Emphysematous Cystitis

Sagittal-plane ultrasound image of the bladder shows a linear hyperechoic structure with posterior "dirty shadowing" in the anterior aspect of the urinary bladder. There is no recent bladder catheterization. Upon decubitus positioning, this abnormality is immobile, suggesting extraluminal location. 

Axial non-contrast CT of the same patient demonstrates gas within the anterior and posterior walls of the urinary bladder (arrows).

Facts:

• Rare bladder inflammation with gas in bladder wall and surrounding tissues
• Generally caused by E.coli, K.pneumoniae or anaerobic gas-forming organisms
• Pathology: numerous gas filled intramural cysts on mucosal surface
• Risk factors: diabetes, immunocompromised state, urinary tract obstruction
• Most patients have mild forms of disease and respond well to antibiotics. Some have severe inflammation, gangrene and sepsis

Imaging:

• X-ray and CT usually is diagnostic with gas in the bladder wall, surrounding tissues and in the lumen in the absence of prior catheterization
• Ultrasound may show gas in the wall as hyperechoic lesions with posterior dirty shadowing. Visualization of posterior wall of urinary bladder may be limited if gas is present in the anterior aspect of the bladder. Decubitus scan helps localizing gas, whether inside the bladder lumen or in the wall
• CT helps detecting complications such as perforation or emphysematous pyelonephritis

Reference

Gillenwater JY, et al. Adult and pediatric urology, volume 1, 2002.

Petersen RO, et al. Urologic pathology, 2009.