Acute Abdominal Pain in Adults

Differential Diagnosis

Common Diagnoses

Occasional Diagnoses

Rare Diagnoses

Ready Reckoner

Key distinguishing features of the most common diagnoses

Peptic UlcerRenal ColicBiliary ColicAppendicitisGastroenteritis
Colicky PainNoYesYesNoYes
Localised PainYesYesYesYesNo
Abdominal TendernessYesNoPossibleYesPossible

Possible Investigations

  • The only test likely to help the GP is urinalysis: This may reveal haematuria (renal colic), evidence of urinary infection or glycosuria in DKA. In general, the following investigations will be done in hospital after acute admission.
  • Full blood count: WCC raised in many causes and confirms acute inflammation or infection.
  • U&E essential as abnormalities common with diarrhoea or vomiting. Amylase raised in ischaemic bowel and acute pancreatitis.
  • LFT may show raised bilirubin in biliary obstruction, and widespread derangement in hepatitis.
  • Helicobacter pylori testing: Strong association with peptic ulcer disease.
  • Upper GI endoscopy: To visualise upper GI tract.
  • Plain erect abdominal X-ray invaluable to confirm perforated viscus (air under diaphragm). Supine also necessary if obstruction suspected. Ninety percent of renal or ureteric stones will be revealed with a plain abdominal X-ray.
  • Ultrasound: Helpful to confirm gallstones.
  • Renal imaging: For ureteric stones.

Top Tips

  • The aim of assessment is correct disposal rather than an exact diagnosis. Colicky pain may be appropriate to manage at home; constant pain with tenderness is likely to need admission.
  • If treating a patient at home, arrange for review as appropriate and ensure that the patient is aware of the symptoms which should prompt urgent reassessment.
  • The examination is likely to contribute significantly to making the diagnosis – so take particular care and don’t forget the basics such as pulse rate, temperature, bowel sounds and a rectal examination.

Red Flags

  • Beware ‘gastroenteritis’ masking or developing into an acute appendicitis. Make arrangements for follow-up and emphasise that constant pain needs urgent review
  • Prejudice is easy if the patient has a history of functional problems or irritable bowel. Surgical pathology can happen to anyone, so be objective.
  • Beware the elderly patient with an irregular pulse: Mesenteric infarction causes severe pain but few signs
  • Don’t forget to examine the hernial orifices, especially if obstruction is a possibility.
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