What physical examination finding is most indicative of acute cholecystitis?

Murphy's sign is the physical examination finding that is most indicative of acute cholecystitis. This sign is elicited by having the patient take a deep breath while the examiner palpates the right upper quadrant of the abdomen. If the patient experiences pain and abruptly stops inhaling due to this discomfort, it suggests that the gallbladder is inflamed and is consistent with acute cholecystitis.

In contrast, the other signs listed are associated with different conditions. Psoas sign typically indicates irritation of the iliopsoas muscle due to an inflammatory process in the retroperitoneal area, often seen in cases of appendicitis or psoas abscess. Rovsing's sign is related to appendicitis as well, where palpation of the left lower quadrant causes pain in the right lower quadrant, indicating peritoneal irritation. Cullen's sign, characterized by periumbilical ecchymosis, is more indicative of hemorrhagic conditions, such as pancreatitis or ruptured ectopic pregnancy, rather than cholecystitis. Hence, Murphy's sign is the most specific for diagnosing acute cholecystitis.