This is the inflammation of the vermiform appendix, which, in its acute form, is the most common abdominal emergency. Symptoms include abdominal pain that often begins over the navel and then moves to the lower right ileac fossa, with pronounced local tenderness. The pain is severe and worsens with movement such as coughing or deep breathing. There may also be nausea and vomiting, diarrhoea, loss of appetite and fever. Eventually, there is abdominal swelling and tenderness. Blockage and subsequent infection of the appendix are the causes of appendicitis.

In its acute form appendicitis requires medical treatment or surgical removal of the appendix