A 52-year-old woman presents to the emergency department with an acute onset of diffuse and colicky abdominal pain accompanied by nonprojectile vomiting and a feeling of being bloated. She states that she has had no flatus in the last 2 days. She has no history ac.painof fever, lightheadedness, syncope, or previous abdominal surgeries. She takes only takes metoprolol for hypertension. On physical examination, her vital signs are a temperature of 37.2°C, a heart rate of 110 beats per minute, and a blood pressure of 138/92 mm Hg. Her abdomen is noticeably distended, with diffuse tenderness to palpation and focal tenderness, which is greatest in the epigastrium. No rebound or guarding is observed. Bowel sounds are present but hypoactive, and the shake and heel-tap findings are negative. No Murphy sign is noted, and no fluid thrill is elicited. Her cardiovascular and respiratory findings are normal. What is the diagnosis?