A 47-year-old female patient presents to the emergency department with severe right upper quadrant pain that began 2 hours after eating a large, fatty meal. Which clinical manifestation would provide the strongest evidence for this diagnosis?

Murphy's sign is the most specific clinical assessment finding for acute cholecystitis, involving inspiratory arrest when the examiner palpates the right subcostal area during deep inspiration due to inflamed gallbladder contact with the examining hand. This is consistent with the patient's presentation of severe right upper quadrant pain after a fatty meal. Rebound tenderness in the left lower quadrant (option 1) is more indicative of conditions like diverticulitis or colitis, not cholecystitis. Clay-colored stools and dark amber urine (option 2) suggest biliary obstruction or liver issues but are less specific and may occur later in cholecystitis. Cramping pain that moves from periumbilical to right lower quadrant (option 4) is classic for appendicitis, not cholecystitis.