Many cases of acute appendicitis occur in teenagers and young adults, but it can occur from infancy to old age. The typical abdominal pain starts in the centre of the abdomen and migrates to the right lower quadrant, is made worse by movement, and accompanied by lethargy and loss of appetite. The pulse rate and temperature may be raised and abdominal examination my reveal tenderness and guarding (muscle tensing) at the site of the pain. Untreated an inflamed appendix may form an “appendix mass”, a palpable swelling in the right lower abdomen formed by adhesion of surrounding organs and possibly containing an abscess. If an inflamed appendix perforates (bursts) and is not contained within a mass, infection may spread rapidly through the abdomen (generalised peritonitis) causing severe, widespread abdominal pain and leading to fatality unless treated rapidly. However, not all presentations are typical, particularly in younger children. Vomiting and diarrhoea may be the dominant symptoms, with abdominal pain and tenderness less marked, and not localised to the right lower abdomen, or the child may simply seem to be “off food”, lethargic and “unwell”.
Many other conditions may mimic appendicitis. Particularly common in children is “mesenteric adenitis”, where a virus infection results in inflammation of the lymph glands in the abdomen. Confusion can arise from urinary tract infections and other less common bowel pathology. In adolescent girls, gynaecological pathology may also cause lower abdominal pain. Vomiting and diarrhoea are more frequently caused by infective agents than an inflamed appendix.