Gallbladder adenomyomatosis: imaging findings, tricks and pitfalls

Abstract

Gallbladder adenomyomatosis (GA) is a benign alteration of the gallbladder wall that can be found in up to 9% of patients. GA is characterized by a gallbladder wall thickening containing small bile-filled cystic spaces (i.e., the Rokitansky-Aschoff sinuses, RAS). The bile contained in RAS may undergo a progressive concentration process leading to crystal precipitation and calcification development. A correct characterization of GA is fundamental in order to avoid unnecessary cholecystectomies. Ultrasound (US) is the imaging modality of choice for diagnosing GA; the use of high-frequency probes and a precise focal depth adjustment enable correct identification and characterization of GA in the majority of cases. Contrast-enhanced ultrasound (CEUS) can be performed if RAS cannot be clearly identified at baseline US: RAS appear avascular at CEUS, independently from their content. Magnetic resonance imaging (MRI) should be reserved for cases that are unclear on US and CEUS. At MRI, RAS can be identified with extremely high sensitivity, but their signal intensity varies widely according to their content. Positron emission tomography (PET) may be helpful for excluding malignancy in selected cases. Computed tomography (CT) and cholangiography are not routinely indicated in the suspicion of GA.

Teaching points: 1. Gallbladder adenomyomatosis is a common benign lesion (1-9% of the patients). 2. Identification of Rokitansky-Aschoff sinuses is crucial for diagnosing gallbladder adenomyomatosis. 3. Sonography is the imaging modality of choice for diagnosing gallbladder adenomyomatosis. 4. Intravenous contrast material administration increases ultrasound accuracy in diagnosing gallbladder adenomyomatosis. 5. Magnetic resonance is a problem-solving technique for unclear cases.

Keywords: Gallbladder; Gallbladder diseases; Magnetic resonance imaging; Rokitansky–Aschoff sinuses of the gallbladder; Ultrasonography.

Fig. 1

Gallbladder adenomyomatosis: pathology findings. Macroscopically (a) GA is characterized by gallbladder wall thickening (lines) containing small cystic spaces (arrows) representing Rokitansky–Aschoff sinuses. Microscopically, at low (2×) magnification (b and c), wall thickening is due to hyperplasia of the muscular layer (lines); a variable degree of epithelial proliferation (arrowheads) is also appreciable and epithelium-lined cystic spaces, representing RAS (arrows), can be observed within the muscular layer. Biliary stones (star) may be present within RAS. At high (40×) magnification (d), the proliferative mucosal glandular component that leads to epithelial infolding (arrowheads) and RAS formation is better recognizable

Fig. 2

Gallbladder adenomyomatosis: patterns of gallbladder wall involvement. Drawings showing localized gallbladder adenomyomatosis (a), annular gallbladder adenomyomatosis (b), segmental gallbladder adenomyomatosis (c) and diffuse gallbladder adenomyomatosis (d)

Fig. 3

Gallbladder cancer: gallbladder adenocarcinoma may involve the gallbladder wall with various patterns. This case of gallbladder adenocarcinoma with annular involvement (white lines) can be differentiated from an adenomyomatosis because of the absence of cystic spaces (RAS) within the wall thickening on ultrasound (a) and because of the presence of hypodense tissue between the gallbladder wall and the adjacent liver (arrows) on contrast-enhanced CT (b)

Fig. 4

Gallbladder adenomyomatosis: typical oral cholecystography findings. In this case of fundal type GA, RAS (arrows) are filled by contrast material as a consequence of their communication with the gallbladder lumen. Courtesy of Marco Ferigato, radiographer at Bolzano Central Hospital

Fig. 5

Gallbladder adenomyomatosis: typical US findings in annular type (a), fundal type (b and d), segmental type (c) and diffuse type (e). Gallbladder wall thickening (line) is always seen in gallbladder adenomyomatosis, but it is non-specific. On b-mode images, Rokitansky–Aschoff sinuses (arrows) typically appear anechoic (a), but they can also appear hyperechoic if cholesterine crystals or calcifications are present (b and c). Comet-tail reverberation artefacts (Figures b and e, arrowheads) or acoustic shadowing (c, arrowheads) are usually observed profoundly in RAS. On colour Doppler images (d), twinkling artefacts (arrowheads) may be observed profoundly in RAS

Fig. 6

US of gallbladder adenomyomatosis: use of different frequencies probes. In this patient with diffuse GA, the gallbladder wall is poorly evaluable by means of a conventional 5-MHz convex probe (a). Using a high-resolution 7-MHz linear probe (b) hyperechoic Rokitansky–Aschoff sinuses (arrows) can be highlighted within a diffusely thickened gallbladder wall; moreover, the serosa maintains sharp margins (arrowheads)

Fig. 7

US of gallbladder adenomyomatosis: differential diagnosis with cholesterine polyps. Cholesterine polyps (arrow) must not be confused with gallbladder adenomyomatosis (line); however, the two alterations may coexist in the same patient

Fig. 8

US of gallbladder adenomyomatosis: pitfalls. Cholesterine crystals may accumulate within large Rokitansky–Aschoff sinuses, determining a hyperechoic aspect (arrows) without acoustic shadowing

Fig. 9

Gallbladder adenomyomatosis: typical contrast-enhanced ultrasound (CEUS) findings. On CEUS, the thickened gallbladder wall shows discrete contrast enhancement, whereas Rokitansky–Aschoff sinuses (arrows) appear as avascular structures during every phase of the exam

Fig. 10

Gallbladder adenomyomatosis: typical MRI findings. On MRI, GA can be identified as a mural thickening (line) containing small T2-hyperintense spaces representing RAS (arrows). RAS can be better identified on fat-saturated T2-weighted images (b) than on non-fat-saturated ones (a)

Fig. 11

MRI of gallbladder adenomyomatosis: T1-hyperintense Rokitansky–Aschoff sinuses. Rokitansky–Aschoff sinuses (arrow) may appear hyperintense on T1-weighted images if containing concentrated bile or calcifications

Fig. 12

MRI of gallbladder adenomyomatosis: the pearl necklace sign. On heavily T2-weighted images, like in this maximum intensity projection reconstruction of a volumetric MRCP, a lot of RAS can be identified one next to the other around the gallbladder, leading to the so-called pearl necklace sign

Fig. 13

Gallbladder adenomyomatosis: typical CT findings. At CT, gallbladder adenomyomatosis is characterized by mural thickening (line) containing cystic spaces representing Rokitansky–Aschoff sinuses (arrows). Large RAS can be easily identified on 3-mm-thick reconstructions (a), whereas for identifying smaller RAS thin slices evaluation is crucial (b)

Fig. 14

CT of gallbladder adenomyomatosis: intramural calcifications. CT accurately depicts intramural calcifications (arrows) that may develop within Rokitansky–Aschoff sinuses and which are pathognomonic for gallbladder adenomyomatosis

Fig. 15

Gallbladder adenomyomatosis: typical PET-CT findings. Gallbladder adenomyomatosis (circle) usually shows an F-18FDG uptake equal or lower than the adjacent liver