# Abscessed Lumbar Hypodermatitis Revealing Pyonephrosis: A Diagnosis to Keep in Mind

## TL;DR

A rare case shows how a kidney infection can appear as a skin abscess, highlighting the importance of recognizing unusual symptoms.

## Contribution

Highlights a rare clinical presentation of pyonephrosis mimicking an abdominal wall abscess.

## Key findings

- Pyonephrosis can present as an abscessed lumbar hypodermis, leading to diagnostic confusion.
- Delayed diagnosis due to misinterpretation can have fatal consequences.
- The case emphasizes the need for awareness among physicians about this rare manifestation.

## Abstract

Pyonephrosis resulting from an obstructing calculus commonly presents with symptoms such as loin pain, fever, and signs indicative of a urinary tract infection. In some cases, significant thinning of the renal parenchyma in pyonephrosis may lead to direct rupture into the retroperitoneum, and exceptionally rarely, into the lumbar abdominal wall, potentially mimicking an isolated abdominal wall abscess, which can be mistaken for a complication of hypodermatitis. Our case is a good illustration of a condition that is not well known among practitioners, particularly family physicians and dermatologists. This lack of awareness can explain the diagnostic delay, which may sometimes result in the patient's death.