Abdominal pain - acute
Exam Tips
- In OSCEs, start with ABCDE plus observations before abdominal examination; instability is a management diagnosis, not a wait-for-imaging diagnosis.
- Pain pattern matters: visceral pain is diffuse/poorly localized, while peritoneal irritation produces localized pain with guarding and rebound.
- Constipation with absolute obstipation, colicky pain, vomiting, distension, and tinkling bowel sounds strongly suggests bowel obstruction.
- Do not miss extra-abdominal causes (MI, pneumonia, DKA) and always do beta-hCG in reproductive-age patients with acute abdominal/pelvic pain.
- If fever develops after onset of pain/vomiting with peritoneal signs, think evolving peritonitis and escalate urgently.
- Image reference: see Figure from Bailey & Love acute abdomen chapter showing visceral-to-parietal pain localization and common referral patterns by abdominal quadrant.
Definition
Acute abdominal pain is pain arising from the abdomen with a duration of less than 7 days, ranging from self-limiting illness to time-critical surgical pathology. The term acute abdomen describes severe, rapidly evolving pain with features suggesting peritoneal irritation, obstruction, ischaemia, perforation, sepsis, or other causes requiring urgent specialist assessment.
Pathophysiology
Pain may arise from visceral afferent stimulation (stretch, distension, ischaemia, inflammation) causing dull, poorly localized midline pain, then localize when parietal peritoneum becomes inflamed (sharper somatic pain). Common mechanisms include luminal obstruction (for example appendiceal, biliary, ureteric, or bowel), infection/inflammation (appendicitis, cholecystitis, diverticulitis, pancreatitis), perforation with chemical/bacterial peritonitis, haemorrhage, and mesenteric hypoperfusion. Systemic inflammatory response causes tachycardia, fever or hypothermia, capillary leak, and organ dysfunction in severe disease. In oncology patients, consider malignant bowel obstruction, perforation through tumour, hepatobiliary obstruction, treatment-related neutropenic sepsis, and venous thromboembolism with bowel ischaemia.
Risk Factors
- Older age or immunosuppression (atypical presentations, delayed diagnosis)
- Previous abdominal surgery (adhesional bowel obstruction risk)
- Gallstones, obesity, female sex, and increasing age (biliary disease)
- Alcohol excess and hypertriglyceridaemia (pancreatitis risk)
- NSAID or steroid use, Helicobacter pylori history (peptic ulcer/perforation risk)
- Atrial fibrillation or atherosclerotic disease (mesenteric ischaemia risk)
- Pregnancy and ectopic pregnancy risk factors (acute pelvic/abdominal emergencies)
- Known malignancy, unexplained weight loss, iron-deficiency anaemia, family history of GI cancer
Clinical Features
Symptoms
- Pain onset, site, migration, character (colicky vs constant), radiation, severity, progression
- Nausea and vomiting (bilious vomiting suggests proximal obstruction)
- Constipation or absolute constipation (no stool/flatus) suggesting obstruction
- Change in bowel habit, diarrhoea, PR bleeding or melaena
- Urinary symptoms (dysuria, frequency, haematuria, strangury) suggesting GU causes
- Fever, anorexia, malaise, or rigors
- Gynaecological symptoms: amenorrhoea, vaginal bleeding/discharge, pelvic pain
- Red-flag associated features: trauma, syncope, jaundice, polyuria/polydipsia, cough/dyspnoea, testicular/labial pain
Signs
- Abnormal observations: tachycardia, hypotension/orthostatic drop, fever or low temperature, tachypnoea, prolonged capillary refill
- Localized or generalized abdominal tenderness; rebound/percussion tenderness
- Guarding or rigid abdomen indicating peritoneal irritation
- Distension, visible hernia, abdominal scars, palpable mass, palpable faeces
- Bowel sounds: early high-pitched tinkling in obstruction, later reduced/absent sounds
- Signs of dehydration, jaundice, anaemia, sepsis, or shock
- Cullen or Grey Turner bruising in severe haemorrhagic pancreatitis
- Selective PR/pelvic findings (blood, mass, cervical motion tenderness, discharge) when clinically indicated
Investigations
Management
Lifestyle Modifications
- Urgent same-day assessment for red flags; advise not to drive if severe pain or opioid use
- Nil by mouth initially if surgical pathology is possible; early senior review and safety-netting
- Oral rehydration only when stable and surgical cause excluded; clear return advice for worsening pain, fever, vomiting, bleeding, syncope, or reduced urine output
Pharmacological Treatment
Analgesia
- Paracetamol 1 g orally/IV every 4-6 hours (maximum 4 g/24 h; lower maximum if low body weight or liver disease)
- Morphine sulfate 2.5-5 mg IV every 5-10 minutes titrated to effect (or 5-10 mg IM where IV unavailable)
Give timely analgesia; do not delay diagnosis. Avoid or use caution with NSAIDs in renal impairment, active GI bleeding, peptic ulcer disease, anticoagulation, and third trimester pregnancy. Opioids require monitoring for respiratory depression, hypotension, sedation, and ileus.
