Acute Abdominal Pain in Adults

Differential Diagnosis

Common Diagnoses

  • Peptic Ulcer
  • Biliary Colic
  • Appendicitis
  • Gastroenteritis
  • Renal Colic

Occasional Diagnoses

  • Cholecystitis (May Follow Biliary Colic, but Pain is Constant and Fever Present)
  • Diverticulitis
  • Acute or Subacute Bowel Obstruction (Adhesions, Carcinoma, Strangulated Hernia, Volvulus)
  • Pyelonephritis
  • Muscular Wall Pain
  • Pancreatitis
  • Meckel’s Diverticulum

Rare Diagnoses

  • Perforation (e.g. Duodenal Ulcer [DU], Carcinoma) Resulting in Peritonitis
  • Hepatitis
  • Crohn’s and Ulcerative Colitis
  • Ischaemic Bowel
  • Dissecting/Leaking Aneurysm
  • Diabetic Ketoacidosis (DKA) and other Occasional Medical Causes (e.g. Myocardial Infarction [MI], Pneumonia, Sickle Cell Crisis)

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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