<prompt> An elderly patient presents with a prolonged history of weakness and lethargy. On examination he is found to be anemic and stool is positive for occult blood. Which of the following is the investigation of choice:ColonoscopyBarium mealBarium enemaCT abdomen  <response>: Answer is A Colonoscopy Colonoscopy is the investigation of choice in elderly patients presenting with occult fecal blood and anemia to evaluate the possibility of a colorectal cancer. Colonoscopy is the test of choice in a case with occult fecal blood, rectal bleeding, anemia, or weight loss in an older patient, all of which suggest the possibility of colorectal cancer - Primary Care Medicine Lippincott6th522 In elderly patients who often tolerate barium enema badly, colonoscopv should be the first-line investigation for unexplained rectal bleeding or anemia and is the investigation of choice for all patients with a positive fecal occult blood test - General surgical operations by Kirk Elsevier 2006228. 