Acute Abdominal Pain in Adults

Related Subjects:Acute Cholecystitis |Acute Appendicitis |Chronic Peritonitis |Abdominal Aortic Aneurysm |Ectopic Pregnancy |Acute Cholangitis |Acute Abdominal Pain |Penetrating Abdominal Trauma |Abdominal Masses: Clinical Approach and Considerations |Abdominal Distension |Vomiting |Substance Misuse |Cannabinoid Hyperemesis Syndrome (CHS) |Cyclical Vomiting Syndrome

Acute abdominal pain accounts for ~5–10% of emergency department visits. Approximately 15–25% of cases require surgical intervention. The goal is rapid identification of surgical emergencies while avoiding unnecessary operations.

✅ Key Clinical Advice

• Always assess and stabilise with ABCDE before focusing on diagnosis.
• In unstable patients → urgent surgical review, do not delay for imaging.
• Consider broad differentials; elderly and immunosuppressed may have atypical presentations.

💊 Management

• 🔄 Resuscitation: ABCs, O₂, IV fluids, Fast patient NBM, catheter for urine output.
• 💉 Antibiotics: Broad-spectrum IV (e.g., Tazocin ± metronidazole).
• 💊 Analgesia: IV morphine (2.5–5 mg), antiemetics.
• 🧑‍⚕️ Urgent surgical referral: Early laparotomy/laparoscopy.
• 🧑‍⚕️Diagnostic triggers
  • Abdominal pain + low BP → think sepsis
  • Abdominal pain + low BP + >50 yrs → leaking AAA
  • Abdominal pain + fertile female → ectopic pregnancy
  • Abdominal pain + AF/MI → ischaemic bowel
  • Abdominal pain + gallstones/alcohol → pancreatitis

🔪 Surgical Management

• Indicated for perforated viscus, bowel ischaemia, or generalised peritonitis.
• Procedures:
  • Exploratory laparotomy/laparoscopy
  • Resection of necrotic bowel, repair perforations
  • Peritoneal lavage, drain abscesses
• Continue IV antibiotics post-op.

1. Initial Assessment & Red Flags

• ABCDE + vital signs + NEWS score
• Two large-bore IV access, bloods (FBC, U&E, CRP, lactate, amylase/lipase, LFTs, group & save ± crossmatch), urinalysis, pregnancy test (all women of childbearing age)
• Red flags requiring urgent senior/surgical input:
  • Hypotension / tachycardia / shock
  • Board-like rigid abdomen / generalised peritonism
  • Pain out of proportion to examination findings
  • Rising lactate (>2–4 mmol/L) or metabolic acidosis
  • Free subdiaphragmatic air on erect CXR
  • Elderly, diabetics, steroid/immunosuppressed patients (atypical / muted signs)

2. Differential Diagnosis by Anatomical Location

3. Key Investigations – Tiered Approach

1. Bedside / immediate: Pregnancy test, urinalysis, erect CXR (free air), ECG (exclude cardiac), FAST / POCUS (free fluid, AAA)
2. Blood tests: FBC, U&E, CRP, lactate, amylase/lipase, LFTs, group & save / crossmatch, blood gas
3. Imaging:
   • Ultrasound: First-line for biliary, gynaecological, appendix (slim patients), AAA screening
   • CT abdomen/pelvis with IV contrast: Gold standard for most acute surgical pathologies (perforation, ischaemia, diverticulitis, appendicitis in adults)
   • CTA: Mesenteric ischaemia, aortic pathology

4. Antibiotic Choices (Empiric – Community-acquired)

• Mild–moderate: Co-amoxiclav IV or cefuroxime + metronidazole
• Severe / generalised peritonitis / healthcare-associated: Piperacillin-tazobactam (Tazocin) ± gentamicin (local policy)
• Cholangitis / biliary: Piperacillin-tazobactam or ceftriaxone + metronidazole
• Post-source control: Usually 4–5 days total; de-escalate / stop when clinically improved

5. Surgical vs Conservative Management Triggers

6. Final Key Take-home Messages

• Unstable or peritonism → theatre, not CT scanner
• Pregnancy test mandatory in women of reproductive age
• CT is the most useful single investigation in diagnostically uncertain cases in adults
• Pain out of proportion + atrial fibrillation / vascular risk → think acute mesenteric ischaemia
• Elderly / frail → assume surgical pathology until proven otherwise
• Early antibiotics + source control save lives in perforation / peritonitis

Always follow local protocols, consult senior clinicians, and refer to current trust / national guidelines (e.g., WSES 2024, NICE NG156, UpToDate 2026).

Case 1 – Perforated duodenal ulcer

A 48-year-old man with NSAID use develops sudden, severe epigastric pain radiating to the shoulder, rigid abdomen, and absent bowel sounds; vitals show tachycardia, low-grade fever, and mild hypotension. Erect CXR shows free subdiaphragmatic air. Manage with ABCDE, IV fluids, broad-spectrum antibiotics, PPI, NG tube, and urgent CT abdomen; refer for emergency surgery (laparoscopic Graham patch vs definitive ulcer surgery) and test/treat H. pylori after recovery.

Case 2 – Ruptured abdominal aortic aneurysm (AAA)

A 72-year-old man with smoking and hypertension presents with sudden tearing back/abdominal pain, hypotension, and a pulsatile abdominal mass. Avoid excessive fluids (permissive hypotension), give O₂, activate massive haemorrhage protocol, crossmatch, and call vascular surgery for immediate EVAR/open repair. POCUS/bedside ultrasound confirms large infrarenal AAA; do not delay for CT if unstable.

Case 3 – Ruptured ectopic pregnancy

A 30-year-old with 7 weeks’ amenorrhoea and vaginal spotting presents with worsening lower abdominal pain, dizziness, and shoulder tip pain; she is tachycardic and hypotensive with abdominal guarding. β-hCG positive; FAST scan shows free fluid. Resuscitate (O₂, IV access, bloods/crossmatch), consult gynae for urgent salpingectomy (or salpingostomy if appropriate), give anti-D if rhesus negative, and manage pain; differentials include ovarian torsion and ruptured corpus luteum.

Case 4 – Acute appendicitis

A 24-year-old develops periumbilical pain migrating to the RIF with anorexia, mild fever, and rebound tenderness; WBC/CRP raised. Ultrasound (slim female) or CT abdomen confirms inflamed, non-compressible appendix. Give IV fluids, analgesia, and broad-spectrum antibiotics; proceed to laparoscopic appendicectomy. Consider differentials (gynae, mesenteric adenitis); beware atypical retrocaecal pain.

Case 5 – Acute mesenteric ischaemia

A 78-year-old with AF has sudden, severe, diffuse abdominal pain out of proportion to scant early signs; lactate rising, metabolic acidosis. Urgent CTA shows SMA embolus. Resuscitate, start IV heparin and broad-spectrum antibiotics, involve vascular/HPB surgery for embolectomy/revascularisation ± bowel resection if non-viable; mortality is high-act fast.

Case 6 – Sigmoid volvulus

An 82-year-old in a care home presents with abdominal distension, pain, constipation, and tympany; X-ray shows the classic coffee-bean sign pointing to the RUQ. If no peritonitis/ischemia, perform flexible sigmoidoscopy with decompression and rectal tube; arrange definitive surgery (e.g., sigmoid colectomy) due to recurrence risk. If peritonitis or perforation, urgent laparotomy.

📚 References

• Peritonitis: Pathophysiology & Management
• UpToDate: Acute Peritonitis
• Medscape: Peritonitis Overview