Adenomyomatosis of the gallbladder is a hyperplastic growth of the internal wall of the gallbladder causing intramural diverticula.1
Cholesterol deposits are then trapped in the diverticula and are responsible for the comet tail artifacts seen on ultrasound.
Focal adenomyomatosis is a relatively common finding seen in about 9% of all cholecystectomy specimens.2
Thought to be a reactive change secondary to chronic inflammation.
Difficult to differentiate from malignancy so sometimes leads to cholecystectomy.3
Initially can be confused with emphysematous cholecystitis (as I initially thought in this patient). Cholesterol crystals however give a characteristic V-shaped comet tail as opposed to a linear reverberation artifact or “dirty” shadow of emphysematous cholecystitis.
If unsure of diagnosis, CT scan is more specific for emphysematous cholecystitis.4
Boscak AR, Al-hawary M, Ramsburgh SR. Best cases from the AFIP: Adenomyomatosis of the gallbladder. Radiographics. 2006;26(3):941-6.
Poonam Y, Ashu S, Rohini G. Clinics in diagnostic imaging (121). Gallbladder adenomyomatosis. Singapore Med J. 2008;49(3):262-4.
Raghavendra BN, Subramanyam BR, Balthazar EJ, Horii SC, Megibow AJ, Hilton S. Sonography of adenomyomatosis of the gallbladder: radiologic-pathologic correlation. Radiology. 1983;146(3):747-52.
Sunnapwar A, Raut AA, Nagar AM, Katre R. Emphysematous cholecystitis: Imaging findings in nine patients. Indian J Radiol Imaging. 2011;21(2):142-6.