A patient presents with black tarry stool and hyperactive bowel sounds. What diagnosis is most likely?

The presence of black tarry stool, known as melena, is indicative of upper gastrointestinal bleeding. This occurs when there is bleeding from a source higher in the GI tract, such as the esophagus, stomach, or duodenum, and the blood has had time to be digested, giving it a dark, tar-like appearance. Hyperactive bowel sounds often accompany gastrointestinal bleeding due to increased peristalsis as the body responds to the presence of blood in the digestive tract.

While lower gastrointestinal bleeding can cause dark stools, it typically presents with more fresh red blood or maroon-colored stools rather than the black tarry appearance associated with upper GI bleeding. Acute gastritis can lead to bleeding but is more likely to produce nausea, vomiting, and potentially red blood in vomit rather than melena. Diverticulitis may also cause bleeding, but it normally presents with changes in bowel habits, local abdominal pain, and not typically with black tarry stools.

Thus, the correct interpretation leads to the conclusion that the described symptoms align most closely with a diagnosis of upper gastrointestinal bleeding, which explains the choice in this instance.