Surgery: Acute abdomen and emergency general surgery

• Approach: History and Examination | Causes by Region | Investigations | Initial Management | Emergency Laparotomy
• Conditions: Acute Appendicitis | Peritonitis and Perforation | Small Bowel Obstruction | Large Bowel Obstruction | Volvulus and Pseudo-obstruction | Mesenteric Ischaemia | Acute Pancreatitis | Complications of Pancreatitis
• Other causes: Gynaecological Causes | Urological Causes | Medical Causes of Abdominal Pain | Special Groups
• Revision: The Acute Abdomen at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

🚑 Acute abdomen and emergency general surgery. The "acute abdomen" is severe abdominal pain of recent onset that may need urgent surgery. Most patients can be sorted by where the pain is, how it started, and whether there are signs of peritonitis, obstruction or sepsis. Always think of pregnancy in women, AAA and ischaemia in older people, and medical causes that mimic surgical ones. Biliary disease is on the Upper GI and Hepatobiliary page; diverticulitis and colorectal emergencies on the Colorectal page; hernias on their own page.
Your four questions for every patient: Is the patient septic or shocked (resuscitate first)? Is there peritonitis, obstruction or ischaemia? Could this be a gynaecological, urological, vascular or medical cause? Does the patient need imaging now and a senior surgical decision about theatre?

History and Examination

• The pain (SOCRATES):
  • Onset — sudden (perforation, ruptured AAA, torsion, ectopic rupture, mesenteric embolus) versus gradual (inflammation — appendicitis, cholecystitis, diverticulitis).
  • Character — colicky (obstruction of a hollow tube — bowel, ureter, bile duct) versus constant (inflammation, ischaemia, peritonitis).
  • Site and movement — e.g. central then right iliac fossa (appendicitis); radiation to the back (pancreatitis, AAA), shoulder tip (diaphragm irritation — blood, pus, bile, ectopic), loin to groin (renal colic).
  • Severity — pain out of proportion to examination suggests mesenteric ischaemia.
• Associated symptoms — vomiting (bilious, faeculent, coffee-ground), bowel habit (diarrhoea, absolute constipation — no stool or flatus), bleeding, urinary symptoms, fever, jaundice, weight loss.
• Women — last menstrual period, possibility of pregnancy, vaginal bleeding or discharge, contraception, sexual history.
• Background — previous surgery (adhesions), hernias, gallstones, IBD, AF (emboli), vascular disease, alcohol, NSAIDs and steroids (perforation, masked signs), anticoagulants, immunosuppression, recent travel.
• Examination:
  • Observations — sepsis and shock (NEWS2, lactate).
  • General — lying still (peritonitis) versus writhing (colic), jaundice, dehydration.
  • Abdomen — distension, scars, tenderness, guarding, rigidity, rebound or percussion tenderness (peritonism), masses, pulsatile mass (AAA), bowel sounds (absent in peritonitis and ileus; high-pitched "tinkling" in obstruction).
  • Always examine the hernial orifices (inguinal, femoral, umbilical, incisional) and, in males, the testes.
  • Digital rectal examination when indicated (bleeding, masses, pelvic tenderness); chest examination (lower lobe pneumonia).
• Peritonism may be absent in older people, those on steroids or immunosuppressants, and in retrocaecal or pelvic appendicitis.

Causes by Region

Investigations

• Bedside — observations, urine pregnancy test in every woman of reproductive age, urinalysis (blood in renal colic — but also in appendicitis near the ureter), capillary glucose and ketones, ECG (MI, AF).
• Bloods — FBC, U&E, LFTs, amylase or lipase, CRP, lactate and blood gas, calcium, clotting, group and save (crossmatch if bleeding or likely theatre), blood cultures if febrile; β-hCG quantitative if pregnant.
• Imaging:
  • Erect chest X-ray — free gas under the diaphragm (perforation); lower lobe pneumonia. A normal film doesn't exclude perforation.
  • Abdominal X-ray — limited use; bowel obstruction (dilated loops), volvulus, some stones.
  • CT abdomen and pelvis with contrast — the key test in most adults: perforation, obstruction (site and cause), ischaemia, abscesses, appendicitis, diverticulitis, pancreatitis complications, AAA (CT angiography).
  • Ultrasound — gallbladder and bile ducts, gynaecological causes (transvaginal), appendicitis in children and pregnancy, kidneys (hydronephrosis), free fluid (FAST in trauma).
  • MRI — in pregnancy (appendicitis) when ultrasound is inconclusive.
• Lactate is raised late in mesenteric ischaemia — a normal lactate doesn't exclude it.
• Diagnostic laparoscopy — when the diagnosis is uncertain (e.g. young women with right iliac fossa pain); can also treat.

