Well, diarrhea is not typical for colorectal cancer to get straight to the point. The most probable cause of diarrhea with blood is a food poisoning with bacteria like E.coli, which cause rectal ulcers. Other causes are inflammatory bowel disease, or diverticulitis.
Contaminated food does not necesary smell or looks spoiled.
Go to the doctor and have a hemoccult test and stool culture for bacteria/parasites.
Many thanks for your reassurance, I shall see a Doctor in a couple of days.
Regards,
Rod