Acute emphysematous cholecystitis (AEC) and abscess in the liver: The sonogram of the right upper quadrant (see Image 1) demonstrates a curvilinear pattern of poorly marginated, high-level echoes outlining the gallbladder wall, a finding that suggests the presence of air (arrows). The image also shows high-level echoes in the liver parenchyma, another finding suggestive of air (arrowhead). The follow-up CT scan confirms these findings (see Image 2). Multiple foci of air are seen in the wall of the gallbladder (arrowheads), with inflammation of surrounding fat consistent with AEC. In addition, large focus of air is seen in the liver parenchyma with an associated hypoattenuating area consistent with an abscess (arrowhead).

AEC is a variant of acute cholecystitis distinguished by air in the gallbladder wall. It usually occurs in men older than 60 years who have predisposing factors of atherosclerotic disease, diabetes mellitus (20-50%), and other debilitating diseases. Patients with long-standing diabetes and an element of peripheral neuropathy may not complain of the classic symptom of right upper quadrant pain radiating to the back. Unlike other organs, the gallbladder lacks collateral blood flow, and it receives all of its vascular supply from the solitary cystic artery.

Calculous AEC with secondary inflammation and occlusion of the cystic artery accounts for 70-80% of observed cases. The rest of the cases result from acalculous AEC and are due to compromised flow through the cystic artery due to primary vascular occlusion, watershed hypotension, or secondary embolic disease. Regardless of the etiology, the result is the proliferation of gas-forming organisms in the lumen of the gallbladder with subsequent development of mural crepitus. Usual pathogenic isolates include Clostridium perfringes, Escherichia coli, Bacteroides fragilis, anaerobic staphylococci, and streptococci.

In the United States, AEC accounts for approximately 5000 cases, or 1% of all cases of acute cholecystitis, each year. CT scanning is superior to plain radiography and ultrasonography because of its nearly 100% sensitivity for the detection of air and its high specificity of the observed findings. AEC increases the surgical mortality risk compared with nonemphysematous cholecystitis. Mortality rates vary from 15-25% and are mainly secondary to sepsis and underlying comorbidities.



References

• Bloom AA, Prospere R: Emphysematous cholecystitis. eMedicine Journal [serial online]. Accessed June 27, 2005. Available at: http://www.emedicine.com/med/topic655.htm.
• Cakirer S, Demir K, Beser M: Case 1150. Acute emphysematous cholecystitis. European Association of Radiology Journal [serial online]. Accessed June 27, 2001. Available at: http://www.eurorad.org/case.php?id=1150.
• Kane RA, Costello P, Duszlak E: Computed tomography in acute cholecystitis: new observations. Am J Roentgenol AJR 1983 Oct;141(4):697-701.