Final answer:
The most appropriate next step for this patient is a gastroscopy, as her symptoms and risk factors warrant further evaluation to rule out gastrointestinal bleeding.
Step-by-step explanation:
The most appropriate next step for this patient is:
Gastroscopy
The patient's symptoms, such as abdominal pain and black stools, along with the presence of risk factors like family history of cancer and cardiovascular disease, warrant further evaluation to rule out gastrointestinal bleeding.
A gastroscopy, also known as an upper endoscopy, is a procedure in which a flexible tube with a camera is inserted through the mouth into the stomach and upper part of the small intestine to visualize the upper digestive tract. This can help identify any potential source of bleeding or other abnormalities in the stomach or esophagus.