Large Bowel Obstruction

Dheeraj Reddy

Overview

  • Large bowel obstruction accounts for ~25% of bowel obstruction presentations but is less common than small bowel obstruction (SBO).
  • Prompt recognition is critical due to risk of ischemia, perforation, and underlying malignancy.

Etiology

  • Malignant (~60%) 
    • Colorectal cancer is the most common cause and may be the initial presentation. 
  • Benign 
    • Volvulus (sigmoid, cecal): 15–20%.
    • Strictures: prior colorectal resection, diverticulitis, or IBD.
    • Fecal impaction.
    • Less common: adhesions, hernia (~2.5%).

Clinical Presentation (varies by etiology and acuity)

  • Acute onset (e.g., volvulus): 
    • Abdominal pain (typically infraumbilical, crampy, colicky). 
    • Obstipation (inability to pass stool or flatus).
    • Progressive abdominal distension.
    • Pain may occur in paroxysms every 20–30 minutes.
    • Sudden pain relief followed by worsening pain suggests perforation.
    • Peritoneal signs indicate possible ischemia or perforation.
    • Nausea and vomiting may be absent if the ileocecal valve is competent.
  • Subacute or indolent onset (e.g., malignancy): 
    • Progressive change in bowel habits over weeks to months.
    • Abdominal distension.
    • Weight loss.
    • Dehydration.

Evaluation

  • Laboratory studies: 
    • CBC, BMP.
    • CEA if imaging suggests malignancy.
  • CT abdomen/pelvis with contrast (preferred): >90% sensitivity and specificity 
    • Findings: proximal colonic dilation with distal collapse and transition point.
    • Suggestive features: 
    • “Apple core” lesion → malignancy.
    • Two adjacent transition points → volvulus.
    • Normal bowel diameter (“3–6–9 rule”): small bowel <3 cm, colon <6 cm, cecum <9 cm.
  • Abdominal X-ray: 
    • Poor sensitivity and specificity.
    • May show “coffee bean sign” in volvulus.

Differential

ConditionKey Features
Small bowel obstructionPrior abdominal surgery, early vomiting, small bowel dilation
Toxic megacolonSystemic toxicity, associated with C. difficile or IBD, diffuse colonic dilation without transition point
Ogilvie syndromeColonic dilation without mechanical obstruction or transition point
Paralytic ileusDiffuse dilation involving both small and large bowel, commonly postoperative

Management

  • Initial management (all patients): 
    • Bowel rest (NPO).
    • IV fluid resuscitation.
    • Electrolyte correction.
    • Nasogastric decompression if significant distension or vomiting.
    • Oral bowel preparation is contraindicated.
  • Urgent surgery indications: 
    • Hemodynamic instability.
    • Peritonitis.
    • Evidence of ischemia, perforation, or closed-loop obstruction.
  • Stable patients: 
    • Malignant obstruction: 
      • Endoscopic stenting (particularly left-sided lesions) may be used as a bridge to surgery or for palliation.
      • Definitive treatment is surgical resection.
    • Volvulus: 
      • Sigmoid volvulus: endoscopic detorsion followed by semi-elective surgical resection.
      • Cecal volvulus: surgery.
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