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 Ulcer | Renal Colic | Biliary Colic | Appendicitis | Gastroenteritis | |
|---|---|---|---|---|---|
| Colicky Pain | No | Yes | Yes | No | Yes |
| Localised Pain | Yes | Yes | Yes | Yes | No |
| Abdominal Tenderness | Yes | No | Possible | Yes | Possible |
| Fever | No | No | No | Yes | Possible |
| Diarrhoea | No | No | No | Possible | Yes |
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.