Adenomyomatosis

Etiology

The cause of adenomyomatosis is unknown, although some have proposed that it is a response to chronic inflammation of the gallbladder. Since patients are most frequently diagnosed in their 50s, the idea of chronic inflammation as the etiology seems plausible.[3][4] Adenomyomatosis of the gallbladder was initially recognized as a precancerous lesion; recent studies currently consider it a benign gallbladder alteration often associated with cholecystitis and cholecystolithiasis. Gallbladder carcinoma is an extremely malignant disease with a 5-year survival rate of less than 5 percent.[4]

Epidemiology

Adenomyomatosis has been found in 1 to 8.7 percent of cholecystectomy specimens. Although there is a wide age range of patients diagnosed with adenomyomatosis, patients are most frequently diagnosed in their 50s. There are discrepancies in the literature regarding the prevalence of adenomyomatosis in males and females. It is well known that adenomyomatosis is more prevalent in women than in men (3 to 1). Other authors declare that the prevalence is similar in men and women. There is no known race predilection.[5]

Pathophysiology

Hyperplasia of the wall of the gallbladder is seen with characteristic Rokitansky-Aschoff sinuses. Another finding is the presence of calculi and cholesterol crystals within the sinuses. The cause of hyperplasia and sinus formation is unknown, although reactive changes to chronic inflammation have been proposed. The hypothesis of chronic inflammation as the underlying cause of adenomyomatosis is supported by the fact that patients are most frequently diagnosed in their 50s.

Histopathology

Several Rokitansky-Aschoff sinuses are seen on histopathologic examination of an adenomyomatosis specimen. Thickening of the subserosa is seen. Nerve trunks are often seen in the subserosa. There is often smooth muscle hypertrophy in the gallbladder wall. The surface epithelium has a variable appearance, sometimes showing reactive epithelial changes, papillary appearance, or metaplasia. More rarely, there is a perineural and intraneural invasion into the subserosa.

History and Physical

Most patients with adenomyomatosis of the gallbladder are thought to be asymptomatic. Right upper quadrant pain has been seen in association with adenomyomatosis. Some patients have coexistent cholelithiasis, which can be symptomatic.

Evaluation

During the evaluation of patients presenting with right upper quadrant abdominal pain, ultrasound should be the primary modality to assess such patients initially. The ultrasound findings could be characteristic of adenomyomatosis, and it could greatly help providers reach a diagnosis. Sometimes, gallbladder wall thickening is seen on ultrasound but cannot be well characterized. In such a case, further characterization could be achieved via magnetic resonance imaging of the abdomen. Gallbladder wall thickening could be an incidental finding on a computed tomography scan; an ultrasound or a magnetic resonance imaging scan may be useful for further characterization. The characteristic findings of adenomyomatosis are gallbladder wall thickening, Rokitansky-Aschoff sinuses, and the calculi or cholesterol crystals often found in sinuses. On ultrasound scanning, adenomyomatosis is seen as gallbladder wall thickening, intramural cystic spaces, and echogenic intramural foci (cholesterol crystals in the Rokitansky-Aschoff sinuses) that show comet tail artifacts. In most cases, all of the characteristic findings are not present.[6][7][8]

Of the ultrasound findings described, the echogenic foci with associated V-shaped comet tail artifacts have been described as specific for adenomyomatosis (see Image. Adenomyomatosis). On magnetic resonance imaging, adenomyomatosis shows gallbladder wall thickening and T2 hyperintense intramural cystic spaces. Calculi are seen as signal voids. The T2 hyperintense cystic areas can align in a curvilinear fashion, producing a “pearl necklace sign.” On computed tomography imaging, nonspecific gallbladder wall thickening and wall enhancement are sometimes seen. The “rosary sign” can be present, caused by a thin layer of enhancing epithelium lining the intramural diverticula, surrounded by hypo-enhancing hypertrophied muscularis, causing the gallbladder wall to resemble a rosary.

Treatment / Management

In cases where it is difficult to distinguish adenomyomatosis from gallbladder cancer or adenomyomatosis is associated with right upper quadrant pain, adenomyomatosis may be treated with cholecystectomy. If adenomyomatosis is found incidentally and is asymptomatic, no treatment is recommended.[9][10]

Differential Diagnosis

The differential diagnosis for adenomyomatosis of the gallbladder includes gallbladder malignancies (eg, adenocarcinoma, cholangiocarcinoma, metastatic disease), gallbladder polyps, and benign gallbladder tumors (eg, adenoma). Normal variant appearances of the gallbladder, such as gallbladder folds (“Phrygian cap”), are also within the differential diagnosis.

Prognosis

Apart from the right upper quadrant abdominal pain that some patients experience, this is a benign condition and carries a good prognosis. Not all patients are symptomatic. Adenomyomatosis is often asymptomatic and detected incidentally. It is important to note that gallbladder malignancy can have a similar appearance to adenomyomatosis on imaging, and gallbladder carcinoma has a much worse prognosis than adenomyomatosis. Therefore, it is vital to ensure that the imaging diagnosis of adenomyomatosis is confident before dismissing this abnormality.

Complications

Adenomyomatosis has not been definitively linked to cancer but can have inflammatory complications.