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Type:
Educational Exhibit
Keywords:
Diagnostic procedure, Ultrasound, MR, CT, Biliary Tract / Gallbladder, Abdomen, Calcifications / Calculi
Authors:
M. Bonatti1, N. Vezzali1, F. Ferro1, L. Gentile1, R. Pozzi-Mucelli2, G. Bonatti1; 1Bolzano/IT, 2Verona/IT
DOI:
10.1594/ecr2014/C-0198
Background
GALLBLADDER ADENOMYOMATOSIS: WHAT IS IT?
Gallbladder adenomyomatosis (GA) is an alteration of gallbladder wall characterized by benign hyperplastic epithelial proliferation associated with hypertrophy of the muscularis propria.
The excessive epithelial proliferation leads to the formation up to 8 mm large epithelium-lined diverticular pouches,
the so-called Rokitansky-Aschoff sinuses (RAS),
which extend profoundly within the hypertrophic muscular layer.
The content of Rokitansky-Aschoff sinuses originally consists of clear bile,
but it undergoes a progressive concentration process that finally leads to cholesterine crystals precipitation.
Cholesterine crystals induce a chronic inflammatory reaction that may sometimes lead to intramural dystrophic calcifications development.
Gallbladder adenomyomatosis represents a frequent finding in cholecystectomy specimen,
with a reported incidence of 1-9% in pathology series,
but it is a relatively uncommon finding in radiological reports. This discrepancy may be a consequence of the slight conspicuity of many cases of histologically diagnosed GA,
that is beyond the spatial resolution of currently available radiological techniques,
but it might also reflect an unsatisfactory knowledge of this pathology among radiologists.
The pathogenesis of GA is not well understood and even the association of GA with chronic biliary inflammation and gallstones,
that has been postulated in pathology series,
is probably only a consequence of selection bias.
Although neoplastic lesions may also arise from its hyperplastic epithelium,
GA is not a pre-malignant lesion,
showing no higher neoplastic potential than that of normal gallbladder epithelium.
Adenomyomatosis can involve the gallbladder according to four main patterns (Fig.
1):
- Localized pattern (a) is the most common one and represents a focal adenomyomatous proliferation,
usually involving gallbladder fundus,
with the remaining gallbladder walls appearing physiologically thin.
The overall gallbladder shape is usually normal,
but a focal shrinkage may be observed in large lesions.
- Annular pattern (b) is usually considered the initial form of segmental GA (c).
Adenomyomatous proliferation involves a “ring” of gallbladder wall,
usually in the middle of the organ,
producing an “hourglass shaped” gallbladder.
If the proliferation becomes conspicuous,
gallbladder lumen may be subdivided into two independent compartments; as a consequence,
biliary sludge and stones may accumulate into the isolated fundal compartment,
whereas the proximal compartment may even show a completely clear biliary content.
- Segmental pattern (c) is represented by an adenomyomatous proliferation involving the distal portion of the gallbladder (the distal part of the body and the fundus) that,
therefore,
appears contracted,
whereas the proximal portion of the body and gallbladder neck show a normal shape .
- Diffuse pattern (d) represents the involvement of the whole gallbladder walls by adenomyomatous proliferation; therefore the gallbladder appears overall contracted,
even if the patient has regularly fasted.
Imaging clue for radiological diagnosis of gallbladder adenomyomatosis is the detection of Rokitansky-Aschoff sinuses within a focal or diffuse gallbladder wall thickening: these findings enable the differential diagnosis with early stage wall-thickening type gallbladder adenocarcinoma,
in which cystic spaces are not present within wall thickening.
Differential diagnosis with gallbladder carcinoma is fundamental being gallbladder adenomyomatosis an absolutely benign lesion,
necessitating of no surgical nor medical treatment.