Pathophysiology of Colonic Stercoral Perforation
Stercoral perforation of the colon is caused by pressure necrosis of the bowel wall from impacted fecal masses (fecalomas), leading to ischemia, ulceration, and eventual perforation through the weakened colonic wall.
Mechanism of Stercoral Perforation
Primary Pathophysiological Process
- Pressure-induced ischemia: Hard fecal masses (scybala) exert sustained pressure on the colonic wall, causing compression of mucosal blood vessels 1
- Ischemic necrosis: The prolonged pressure leads to impaired blood flow and ischemic necrosis of the bowel wall 2
- Ulceration: Progressive ischemia causes mucosal ulceration and thinning of the bowel wall 1
- Perforation: Eventually, the weakened colonic wall ruptures, typically at the antimesenteric border where blood supply is poorest 2
Anatomical Considerations
- Over 90% of stercoral perforations occur in the sigmoid or rectosigmoid colon 2, 3
- The sigmoid colon is particularly vulnerable due to:
- Narrower lumen compared to other colonic segments
- Higher intraluminal pressure during defecation
- Relatively poor blood supply at the antimesenteric border
- Slower transit time allowing for greater water reabsorption and harder stool formation
Histopathological Features
- Localized mucosal ulceration at the site of pressure from fecaloma
- Thinning of the bowel wall with loss of normal architecture
- Inflammatory changes in surrounding tissues
- Perforation is typically found on the antimesenteric border of the colon 1
- The perforation is usually surrounded by an area of ischemic necrosis
Risk Factors and Contributing Conditions
Primary Risk Factors
- Chronic constipation: The fundamental predisposing factor 4
- Advanced age: More common in patients over 70 years 4
- Immobility: Contributes to decreased bowel motility 4
Medication-Related Risk Factors
- Opioid use: Significantly increases risk by reducing intestinal motility 5
- Acts on mu-opioid receptors in the intestine, decreasing peristalsis
- Increases water absorption from stool, making it harder
- NSAIDs: May contribute to stercoral perforation by:
- Impairing mucosal protective mechanisms
- Reducing mucosal blood flow
- Increasing susceptibility to pressure-induced damage 1
- Multiple medications: Polypharmacy in elderly patients often includes drugs with constipating effects 4
Comorbid Conditions
- Neurological disorders affecting bowel motility
- Systemic diseases that affect colonic blood flow
- Colonic motility disorders
- Dehydration contributing to harder stool consistency
Clinical Significance and Outcomes
- Stercoral perforation accounts for approximately 3.2% of all colonic perforations 4
- Mortality rates vary based on surgical approach:
- 57% with closure of perforation and proximal colostomy
- 43% with exteriorization alone
- 32% with resection of the diseased segment and exteriorization 3
- Early recognition is critical as the condition presents with peritonitis and can rapidly progress to septic shock 4
Diagnostic Considerations
- Only 11% of cases are correctly diagnosed preoperatively 3
- Key diagnostic findings include:
- History of chronic constipation
- Acute abdominal pain and distension
- Signs of peritonitis
- Free air under the diaphragm on imaging
- Fecal impaction visible on CT scan 5
Understanding the pathophysiology of stercoral perforation is essential for early diagnosis and appropriate surgical management, as this condition carries significant morbidity and mortality if not promptly addressed.