Large Bowel Obstruction

DEFINITION

Blockage of the colon with upstream distention, a serious and rapidly progressive disorder that often requires surgical intervention.
Also discusses role of stents in colonic obstruction
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INCIDENCE

 By cause; common surgical emergency.
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AETIOLOGY

Pathogenesis

May come from inside the bowel, the bowel wall, or outside the wall.

Within Lumen
Eg foreign body, bezoar, inspissated barium, rock-hard faeces.

Within Wall
Cancer (90%)
- 20% present this way, typically stage III-IV.
Volvulus (5%)
Divertic (3%).
Strictures, eg IBD, TB, post-ischemic colitis
Post-surgical adhesions/strictures.
Intussusception
Hirschsprung (kids)

Outside wall (less common in LB)
Hernias.
Tumours in adjacent organs.
Bands and adhesions.

Must differentiate from pseudo-obstruction
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BIOLOGICAL BEHAVIOUR

Pathophysiology
Large peristaltic movements try to overcome the obstruction.
Colicky pain

Complications
Wall may become ischaemic +/- over-distended.
And perforate.
Typically at caecum due to LaPlace's law (tension proportional to radius and inversely to wall thickness):
- T=Pr/2t where T=tension, P=pressure, r=radius, t=wall thickness.
--> circular muscle layer can tear, or can get ischaemic necrosis with subsequent perforation.
May also perforate at a diverticulum proximal to the obstruction.

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MANIFESTATIONS

Symptoms

 Increasing 'constipation' over days or weeks.
Distention
Severe colicky pain, low abdo / LIF, cramping
Emesis of foul smelling contents
May pass some flatus or stool with complete obstruction

Complicated
Peritonitis may ensue.

Underlying Cause
Interrogate for cause
E.g. weight loss, passing blood, family history
E.g. recurrent episodes in volvulus, past diverticulitis

Signs
Observe
Abdominal distension, particularly around the flanks.
Generalised distension if ileocaecal valve incompetent.
Perhaps localised if volvulus.
Look for previous scars and hernia.

Palpate
Tenderness localised to RIF may be a sign of impending caecal perforation.
Examine inguinal regions.
DRE essential

Percuss
Tympany

Auscultation
Sounds may be high pitched.
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INVESTIGATIONS

Routine labs

Imaging
AXR (and CXR; exclude free air).
Distended colon may show irregular haustra folds.
Note air pattern; ?in rectum.
If caecum dilated >10-12 cm, perf may be imminent.
--> Consider proceeding to urgent surgery / decompression.
CT typically diagnostic
- but cannot readily demonstrate intraluminal mass lesions; need colonoscopy.
Contrast enema can confirm obstruction site; can be therapeutic for fecal impaction.
- avoid barium.

Other
Flex sig / colonoscopy.
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MANAGEMENT

Principles
1. Establish exact cause; then at surgery:
2. Resuscitate
3. Decompress the colon.
3. Resect cause
4. Decide on primary anastomosis or ostomy.

Medical
Drip and replacement fluid
NG suction - i.e. esp. if incompetent ileocaecal valve and risk of vomiting.
IDC often useufl.

Surgical

Partial vs complete?
Partial may be amenable to slow prep; reduces chances of bag.
Resection and primary anastomosis.

Inspect the ascending colon
Tears or necrosis due to distension?
If extensive or necrotic, may need a subtotal colectomy.

Decompression?
If difficult to manipulate bowel or to expose a left sided lesion.
Enterotomy and large nasogastric tube attached to suction
- optionally do this through the terminal ileum - possibly secure and less likely to leak.
If mostly gas, can connect a large needle or angiocath to suction tubing and Z-step through tinea.