Initial Management

• Resuscitate — ABC, oxygen, IV access, fluids (sepsis or hypovolaemia), Sepsis Six if septic (antibiotics within 1 hour).
• Analgesia — give adequate pain relief early (including IV opioids); it does not mask the diagnosis or harm examination.
• Antiemetics; nil by mouth if surgery is possible; NG tube for vomiting or obstruction; urinary catheter and fluid balance if unwell.
• Antibiotics — for sepsis, peritonitis, cholangitis, appendicitis or diverticulitis per local guidelines (e.g. co-amoxiclav, or a cephalosporin plus metronidazole, or piperacillin–tazobactam if severe).
• VTE prophylaxis (unless bleeding or theatre imminent); review anticoagulants; correct clotting.
• Hold nephrotoxic and hypotensive drugs; manage diabetes (VRIII if nil by mouth); steroid cover if on long-term steroids.
• Early senior review and timely imaging; record a risk assessment and treatment escalation plan; involve critical care for sick patients.

Emergency Laparotomy

• High risk — 30-day mortality around 1 in 10 overall, higher in older and frail patients; NELA (National Emergency Laparotomy Audit) standards improve outcomes.
• Key standards:
  • Risk assessment documented before surgery (e.g. NELA risk score), and discussed with the patient and family.
  • CT reported before surgery (by a consultant radiologist where possible).
  • Antibiotics within 1 hour for sepsis; arrival in theatre within a time appropriate to urgency.
  • Consultant surgeon and anaesthetist present in theatre for higher-risk patients (e.g. predicted mortality 5% or more).
  • Post-operative critical care for higher-risk patients.
  • Geriatric medicine assessment for older or frail patients.
• Common reasons — perforation, obstruction with ischaemia or failure of conservative treatment, ischaemic bowel, anastomotic leak, intra-abdominal sepsis, bleeding.
• Shared decision-making — in very frail patients or those with a poor prognosis, surgery may not be in their interests; palliative care is a valid choice.

Acute Appendicitis

• The commonest surgical emergency — peak in teenagers and young adults but any age; caused by blockage of the appendix (faecolith, lymphoid swelling) and infection.
• Classic features — central abdominal pain moving to the right iliac fossa, anorexia, nausea and vomiting, low-grade fever; tenderness at McBurney's point (one-third of the way from the anterior superior iliac spine to the umbilicus).
• Signs — Rovsing's sign (pressing the left iliac fossa causes right-sided pain), psoas sign (pain on hip extension — retrocaecal appendix), obturator sign (pain on internal rotation of the flexed hip — pelvic appendix), percussion tenderness and guarding.
• Atypical presentations — retrocaecal (flank pain, psoas sign), pelvic (diarrhoea, urinary frequency, rectal tenderness), children and older people (rapid perforation, vague signs), pregnancy (pain higher as the uterus pushes the appendix up).
• Scores — Alvarado (MANTRELS), Adult Appendicitis Score or AIR score help decide who needs imaging, observation or surgery.
• Investigations — raised white count and CRP (can be normal early); pregnancy test; urinalysis; imaging — ultrasound in children and pregnancy, CT in most adults (especially older people, to exclude cancer and other causes), MRI in pregnancy if ultrasound is unclear.
• Management:
  • Laparoscopic appendicectomy — the standard; antibiotic prophylaxis; a short post-operative course for complicated (perforated or gangrenous) appendicitis.
  • Antibiotics alone — an option for some adults with uncomplicated appendicitis without an appendicolith (about a third later need surgery).
  • Appendix mass (inflamed appendix walled off by omentum, presenting after several days) — antibiotics ± drainage of any abscess; check for cancer later (colonoscopy or CT in older adults); interval appendicectomy in some.
• Complications — perforation, abscess (right iliac fossa or pelvic — swinging fever, diarrhoea, tender on rectal examination), wound infection, adhesions; rarely an appendiceal tumour found on histology (neuroendocrine or mucinous).
• Differential — ectopic pregnancy, ovarian torsion or cyst, PID, mesenteric adenitis (children — recent viral illness), Meckel's diverticulitis, Crohn's ileitis, UTI and renal colic, testicular torsion, caecal cancer (older adults), gastroenteritis.

