Does cover change the calibre of stools if one has cancer.

Colo Rectal Cancer: Colo-rectal cancers in the descending colon often "encircle" and narrow the bowel lumen, causing stools to decrease in caliber. However, temporary propulsive changes in gut motility can do the same, caused by stress, constipation, irritable bowel syndrome, and the like. At your age, motility changes are much more likely. If the issue continues and/ or there is blood in the stools, consult ur md.

Caliber of stool: The caliber and color of your stool can change with many many things - if you have a significant and persistent change in either you should see your doctor - but it does not necessarily mean cancer at all!