Acute abdominal pain
Resuscitate, give pain relief, pregnancy test in every woman who could be pregnant, and look for the killers first: ruptured aneurysm, ectopic, perforation, ischaemic bowel and obstruction.
A 71-year-old man with hypertension has had sudden severe pain in his belly and back for an hour. He fainted at home. Pulse 116, BP 88/54. His belly is tender in the middle and you can feel a pulsating mass.
What is the most likely diagnosis, and what do you do?
- A to E and full observationsShocked with sudden pain is a surgical emergency.
- Two cannulas and bloodsCBC, urea, creatinine, electrolytes, LFTs, lipase or amylase, lactate, group and cross-match.
- Pregnancy testIn every woman who could be pregnant, before anything else.
- Pain relief and antiemeticIV morphine titrated. It does not hide the diagnosis.
- ECG and urine dipstickInferior MI and DKA can present as belly pain. Blood in urine suggests a stone.
- Nil by mouthIf surgery is possible.
- Examine everywhereHernial orifices, testes in men, chest, and a rectal examination where indicated.
- ImageErect chest X-ray for free air, ultrasound, or CT as directed by the senior.
- Shocked with sudden pain
- Rigid, board-like abdomen
- Pulsatile mass in an older patient
- Positive pregnancy test with pain
- Pain out of proportion to a soft belly, especially with AF
- Ruptured AAA
- Ectopic pregnancy
- Perforation
- Mesenteric ischaemia
- Pancreatitis
- Bowel obstruction or strangulated hernia
- Inferior MI or DKA presenting as abdominal pain
| Pregnancy test | Every woman who could be pregnant |
| Pain relief | Paracetamol 1 g IV, then morphine 2.5–5 mg IV titrated to effect |
| Shocked with sudden pain | Senior and surgeon now: think AAA, ectopic, perforation, ischaemia |
| Lactate | Raised with a soft belly and severe pain: think mesenteric ischaemia |
| Elderly | Few signs even with serious disease. Low threshold for CT |
Check every dose against a current drug reference and your hospital protocol.
On this page
The killers first
- Older man, smoker, hypertensive
- Pain in belly and back, fainting
- Pulsatile mass, shock
- Vascular surgeon now. Do not over-transfuse: permissive low BP
- Woman, missed period, positive test
- Pain, shoulder tip pain, fainting
- See Ectopic pregnancy
- Sudden severe pain, then rigid belly
- Peptic ulcer, NSAIDs, typhoid
- Free air under the diaphragm
- Elderly, AF
- Severe pain, soft belly
- High lactate
- CT angiogram
Where is the pain?
| Location | Think of |
|---|---|
| Right upper quadrant | Gallstones, cholecystitis, cholangitis, hepatitis, liver abscess (amoebic is common in Pakistan), right lower lobe pneumonia |
| Epigastric | Peptic ulcer, perforation, pancreatitis, gastritis, inferior MI, AAA |
| Left upper quadrant | Spleen (rupture after injury or in malaria), pancreatitis, pneumonia |
| Central (periumbilical) | Early appendicitis, small bowel obstruction, mesenteric ischaemia, AAA |
| Right iliac fossa | Appendicitis, ectopic, ovarian cyst or torsion, ileocaecal TB, Crohn's, stone |
| Left iliac fossa | Diverticulitis, sigmoid volvulus, ectopic, ovarian, stone |
| Loin to groin | Renal colic, pyelonephritis, AAA in the elderly |
| Suprapubic | Urinary retention, cystitis, pelvic inflammatory disease |
| Generalised | Peritonitis, obstruction, ischaemia, DKA, gastroenteritis |
Medical causes of belly pain
- DKA: vomiting, belly pain, deep breathing. Check sugar and ketones.
- Inferior MI: epigastric pain, sweating. ECG.
- Lower lobe pneumonia: fever, cough, crackles.
- Sickle cell crisis, porphyria, lead poisoning (rare).
- Typhoid: fever for a week or more, then pain.
