# Predictors of poor kidney function in patients with emphysematous pyelonephritis: a retrospective observational study

## TL;DR

This study identifies factors that predict poor kidney function in patients with a severe kidney infection called emphysematous pyelonephritis.

## Contribution

The study identifies >50% renal parenchymal involvement on initial imaging as an independent predictor of poor kidney function in emphysematous pyelonephritis.

## Key findings

- More than 50% parenchymal involvement on initial imaging was the strongest predictor of poor kidney function.
- High blood sugar (>200 mg/dL) and Huang-Tseng Class 3b were also significant risk factors.
- Persistence of gas in the kidney on follow-up imaging was associated with poor outcomes.

## Abstract

Emphysematous pyelonephritis (EPN) is a well-known clinical condition characterized by an aggressive, gas-forming infection of the kidney caused by uropathogenic bacteria. There is growing interest in identifying the effects of EPN on long-term renal function and the factors that can help predict its impact.

This study evaluated risk factors for the development of poorly functioning kidneys (PFK) in patients diagnosed with EPN.

A retrospective study was conducted at a university teaching hospital on patients with EPN from January 2019 to December 2024.

Data were collected from the prospectively maintained patient records, and patient demographics, comorbidities, clinical presentation, laboratory investigations, imaging characteristics, and interventions were analyzed. PFKs were defined as those with less than 15% differential function on radionuclide renography performed at follow-up. Data were analyzed using SPSS version 23 (IBM Corp.). A p-value <0.05 was considered statistically significant.

A total of 151 patients met the eligibility criteria. PFK was present in 23 patients (15.2%) on follow-up. Univariate analysis revealed random blood sugar (RBS) at presentation >200 mg/dL (p < 0.0001), >50% parenchymal involvement on imaging (p < 0.00001), Huang-Tseng Class 3b (p < 0.00001), and persistence of gas in the renal parenchyma on follow-up imaging (p < 0.0001) to be significantly associated with the development of PFK. Multivariate Analysis revealed that >50% parenchymal involvement on initial imaging was an independent and significant predictor of PFK.

EPN is a fulminant renal infection with a high risk of renal functional deterioration. Renal parenchymal involvement of >50% on initial imaging emerged as the most significant and independent predictor of poor renal function. Additional contributory factors included RBS >200 mg/dL, Huang-Tseng Class 3b, and persistence of gas in the renal parenchyma on follow-up. Recognizing these clinical and radiological predictors can support early risk stratification, guide patient counseling, and inform individualized management strategies aimed at preserving renal function.

Poorly functioning kidneys in patients with severe infection of kidneys

Emphysematous pyelonephritis (EPN) is a dangerous gas-forming kidney infection, often linked to diabetes, that can cause long-term kidney damage. In a study of 151 patients, 15% ended up with poorly functioning or nonfunctioning kidneys. The strongest predictor of poor outcome was more than 50% of the kidney being affected by gas on the first computed tomography (CT) scan. Other risk factors included high blood sugar at diagnosis (>200 mg/dL), severe disease on CT (Huang-Tseng Class 3b), and gas persisting in the kidney on follow-up imaging. Recognizing these signs early can help guide treatment and improve long-term kidney health.