What is adenomyomatosis of the gallbladder?

Adenomyomatosis of the Gallbladder

Adenomyomatosis of the gallbladder is a benign, degenerative condition characterized by proliferation of the gallbladder mucosa forming invaginations and diverticula (Rokitansky-Aschoff sinuses) that penetrate a thickened muscular layer, which can occasionally cause symptoms but has minimal malignancy risk in most forms. 1, 2

Definition and Pathology

Adenomyomatosis is characterized by:

• Excessive epithelial proliferation with hypertrophy of the muscularis propria
• Formation of mucosal outpouchings (intramural diverticula) known as Rokitansky-Aschoff sinuses (RAS)
• Thickening of the gallbladder wall with cystic spaces within the wall 3, 2

Classification

Adenomyomatosis occurs in three distinct types:

1. Fundal type: Focal thickening limited to the gallbladder fundus
2. Segmental type: Circumferential wall thickening creating separate compartments
3. Diffuse type: Generalized thickening and irregularity throughout the gallbladder wall 2

Diagnostic Features

Adenomyomatosis has characteristic imaging findings:

• Ultrasound: Thickened gallbladder wall containing small cystic spaces with "comet-tail" artifacts and "twinkling" artifacts on Doppler
• MRI: "Pearl-necklace sign" representing the Rokitansky-Aschoff sinuses
• CT: "Rosary sign" showing the intramural diverticula 1, 2

When evaluating gallbladder lesions, it's crucial to differentiate adenomyomatosis from other conditions such as:

• Gallbladder polyps
• Tumefactive sludge
• Gallbladder carcinoma 1

Clinical Significance

Most patients with adenomyomatosis remain asymptomatic, with the condition discovered incidentally during imaging for other reasons. However:

• Some patients may experience dull right upper quadrant pain 3, 4
• The condition can coexist with gallstones, which may cause typical biliary symptoms
• Segmental adenomyomatosis carries a slightly higher risk of malignancy than other types 2

Management Approach

Management depends on symptoms and type:

• Symptomatic adenomyomatosis: Cholecystectomy is recommended for patients with persistent symptoms regardless of type 2
• Asymptomatic adenomyomatosis:
  • Fundal type: Can be safely monitored with ultrasound
  • Segmental type: Consider cholecystectomy due to increased malignancy risk
  • Diffuse type: Consider cholecystectomy as coexisting malignancy may be difficult to visualize 2

Important Considerations

• Adenomyomatosis must be distinguished from gallbladder polyps, which have different management algorithms
• When diagnosis is uncertain, contrast-enhanced ultrasound (CEUS) or MRI can help differentiate adenomyomatosis from other gallbladder pathologies 1
• The Society of Radiologists in Ultrasound (SRU) consensus recommends that when a gallbladder lesion cannot be clearly distinguished between adenomyomatosis and a polyp, further characterization with CEUS or MRI should be pursued 1

Pitfalls and Caveats

• Adenomyomatosis can mimic gallbladder malignancy on some imaging studies
• The optimal frequency and duration of ultrasound monitoring for asymptomatic fundal adenomyomatosis remains undefined 2
• When diagnostic uncertainty exists, cholecystectomy should be considered to avoid missing a potential malignancy 2
• Adenomyomatosis is rarely a premalignant condition, but chronic inflammation may theoretically lead to dysplastic changes 4, 5