- Abdominal TB: weeks of pain, weight loss, fever, ascites, a mass. Common in Pakistan.
History
- Onset (sudden or gradual), site, spread, character (colicky or constant), severity.
- Vomiting (before or after the pain), bowels, last flatus.
- Women: last period, contraception, discharge, pregnancy.
- Previous surgery (adhesions), hernias, gallstones, ulcers.
- NSAIDs and painkiller injections, alcohol, steroids.
- Fever, urinary symptoms, weight loss.
Examination
- Observations, look from the end of the bed (lying still suggests peritonitis, rolling around suggests colic).
- Gentle palpation, starting away from the pain. Guarding, rebound, rigidity.
- Pulsatile, expansile mass in the middle (AAA).
- All hernia sites, including femoral (below and lateral to the pubic tubercle) and the umbilicus.
- Testes in boys and men (torsion).
- Bowel sounds, rectal and vaginal examination where indicated (by the right person, with a chaperone).
Investigations
| Test | Why |
|---|---|
| Pregnancy test | Every woman who could be pregnant |
| CBC, CRP | Infection, bleeding |
| Urea, creatinine, electrolytes | Dehydration, kidney injury |
| LFTs, lipase or amylase | Biliary disease, pancreatitis |
| Lactate (blood gas) | Ischaemia, sepsis |
| Sugar and ketones | DKA |
| Urine dipstick | Infection, blood (stone) |
| ECG | Inferior MI |
| Erect chest X-ray | Free air under the diaphragm |
| Ultrasound | Gallbladder, kidneys, pelvis, free fluid, AAA at the bedside |
| CT abdomen and pelvis | The most useful scan in most adults when the diagnosis is unclear |
Pain relief
Painkillers do not hide the diagnosis. A comfortable patient is easier to examine. Never withhold pain relief "for the surgeon".
Common mistakes
- No pregnancy test.
- Calling an older man's belly and back pain "renal colic" without checking for an AAA.
- Missing a strangulated femoral hernia in an elderly woman.
- Missing mesenteric ischaemia because the belly is soft.
- Forgetting the ECG and sugar.
- Painkiller injection and discharge without a diagnosis.
Frequently asked questions
What are the dangerous causes of acute abdominal pain?
Ruptured abdominal aortic aneurysm, ruptured ectopic pregnancy, perforation, mesenteric ischaemia, bowel obstruction with strangulation, and severe pancreatitis. Medical causes such as MI and DKA must also be excluded.
Do painkillers mask the diagnosis of acute abdomen?
No. Opioid pain relief does not reduce diagnostic accuracy and should not be withheld.
Why is a pregnancy test needed in abdominal pain?
To identify ectopic pregnancy, which can be fatal if missed, and to guide imaging and drug choices.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 71-year-old has abdominal and back pain, fainted, has BP 88/54 and a pulsatile abdominal mass. What is the best management?
Answer: Vascular surgeon now, permissive hypotension. Suspected ruptured AAA in an unstable patient is a surgical emergency. Keep systolic around 70–90 if conscious.
- CT before calling surgeons: Unstable: theatre decision first.
- Ultrasound in the morning: Too late.
- Large fluid boluses to normal BP: Raises BP and worsens bleeding.
- Analgesia and observation: Fatal delay.
2. An elderly woman with AF has severe abdominal pain but a soft, barely tender abdomen. Lactate is 6 mmol/L. What should be feared?
Answer: Mesenteric ischaemia. Pain out of proportion to examination in a patient with AF suggests mesenteric embolism. CT angiogram and surgery now.
- Gastritis: Doesn't explain the lactate.
- Irritable bowel: No.
- Renal colic: Less likely.
- Constipation: Doesn't explain the lactate.
3. A diabetic man has epigastric pain and sweating. His abdomen is soft. Which test must not be missed?
Answer: ECG. Inferior myocardial infarction can present as epigastric pain, especially in diabetics.
- Urine dipstick only: Not enough.
- Amylase only: Check, but ECG first.
