Shorter observation times and smaller gauge needles in outpatient kidney biopsies

Controversy exists as to the optimal observational time (OT) after outpatient percutaneous kidney biopsy. Further, there is some uncertainty about the benefit of smaller (18-gauge) vs. larger (16-gauge) biopsy needles. At our institution, we have been lowering the OT after outpatient kidney biopsies. Initially in 2015, we were monitoring for 6 hours and gradually began to decrease the OT over time. From 2020, we have adopted an OT of less than 4 hours. During this time period (in 2018), we also began using a smaller gauge needle (18 gauge). We reviewed all outpatient kidney biopsies performed by the nephrology division at our institution since 2015. There were 137 biopsies reviewed. 63 had OT of 4 - 6 hours, and 74 had OT < 4 hours. There was a total of 4 significant complications (2.9%). Two complications, symptomatic retroperitoneal bleeds, were detected in less than 3 hours. The other 2 complications were seen at 9 hours (clot retention) and 72 hours (retroperitoneal bleed after anticoagulation restarted). 63% of the biopsies were done using 18-gauge needles with 1 complication in this group vs. 3 in the 16-gauge group. All cases had adequate tissue for interpretation based on the ability to make a kidney diagnosis. The number of glomeruli obtained in the 18-gauge group was 29 ± 13 glomeruli, and in the 16-gauge group was 25 ± 10, which did not differ between groups. In summary, in an outpatient population, all significant post-biopsy complications were evident either within the first 3 hours or after 9 hours, and this suggests the feasibility of using shorter than standard OT in outpatient kidney biopsies. Furthermore, an 18-gauge needle may lower the risk of complications and obtain adequate tissue.