Large Bowel Obstruction

Obstruction distal to the ileocecal valve — see Small Bowel Obstruction for the proximal analog. Content below is from a textbook reference chapter (Sabiston Ch52 - Diverticular Disease, Obstruction & Pseudo-Obstruction), not primary literature — treat as background/orientation rather than critically-appraised evidence.

Classification and etiology

Mechanical (dynamic):

Location	Common causes
Intraluminal	Neoplasm, foreign body, bezoar, fecal impaction
Mural	Diverticular stricture, Crohn stricture, ischemic stricture, radiation stricture, infectious (LGV, TB, schistosomiasis), Hirschsprung disease
Extraluminal	Sigmoid/cecal volvulus, hernia (inguinal/ventral/internal), metastatic/intraabdominal tumor, abdominal abscess, retroperitoneal fibrosis, adhesions (uncommon in large bowel)

Functional (adynamic/pseudo-obstruction): colonic pseudo-obstruction (Ogilvie syndrome — see Colonic Pseudo-Obstruction (Ogilvie Syndrome)), toxic megacolon, paralytic ileus.

Colorectal cancer is the most common cause of large bowel obstruction in the US. Volvulus (mostly sigmoid) is more common worldwide in Russia, Eastern Europe, Africa, the Middle East, and India, and is estimated to cause roughly a third of large bowel obstructions globally.

Closed-loop obstruction

Both the proximal and distal segments of a bowel loop are blocked (classically volvulus or strangulated hernia; also an obstructing cancer with a competent ileocecal valve, which prevents retrograde decompression into the small bowel). High-risk pattern — progressive distension raises intraluminal pressure toward capillary pressure, causing ischemic necrosis and perforation with little warning. Must be promptly recognized and treated. Obstructing cancers with an incompetent ileocecal valve decompress retrograde into the small bowel and present less acutely.

Diagnosis

• Plain film: localizes/screens, shows degree of distension and ileocecal valve status.
• Water-soluble or IV-contrast CT: location and etiology (including diverticulitis, IBD, extraluminal causes), plus signs of ischemia/impending perforation.
• Flexible endoscopy: diagnostic and can be therapeutic (detorsion of sigmoid volvulus, stenting).
• Labs: leukocytosis, elevated lactate, base excess, and decreased pH all associate with more severe/urgent presentations.

Treatment (etiology-specific)

• Sigmoid volvulus: endoscopic decompression (rigid or flexible sigmoidoscope, rectal tube proximal to the torsion) first-line. If unsuccessful → surgery (resection, colostomy, Hartmann’s). If decompression succeeds → elective sigmoid resection with primary anastomosis is recommended given the high recurrence rate without resection.
• Cecal volvulus: primary resection and anastomosis (typically not managed with endoscopic detorsion, unlike sigmoid volvulus).
• IBD-related obstruction: active-disease strictures often respond initially to steroids; fibrostenotic strictures may need surgery.
• Paracolic abscess: percutaneous drainage.
• Foreign body: usually endoscopic removal.
• Fecal impaction: stool softeners/laxatives plus manual disimpaction (bedside or OR).
• Hernia causing obstruction: usually requires surgery.
• Malignant obstruction:
  • Low/mid rectal cancer: usually needs an initial diverting stoma to allow neoadjuvant chemoradiation before definitive surgery.
  • Sigmoid/left colon: endoscopic stenting as a bridge to surgery, or straight to surgery. Surgical options: Hartmann’s procedure, or primary anastomosis with or without a diverting stoma.
  • Ischemic/nonviable cecum: subtotal colectomy.
  • Right-sided obstruction: right hemicolectomy with primary anastomosis (generally well tolerated even in the obstructed setting).
  • Unstable patients at high risk of anastomotic failure: temporary diverting stoma, or exteriorization of the anastomosis as a loop ileostomy.

Open items / gaps

• No primary trial data yet in the wiki on stenting-as-bridge-to-surgery vs. straight-to-surgery for malignant obstruction (a genuinely contested area in the literature) — this chapter states both as options without comparative data.
• Endoscopic stent outcomes/complication rates not covered here.
• Cross-link to Diverticulitis for diverticular stricture as a mural cause once that overlap is worth spelling out explicitly.