Abdominal Pain

Note: there are separate articles on Abdominal Pain in Children and Abdominal Pain in Pregnancy.

Note: pitfalls in diagnosis

Some serious pathologies may present with subtle symptoms, or may mimic non-severe problems:

• Ectopic pregnancy:
  • Can present with syncope, urinary or bowel symptoms; adnexal tenderness may be absent.
  • A bleeding ectopic may present with only subtle changes in vital signs.
  • History of 'missed period' may be absent if vaginal bleeding is mistaken for a normal period.
• Appendicitis and ectopic pregnancy may cause misleading urinary symptoms and positive dipstick results - this is due to the pelvic irritation involved.
• Ruptured abdominal aortic aneurysm:
  • Can mimic renal colic² - always consider this in older patients; be aware that haematuria can occur with leaking aneurysms as well as from renal causes.
  • Often presents with back pain.
• Pre-eclampsia can present with hepatic or epigastric pain.
• Testicular torsion may present with abdominal rather than scrotal pain.
• Mesenteric infarction is easily missed - has few signs until shock develops.
• Acute pancreatitis - when severe, presents with very ill patient and mimics other urgent surgical/medical problems, e.g. ruptured aortic aneurysm, MI.
• Children, those with learning difficulties and the elderly are harder to assess.
• Steroids can mask signs of peritonism.
• Be aware of "medical" problems presenting with abdominal pain.

History

• Pain: onset, nature, time course, radiation.
• Women: is pregnancy possible? LMP date, was this a normal period?
• Related symptoms: dysphagia, vomiting, anorexia, micturition and bowels, bleeding, systemic symptoms, weight loss.
• Past medical history, recent injury or surgery, medication, allergies, last meal.

Examination

• Note if well or ill, vital signs; chest exam if appropriate.
• Abdominal examination including hernial orifices.
• Urinalysis +/- bedside urine pregnancy test.
• Consider rectal and/or pelvic examination:
  • In the community these may be difficult, and should be omitted unless they are likely to add useful diagnostic information that might prevent hospital referral.
  • Never do vaginal examination if placenta praevia suspected (vaginal bleeding in 2nd half of pregnancy) - it could cause a massive bleed.

Initial investigations

• Pregnancy tests:
  • Urine β-HCG tests are sensitive, detecting β-HCG at 25 iu/L (a level normally reached 9 days post-conception).³ Serum testing detects levels down to 5 iu/L. Usually, a urine test is sufficient screening, but if pregnancy or ectopic pregnancy are strongly suspected with a negative urine test, serum testing is definitive.⁴
  • Serial serum β-HCGs aid diagnosis and management decisions for suspected ectopic pregnancy and miscarriage.³
• ECG - for cardiac ischaemia or preoperative.
• Blood tests - cross-match if bleeding; full blood count, renal and liver function, glucose; consider sickle test, calcium, amylase, hepatitis serology, ESR/CRP, bicarbonate. Do serial serum β-HCG for suspected ectopic.
• Urine - microscopy and culture (plus dipstick and pregnancy test, above).
• X-ray (if pregnancy excluded) - upright chest X-ray if suspected perforation (to show air under diaphragm); upright abdominal x-ray for obstruction (may show air-fluid levels).

Further investigations

• Pelvic ultrasound gives useful information in most gynaecological/obstetric problems. Transvaginal ultrasound may be more helpful in early pregnancy.
• Abdominal ultrasound useful for masses, organomegaly, ascites, abscess; may show acute appendicitis.
• CT or MRI: CT is increasingly used in diagnosis of acute abdominal pain.
• Endoscopy.
• Diagnostic laparoscopy (followed by laparoscopic surgery if appropriate).

In the primary care or A&E setting, use "management of uncertainty" principles. Rather than making a diagnosis, it is more important to decide whether the patient needs surgery, admission or further investigation - and how urgently.¹

• Identify emergencies and resuscitate/transfer (see emergencies box).
• Pain relief may be needed:
  • Intravenous opiate analgesia can be given, but titrate small doses and monitor BP in unstable patients.¹
  • Evidence suggests that pain relief does not adversely affect clinical assessment; it can remove harmful physiological stresses and can improve accuracy of examination.⁵
• Have a low threshold for referring/admitting children, the elderly,^1,6 and others where diagnosis may be difficult, e.g. those with learning difficulties.
• The clinical picture can change over time - re-assessment is an important tool.¹
• Consider referral/admission if a patient re-consults with undiagnosed pain.¹
• 'Safety-net' if discharging the patient so they understand when to seek help.