and we list specific scenarios where an SRM biopsy may be helpful. Advances in knowledge: SRM size does not affect the likelihood of a diagnostic biopsy.