What are the key clinical features to differentiate between appendicitis and other causes of acute abdominal pain in adults?

When differentiating between appendicitis and other causes of acute abdominal pain in adults, the provided guidelines for appendicitis primarily focus on the need for emergency hospital admission for specialist assessment and management if acute appendicitis is suspected, rather than detailing specific differentiating clinical features of appendicitis itself ¹. However, features of other conditions causing acute abdominal pain can help in differentiation:

• Acute Diverticulitis: Suspect acute diverticulitis if a person presents with constant, usually severe, abdominal pain localising in the left lower quadrant ². This pain may be accompanied by fever, a sudden change in bowel habit with significant rectal bleeding or passage of mucus, or tenderness, a palpable abdominal mass, or distention in the left lower quadrant on examination, especially with a history of diverticulosis or diverticulitis ². It is important to be aware that in a minority of people, and in people of Asian origin, pain and tenderness may be localised in the right lower quadrant ².
• Suspected Cancer: Abdominal pain may indicate cancer if it is unexplained and accompanied by weight loss in individuals aged 40 and over, or unexplained with rectal bleeding in adults under 50, or unexplained in those aged 50 and over, which may suggest colorectal cancer ³. Upper abdominal pain with weight loss in individuals aged 55 and over may suggest oesophageal or stomach cancer ³. Persistent or frequent abdominal or pelvic pain (particularly more than 12 times per month) in women, especially those aged 50 and over, may suggest ovarian cancer ³.
• Diarrhoea-related Abdominal Pain: Abdominal pain is often present in inflammatory bowel disease, irritable bowel syndrome, and ischaemic colitis ⁵. Features suggesting an infectious cause include fever, vomiting, recent contact with a person with diarrhoea, or exposure to possible sources of enteric infection ⁵. The quantity and character of stools (watery, fatty, containing blood or mucus) are also important to assess ⁵.