Ultrasound-guided core biopsy of small renal masses: diagnostic rate and limitations.

Purpose: To evaluate the feasibility and complications of ultrasound (US)-guided biopsy of small renal masses (SRMs) and to determine factors that contribute to nondiagnostic biopsy specimens.
Materials and Methods: Between June 2004 and May 2011, 58 consecutive patients underwent US-guided core biopsy of a SRM (>1 cm and ≤4 cm) using an 18-gauge core biopsy device. The diagnostic rate, histologic diagnosis, and complications of US-guided core biopsy were assessed. Mann-Whitney U and Fisher exact tests were used to compare diagnostic and nondiagnostic biopsy specimens. Univariate analysis was performed to determine the predictive factors for nondiagnostic biopsy specimens.
Results: There were 59 biopsies of SRMs performed, and the diagnostic rate was 81% (48 of 59). The mass size of diagnostic and nondiagnostic biopsy specimens ranged from 1.2-3.9 cm (2.4 cm±0.7) for diagnostic specimens and from 1.1-3.5 cm (1.9 cm±0.7) for nondiagnostic specimens (P = .024). Of the diagnostic biopsy specimens, 77% (37 of 48) were malignant, and 23% (11 of 48) were benign. Minor complications developed in 20.3% (12 of 59) of biopsies. The lesion size or core number threshold for decreasing diagnostic rate was 2 cm or three cores. A cystic mass, fewer cores (three or fewer cores), an upper pole mass, and a small mass (≤2 cm) significantly predicted a nondiagnostic biopsy specimen (P = .007-.046).
Conclusions: US-guided core biopsy is a feasible and safe procedure for histologic diagnosis of a SRM. However, nondiagnostic rates may increase when a cystic mass is biopsied, a mass is located in an upper pole mass, a mass is 2 cm or less, and three cores or fewer are sampled.
(Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.)