Unmasking atypical emphysematous pyelonephritis: A rare diagnostic challenge

Emphysematous pyelonephritis (EPN) is a severe, life-threatening renal infection primarily seen in diabetic patients, characterized by gas formation within the renal parenchyma. However, atypical presentations in non-diabetic individuals pose significant diagnostic challenges. This case report details a rare presentation of EPN in a 31-year-old non-diabetic female with retrovertebral abscess, a complication rarely associated with EPN. The patient initially presented with retrovertebral swelling without the typical symptoms of fever, flank pain, or dysuria. Imaging revealed gas within the pelvicalyceal system and retrovertebral space, confirming the diagnosis of advanced EPN (Huang-Tsuang stage 3B). Despite early management with percutaneous nephrostomy and broad-spectrum antibiotics, the patient progressed to septic shock, ultimately requiring nephrectomy due to non-functional renal tissue. This case highlights the need for a flexible diagnostic approach, especially in patients with atypical symptoms or absent classic risk factors such as diabetes. Advanced imaging, particularly non-contrast computed tomography, plays a pivotal role in detecting EPN, even in unusual presentations. Early recognition and aggressive intervention, including renal decompression and appropriate antibiotic therapy, are essential for improving patient outcomes. This case underscores the importance of considering EPN in the differential diagnosis of atypical infections, particularly when unusual abscesses are present.