A bowel obstruction is an intestinal obstruction and a rectal cancer is a rectal cancer; both are common but fundamentally different conditions in general surgery. Bowel obstruction may be caused by rectal cancer or may have many other causes. Bowel obstruction includes mechanical bowel obstruction, hemodynamic bowel obstruction, and dynamic bowel obstruction. There are many causes of bowel obstruction, and tumor is only one of them. Therefore, if you have intestinal obstruction, you must go to regular hospital for diagnosis and treatment in time, so as to clarify the cause of the disease, which will be helpful for relieving the obstruction. Rectal cancer often has no obvious symptoms in the early stage, but in the progressive stage, or even in the late stage, the tumor of rectal cancer may increase in size, leading to the symptoms of intestinal obstruction, which may be manifested as difficulty in defecation, seldom stool, unshapely stool, or even inability to defecate. They are totally different diseases, while rectal cancer can lead to intestinal obstruction, intestinal obstruction contains many causes.