Stercoral Perforation and Faecal Impaction
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Direct answer
Stercoral perforation is bowel rupture caused by a hard faecal mass: impacted faeces compress the mucosa against the rigid wall, pressure necrosis carves a stercoral ulcer, and the weakened wall bursts — accounting for roughly 3% of colonic perforations. The sigmoid colon and rectosigmoid are the favourite sites, and the typical patient is an elderly, chronically constipated person on opioids or psychotropics. Presentation is usually sudden faecal peritonitis, though a smouldering sealed-off form exists. Plain films show pneumoperitoneum over a pelvis loaded with faeces; CT is diagnostic. Treatment is resuscitation and laparotomy with resection — usually Hartmann's procedure — and mortality is high, driven by faecal contamination, delay and frailty.
What you must remember
- Mechanism in three steps: inspissated faeces create a "pressure" effect against the wall — the classical teaching invokes localised antiperistaltic contractions raising intraluminal pressure over the mass; pressure necrosis produces a stercoral ulcer; perforation follows at the thinned site.
- Site preference: sigmoid and rectosigmoid — the narrowest, least vascular and most faeces-holding segment; antimesenteric border perforation is typical.
- Risk profile: elderly, chronic constipation, opiate and anticholinergic or psychotropic drugs, chronic renal failure with phosphate enemas or binders, hypothyroidism, neurological disease, and institutionalised immobility; faecal impaction in children suggests Hirschsprung disease until excluded.
- Two clinical patterns: acute catastrophic peritonitis with shock, or chronic smouldering sealed perforation with mass, fever and weight loss that mimics malignancy or diverticulitis.
- Imaging signature: pneumoperitoneum with striking faecal loading; CT shows discontinuity of the bowel wall adjacent to a large faecolith, extraluminal gas and fluid — findings that preclude any endoscopic or conservative plan.
- Operation of choice: segmental resection of the perforated colon with end colostomy (Hartmann's) or primary anastomosis with diversion depending on contamination and the patient's state; simple suture of a stercoral ulcer fails because the whole wall around it is diseased.
- Mortality: historically 30-45% — faecal peritonitis in an elderly patient is among the worst surgical abdominal emergencies.
How the exam frames it
The discriminating stem contrasts stercoral perforation with diverticular perforation and with colorectal cancer: the tell is faecal loading plus chronic constipation and no mass lesion. Expect the 3% share of colonic perforations, the sigmoid predilection, and the reason suture repair alone fails — the pressure necrosis extends beyond the visible defect. In vivas, the pressure-mechanism explanation and the Hartmann's rationale (contamination, age, diseased wall) are the quotable anchors; the paediatric hook — faecal impaction suggesting Hirschsprung disease — is the cross-link examiners add to the same question.
Frequently asked questions
What is a stercoral ulcer?
A pressure necrosis ulcer of the colonic wall created by a hard impacted faecal mass; it precedes most stercoral perforations and is found at the sigmoid or rectosigmoid.
Why does simple oversewing fail?
Necrosis extends beyond the visible hole into a devitalised wall under continuing luminal pressure, so the segment needs resection rather than repair.
Which imaging findings are diagnostic?
CT demonstrating bowel wall discontinuity adjacent to a large faecolith with extraluminal gas and fluid; plain films add pneumoperitoneum over faecal loading.
What is the usual operation?
Hartmann's procedure — resection of the perforated sigmoid with end colostomy and closed rectal stump — or resection with diversion in selected fitter patients.
How is stercoral perforation prevented?
A regulated bowel regimen in high-risk elderly and immobile patients: stool softeners, avoidance of constipating drugs, and early attention to missed bowel actions.