Antiemetics
- Cyclizine 50 mg IV/IM/oral up to three times daily
- Ondansetron 4 mg IV/IM or 4-8 mg oral every 8-12 hours as needed
Choose based on comorbidity and QT risk. Ondansetron can prolong QT; use caution with electrolyte disturbance or other QT-prolonging drugs.
Fluid resuscitation and metabolic correction
- Sodium chloride 0.9% IV bolus 500 mL over <15 minutes, repeated according to response
- Balanced crystalloid (for example Hartmann's solution) for ongoing replacement as clinically indicated
Use sepsis/shock principles with repeated reassessment (pulse, BP, urine output, lactate). Caution in heart failure or advanced renal disease; avoid fluid overload.
Empiric IV antibiotics for suspected intra-abdominal sepsis
- Co-amoxiclav 1.2 g IV every 8 hours
- If penicillin allergy: Cefuroxime 1.5 g IV every 8 hours plus Metronidazole 500 mg IV every 8 hours (only if cephalosporin appropriate), or local microbiology-approved alternative
Give promptly after cultures when sepsis likely; then tailor to cultures and source control. Check allergy history, renal dosing, C. difficile risk, and local antimicrobial guidance.
Condition-specific adjuncts
- Omeprazole 40 mg IV once daily in suspected upper GI ulcer disease/perforation pathway
- Tamsulosin 400 micrograms oral once daily for selected distal ureteric stones
Adjuncts do not replace definitive diagnosis. Review contraindications, interactions, and stop when no longer indicated.
Surgical / Interventional
- Immediate surgical review for peritonitis, perforation, bowel obstruction, irreducible hernia, ischaemia, uncontrolled sepsis, or haemodynamic instability
- Urgent source-control procedures: laparoscopic/laparotomy washout, appendicectomy, cholecystectomy, bowel resection, abscess drainage
- Cancer-related emergencies: management of malignant bowel obstruction (nasogastric decompression, stoma or bypass, resection where appropriate, or colonic stenting in selected large-bowel obstruction)
Complications
- Peritonitis and intra-abdominal abscess
- Sepsis and septic shock
- Bowel ischaemia, necrosis, perforation, and multi-organ failure
- Acute kidney injury from hypovolaemia/sepsis
- Delayed diagnosis of malignancy or other life-threatening pathology
- Death
Prognosis
Outcome is cause-dependent: many presentations are benign and self-limiting, but a clinically important minority have urgent surgical or life-threatening disease. Severe pathology is seen in roughly up to one in ten emergency presentations, so early risk stratification is essential. In primary care cohorts, overall 1-year mortality is low but non-trivial (about 3%), with risk concentrated in older, frail, and comorbid patients.
Sources & References
✅NICE Guidelines(1)
- Abdominal pain - acute[overview]
📖Textbook References(12)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 775, 776)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 775, 776)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 261, 262)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 262, 263)[context]
- Emergencies in - Obstetrics and Gynaecology, Second Edition (Stergios K. Doumouchtsis, S. Arulkumaran) (Z-Library).pdf(pp. 264, 265)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 646, 647)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 647)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 345, 346)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 345, 346)[context]
- Oxford Handbook of Clinical Diagnosis (Huw Llewelyn, Hock Aun Ang, Keir Lewis etc.) (Z-Library).pdf(pp. 653, 654)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 746, 747)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 959)[context]