Renal biopsy: Comparative yield of cranial versus caudal needle trajectory. An ex vivo analysis

Aim To compare the diagnostic quality of tissue cores obtained using cranial and caudal angulation of the renal biopsy needle. Comparison was made in terms of the number of glomeruli and proportion of renal cortex with medulla on pathological analysis. Methods A total of 40 desktop, renal biopsies were performed on 10 ex vivo porcine kidneys using two different targeting angles. Biopsies were obtained from the 'lower pole' of each kidney using both cephalad and caudad angulations of the biopsy needle. Ten 18-gauge semi-automated cutting needles were used during twenty biopsies obtained per each angle; two biopsies were made using each needle. The resulting samples were collected in 40 separate and labelled formalin containers according to the used targeting angle. Two pathologists blinded to the corresponding biopsy angles reviewed the samples in consensus. Results Samples with a cephalad targeting angle had a mean length of 14.5 mm with mean number of 9.6 glomeruli and average 82% cortex and 18% medulla. Samples obtained using a caudad needle angulation had a mean length of 14.1 mm with mean number of 11.6 glomeruli and on the average 99% cortex. The P-values comparing the two samples were as follows: 0.63 comparing the mean length of cores, 0.08 for number of glomeruli and 0.002 comparing the proportion of cortex. Conclusion The proportion of cortical tissue in the core biopsy specimen using the caudad angle approach was statistically significantly higher, compared with the cephalad needle trajectory. Summary at a Glance This paper demonstrated the better diagnostic yield of a renal biopsy sample using a caudal as opposed to a cranial biopsy needle trajectory in an ex vivo study. Given the potentially better yield and less risk of bleeding this approach now awaits clinical confirmation.