Peritonitis and Perforation

• Peritonitis — inflammation of the peritoneum from infection or irritants (gastric acid, bile, bowel content, blood).
  • Localised — e.g. around an inflamed appendix or diverticulum.
  • Generalised — rigid "board-like" abdomen, patient lying still, pain on any movement, absent bowel sounds, sepsis and shock.
• Causes of perforation — perforated peptic ulcer (NSAIDs, steroids, smoking, H. pylori — sudden severe epigastric pain becoming generalised), diverticular perforation, perforated appendicitis, perforated colorectal cancer, ischaemic bowel, obstructed bowel (caecum), anastomotic leak, trauma, endoscopy, oesophageal rupture (Boerhaave — after forceful vomiting: chest pain, surgical emphysema — see the Upper GI page).
• Investigations — erect chest X-ray (free gas under the diaphragm — not always seen), CT (more sensitive; finds the source), bloods including amylase (can be mildly raised in perforation), lactate, cultures.
• Management:
  • Resuscitation, analgesia, IV broad-spectrum antibiotics, nil by mouth, NG tube, catheter; IV PPI for suspected ulcer.
  • Urgent surgery — laparoscopy or laparotomy: washout and repair (e.g. omental patch for a perforated duodenal ulcer), resection (Hartmann's procedure for perforated sigmoid diverticulitis with faecal peritonitis).
  • Conservative or radiological management for small contained perforations or abscesses (percutaneous drainage) in selected patients, or when surgery isn't in the patient's interests.
  • After a perforated ulcer — H. pylori testing and eradication, stop NSAIDs, long-term PPI as needed; endoscopy for gastric ulcers (exclude cancer).
• Spontaneous bacterial peritonitis (cirrhosis with ascites) is a medical condition — ascitic tap, antibiotics, no surgery (see the Gastroenterology chapters).

Small Bowel Obstruction

• Causes:
  • Adhesions from previous abdominal or pelvic surgery — the commonest cause in the UK.
  • Hernias — inguinal, femoral (often missed in older women), umbilical, incisional, internal.
  • Tumours (small bowel, or caecal cancer blocking the ileocaecal valve), Crohn's strictures, gallstone ileus (older women — gas in the bile ducts plus SBO), intussusception (in adults usually with a tumour as lead point), bezoars, radiation strictures, volvulus.
• Features — colicky central pain, early vomiting (bilious, later faeculent), distension, absolute constipation (later); tinkling bowel sounds; dehydration and electrolyte loss.
• Signs of strangulation (compromised blood supply — emergency) — constant rather than colicky pain, peritonism, fever, tachycardia, raised white count and lactate, a tender irreducible hernia.
• Imaging:
  • AXR — dilated small bowel over 3 cm, central loops with valvulae conniventes crossing the full width ("3, 6, 9 rule" — small bowel 3 cm, colon 6 cm, caecum 9 cm).
  • CT with IV contrast — confirms obstruction, finds the transition point and cause, and shows closed loops or ischaemia (poor wall enhancement, free fluid, mesenteric swelling, pneumatosis).
• Conservative management ("drip and suck") for uncomplicated adhesional obstruction:
  • Nil by mouth, NG tube on free drainage, IV fluids with potassium, analgesia, fluid balance, daily U&E.
  • Water-soluble contrast (Gastrografin) by mouth or NG — if it reaches the colon on X-ray within about 24 hours, the obstruction is likely to settle (and it may help resolution).
  • Most adhesional obstructions settle within 48–72 hours.
• Surgery (laparoscopy or laparotomy — adhesiolysis, resection, hernia repair) for strangulation or ischaemia, closed-loop obstruction, an obstructed hernia, failure to settle (usually 48–72 hours), or obstruction in a patient with no previous surgery ("virgin abdomen" — look hard for another cause on CT).
• Nutrition — consider parenteral nutrition if nil by mouth for a prolonged period, especially if already malnourished.

Large Bowel Obstruction

• Causes — colorectal cancer (most common), volvulus (sigmoid, caecal), diverticular stricture, faecal impaction, extrinsic compression (pelvic tumours), hernias (rarely).
• Features — gradual distension, absolute constipation, colicky lower abdominal pain, vomiting late; may have a history of change in bowel habit, weight loss or rectal bleeding.
• Closed-loop danger — if the ileocaecal valve is competent, gas can't escape back into the small bowel, so the caecum dilates — tenderness in the right iliac fossa and a caecum over about 9–12 cm risk perforation (faecal peritonitis — high mortality).
• Investigations — CT (site and cause, metastases, perforation); AXR shows dilated peripheral colon with haustra (which don't cross the full width).
• Management:
  • Resuscitation, analgesia, NG tube if vomiting, correct electrolytes, senior surgical review.
  • Obstructing left-sided cancer — emergency resection (Hartmann's procedure or resection with anastomosis ± defunctioning stoma), a loop colostomy, or a colonic stent (as a bridge to planned surgery or for palliation).
  • Right-sided cancer — right hemicolectomy (usually with primary anastomosis).
  • Perforation or impending perforation — emergency surgery.
• Pseudo-obstruction and volvulus — see the next section; faecal impaction — enemas, manual disimpaction, laxatives.

