Adenomyomatosis, which is also known as adenomyoma or adenomyomatous hyperplasia of the gallbladder, is one of the two hyperplastic cholecystoses. The other hyperplastic cholecystosis is cholestesterolosis, also known as "strawberry gallbladder." Adenomyomatosis is a benign condition that is pathologically characterized by hyperplasia of the gallbladder wall mucosa and muscularis propria, with pathognomonic epithelial invaginations forming cystic pockets (Rokitansky-Aschoff sinuses). These sinuses may contain calculi and/or cholesterol crystals. The gallbladder wall thickening, Rokitansky-Aschoff sinuses, and the calculi and/or cholesterol crystals that are often found in sinuses characterize the imaging appearance of adenomyomatosis. Sometimes, particularly when the characteristic imaging findings are not present, adenomyomatosis can be difficult to distinguish from gallbladder cancer based on the diagnostic imaging findings. Adenomyomatosis is often asymptomatic and incidentally detected, requiring no specific treatment. Adenomyomatosis also can be associated with right upper quadrant pain. In cases where it is difficult to distinguish adenomyomatosis from gallbladder cancer or when adenomyomatosis is associated with right upper quadrant pain, this condition may be treated with a cholecystectomy.
Adenomyomatosis has been found in 1% to 8.7% of cholecystectomy specimens. Although there is a wide age range of patients who are 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. Specifically, some authors state that adenomyomatosis is more prevalent in women than men (3:1). Other authors state that the prevalence is similar in men and women. There is no known race predilection.
Hyperplasia of the gallbladder wall is seen, with characteristic Rokitansky-Aschoff sinuses. Calculi and cholesterol crystals form within the sinuses. The cause of the hyperplasia and sinus formation is unknown, although reactive changes to chronic inflammation have been proposed. The hypothesis of chronic inflammation as the etiology of adenomyomatosis is supported by the fact that patients are most frequently diagnosed in their 50s.
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, having a papillary appearance, and/or showing metaplasia. More rarely, there is a perineural and intraneural invasion into the subserosa.
Most cases of 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.
Abdominal ultrasound is the suggested diagnostic imaging test when a patient presents with right upper quadrant pain. Sometimes the ultrasound findings are characteristic of adenomyomatosis, and a confident diagnosis can be made. However, if gallbladder wall thickening is seen on ultrasound but cannot be well characterized, a magnetic resonance imaging (MRI) scan of the abdomen may be helpful for further characterization. If gallbladder wall thickening is seen incidentally on a computed tomography (CT) scan, an ultrasound and/or an MRI scan may be helpful for further characterization. Regardless of the modality used, the appearance of adenomyomatosis on imaging is related to the presence of characteristic gallbladder wall thickening, Rokitansky-Aschoff sinuses, and the calculi and/or cholesterol crystals that are often found in sinuses. By ultrasound, 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.
Of the ultrasound findings described, the echogenic foci with associated V-shaped comet tail artifacts have been described as specific for adenomyomatosis. On MRI, adenomyomatosis shows gallbladder wall thickening and T2 hyperintense intramural cystic spaces. Calculi are seen as signal voids. The T2 hyperintense cystic spaces can align in a curvilinear fashion, producing a “pearl necklace sign.” On CT imaging, nonspecific gallbladder wall thickening and wall enhancement are sometimes seen. The “rosary sign” can be present, which is caused by a thin layer of enhancing epithelium lining the intramural diverticula, which is surrounded by hypo-enhancing hypertrophied muscularis, causing the gallbladder wall to resemble a rosary.
In cases where it is difficult to distinguish adenomyomatosis from gallbladder cancer or when adenomyomatosis is associated with right upper quadrant pain, adenomyomatosis may be treated with a cholecystectomy. If adenomyomatosis is found incidentally and is asymptomatic, no treatment is recommended.
The differential diagnosis for adenomyomatosis of the gallbladder includes gallbladder malignancies (e.g., adenocarcinoma, cholangiocarcinoma, metastatic disease), gallbladder polyps, and benign gallbladder tumors (e.g., adenoma). Normal variant appearances of the gallbladder, such as a gallbladder folds (“Phrygian cap”), are also within the differential diagnosis.
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. In fact, 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 important to ensure that the imaging diagnosis of adenomyomatosis is confident before dismissing this abnormality.
Adenomyomatosis of the gallbladder is frequently asymptomatic and detected incidentally. However, adenomyomatosis can also be a cause of right upper quadrant pain. Adenomyomatosis is characterized by gallbladder wall thickening and the formation of Rokitansky-Aschoff sinuses, which can collect internal cholesterol crystals and stones. The appearance of adenomyomatosis on diagnostic imaging is closely related to these histopathological changes (gallbladder wall thickening/intramural cystic spaces/cholesterol crystals). On ultrasound, the presence of echogenic foci with V-shaped comet tail artifacts in the gallbladder wall is thought to be specific for adenomyomatosis. Adenomyomatosis is frequently asymptomatic and, in those cases, requires no treatment. However, adenomyomatosis can sometimes be difficult to distinguish from gallbladder cancer. Therefore, in cases where there is right, upper quadrant abdominal pain or where a gallbladder abnormality/gallbladder wall thickening cannot be confidently described as adenomyomatosis rather than gallbladder malignancy, cholecystectomy may be indicated.
Adenomyomatosis of the gallbladder is a rare presentation but can be mistaken for several other GI tract disorders. Because the condition is benign, it is important for the primary care provider or nurse practitioner to consult with a gastroenterologist or general surgeon on the management. Most cases do not require any treatment. However, if the RUQ pain persists, the onus is on the healthcare provider to rule out a malignancy.