A 22-year-old male presents to the emergency department with abdominal pain, anorexia, nausea, and low-grade fever. Pain started in the mid-abdominal region 6 hours ago and is now in the right lower quadrant of the abdomen. The pain was steady in nature and aggravated by coughing. Physical examination reveals a low-grade fever (38°C; 100.5°F), pain on palpation at right lower quadrant (McBurney's sign), and leukocytosis (12 x 10^9/L or 12,000/microlitre) with 85% neutrophils.
A 12-year-old girl presents with sudden-onset severe generalised abdominal pain associated with nausea, vomiting, and diarrhoea. On examination she appears unwell and has a temperature of 40°C (104°F). Her abdomen is tense with generalised tenderness and guarding. No bowel sounds are present.
Atypical appendiceal anatomy, such as retrocaecal or long appendix, may present with back, hip, or left-sided abdominal pain that is confused with an alternative intra-abdominal diagnosis. Older patients are less likely to have classical symptoms and may present with non-specific abdominal pain without associated features, or confusion. The delay in presentation or diagnosis in this group results in increased risk of morbidity and mortality. The diagnosis of acute appendicitis during pregnancy is often delayed, as the location of the pain is affected by displacement of the appendix by the uterus, and symptoms such as nausea and vomiting are frequently associated with pregnancy itself. 
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