Kidney Biopsy Yield: An Examination of Influencing Factors.

Kidney biopsies are conducted under varying scenarios, presenting variables that could potentially influence yield and adequacy of tissue collected. We retrospectively reviewed 636 native and allograft kidney biopsies, and compared tissue collected between differing practitioners performing the biopsy (nephrologists or radiologists), imaging modalities for guidance (ultrasound or computed tomography), gauge needle used (18 or 16 G), and between on-site evaluators of biopsy adequacy conducted at the time of biopsy (general pathologists, renal pathologists, nephrologists). For radiologists using ultrasound guidance and 18 G needles, those using on-site evaluation of adequacy collected more glomeruli and glomeruli per length of tissue core than those not using on-site evaluation. Radiologists not using on-site evaluation but who used a larger bore needle (16 vs. 18 G) could generally collect comparable tissue as other biopsy performers who used on-site evaluation. Radiologists performing ultrasound-guided biopsies with 18 G needles without on-site evaluation consistently provided poorer tissue yield and had a higher rate of providing insufficient tissue so that a diagnosis could not be rendered. Nephrologists collected less total length of tissue cores, glomeruli, and arteries per case (whether performing the biopsy and/or performing on-site adequacy) compared with other groups using on-site evaluation, however, providing comparable density of glomeruli and arteries. Complication rates did not differ between compared groups using 18 G needles. It is our observation that the various conditions by which a kidney biopsy is obtained influences the yield of tissue collected and the subsequent ability for a pathologist to effectively provide a diagnosis.