CD can progress to cause bowel damage, which in severe cases can lead to the patient requiring surgery. CD patients may also have symptoms of bowel obstruction such as bloating, abdominal pain, stomach distention, nausea and vomiting and even constipation. This is often caused by narrowing parts of the intestine (strictures) preventing food from moving through the bowel, therefore potentially causing a blockage. Multiple areas of narrowed bowel and strictures are known as skip lesions.  

Bowel perforation is a rare medical emergency and patients may present with a fever, severe abdominal pain, nausea and vomiting. Some CD patients may develop a fistula, which is a tract connecting one organ to another. 

Complications of UC include persisting toxic megacolon – an acute form of colonic distension, perforation, severe bleeding and malignancy.