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

<b><i>Introduction:</i></b> 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. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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. <b><i>Conclusions:</i></b> 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.

<b><i>引言：</i></b> 肾活检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，因此不同医疗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，对比自体肾与移植肾活检的并发症发生率，评估将肾活检作为门诊操作的可行性以及出院前活检后超声检查的价值，并明确并发症的危险因素。<b><i>方法：</i></b> 本研究为单中心回顾性观察研究，纳入2005年1月至2017年12月期间在苏黎世大学医院肾脏内科接受肾活检的所有患者。以大出血（主要结局指标）以及其他所有出血性或非出血性并发症（次要结局指标）为观察指标，对比自体肾与移植肾活检、住院操作与门诊操作的并发症发生情况，并将其与可能影响出血风险的临床因素进行关联分析。<b><i>结果：</i></b> 本研究共纳入1468例患者，实施肾活检2239例次，其中住院活检732例次，门诊活检1507例次。住院活检患者中28例（3.8%）发生大出血，门诊活检患者中15例（1.0%）发生大出血，整体大出血发生率为1.9%（43例次）。需进行干预的大出血发生率为1.0%，其中门诊患者占0.5%。自体肾与移植肾活检的大出血发生率无显著差异。计划行门诊活检的患者中，15例出血事件里有13例（87%）在4小时的观察期内被检出。出血的危险因素包括服用阿司匹林、估算肾小球滤过率（estimated glomerular filtration rate, eGFR）降低、贫血、肝硬化以及淀粉样变性。常规活检后超声检查并未改变临床诊疗方案。<b><i>结论：</i></b> 肾活检整体安全性良好，多数患者可接受门诊活检，观察期仅需4小时。常规活检后超声检查的临床价值尚存争议。