Neutrophils are seen infiltrating the mucosa and submucosa of the gallbladder in this patient with acute cholecystitis. This patient's acute inflammatory process was evidenced by right upper quadrant abdominal pain with tenderness on palpation.

Question: What may have been present within the gallbladder to elicit this inflammatory response?

AnswerMost cases of cholecystitis occur in association with cholelithiasis (gallstones).