Can chronic constipation be an onset for colon cancer?

A.  I note that you have been passing blood when you evacuate your bowels and that you have chronic constipation and have been diagnosed as having IBS , that you are 31 years old and are receiving treatment for anal fissure. My advice is that any rectal blood loss needs investigations, ideally an endoscopic examination of the colon called colonoscopy, which will help diagnosis if inflammation of the lining is noted, (called colitis), which will need appropriate treatment. Secondly, there can be polyps which can cause bleeding and this needs to be diagnosed and removed as they can turn cancerous if allowed to grow and not removed. Thirdly, IBS is a chronic condition causing a multitude of bowel symptoms but never blood loss. I suggest you consult a gastroenterologist for a colonoscopy, to exclude any pathology that may need exclusion. Colonic cancer is very rare in a young person.