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Adenomyomatosis of the gallbladder

Adenomyomatosis of the gallbladder is a hyperplastic cholesterolosis of the gallbladder wall. It is a relatively common and benign condition.

Epidemiology

Adenomyomatosis is relatively common, found in 1-9% of all cholecystecomy specimens1-3 and is typically seen in patients in their 5th decade. The incidence increases with age which may be the result of protracted inflammation (see below). There is a female predilection (M:F = 1:3). 

It is most often an incidental finding, has no intrinsic malignant potential, and usually requires no treatment.

Clinical presentation

Adenomyomatosis per se is usually asymptomatic. It is however frequently associated with chronic biliary inflammation, most commonly gallstones (25-75%) but also seen in cholesterolosis (33%) and pancreatitis2.

Pathology

Adenomyomatosis is one of the hyperplastic cholecystoses. There is hyperplasia of the wall with formation of intramural mucosal diverticula (Rokitansky-Aschoff sinuses) penetrating into the muscular wall of the gallbladder, with or without gallbladder wall thickening. Cholesterol accumulation in adenomyomatosis is intraluminal, as cholesterol crystals precipitate in the bile trapped in Rokitansky-Aschoff sinuses (intramural diverticula lined by mucosal epithelium).

Radiographic features

Three morphological types of adenomyomatosis are described:

  1. generalised (diffuse)
  2. segmental (annular)
  3. fundal (localised) - also termed adenomyoma
Ultrasound
  • mural thickening (diffuse, focal, annular)
  • comet-tail artifact - echogenic intramural foci from which emanate V-shaped comet tail reverberation artifacts are highly specific for adenomyomatosis, representing the unique acoustic signature of cholesterol crystals within the lumina of Rokitansky-Aschoff sinuses 4
CT
  • abnormal gallbladder wall thickening and enhancement are common but non-specific CT features of adenomyomatosi.
  • Rokitansky-Aschoff sinuses of sufficient size can be visualized; a CT rosary sign has been described, formed by enhancing epithelium within intramural diverticula surrounded by the relatively unenhanced hypertrophied gallbladder muscularis
Oral cholecystogram and MRCP

Historically oral cholecystograms were performed, however due to low sensitivity and a high rate of contrast allergies it has now largely been replaced by MRCP which does not rely on contrast opacification of the lumen of the gallbladder. 

MRCP would be also to detect :

  • mural thickening
  • focal sessile mass
  • pearl necklace sign (fluid filled intramural diverticula)
  • hourglass configuration in annular types
MRI
  • The pearl necklace sign alludes to the characteristically curvilinear arrangement of multiple rounded hyperintense intraluminal cavities visualized at T2-weighted MR imaging and MR cholangiopancreatography of adenomyomatosis 4.

Treatment and prognosis

In general cholecystectomy is performed as a result of one or more of the following:

  • patient symptomatic with right upper quadrant pain (often due to gallstones)
  • appearances (especially when focal) may be difficult to distinguish from malignancy

Differential diagnosis

General imaging differential considerations include

Exclusion of gallbladder cancer may be most problematic in segmental and focal cases. Focal adenomyomatosis may appear as a discrete mass, known as an adenomyoma.

Metabolic characterisation with PET may be a useful adjunct in problematic cases 4.

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