Resection / Join?
Do a formal cancer resection unless it is disseminated (then colostomy)
- usual 5cm margins; 2cm for low rectal, with wide excision of the accompanying mesentery.
Typically Hartmann's, primary anastomosis or subtotal with ileosigmoid anastomosis
- if cancer is transverse or descending, often better to do subtotal and ileosigmoid anastomosis
- well perfused small bowel joined to normal colon below obstruction
--> usually managed without much diarrhoea / incontinence
--> unlike ileorectal joins, where pt needs to have normal continence before the current illness.
In divertic stricture, safest to do a Hartmann's.
- interval colonoscopy and reversal.
If patient is elderly and in bad general condition
- consider Hartmann's, knowing that 50% will never be reversed and that it is a big operation to reverse.
Use a stapler to zip the 2 bowel ends with complete control and no leakage

Irrigation?
Prolongs operation substantially and is 'negative damage control'
No bowel prep required anyway, although this is a little different.
- primary anastomosis is safe on an unprepared bowel but massive loading is a contraindication
An alternative is subtotal (or total) abdominal colectomy with anastomosis of ileum to sigmoid or rectum.
- this is a bigger operation and takes longer
RCT (SCOTIA group) showed no difference in anastomotic healing with either method.
Conclusion: aim for primary anastomosis after decompression with suctioning; irrigation is old-school and will take an hour.
- if massive loading cannot be decompressed, and depending on pt physiology, stoma may be quicker more sensible option for damage control.

Two-stage procedure: decompressive colostomy with later resection of obstruction?
1. Consider it in rectal cancer. Allows elective staging and adjuvant chemoradiotherapy.
2. Critically ill patients who cannot tolerate a proper operation, e.g. recent MI.
3. Widespread metastatic disease.

Proximal protective ostomy for anastomosis?
No. Choose either a join or a colostomy.
Protective ostomy is of disputable value in this context and no evidence this is a good idea.
Colon was not clean for starters, so leak will leak shit.
- reoperation will be needed regardless.

Summary of options (Schein)
1. Resection and primary anastomosis should be safely achievable in most patients.
2. Sigmoidectomy and colorectal anastomosis if sigmoid lesion.
3. Subtotal colectomy if proximal colon excessively loaded or compromised.
4. Subtotal colectomy often needed for transverse or descending colon lesions.
5. Hartmann's procedure in poorly nourished or high-risk patients.

Role of Stents

Role of Stents?
If available with skilled practitioner, then it should certainly be considered if:
1. Bridge to surgery in patients with resectable cancer, especially if associated with resectable liver mets.
--> allows an elective treatment pathway; with decompression, full colonoscopy, and likely primary anastomosis
2. Definitive treatment for metastatic disease; palliative in short life expectancy.
--> Excellent results and reduced risk.
Stents are not established in benign disease e.g. diverticular stricture, but under investigation.

How?
Use an endoscopic approach with fluoroscopic guidance
Patient in left-lateral (colonoscopy) position.
Under sedation, monitoring and oxygen
Colonoscope advanced to obstruction lesion; fluoroscopic check.
Guidewire passed if tight, stent over-run, expanded under fluoroscopic guidance
- fluoroscopy use confirms guidewire passage, stent position, allows to watch deployment.
May be deployable through a scope
Optimally flares proximally and distally, holds narrow centre over stricture; reduced migration.
Generally only if >5cm from anus and left colon
- though have been used in the distal rectum and right colon.
Long lesions can be handled by stent-within-a-stent overlap approach.

What type of Stent?
Self-expanding metallic stents
Coated and non-coated
Pre-deployment 10-30Fr, expand to 2-3.5cm and 4-12cm
Eg Enteral Wallflex (TTS; through the scope) 120 mm.
Or Ultraflex Precision (OTW; over the wire).

Outcomes?
Good for shorter, distal lesions.
Failure usually due to inability to pass guidewire / angulation of colon.
~90% success rate.
Systematic reviews show lower morbidity and fewer stomas with stenting bridge-to-surgery than with emergency surgery
- also reduced hospital stays, lower overall complication rates.

Complications?
Generally low risk
Bleeding, perforation (3%), recurrent obstruction (7%)
Stent migration (10%)
Ingrowth / overgrowth (over edges)
Stool impaction
Pain / tenesmus


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