The acute abdomen — Free Resources

Causes by site of pain

Site	Surgical causes	Do not miss
Right upper quadrant	Biliary colic, cholecystitis, cholangitis, liver abscess, perforated duodenal ulcer	Right lower lobe pneumonia, hepatitis, myocardial infarction, sickle cell crisis
Epigastrium	Perforated or bleeding peptic ulcer, pancreatitis, gastric outlet obstruction	Myocardial infarction, aortic dissection, DKA
Left upper quadrant	Splenic rupture, splenic infarct (sickle cell), pancreatitis	Left lower lobe pneumonia
Periumbilical	Early appendicitis, small bowel obstruction, mesenteric ischaemia, ruptured abdominal aortic aneurysm	—
Right iliac fossa	Appendicitis, appendix mass, ileocaecal tuberculosis, typhoid perforation, Crohn's disease, ureteric colic, Meckel's diverticulitis	Ectopic pregnancy, ovarian torsion, pelvic inflammatory disease, testicular torsion
Left iliac fossa	Sigmoid volvulus, diverticulitis, colorectal carcinoma, ureteric colic	Ectopic pregnancy, ovarian pathology
Loin	Ureteric colic, pyelonephritis, renal abscess	Ruptured aneurysm
Suprapubic	Acute urinary retention, cystitis	Pregnancy complications
Generalised	Peritonitis (any perforation), obstruction, mesenteric ischaemia, pancreatitis	DKA, sickle cell crisis, porphyria, lead poisoning

Peritonitis or colic?

Feature	Peritonitis (inflammation)	Colic (obstruction of a hollow tube)
Pain	Constant, worse on movement and coughing	Comes in waves, with pain-free spells
Patient	Lies still	Restless, rolling about
Signs	Guarding, rebound or percussion tenderness, rigidity	Tenderness may be mild between spasms
Bowel sounds	Reduced or absent	Normal or hyperactive (obstruction)
Examples	Perforation, appendicitis, cholecystitis	Biliary, ureteric, intestinal colic

Intestinal obstruction

Feature	Small bowel	Large bowel
Common causes (Nigeria)	Obstructed hernia, adhesions, intussusception, tuberculosis, worm bolus in children	Sigmoid volvulus, colorectal cancer, faecal impaction
Common causes (world)	Adhesions, hernias, Crohn's disease, tumours	Colorectal cancer, diverticular stricture, volvulus
Vomiting	Early, bilious, then faeculent	Late
Distension	Mild to moderate, central	Marked, flanks
Constipation	Late	Early, absolute
X-ray	Central loops over 3 cm with valvulae conniventes crossing the whole width ("stack of coins")	Peripheral loops over 6 cm (caecum over 9 cm) with haustra that do not cross the full width

Signs of strangulation

Constant pain, fever, tachycardia, localised tenderness, peritonism, a tender irreducible hernia, leucocytosis, raised lactate and acidosis. Any of these means surgery now.

Non-operative management of adhesive small bowel obstruction

"Drip and suck": nasogastric decompression, IV fluids, correct electrolytes
Water-soluble contrast challenge (100 mL of Gastrografin via nasogastric tube): contrast in the colon on an X-ray within 24 hours predicts resolution
Operate if there are signs of strangulation, contrast fails to reach the colon, or no resolution in 48–72 hours

Plain X-ray signs to recognise

Sign	Meaning
Free gas under the diaphragm on an erect chest X-ray	Perforated viscus (or recent surgery)
Rigler's sign — both sides of the bowel wall visible	Pneumoperitoneum on a supine film
Coffee-bean loop from the pelvis	Sigmoid volvulus
Thumbprinting	Colonic wall oedema — ischaemic colitis, severe colitis
Toxic megacolon — transverse colon over 6 cm	Severe colitis
Air in the biliary tree with small bowel obstruction	Gallstone ileus (Rigler's triad adds an ectopic gallstone)
Sentinel loop, colon cut-off sign	Acute pancreatitis
Portal venous gas, pneumatosis intestinalis	Bowel ischaemia

Acute pancreatitis

Diagnosis — two of three: typical epigastric pain radiating to the back; lipase or amylase over 3 times the upper limit; characteristic imaging.

Causes — "I GET SMASHED": Idiopathic, Gallstones, Ethanol, Trauma, Steroids, Mumps and other viruses, Autoimmune, Scorpion venom, Hypertriglyceridaemia and hypercalcaemia, ERCP, Drugs (azathioprine, valproate, thiazides, HIV drugs).

Revised Atlanta severity

Severity	Definition
Mild	No organ failure, no local or systemic complications
Moderately severe	Transient organ failure (resolves within 48 hours), or local complications
Severe	Persistent organ failure (over 48 hours)

Modified Glasgow (Imrie) score — within 48 hours; 3 or more predicts severe disease

PANCREAS: PaO₂ under 8 kPa; Age over 55; Neutrophils (WBC) over 15 × 10⁹/L; Calcium under 2 mmol/L; Renal — urea over 16 mmol/L; Enzymes — LDH over 600 IU/L or AST over 200 IU/L; Albumin under 32 g/L; Sugar — glucose over 10 mmol/L.

Management principles

Moderate, goal-directed fluids with Hartmann's — for example 1.5 mL/kg/hour after a 10 mL/kg bolus only if hypovolaemic (WATERFALL trial: aggressive fluids increased fluid overload without benefit)
Early oral or enteral feeding as tolerated; nasojejunal or nasogastric feeding if not
No prophylactic antibiotics; treat proven infection
CT at 72–96 hours only if not improving or diagnosis unclear — not on admission
Gallstone pancreatitis: ERCP within 24 hours only for coexisting cholangitis; cholecystectomy during the same admission for mild disease
Infected necrosis: antibiotics, then the step-up approach — percutaneous or endoscopic drainage first, delayed necrosectomy (ideally after 4 weeks when walled off)

Emergency laparotomy pathway

Senior review and risk score (NELA or P-POSSUM) documented
Antibiotics within 1 hour if sepsis is suspected
CT reported before surgery where the patient is stable
Theatre within the NCEPOD timeframe; consultant surgeon and anaesthetist for high-risk patients
Post-operative critical care for predicted mortality over 5%
Frailty assessment and geriatric input for those over 65

Examiner questions

References

O'Connell PR, McCaskie AW, Sayers RD, eds. Bailey & Love's Short Practice of Surgery. 28th ed. Boca Raton: CRC Press; 2023.
Banks PA, Bollen TL, Dervenis C, et al. Classification of acute pancreatitis — 2012: revision of the Atlanta classification and definitions by international consensus. Gut. 2013;62:102–11.
Di Saverio S, Podda M, De Simone B, et al. Diagnosis and treatment of acute appendicitis: 2020 update of the WSES Jerusalem guidelines. World Journal of Emergency Surgery. 2020;15:27.