Volvulus and Pseudo-obstruction

• Sigmoid volvulus — the sigmoid colon twists on its mesentery:
  • Typically older, frail, chronically constipated people, care home residents, neurological or psychiatric conditions (and their drugs).
  • Sudden massive distension, pain, absolute constipation.
  • AXR — a huge dilated loop ("coffee bean" sign) rising from the pelvis; CT confirms and checks for ischaemia.
  • Treatment — flexible sigmoidoscopy decompression with a rectal (flatus) tube left in place; emergency surgery if ischaemia or perforation; recurrence is common — consider elective sigmoid colectomy if fit.
• Caecal volvulus — younger patients; dilated caecum in the left upper abdomen; usually needs surgery (right hemicolectomy).
• Midgut volvulus (malrotation) — babies and children with bilious vomiting — a surgical emergency (see the Paediatric Surgery chapter).
• Acute colonic pseudo-obstruction (Ogilvie's syndrome) — massive colonic dilatation without a mechanical blockage:
  • Risk factors — older age, recent surgery (especially orthopaedic and cardiac), serious illness, low potassium, magnesium or calcium, drugs (opioids, anticholinergics, calcium channel blockers), Parkinson's disease.
  • CT excludes a mechanical cause.
  • Treatment — correct electrolytes, stop drugs that slow the gut, mobilise, NG and rectal tubes; neostigmine (with cardiac monitoring — bradycardia; atropine available) if not settling; colonoscopic decompression; surgery if perforation or a very large caecum.

Mesenteric Ischaemia

• Acute mesenteric ischaemia — sudden loss of blood flow to the gut (see the Gastroenterology Anatomy, Physiology and Pharmacology chapter):
  • Causes — embolus to the SMA (AF, recent MI), thrombosis of a narrowed SMA (vascular disease), non-occlusive ischaemia (low cardiac output, vasopressors), mesenteric venous thrombosis (clotting disorders, cancer, portal hypertension).
  • Pain out of proportion to examination early; later peritonism, bloody diarrhoea, sepsis, shock.
  • Lactate rises late; CT angiography urgently.
  • Treatment — resuscitation, heparin, antibiotics, urgent revascularisation (embolectomy, angioplasty or stenting) and resection of dead bowel, often with a planned "second look" operation; high mortality; palliation may be appropriate in some.
• Ischaemic colitis — usually a less severe, non-occlusive ischaemia of the colon (watershed areas — splenic flexure, rectosigmoid) in older people: sudden left-sided pain then bloody diarrhoea; most settle with fluids and antibiotics; surgery if gangrene or perforation.
• Chronic mesenteric ischaemia — pain after eating, fear of food, weight loss — revascularisation (vascular surgery).

Acute Pancreatitis

• Causes ("I GET SMASHED"):
  • Gallstones and alcohol — about 80% together.
  • Idiopathic, trauma, steroids, mumps and other viruses, autoimmune, scorpion venom, hypercalcaemia, hypertriglyceridaemia (often over 10 mmol/L), hypothermia, ERCP, drugs (azathioprine, valproate, thiazides, mesalazine, GLP-1 agonists and others), pancreatic cancer.
• Features — severe constant epigastric pain radiating to the back, eased by sitting forward; vomiting; tachycardia, fever; rarely flank (Grey Turner's) or periumbilical (Cullen's) bruising in severe haemorrhagic pancreatitis.
• Diagnosis — two of: typical pain, amylase or lipase over 3 times the upper limit, imaging changes. CT is only needed early if the diagnosis is uncertain.
• Find the cause — ultrasound for gallstones in everyone, LFTs, calcium, triglycerides, alcohol history, drug history.
• Severity:
  • Glasgow (Imrie) score within 48 hours ("PANCREAS" — PaO2 under 8 kPa, Age over 55, Neutrophils/WCC over 15, Calcium under 2 mmol/L, Renal — urea over 16, Enzymes — LDH or AST high, Albumin under 32 g/L, Sugar — glucose over 10) — 3 or more = severe; CRP over 150 mg/L at 48 hours also predicts severity.
  • Revised Atlanta — mild (no organ failure or complications), moderately severe (organ failure under 48 hours or local complications), severe (organ failure over 48 hours).
• Management (NICE NG104):
  • IV fluids — goal-directed (balanced crystalloid); avoid both under-resuscitation and fluid overload.
  • Analgesia (opioids are fine), antiemetics, oxygen, monitor urine output, glucose and calcium; HDU or ICU for organ failure.
  • Early feeding — oral as tolerated, or enteral (NG or NJ) tube feeding in severe disease (better than parenteral nutrition).
  • No prophylactic antibiotics — give antibiotics only for proven infection (e.g. cholangitis, infected necrosis, pneumonia).
  • ERCP — urgently for cholangitis or persisting bile duct obstruction; not routinely for gallstone pancreatitis.
  • Cholecystectomy — during the same admission (or within 2 weeks) for mild gallstone pancreatitis; after recovery in severe cases.
  • Alcohol — thiamine, withdrawal management (see the Gastroenterology chapters), support to stop drinking.

