A 69-year-old man was admitted to the hospital because of severe abdominal pain.The patient had become anorectic two days before admission. On the next day he had diffuse, dull abdominal pain with nausea and "dry heaves." That evening he passed a formed brown stool, followed by flatus. He came to the hospital.The patient was a retired boilermaker with a complex medical history of repeated bouts of deep venous thrombosis beginning at the age of 25 years. He also had a history of hypertension, hyperlipidemia, and exposure to asbestos. A stroke and silent anterior and inferior myocardial infarctions had occurred many years earlier, followed by chronic congestive heart failure. Ligation and stripping of veins in the left leg had been performed, as well as bilateral total knee replacements, an inguinal herniorrhaphy, and a hemorrhoidectomy. Seven years before admission, deep venous thrombosis with pulmonary embolism occurred, and a filter was inserted in the inferior vena cava. A left nephrectomy was performed for a renal-cell carcinoma several months later. A cerebral transient ischemic attack occurred three years before admission. A left carotid endarterectomy and clipping of an aneurysm in the anterior communicating artery were performed the same year.Twenty-six months before admission, a thallium stress test showed slight septal and anterior redistribution, with a fixed apical defect. One year before admission, a cardiac ultrasonographic study showed that the left ventricular ejection fraction was 45 percent, with septal and apical akinesis. Recent pulmonary-function studies showed that the forced expiratory volume in one second was 43 percent of the predicted value. Seven weeks before admission, an evaluation for sleep apnea showed that the oxygen saturation declined to 84 percent during sleep, and oxygen (2 liters per minute) was prescribed for use during sleep and physical exertion.The patient was sedentary because of exertional dyspnea. His medications comprised inhaled albuterol, flunisolide, and ipratropium; daily furosemide; and aspirin. He was allergic to sulfonamides and penicillin and had an intolerance of angiotensinconverting-enzyme inhibitors and diltiazem. He had stopped abusing alcohol and using tobacco 15 years before admission. There was no history of recent angina pectoris, vomiting, hematochezia, melena, diarrhea, pharyngitis, cough, rash, fever, chills, or dysuria.The temperature was 36.4°C, the pulse was 108, and the respirations were 24. The blood pressure was 155/80 mm Hg.On examination, the patient was an obese man who appeared mildly ill. His head was normal. A surgical scar was present over the left carotid artery, without bruit; the jugular venous pressure was normal. Breath sounds were diminished over both lungs, with dry crackles at both lung bases. The heart sounds were normal. An abdominal examination revealed distention, with diminished bowel sounds, diffuse tenderness, and rebound tenderness. There was ϩϩ peripheral edema without evidence of deep venous thrombosis. The results of t...