Plain film radiographs have not indicated any fractures. At the time of admission, his abdomen has some bruising but no distension or tenderness. After 8 hours of observation, the nurses call the physician because the patient’s urine output has been decreasing steadily. His blood pressure is normal but lower than it was when he presented to the hospital, and he has slightly increased heart rate. His abdomen is now distended and tender. An intravenous fluid bolus of normal saline is performed, and his urine output increases to the normal range. The surgeon makes the diagnosis of hypovolumia that probably is due to intra-abdominal hemorrhage and prepares the patient for exploratory surgery.