Altered bowel habit with blood and mucus PR

Dear Ask The Doctor: Hi, for several months I have had general abdominal pain that can occur anywhere in the abdomen and can come and go throuout a day or disappear for several prior to returning. I also was passing pellet like hard stools with slight constipation. Lately the stools have flattened slightly and are still hard to pass, either being flat on one side or completely flattened but occasionally I will have a "normal" bowel movement. Last couple of days I have had two bowel movements with a small hard stool and a minute amount of mucas attached with tiny amount of bright red blood in. Sigmoidoscopy scheduled for a week but obviously very concerned, does this sound like IBS? or more serious? I should add I am a 25 year old male, don't drink, smoke no family history of cancer or polyps. But obviously this is what is worrying me.

Dear Luke:Your symptoms of altered bowel habit with predominantly constipation, mucus and blood per rectum, could be suggestive of Irritable Bowel Syndrome. However IBS can only be diagnosed in the absence of other organic disease, with reference to standardised criteria. If you have been chronically constipated, you may also have haemorrhoids, which could explain the bleeding from the back passage. These symptoms warrant further investigation to exclude other organic disease, such as inflammatory bowel disease, polyps, and malignancy (which is rare in someone of your age). I advise attending your gastroenterologist for sigmoidoscopy or colonoscopy, which will help your physician to confirm a diagnosis and arrange treatment depending on the cause of your symptoms.