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ukmla 2026

GI Perforation and Peritonitis

Full-thickness breach of the GI tract wall leading to leakage of luminal contents into the peritoneal cavity, causing peritonitis — a surgical emergency with high mortality if untreated

Review date
reviewed 2026-04-05
Reading time
5 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Gastroenterology & Hepatologyless-commonacute
On this page
Condition details
Gastroenterology & Hepatology
less-common
5 min read
reviewed 2026-04-05
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About This Page

This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.

Key points

  • GI perforation = full-thickness bowel wall breach → leakage of contents into peritoneum → peritonitis
  • Common causes: perforated peptic ulcer (anterior DU), perforated appendicitis, diverticular perforation, colorectal cancer, toxic megacolon
  • Classic presentation: sudden severe abdominal pain → rigid "board-like" abdomen with generalised guarding, absent bowel sounds, sepsis
  • Erect CXR: free air under the diaphragm (pneumoperitoneum) in ~75% of perforations. CT is more sensitive
  • Management: aggressive resuscitation + IV antibiotics + emergency laparotomy (or laparoscopy)

Overview

GI perforation occurs when there is a full-thickness breach of the gastrointestinal tract wall, allowing luminal contents (gastric acid, bile, faeces, bacteria) to contaminate the peritoneal cavity. This triggers an intense inflammatory response (chemical peritonitis from gastric/duodenal contents, or bacterial peritonitis from colonic contents). The severity depends on the site of perforation (upper GI = chemical initially, lower GI = faecal peritonitis with higher mortality), the degree of contamination, and the time to intervention. Peritonitis may be localised (abscess formation) or generalised (diffuse peritoneal contamination), and can be primary (spontaneous bacterial peritonitis in cirrhotics), secondary (from perforation), or tertiary (persistent infection post-surgery).

Epidemiology

The most common cause of peritonitis requiring emergency surgery in the UK is perforated appendicitis, followed by perforated peptic ulcer and perforated diverticular disease. Overall mortality from faecal peritonitis is 30–50%. Mortality from perforated peptic ulcer is approximately 5–10% with prompt treatment. Risk factors for perforation include NSAID use (peptic ulcer), immunosuppression (delayed presentation), and bowel obstruction (caecal perforation from closed-loop LBO).

Clinical Features

Symptoms
Sudden onset severe abdominal pain (often described as "worst ever" — may be initially localised then becomes generalised)
Pain worsened by any movement, breathing, or coughing
Nausea and vomiting
Inability to pass flatus or open bowels (paralytic ileus)
Shoulder tip pain (diaphragmatic irritation from subphrenic free air/fluid)
Signs
Rigid "board-like" abdomen with involuntary guarding (peritonism)
Generalised abdominal tenderness with rebound
Absent bowel sounds (paralytic ileus)
Tachycardia, hypotension, fever (sepsis/septic shock)
Lying very still (any movement worsens peritoneal irritation)
Percussion tenderness (gentle tap causes pain)
Loss of liver dullness on percussion (free air replacing normal liver dullness)

Investigations

First-line
Erect chest X-rayFree air (pneumoperitoneum) under the diaphragm — present in ~75% of perforations. Quick, readily available
BloodsFBC (leucocytosis), CRP (markedly raised), U&Es, lactate (raised = tissue hypoperfusion/ischaemia), amylase (raised in upper GI perforation — can mimic pancreatitis), blood gas, group and save/crossmatch
Blood culturesBefore starting antibiotics — peritonitis is a septic emergency
Second-line
CT abdomen/pelvis with contrastGold standard if diagnosis uncertain. More sensitive than CXR for pneumoperitoneum. Identifies site, cause, and extent of contamination
Specialist
Diagnostic peritoneal lavageRarely needed — historical investigation largely replaced by CT

Management

Sepsis guidelines and emergency surgery protocols
1
Resuscitation
  • ABCDE approach
  • Sepsis 6: blood cultures, lactate, IV antibiotics, IV fluids, urine output monitoring, oxygen
  • IV broad-spectrum antibiotics: piperacillin-tazobactam 4.5 g TDS or cefuroxime 1.5 g TDS + metronidazole 500 mg TDS
  • NG tube on free drainage (decompression)
  • Urinary catheter (fluid balance)
  • Analgesia (IV opioid — do NOT withhold analgesia)
2
Surgical management
  • Emergency laparotomy (or laparoscopy): indicated in virtually all cases of generalised peritonitis from perforation
  • Perforated peptic ulcer: omental patch (Graham patch) repair + peritoneal washout
  • Perforated appendicitis: appendicectomy + washout
  • Perforated diverticulitis: Hartmann procedure (sigmoid resection + end colostomy) — or primary anastomosis ± defunctioning ileostomy in selected cases
  • Perforated colorectal cancer: resection + stoma (usually Hartmann's) + MDT referral post-recovery
  • Peritoneal washout and drainage in all cases
3
Post-operative
  • ICU/HDU care for septic patients
  • Continue IV antibiotics (typically 5–7 days)
  • Monitor for complications: anastomotic leak, wound infection, intra-abdominal abscess, organ failure
  • VTE prophylaxis, nutritional support

Complications

  • Septic shock and multiorgan failure: The leading cause of death — from overwhelming bacterial contamination
  • Intra-abdominal abscess: Localised collection post-perforation or post-operatively — may require percutaneous drainage
  • Wound infection: High rate after contaminated surgery
  • Adhesional bowel obstruction: Long-term complication of any abdominal surgery/peritonitis
  • Death: Faecal peritonitis carries 30–50% mortality even with surgery
UKMLA Exam Tips
  • 1Free air under diaphragm on erect CXR = pneumoperitoneum = visceral perforation until proven otherwise
  • 2Anterior DU is the commonest peptic ulcer to perforate. Posterior DU is the commonest to bleed (gastroduodenal artery)
  • 3Rigid "board-like" abdomen with absent bowel sounds = peritonitis — do NOT delay surgery for imaging if clinical picture is clear
  • 4Raised amylase in perforation can mimic pancreatitis — CT differentiates
  • 5Do NOT withhold analgesia in suspected peritonitis — opioids do NOT mask peritoneal signs in a meaningful way
  • 6Loss of liver dullness on percussion = free intraperitoneal air — a classic clinical sign

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Verified Sources & References

NICE NG51 — Sepsis
NELA (National Emergency Laparotomy Audit)
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