Gallbladder polyps and adenomyomatosis

Abstract

Incidental findings are commonly detected during examination of the gallbladder. Differentiating benign from malignant lesions is critical because of the poor prognosis associated with gallbladder malignancy. Therefore, it is important that radiologists and sonographers are aware of common incidental gallbladder findings, which undoubtedly will continue to increase with growing medical imaging use. Ultrasound is the primary imaging modality used to examine the gallbladder and biliary tree, but contrast-enhanced ultrasound and MRI are increasingly used. This review article focuses on two common incidental findings in the gallbladder; adenomyomatosis and gallbladder polyps. The imaging features of these conditions will be reviewed and compared between radiological modalities, and the pathology, epidemiology, natural history, and management will be discussed.

Figure 1.

(a) Greyscale ultrasound of the gallbladder demonstrating multiple hyperechoic foci in the gallbladder lumen. The solid dependent areas show post-acoustic shadowing consistent with stones (yellow arrow). Solid material at the fundus is more concerning being non-dependent with irregular margin (white arrow). MRI of the same patient (b) T2-HASTE, (c) T1-VIBE unenhanced, (d) T1-VIBE with gadolinium, (e) diffusion-weighted, and (f) apparent diffusion coefficient images demonstrate low T2/high T1 signal gallstones as well as low T2/low T1 signal asymmetric soft tissue along the lateral wall of the gallbladder (white arrows). The soft tissue shows post-contrast enhancement and strong diffusion restriction consistent with malignancy. The changes in the surrounding liver were attributed to local inflammation with no focal lesion seen on image c or d. Cholecystectomy was performed and histology confirmed gallbladder adenocarcinoma with no liver involvement. HASTE, half-Fourier single-shot turbo spin-echo; VIVE, volumetric interpolated breath-hold examination.

Figure 2.

(a, b) Greyscale ultrasound images in transverse and longitudinal sections demonstrating multiple subcentimetre echogenic foci within the gallbladder arising from the posterior wall. Appearances are typical of small polyps (although difficult to differentiate true polyps from pseudopolyps on imaging). The polyps are non-mobile with no associated posterior acoustic shadowing helping to differentiate from stones.

Figure 3.

Sludge mimicking gallbladder pathology. (a) Greyscale ultrasound image in longitudinal section demonstrating a non-mobile gallbladder “polypoid mass”. (b) Unenhanced T1-VIBE image from subsequent MRI shows layering of high T1 signal within the gallbladder lumen, typical of the paramagnetic effect caused by metal ions within sludge, with no evidence of a soft tissue mass (white arrow). VIBE, volumetric interpolated breath-hold examination

Figure 4.

(a) Greyscale ultrasound images in longitudinal section demonstrating a “polypoid mass” with twinkling artefact on Doppler assessment. The twinkling artefact is thought to result from the presence of either calcifications or cholesterol deposits and it mimics high-velocity blood flow which can raise concern for a soft tissue lesion. (b) Subsequent coronal contrast-enhanced CT demonstrates sludge in the gallbladder lumen, appearing mildly bright with intact gallbladder wall and no evidence of a mass.

Figure 5.

Contrast-enhanced ultrasound images for assessment of indeterminate gallbladder findings and problem solving. (a) Typical appearance of gallstones within the gallbladder lumen causing posterior acoustic shadowing. (b) A polypoid lesion at the posterior wall of the gallbladder on the greyscale image does not demonstrate enhancement on the corresponding contrast-enhanced image and is therefore in keeping with adherent sludge or pseudopolyp (white arrow).

Figure 6.

(a) Greyscale ultrasound demonstrating a large non-dependent polypoid hyperechoic focus within the gallbladder lumen adherent to the anterior wall. There is also echogenic debris within the gallbladder in a more dependent position along the posterior wall. Note the lack of internal vascularity, which should not be relied upon as a reassuring feature. MRI of the same lesion (b) T2-HASTE, (c) T1-VIBE unenhanced, (d) T1-VIBE with gadolinium, (e) diffusion-weighted, and (f) apparent diffusion coefficient images demonstrating the polypoid lesion with enhancement and diffusion restriction. No local invasion seen into the hepatic parenchyma. The gallbladder was resected and final histology showed a large adenomatous polyp with no malignant change. The patient had background PSC, which is a risk factor for gallbladder malignancy (note the dilated intrahepatic ducts). HASTE, half-Fourier single-shot turbo spin-echo; VIVE, PSC, primary sclerosing cholangitis; VIVE, volumetric interpolated breath-hold examination.

Figure 7.

Management algorithm for gallbladder polyps detected on TAUS. Reproduced from Foley et al with permission under a Creative Commons Attribution 4.0 International License. Copyright 2021. PSC, primary sclerosing cholangitis; TAUS, transabdominal ultrasound.

Figure 8.

(a) Axial contrast-enhanced CT showing discrete focal thickening of the gallbladder fundus with normal mucosal enhancement, typical of fundal adenomyomatosis. (b) Greyscale ultrasound confirms nodular, hyperechoic foci studding the wall of the gallbladder causing reverberation artefact of the cholesterol crystals trapped in the mucosal sinuses—the classical “comet-tail” artefact (white arrow). Comet tail artefact can also be a feature of pseudopolyps and cholesterol polyps.

Figure 9.

(a) Greyscale ultrasound showing anechoic cystic spaces in a thickened gallbladder fundus consistent with adenomyomatosis. (b) Axial contrast-enhanced CT also demonstrating cystic spaces within a thickened gallbladder fundus. Note the gallbladder mucosa enhances normally and appears intact. The cystic spaces are usually a sign of a benign process and are typical of adenomyomatosis.

Figure 10.

(a) Coronal contrast-enhanced CT, and (b, c) axial T2-HASTE MRI demonstrating classic “rosary bead” or “string of pearls” sign indicating the presence of Rokitansky-Aschoff sinuses within the thickened gallbladder wall seen in adenomyomatosis. Note the string of pearls appearance extends to involve the cystic duct in (c).