#281 AVF formation is a common complication of percutaneous ultrasound-guided renal biopsy: a single-center analysis of risk factors and clinical outcome
Authors: Mortari Gabriele , Manenti Chiara , Russo Noemi , Silva Laura , Oldrati Sara , Padelli Martina , Monchieri Francesca , Zubani Roberto , Viola Battista Fabio , Mescia Federica , Alberici Federico 
Published: May 2024

Abstract

Background and Aims
Percutaneous renal biopsy is a key procedure for the work-up of renal diseases. Among the possible complications of such procedure, prevalence, risk factors and clinical outcome of arterio-venous fistula (AVF) formation is unclear. We present here a single-center experience on renal biopsy-related complications with a focus on risk factors for AVFs formation and their management.

Method
We retrospectively analyzed all the kidney biopsies performed in our center between January 2012 and December 2022. All biopsies were conducted under real-time ultrasound (US) guidance by trained nephrologists. Kidney US and doppler mapping were performed routinely 6 and 24 hours post-procedure. In accordance with the description provided in the US report, AVFs were categorized into small, moderate, and high-flow rates. Patients’ comorbidities, histologic sample characteristics, blood tests results and the clinical course were recorded. Logistic regression was employed to investigate potential risk factors for complications.

Results
1016 adult native renal biopsies were performed. The average age of patients was 55 ± 17 years, and 677/1016 (66.6%) were males. The histological sample was unsuitable in 29/1016 (2.9%) of the cases; moreover, prevalence of renal medulla and presence of large-caliber arteriole were observed in 88/1016 (8.7%) and 38/1016 (3.7%) of the samples, respectively. The most common complication was hematoma, detected by US in 175/1016 (17.2%), which was considered “complicated” in 21/1016 (2.1%) due to the association with macroscopic hematuria (n = 10), blood transfusion requirement (n = 8), or signs of active bleeding (n = 8), requiring embolization in 6/1016 patients (0.6%). AVFs were identified in 119/1016 (11.7%) biopsies; of these 20/119 (16.8%) required embolization after a median time of 16 days (IQR 5-65). Spontaneous resolution was documented in 65/119 (55%) of cases and occurred after a median of 27 days (IQR 15-49), with 50/55 (90.9%) of cases spontaneously resolving within the first month and the remaining cases no later than the fourth month (Fig. 1). High-flow AVFs more frequently necessitated angiographic intervention compared to moderate and small AVFs (75% vs 25% vs 7%), with a prolonged spontaneous resolution time (median 78 days; IQR 51-106) (Table 1). In the cases requiring embolization, the median creatinine level before and 6 months after procedure was respectively 1.7 mg/dL and 1.9 mg/dL (paired Wilcoxon signed-rank test: p = 0.908). In three cases post-embolization, a loss of renal vascularization at angiography higher than 30% was reported; however, even in these cases no differences in terms of renal function were observed at 6 months compared to the baseline. At multivariate logistic regression, hypertension (OR = 2,2; p = 0.003; 95% CI [1.3-3.7]), renal medulla prevalence (OR = 2,8; p = 0,001; 95% CI [1.6-4.8]), and large-caliber arteriole presence (OR = 2,9; p = 0,008; 95% CI [1.3-6.3]) were associated with a higher risk of AVFs, while obesity emerged as a protective factor (OR = 0,27; p = 0,013; 95% CI [0.1-0.8]).

Conclusion
AVF is a common complication following renal biopsy but therapeutic intervention is rarely required, as spontaneous resolution is typically observed within one month. In case of symptomatic or persistent AVFs, embolization may be required without an apparent impact on the renal function, at least in the short term. Hypertension and surrogate factors associated with a deeper penetration of the needle into the renal parenchyma are associated with an increased risk of AVF. Conversely, obesity was protective toward the risk of AVF development.