Would abd ultrasound and full blood count show something is wrong possibly colon cancer? No blood visible only loose stool. Diagnosed with ibs.

Loose stool. At your age colon cancer would be very rare. Abd US and full blood count are not the best tests to screen for colon cancer. A colonoscopy would be the better test. If your tests thus far are normal but still have symptoms, I would see your doctor for further testing. Colonoscopy would be the best test as I stated before if all other tests were normal. .