Colonic perforation

Overview

•Decreased mesenteric blood flow → mucosal ischaemia → transmural necrosis → perforation

•Causes: atherosclerosis, thrombosis, or embolism (e.g. from atrial fibrillation)

•Splenic flexure and sigmoid colon most vulnerable - watershed blood supply between SMA and IMA territories

Presentation

•Sudden-onset severe abdominal pain - may begin focally (e.g. left iliac fossa) then generalise

•Bloody stool - marker of mucosal ischaemia

•Nausea and vomiting

•Guarding and rigidity - involuntary, board-like abdomen in generalised peritonitis

•Tachycardia and hypotension - early sepsis and hypovolaemia

•Tachypnoea - compensatory response to metabolic acidosis

🎯

Classic ischaemic colitis triad: sudden-onset abdominal pain + bloody stool + new-onset AF + thumbprinting on AXR. New AF → embolic cause → risk of transmural infarction and perforation.

Investigations

•Arterial blood gas - metabolic acidosis (low pH, low HCO3, elevated lactate); lactate is a key severity marker for bowel ischaemia/sepsis

•Erect CXR - free air under diaphragm confirms perforation; absent in up to 30% so negative result does not exclude perforation

•Abdominal X-ray - thumbprinting (mucosal oedema in ischaemia), dilated loops, or free air; limited sensitivity

•FBC - raised WCC (neutrophilia); CRP - markedly elevated; U&Es - AKI common in sepsis

🏆 Gold standard

•CT abdomen/pelvis with IV contrast - confirms free air and free fluid, localises perforation, identifies underlying cause (ischaemia, tumour, diverticular disease), guides surgical planning

Management

•Colonic perforation is a surgical emergency - resuscitate and plan surgery in parallel, do not delay theatre

•Analgesia, IV fluids, nil by mouth

•IV broad-spectrum antibiotics (e.g. piperacillin-tazobactam) - before surgery; blood cultures first where possible

•Ischaemic colitis - additional options: thrombolytic therapy, angioplasty, or surgery; anticoagulation for embolic causes (e.g. AF); vascular surgery/IR input for mesenteric vessel assessment

•Hartmann's procedure - appropriate emergency operation for generalised faecal peritonitis (e.g. perforated sigmoid diverticulum); stoma reversal planned 3-6 months later

⚠️

Anti-diarrhoeal drugs (e.g. loperamide) are absolutely contraindicated in toxic megacolon - they reduce colonic motility, worsen distension, and markedly increase perforation risk.

Prognosis

•Mortality from generalised faecal peritonitis up to 40%, particularly in elderly patients with co-morbidities

•Key determinants of outcome: early surgery, aggressive resuscitation, targeted antibiotic therapy

•Localised perforation managed with antibiotics and drainage carries significantly better prognosis