Nonfocal Renal Biopsies: Adequacy and Factors Affecting a Successful Outcome

Purpose: The purpose of this study was to evaluate factors affecting the success of ultrasound-guided core biopsy of kidneys and determine the optimum number of passes. Methods: This retrospective study evaluated 484 nonfocal renal biopsies performed with 18-gauge side-notch biopsy needles. Number of biopsy passes, serum creatinine, body mass index, needle type, transplant age, kidney size, diabetic status, and operator were evaluated as predictors of the number of biopsy passes. Results: Four hundred seventy-four biopsies (338 transplant, 136 native) were included with mean number of passes 2.87 (3.1 native vs 2.78 transplant; P = 0.002). Mean number of glomeruli yielded per pass was 6.9 (7.2 transplant vs 6.1 native; P = 0.0002) with 3 passes adequate for histological diagnosis in 84% of biopsies. Native kidney, increasing serum creatinine level, trainee biopsy operator, and use of a Temno needle were found to be independent predictors of having more than 3 biopsy passes on multivariate analysis. Age, sex, body mass index, diabetic status, and kidney size were not associated with the number of biopsy passes. Conclusions: The success of a nonfocal renal biopsy has many influencing variables, and in the absence of an on-site electron microscopy technologist to immediately evaluate biopsy samples, 3 passes with an 18-gauge needle would be adequate in 84% of kidneys to achieve a histological diagnosis, with 2 passes needed for transplant kidneys to meet the Banff 97 criteria.