<prompt> A 33-year-old woman presents with black stools. Laboratory studies demonstrate a hypochromic, microcytic anemia. Upper GI endoscopy reveals a duodenal ulcer. Which of the following best describes the stools in this patient with peptic ulcer disease?HematemesisHematobiliaHematocheziaMelena  <response>: Melena black stool is a symptom of upper gastrointestinal bleeding. Blood from ruptured esophageal varices or a peptic ulcer is partially digested by hydrochloric acid. Hemoglobin is transformed into a black pigment hematin, which imparts a typical coffee-grounds color to the stool. Hematemesis choice A is vomiting of blood. Hematobilia choice B is bleeding into the biliary passages, as a complication of trauma or neoplasia. Hematochezia choice C is passage of bloody stools caused by lower gastrointestinal hemorrhage. Steatorrhea choice E is passage of fatty stools caused by pancreatic disease and malabsorption.Diagnosis: Peptic ulcer disease 