Complications of Pancreatitis

Gynaecological Causes

• Always do a pregnancy test in women of reproductive age with abdominal pain.
• Ectopic pregnancy — usually 6–8 weeks after the last period; one-sided lower abdominal pain, vaginal bleeding (often light), shoulder tip pain, dizziness or collapse (rupture with internal bleeding); risk factors — previous ectopic, PID, tubal surgery, IVF, IUD in place. Positive pregnancy test with no intrauterine pregnancy on transvaginal ultrasound; serum β-hCG. Ruptured ectopic is an emergency — resuscitate and laparoscopic salpingectomy; methotrexate or expectant management for selected stable cases (NICE NG126).
• Ovarian torsion — sudden severe one-sided pain with nausea and vomiting, often with an ovarian cyst or mass; tender adnexa; ultrasound may show an enlarged ovary (normal Doppler flow doesn't exclude it) — urgent laparoscopy to untwist and save the ovary.
• Ruptured or haemorrhagic ovarian cyst — sudden pain mid-cycle, free fluid; usually conservative.
• Pelvic inflammatory disease — bilateral lower abdominal pain, fever, vaginal discharge, cervical motion tenderness; antibiotics (e.g. ceftriaxone plus doxycycline plus metronidazole); tubo-ovarian abscess may need drainage; Fitz-Hugh–Curtis syndrome (right upper quadrant pain from perihepatitis).
• Endometriosis — cyclical pain, painful periods and intercourse; ruptured endometrioma.
• Pregnancy-related — miscarriage, placental abruption, uterine rupture, HELLP (right upper quadrant pain), fibroid degeneration (see the Obstetrics chapters).

Urological Causes

• Renal colic — severe loin-to-groin colicky pain, restless patient, haematuria; CT KUB (non-contrast); NSAIDs; urgent decompression if infected and obstructed (see the Urology page).
• Pyelonephritis — fever, rigors, loin pain and tenderness, vomiting; urine culture, antibiotics; ultrasound to exclude obstruction if not settling.
• Acute urinary retention — painful, palpable bladder; catheterise; older men (prostate), drugs, constipation, after surgery.
• Testicular torsion — boys and young men may present with lower abdominal pain and vomiting — always examine the testes; emergency scrotal exploration.
• Ruptured AAA can mimic renal colic in older men — think of it in anyone over 60 with "first-ever renal colic" (see the Vascular page).

Medical Causes of Abdominal Pain

Special Groups

• Older people — present late and atypically (little pain, no fever, confusion, falls); higher risk of AAA, mesenteric ischaemia, perforated diverticular disease, cancer causing obstruction, volvulus, and perforated ulcers on NSAIDs; peritonism may be minimal; low threshold for CT.
• Immunosuppressed and steroid-treated patients — perforations and abscesses with few signs; consider CMV colitis, neutropenic enterocolitis (typhlitis) in chemotherapy.
• Pregnancy — appendicitis is the commonest non-obstetric emergency (pain may be higher up); cholecystitis and bowel obstruction also occur; use ultrasound and MRI; obstetric input; avoid delay (perforation risks the fetus).
• Children — appendicitis, intussusception (6–18 months — colicky pain, drawing up legs, redcurrant jelly stool), malrotation with volvulus (bilious vomiting — emergency), mesenteric adenitis, constipation, testicular torsion, DKA (see the Paediatric Surgery chapter).
• Bariatric surgery patients — internal hernia after gastric bypass (intermittent colicky pain — CT; low threshold for laparoscopy).
• Patients on anticoagulants — rectus sheath haematoma (painful mass in the abdominal wall, worse on tensing the muscles), retroperitoneal bleeding.

The Acute Abdomen at a Glance

Spot the Diagnosis