# Urinary N-acetyl-D-glucosaminidase can predict bleeding after a percutaneous kidney biopsy

## TL;DR

This study shows that a urinary biomarker called NAG can predict bleeding after kidney biopsies, suggesting a link to kidney disease severity and blood vessel changes.

## Contribution

The study demonstrates that urinary NAG/Cr is a novel predictor of bleeding risk after percutaneous kidney biopsies.

## Key findings

- Urinary NAG/Cr levels predicted bleeding events with an area under the ROC curve of 0.65.
- Elevated urinary NAG/Cr remained a significant risk factor even after adjusting for known risk factors.
- Arteriosclerosis severity correlated with both urinary NAG/Cr levels and bleeding events.

## Abstract

A percutaneous kidney biopsy (PKB) allows nephrologists to make informed decisions for treating various kidney diseases; however, the risk of bleeding complications should be considered, given the vascularity of the kidney. Many studies have reported risk factors for bleeding events after a PKB. However, while urinary N-acetyl-β-D-glucosaminidase (NAG) is a useful biomarker of kidney disease severity, little is known about whether or not urinary NAG is related to the bleeding risk.

Medical records of patients who underwent a PKB at the National Defense Medical College Hospital between October 2018 and October 2023 were retrospectively studied. Hemoglobin (Hb) loss ≥ 1 g/dL was defined as a bleeding event.

Of the 213 patients, 110 (51.6%) were men, and the median age was 56 years old (interquartile range 40–71). The most frequent diagnosis on a PKB was IgA nephropathy (N = 72; 34.0%). Fifty-four patients (25.3%) experienced Hb loss ≥ 1 g/dL after a PKB, and urinary NAG/Cr levels before the biopsy were able to predict a bleeding event, with an area under the receiver operating characteristic curve of 0.65 (p = 0.005). Using the optimal cutoff value of 35 U/gCr, urinary NAG/Cr was found to be an independent risk factor by multiple logistic regression analysis (odds ratio 3.21, 95% confidence interval 1.42–7.27, p = 0.005). Even after adjusting for previously-reported risk factors, the elevated urinary NAG/Cr ratio remained a statistically significant variable. Compared with the pathological findings, only the severity of multilayered elastic laminae of the small muscular artery was associated with both urinary NAG/Cr levels (p = 0.008) and bleeding events (p = 0.03).

Urinary NAG successfully predicted not only the severity of kidney disorders but also bleeding events after a PKB. Arteriosclerosis in the kidneys may be the mechanism underlying these increased bleeding events.

The online version contains supplementary material available at 10.1186/s12882-024-03658-z.