- Benign hyperplastic cholecystosis
- Mural thickening with Rokitansky-Aschoff sinuses, comet tail artefact
Description
Adenomyomatosis of the gallbladder, also known as hyperplastic cholecystosis, is a benign condition characterised by the hyperplastic growth of the gallbladder mucosa and muscularis, leading to the formation of intramural diverticula known as Rokitansky-Aschoff sinuses.1 This hyperplastic change is often associated with chronic inflammation but is considered a non-neoplastic process. The term “adenomyomatosis” pertains to the involvement of glandular (adeno-) and muscular (-myomatosis) components of the gallbladder wall.
Pathogenesis
The exact pathogenesis of adenomyomatosis is not well understood, but it is frequently associated with chronic inflammation and increased gallbladder wall stress. The process involves hyperplasia of the mucosa and hypertrophy of the muscular layer, leading to the formation of epithelial invaginations or diverticula known as Rokitanksy-Aschoff sinuses, that penetrate into and sometimes through the muscular layer. Intraluminal cholesterol crystals and calculi may precipitate in the bile trapped in Rokitansky-Aschoff sinuses.
Subtypes
- Fundal type (localised) – Most common form, localised to the gallbladder fundus.
- Segmental type (annular) – Involves only a segment of the gallbladder, giving it an hourglass shape.
- Diffuse type (generalised) – Involves the entire gallbladder.
Epidemiology, Risk Factors & Associations
- Most commonly diagnosed in middle age, often incidentally.
- Often associated with gallstones and chronic cholecystitis.
- No significant gender or racial predilection.
Clinical Features
Adenomyomatosis is often asymptomatic and found incidentally on imaging performed for other reasons. When symptoms do occur, they mimic those of gallstones or cholecystitis:
- Episodic right upper quadrant abdominal pain
- Nausea
- Bloating
Complications
- Rarely, adenomyomatosis can lead to complications such as gallbladder obstruction or inflammation.
- Risk of malignant transformation is not definitively established.
Pathological Features
Histopathology
- Macroscopic: Areas of thickening in the gallbladder wall, sometimes forming a palpable mass.
- Microscopic: Proliferation of the mucosal epithelium with deep invagination into the muscularis, forming Rokitansky-Aschoff sinuses.
Serology
Biochemistry
Radiological Features
General Features
- Ultrasonography is the first-line investigation.
- Characteristic findings include wall thickening with comet tail reverberation artefacts from cholesterol crystals in Rokitansky-Aschoff sinuses.
CT
- Non-contrast: May show wall thickening.
- C+ Venous: Mural thickening may enhance homogeneously. Rosary sign caused by thin layer of enhancing epithelium lining the intramural diverticula, surrounded by hypo-enhancing hypertrophied muscularis.
MRI
- Useful in differentiating adenomyomatosis from gallbladder malignancies.
- T2: Shows hyperintense intramural cystic spaces/diverticula/Rokitansky-Aschoff sinuses. Pearl necklace sign refers to the curvilinear arrangement of multiple rounded hyperintense intramural cavities. Mural thickening. Hour-glass configuration in annular types. Low T2 signal may represent bile.
- T1 Gd+: No enhancement.
- MRCP: Can be useful for detailed bile duct evaluation.
US
- B-mode: Shows gallbladder wall thickening with intramural cystic spaces.
- Colour: Doppler typically shows no flow within the sinuses. Comet-tail artefact echogenic intramural foci from which emanate V-shaped comet tail reverberation artefacts representing cholesterol crystals within the lumina of Rokitansky-Aschoff sinuses
Grading and Staging
There is no grading or staging system for adenomyomatosis as it is a benign condition.
Diagnosis
Diagnosed primarily through imaging, particularly ultrasonography, with the identification of gallbladder wall thickening and characteristic “comet tail” artifacts.
Differential Diagnosis
- Gallbladder cancer – Includes adenocarcinoma, cholangiocarcinoma, metastatic disease. Features irregular wall thickening, more invasive appearance.
- Chronic cholecystitis – lacks the specific imaging features of Rokitansky-Aschoff sinuses.
- Xanthogranulomatous cholecystitis – can present with similar imaging features but typically more inflammatory changes.
- Phrygian Cap – Normal variant.
Management
No treatment is necessary for asymptomatic adenomyomatosis. In symptomatic cases, cholecystectomy may be considered, particularly to exclude malignancy.