- Abdominal X-ray: Not first.
- Stool test: No.
4. A 75-year-old with atrial fibrillation has sudden severe central abdominal pain but a soft, minimally tender abdomen. Lactate is 6 mmol/L. What is the most likely diagnosis?
Answer: Mesenteric ischaemia. Acute mesenteric ischaemia (SMA embolus from AF, thrombosis on atheroma, venous thrombosis, non-occlusive low flow): pain out of proportion to examination, raised lactate, metabolic acidosis, later peritonitis and bloody stools. CT angiography confirms. Treat with resuscitation, heparin, and urgent revascularisation (embolectomy/endovascular) plus resection of dead bowel with second-look laparotomy.
- Biliary colic: Biliary colic is RUQ pain with normal lactate.
- Gastroenteritis: Gastroenteritis does not cause pain out of proportion with high lactate.
- Left renal colic: Renal colic causes loin pain.
5. A 74-year-old woman with atrial fibrillation (not anticoagulated) has sudden severe abdominal pain. She is writhing, but her abdomen is soft with little tenderness. Lactate is 6.5 mmol/L. What is the most likely diagnosis and investigation?
Answer: Mesenteric ischaemia — CT angiography. Pain out of proportion to examination findings in a patient with AF suggests an embolus to the superior mesenteric artery. Lactate rises as bowel becomes ischaemic. CT angiography confirms it. Treatment is urgent revascularisation (embolectomy or endovascular) and resection of dead bowel; mortality is high if delayed.
- Renal colic — CT KUB: Renal colic causes loin-to-groin pain with haematuria, and lactate is not usually raised; pain out of proportion with AF suggests mesenteric ischaemia.
- Perforated ulcer — erect CXR: Would cause a rigid abdomen.
- Acute pancreatitis — serum lipase: Unlikely without epigastric tenderness and risk factors.
6. An elderly smoker has severe abdominal pain 30 minutes after every meal, fears eating and has lost weight. Which artery is most likely narrowed?
Answer: Superior mesenteric artery. Chronic mesenteric ischaemia ('abdominal angina') is usually atherosclerotic narrowing of at least two of the coeliac, SMA and IMA, with the SMA most important. Gut demand rises after meals, causing pain, food fear and weight loss. Acute SMA occlusion (often embolic from AF) causes pain out of proportion to examination.
- Inferior mesenteric artery alone: Rarely causes symptoms alone (good collaterals).
- Renal artery: Causes hypertension, not post-meal pain.
- Splenic artery: Splenic infarction pain, not meal-related.
- Inferior phrenic artery: Not related.
7. A woman with a previous episode of pelvic inflammatory disease has a positive pregnancy test, lower abdominal pain and vaginal spotting. Where is an ectopic pregnancy most commonly located?
Answer: Ampulla of the fallopian tube. About 95% of ectopic pregnancies are tubal, most in the ampulla (where fertilisation occurs). Risk factors: previous PID or ectopic, tubal surgery, IUCD in situ, IVF and smoking. Isthmic ectopics rupture earlier because the isthmus is narrow. Diagnosis: β-hCG plus transvaginal ultrasound.
- Isthmus of the fallopian tube: Less common; ruptures earlier.
- Ovary: Rare.
- Cervix: Rare.
- Abdominal cavity: Rare.
References and dose sources
- Royal College of Surgeons of Edinburgh
- World Society of Emergency Surgery
- NICE NG156 — abdominal aortic aneurysm
- NICE NG126 — ectopic pregnancy
- NICE NG104 — pancreatitis
- Paracetamol dosing: Drugs.com: Acetaminophen (paracetamol) dosage (see also our paracetamol dose page)
- Morphine dosing: Drugs.com: Morphine dosage (see also our morphine dose page)
- Ondansetron dosing: Drugs.com: Ondansetron dosage (see also our ondansetron dose page)
- Metoclopramide dosing: Drugs.com: Metoclopramide dosage (see also our metoclopramide dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.