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The aim was to identify diagnostic difficulties for acute abdominal pain at the emergency department and during hospital stay. A total of 3349 patients admitted to Mora Hospital with acute abdominal pain of up to seven days duration, were registered prospectively for history and clinical signs according to a structured schedule. The preliminary diagnosis from the attending physician at the emergency department, any investigations or surgery and final diagnosis were registered at a follow-up after at least one year.

There were no differences in diagnostic performance between physicians with 0.5 to 5 years of medical experience. The information collected and a careful examination of the patient was more important than formal competence. The main differential diagnostic problem was non-specific abdominal pain; this was the same for diagnoses requiring surgery. Patients originally diagnosed as not needing surgery had a median delay before operation of 22 hours (mean 40 hours, with 95% confidence interval of 30-50 hours), compared to 8 hours (mean 15 hours, 95% confidence interval of 12-28 hours) for patients with the same final follow-up diagnosis as the preliminary diagnosis. Constipation was a diagnostic pitfall, as 9% of the patients considered constipated required surgery for potentially life threatening reasons and 8% were later found to have an abdominal malignancy. Both the preliminary diagnosis and the discharge diagnosis were less reliable for elderly patients than for younger patients. Elderly patients often had specific organ disease and arrived at the emergency department after a longer history of abdominal pain.

This study confirms that assessment of suspected appendicitis can still be based on clinical judgements combined with laboratory tests. Classical clinical findings indicating localised inflammation, such as isolated pain in the right iliac fossa, rebound tenderness, right-sided rectal tenderness, pain migration to the right iliac fossa, local guarding and aggravation of pain when moving, were reliable for predicting acute appendicitis. A CT scan can be saved for the more equivocal cases of acute abdominal pain. A generous strategy regarding CT scan among elderly patients with acute abdominal pain, even in the absence of pronounced signs of an inflammatory intra-abdominal process, is recommended.