Acute suppurative appendicitis, computer illustration and light micrograph. Illustration of a human appendix that is red and inflamed in appendicitis. The appendix is a narrow finger-shaped tube that branches off the first part of the large intestine (caecum, left). Inflammation of the appendix in appendicitis is a common cause of abdominal pain in children and young adults. Usually it is due to improperly digested food or a lump of faeces blocking the opening to the appendix. Symptoms include pain in the lower right-hand side of the abdomen, fever, loss of appetite and vomiting. Treatment of acute appendicitis is usually an appendectomy, the surgical removal of the appendix.