A thorough medical history and physical examination is the first step in determining the cause of blood in the stools. Blood tests, such as a complete blood cell count, or CBC, can evaluate the effect of the blood loss.
Stool tests, such as a fecal occult blood test, may be done. A recent study has shown that a screening for fecal occult blood every 1 to 2 years can significantly reduce the incidence of colorectal cancer. A positive test for blood in the stools often detects precancerous lesions that can be removed before colorectal cancer develops.
Scans, endoscopy, an upper GI series, and a barium enema may be used to examine the inside of the stomach and intestines. Ultrasound and rectal exams may also be done.