N Engl J Med 2007;357:2389-93. Copyright © 2007 Massachusetts Medical Society. A 23-year-old black woman presented to the emergency department with diffuse, colicky abdominal pain of 1 hour’s duration. The pain was followed by nausea and episodes of bilious vomiting and did not radiate or change with the patient’s position. She did not report fever, chills, diarrhea, hematochezia, or melena. The differential diagnosis of acute abdominal pain in young adults is broad and includes appendicitis, peptic ulcer disease, nephrolithiasis, infectious enteritis, inflammatory bowel disease, hepatobiliary diseases such as cholecystitis, pancreatitis, and referred pain from pneumonia. In young women, gynecologic conditions (such as ectopic pregnancy, endometriosis, and pelvic inflammatory disease) are additional important considerations. Nausea and bilious vomiting are consistent with hepatobiliary disease, pancreatitis, and small-bowel disorders such as obstruction, infection, and Crohn’s disease. The diffuse nature of the pain in this patient makes hepatobiliary disease unlikely. The absence of reported diarrhea or gastrointestinal bleeding would argue against endoluminal infection or inflammatory bowel disease. Diffuse abdominal pain may also suggest bowel obstruction or ischemia, or metabolic disease such as diabetic ketoacidosis or acute intermittent porphyria, although the latter condition is rare. I would first want to rule out evidence of peritonitis, which in a young woman may result from conditions such as ectopic pregnancy, a ruptured tubo-ovarian abscess or appendix, or a perforated ulcer. The patient reported that a similar episode had occurred 6 months previously. It lasted 30 minutes and resolved on its own. At that time, she passed red blood from the rectum once but did not seek medical attention. Her other medical history included an elective abortion at 20 years of age and anemia and metromenorrhagia, neither of which had been further evaluated. She had no history of abdominal surgeries. She said that she did not use tobacco, alcohol, or illicit drugs, and she worked as a legal assistant. She was unaware of any gastrointestinal or sickle cell disease in her family. A history of bright red blood from the rectum, if confirmed, would indicate endoluminal disease of the gastrointestinal tract — presumably the lower tract; if the source was the upper gastrointestinal tract, red blood would indicate very rapid transit, yet the previous episode was self-limited, without hemodynamic compromise. Bilious vomiting suggests a site proximal to the ileocecal valve. Inflammatory bowel disease is a leading possibility. The combination of vomiting and the absence of changes in stool volume, color, and frequency could be explained by a stricture complicating Crohn’s disease, and it could also explain the patient’s anemia, although her history of metromenorrhagia provides an alternative explanation for that condition. An un