What Does Blood in the Stool Mean?

I have been to a gastroenterologist and ultrasound exam shows small stones and debris in middle bile duct (my gall bladder was removed 18 months ago). After an exam by a doctor, now I have to go for large bowl X-ray due to changes in my bowel habits and blood mixed in my stool. What are they looking for?

The presence of blood in the stool may be an indicator of many things including hemorrhoids, little outpouchings of the colon called diverticuli, polyps of the bowel, tumors, or abnormal blood vessels in the lining of the bowel called arterio-venous malformations. It is less likely but possible that the blood is coming from the upper intestine, for example, from ulcers, stomach erosions due to aspirin or arthritis and pain-killing drugs (NSAIDs), etc. Anyone with blood in the stool should have a careful evaluation and appropriate treatment.