Supplementary Material for: Safety of Kidney Biopsy when Performed as an Outpatient Procedure

Introduction: Kidney biopsy remains the gold standard for the diagnosis of most renal diseases. A major obstacle to performing a biopsy is safety concerns. However, many safety measures are not evidence based and therefore vary widely between centers. We sought to determine the rate and timing of kidney biopsy complications in our center, to compare the complication rate between native and transplant kidney biopsies, to evaluate the feasibility of performing kidney biopsies as an outpatient procedure and the value of a postbiopsy ultrasound before discharge, and to identify risk factors for complications. Methods: We performed a single-center, retrospective, observational study at the Division of Nephrology of the University Hospital Zurich including all patients who underwent renal biopsy between January 2005 and December 2017. Major bleeding (primary outcome) and any other bleeding or nonbleeding complications (secondary outcomes) were compared between native and transplant kidney biopsies and between inpatient and outpatient procedures and correlated with clinical factors possibly affecting bleeding risk. Results: Overall, 2,239 biopsies were performed in 1,468 patients, 732 as inpatient and 1,507 as outpatient procedures. Major bleeding was observed in 28 (3.8%) inpatient and in 15 (1.0%) outpatient procedures, totaling to 43 (1.9%) of all biopsies. Major bleeding requiring intervention amounted to 1.0% (0.5% of outpatient procedures). Rate of major bleeding was similar between native and transplant kidneys. 13/15 (87%) bleeding episodes in planned outpatient procedures were detected during the 4-h surveillance period. Risk factors for bleeding were aspirin use, low eGFR, anemia, cirrhosis, and amyloidosis. Routine postbiopsy ultrasound did not change management. Conclusions: Kidney biopsy is an overall safe procedure and can be performed as an outpatient procedure in most patients with an observation period as short as 4 h. The value of routine postbiopsy ultrasound is questionable.研究背景：肾活检（kidney biopsy）仍是多数肾脏疾病诊断的金标准。开展肾活检的主要障碍在于安全性顾虑，然而诸多安全措施并无循证依据，因此各中心间的操作规范差异显著。本研究旨在明确本中心肾活检并发症的发生率与发生时间，比较自体肾（native kidney）与移植肾（transplant kidney）活检的并发症发生率，评估将肾活检作为门诊操作（outpatient procedure）的可行性及出院前活检后超声（postbiopsy ultrasound）检查的临床价值，并识别并发症的危险因素。 研究方法：本研究为单中心回顾性观察研究，纳入2005年1月至2017年12月期间于苏黎世大学医院肾内科接受肾活检的所有患者。以大出血（major bleeding，主要结局）及其他各类出血与非出血并发症（次要结局）为观察指标，比较自体肾与移植肾活检、住院与门诊操作间的并发症发生率，并将其与可能影响出血风险的临床因素进行相关性分析。 研究结果：本研究共纳入1468例患者，完成肾活检2239例次，其中732例次为住院操作，1507例次为门诊操作。住院组大出血发生率为28例（3.8%），门诊组为15例（1.0%），整体大出血发生率为1.9%。需干预的大出血发生率为1.0%（门诊组为0.5%）。自体肾与移植肾活检的大出血发生率无显著差异。计划实施的门诊操作中，13/15（87%）的出血事件可在4小时监测期内被检出。出血危险因素包括阿司匹林使用、低估算肾小球滤过率（estimated glomerular filtration rate, eGFR）、贫血、肝硬化及淀粉样变性。常规活检后超声检查未改变患者的诊疗方案。 研究结论：肾活检整体而言是安全的操作，多数患者可在仅4小时的观察期后以门诊方式完成活检。常规活检后超声检查的临床价值尚存争议。