A 59 year old man arrives in the E.R. at 2 AM, accompanied by his wife who is wearing curlers on her hair and a robe over her nightgown. He has abdominal pain that began about one hour ago, and is now generalized, constant and extremely severe. He lies motionless in the stretcher, is diaphoretic and has shallow, rapid breathing. His abdomen is rigid, very tender to deep palpation, and has guarding and rebound tenderness in all quadrants.