A 50-year-old diabetic patient presented with fever, dysuria and abdominal pain.
Diagnosis: Emphysematous pyelonephritis
Axial and coronal CT of the abdomen shows gross enlargement and destruction of left renal parenchyma with bubbly areas of gas collection within the parenchyma.
• Emphysematous pyelonephritis is a life-threatening necrotizing infection characterized by gas formation within or surrounding the kidneys.
• Rapidly progressive with high morbidity and mortality.
Epidemiology and Pathology
• Poorly controlled diabetes and immunocompromised status are predisposing conditions.
• E coli, Klebsiella pneumonia, and Proteus mirabilis are common pathogens.
• Mottled gas within the renal fossa or crescentic collections of gas within the Gerota fascia
• Enlarged kidney with nondependent echoes in the renal parenchyma or collecting system
• Kidney may be completely obscured by large amount of perinehric gas
• The distal shadowing have “comet tail” reverberations and low-level echoes that are termed as “dirty shadowing.” Distinguishing them from calculi.
• However, US examination may be affected by the patient’s obesity or bowel meteorism. Additionally bowel gases and calculi are confounding factors.
Computed tomography (CT)
Common findings include:
• Mottled areas of low attenuation extending radially along the pyramids with parenchymal enlargement and destruction.
• Fluid collections and gas-fluid levels
• Type I: Streaky or mottled gas in interstitium of renal parenchyma radiating from medulla to cortex. No fluid collections.
• Type 2: Bubbly and/or loculated intrarenal gas with renal and/or perirenal fluid collection.
• Type I is associated with worse prognosis.
Aggressive medical treatment along with percutaneous drainage and partial or complete nephrectomy.
1. Craig W, Wagner B, Travis M. Pyelonephritis: Radiologic-Pathologic Review. RadioGraphics. 2008;28:255-276.
2. Woodward S, Elsayes K, Akhtar A. Imaging of Emphysematous Pyelonephritis: Self-Assessment Module. American Journal of Roentgenology. 2010;194:S70-S72.