A speck of bright red blood on your tissue when you wipe is probably a small hemorrhoid or harmless fissure, but if there are large amounts, or you see maroon or black-tinged blood, call your doctor. This is a sign that there’s bleeding further up in the colon.

2. Pooping is actually difficult

Everyone gets constipated occasionally, but prolonged problems with pooping can indicate a blockage in the colon. That’s because at the beginning of the colon, your poop is soft and can maneuver around any obstacles in the way. As it progresses to the end of the colon, it gets firmer. If there’s a tumor at the end of the rectum, this harder poop will have a hard time  getting by, says Lisa Ganjhu, Clinical Associate Professor, division of gastroenterology and liver diseases, NYU Langone Medical Center. Diarrhea that lasts more than a few days should also set off warning bells.

3. You’ve got crazy cramping

Out-of-nowhere gut spasms in the lower stomach can just be gas…or something more serious. If the pains are unfamiliar and painful, or you feel like you need to poop but can’t, you should have your doctor check you out as this could be a sign of colon cancer

4. Your poop is pencil thin

If there’s something blocking your colon, your stool is forced into a narrow, ribbon-like shape. Seek a medical attention ASAP if you experience this. It could be as a result of another cause, but it’s always best to be on the safe side.