Large bowel obstruction

Mechanical bowel obstruction distal to the ileocaecal valve.

Epidemiology

Distension of the colon occurs as a result of gas and stool that gather proximal to the obstruction
Pressure within the bowel wall can rise above the capillary pressure, diminishing adequate oxygenation, leading to ischaemic necrosis and perforation
Necrosis and perforation usually occurs in the caecum due to Laplace's law (largest diameter - will distend more under lower pressures and hence develop more wall stress)
Venous ischaemia can also develop due to mesenteric compression in strangulated hernias and volvulus

Increased peristalsis and low-grade colicky pain
- Late obstruction may have decreased bowel sounds
Acute obstructions can be dramatic rapid-onset pain, distension and tenderness
Chronic progressive obstructions may describe more of increasing constipation, pencil-thin stools, and intermittent pain
Functional obstructions usually have distension, vague abdominal pain, and weak or absent bowel sounds
Ask about weight loss, bleeding, bowel habits, night sweats. Check for hernias and incisions. DRE.
Classically, a mechanical obstruction will give a collapsed rectum, while a pseudo-obstruction will give a capacious rectum on DRE. Also need to exclude a synchronous rectal cancer.

Plain film - 'bent inner sign' pointing to RUQ (sigmoid volvulus) and coffee bean sign pointing to LUQ (caecal volvulus)
CT with IV contrast. According to Schein, no need for rectal or oral contrast
- Contrast enema can be useful to evaluate distal causes of LBO (note use water soluble contrast, not barium, so it can't be absorbed into peritoneum if there is a perf)
Check for closed-loop obstructions
- Competent ICV
- Hernia
- Volvulus

- Fluid resus/electrolytes
- Consider IDC
- NGT for most patients
- Stoma marking

- Signs of perforation
- Ischaemia, including closed loop (pneumatosis coli)
- Peritonitis
- Impending caecal perforation (diameter >10cm)
- Tachycardia, hypotension, lactic acidosis

Right-sided obstructing lesion - right hemicolectomy
- If perforation or peritonitis, ischemia or necrosis, poor nutrition, sepsis, immunosuppression or poor overall health, should have end ileostomy (70% of these will never get reconnected)
- Self-expanding metal stent is also an option as a bridge to hemicolectomy
Left-sided obstructing lesions are a bit more diverse in options/less clear-cut
- Hartmann's
- Subtotal colectomy (if significant proximal colon dilatation or ischaemia)
- Proximal diversion
- Loop colostomy

If the large bowel is severely distended and impeding view, decompress it with a 14G needle on a syringe with the plunger removed, and attach to suction. Put that needle through the tenia, ideally at a spot where you will make a hole anyway for the anastomosis. If that fails due to fecal build-up, put a Poole sucker through the hole.
If in doubt, do an oncologic resection
If there is a large fixed mass in the pelvis, don't try too hard to resect it
Consider on-table colonic lavage if doing an anastomosis, however UTD says not necessary
- Divide distally and place the open distal end in a clean dish
- Pass a 16Fr Foley through the base of appendix, run 4-6L of warm saline through until it comes out clear, then close the appendicectomy

Indications
- Poor candidates for surgery
- Locally advanced/metastatic disease (neoadjuvant CTX)
Technically possible in 90% of patients
Complications
- Migration
- Regrowth and re-obstruction
- Perforation
Often used as a bridge to surgery
Surgery is still preferred if there's no need to optimise oncologic outcomes