Murphy's sign is a physical examination maneuver used to diagnose inflammation of the gallbladder or cholecystitis. It is performed by a doctor or healthcare provider by pressing down on the right upper quadrant of the abdomen under the ribcage while the patient takes a deep breath. If the patient experiences a sharp increase in pain and abruptly stops breathing during the maneuver, this is known as a positive Murphy's sign and can indicate inflammation of the gallbladder or acute cholecystitis.