Cholesterolosis is a part of the spectrum of degenerative and proliferative changes seen in the gallbladder, termed as hyperplastic cholecystosis, the other variant being adenomyosis. These changes are more commonly seen in the females, in the 4th and 5th decades and are usually asymptomatic. These changes are detected incidentally in 30-50% of cholecystectomy specimens.
The normal gallbladder wall histologically is comprised of a mucosa, lamina propria, muscle layer and connective tissue. Cholesterolosis results from abnormal deposits of cholesterol esters in macrophages within the lamina propria [foam cells] and in mucosal epithelium. The gallbladder may be affected in a patchy localized or diffuse form. The latter macroscopically appears as a bright red mucosa with yellow mottling [due to lipid], hence the term ‘strawberry gallbladder.’ In its localized form, cholesterolosis may present as multiple, very small polyps arising from the non-dependent wall, which may not be visualized radiologically. These polyps vary in size from 1-10 mm.
Ultrasound imaging of cholesterolosis is very definitive in its appearance. The polyps can be visualized as brightly echogenic non-mobile masses, with a ring down/comet tail or reverberation artifact. These masses do not show shadowing, and there is usually no associated wall thickening. This condition is not associated with an increased risk of malignancy and there is no association noted with cholelithaisis and cholecystitis. Increased serum cholesterol level does not predispose to this condition. It is also not related to diabetes mellitus, atherosclerosis and hyperconcenteration of cholesterol in the bile. If the polyps are small, the patient may simply be followed up; larger polyps need elective cholecystectomy, if symptomatic. The main concern is to rule out gallbladder malignancy.
Adenomyomatosis occurs as a part of same spectrum of degenerative changes as cholesterolosis, is radiologically similar to it, and hence, sometimes it is difficult to distinguish between the two. The two conditions may coexist. Adenomyomatosis occurs secondary to hyperplasia of mucosal and muscular elements, and shows Rokitansky-Aschoff sinuses, which are intramural diverticuli. These sinuses may contain cholesterol crystals, which give the reverberation artifact. There is usually associated gallbladder wall thickening.
CT scan may show a thickened gallbladder wall, with a rosary sign in adenomyomatosis [enhancing mucosal epithelium with intramural diverticuli surrounded by non-enhancing hypertrophied muscle layer of gallbladder]. It mainly helps to distinguish it from gallbladder malignancy. MRI aids in distinguishing cholesterolosis from adenomyomatosis. Nuclear scans [18-FDG] help in distinguishing small cholesterol polyps [no uptake] from gallbladder malignancy [which shows uptake].