Well come to HCM Thank for asking, I appreciate your concern, in your case apart from the ulcerative colitis it could be hemorrhoids too, it could be infection also, differential diagnosis matters the great, occasional bleeding per rectum could be due to constipation and it needs to be ruled out too, because it pretty common condition, if this is so then no need to worry about this, but have more fiber containing diet, and drink more water, in my opinion clinical examination could clear the picture, hope this information helps