Provider-Performed Point-of-Care Ultrasonography Evaluation of the Kidneys after Kidney Biopsy

Background: Real-time ultrasonographic guidance is standard practice for performing kidney biopsies and is also used to identify post-biopsy bleeding complications. In this study, we aimed to evaluate the accuracy of provider-performed Point-of-Care Ultrasound (POCUS) in identifying post-biopsy bleeding complications. Methods: Adult patients undergoing outpatient ultrasound (U/S)-guided native kidney biopsy at the Johns Hopkins Hospital between August 2022 – June 2023 were included in the study. Immediate post-biopsy and 4-hour post-biopsy U/S imaging were performed by U/S technicians. POCUS assessments by the nephrology provider were conducted upon patient arrival to the recovery bay and 4 hours post-biopsy. The nephrology provider was blinded to the findings of the U/S technician. Presence of hematoma, hematoma size, presence of vascular jet, and presence of intra-renal arteriovenous fistula were documented. The prevalence of each complication and sensitivity and specificity of POCUS were calculated. Results: A total of 82 patients were enrolled. Average age of participants was 55.2 years (SD: 16.5), BMI 28.8 (SD: 6.1), 54.9% were male, 37.8% were Black, and a nephrology attending performed most biopsies (86.6%). Formal radiology U/S detected hematoma and AV fistula in 20.7% (17) and 3.7% (3) immediately post-biopsy and in 40.2 % (33) and 13.4% (11) at 4-hours. By POCUS, hematoma was detected in 19.5% (16) and AV fistula in 2.4% (2) of patients immediately post-biopsy and in 32.9% (27) and 4.9% (4) of patients at 4 hours. When compared with the formal radiology performed U/S, the sensitivity of POCUS for hematoma detection immediately post-biopsy and at 4 hours was 82.4% (95%CI 56.5-96.2) and 75.8% (95%CI 57.7-88.9), respectively. The specificity was 96.2% (95%CI 89.2-99.6) immediately post-biopsy and 95.9% (95%CI 86.0-99.5) at 4 hours. Inter-rater agreement between POCUS and formal radiology U/S for hematoma detection was 93.9 % (κ 0.81) immediately post-biopsy and 87.8 % (κ 0.74) at 4 hours. Conclusion: Provider-performed POCUS was able to detect post-biopsy bleeding complications with high sensitivity and specificity. This valuable, easily accessible tool should be considered for immediate assessment post-biopsy to expedite decision-making at the bedside. Additional studies are needed to evaluate the utility of POCUS to determine appropriateness for discharge after kidney biopsy.