Ischaemic Colitis

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DEFINITION

Disruption of the blood supply of the colon, resulting in a spectrum of clinical disorders from transient mucosal ischaemia to fulminant necrotising colitis requiring surgery.

D E A B M I M

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EPIDEMIOLOGY

Elderly vasculopaths and shock states are at high risk
- risk factors are those for general vascular disease
- PVD, CAD, DM, CHF,

Risk correlation with chronic constipation.
History of AAA or colonic surgery.
D E A B M I M  

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AETIOLOGY

Metabolic demand exceeds oxygen and nutrient delivery

A spectrum:
- may be complete disruption of blood supply
- but more commonly a low-flow state with transient ischaemia of vulnerable areas.
--> varies from transient self-limiting mucosal ischaemia to full-thickness necrosis.

1. Large vessel occlusion
- SMA emboli
- thrombus (us. IMA)
- AAA and repair compromising IMA

2. Diseased intramural vessels
Underling comorbidity
Commonly vasculopaths

3. Low-flow states
Sustained shock of any aetiology.
Vasopressin
Extreme physical exertion.

4. Colonic obstruction
Technically ischaemic colon.

5. Hypercoagulable states
- protein C, S deficit, Antithrombin III deficit, anticardiolipin antibodies, SLE

6. Vasculitis
- polyarteritis nodosa, thromboangitis obliterans
D E A B M I M  

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BIOLOGICAL BEHAVIOUR

Colon Anatomy

1. Intramural vascular network is tenuous in colon cf SB; thus more prone to generalized ischaemia

2. Watershed areas particularly susceptible; rectum generally spared.
- R colon susceptible to low flow states (<40 mmHg); tenuous vasa recti; vessels remain pulsatile & intact
- R colon susceptible to SMA emboli, straight shot for small emboli down to the ileocolic branch to colon.
- splenic flexure at midgut-hindgut watershed, particularly in those lacking marginal artery of Drummond. 
- sigmoid as often IMA is chronically diseased in older vasculopaths.
- sigmoid may be at risk after AAA repair; IMA often sacrificed, and sigmoid supply then tenuous.

Pathophysiology
Can involve any part of colon / rectum, rarely pan-colonic
- usually focal but can be patchy and diffuse.
- varying depth of penetration.
Initially mucosal;
- mucosal sloughing, ulceration
May or may not progress to partial then full thickness.
- perforation in severe cases
R sided often more aggressive disease than L colon.

Complications
Stricturing on resolution
D E A B M I M  

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MANIFESTATIONS

1. Transient non-gangrenous
Nonspecific abdo pain
- vague and poorly localized
Associated diarrhoea
Lower GI bleeding
- typically not requiring transfusion
Requires a high index of suspicion

2. Fulminant gangrenous
Localized pain
Peritoneal signs
SIRS and systemic upset
Rapid deterioration

Other
Can occur on top of a severe shock-associated illness.
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INVESTIGATIONS

AXR
Distention possible.
Thumb-printing.

CT
Colon wall thick, often segmental.
Free fluid, pneumatosis coli if severe

Endoscopy
Gold-standard investigation
Pale haemorrhagic mucosa
Haemorrhagic, ulcerative mucosa
Linear ulcer running longitudinally on antimesenteric border (single stripe sign) is classic but insensitive.

D E A B M I M

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MANAGEMENT

1. Transient non-gangrenous
Generally resolves spontaneously.
Supportive: NBM, IVF, O2; NG if ileus
- reduce the metabolic demand of the bowel and optimize delivery.
Discontinue possible contributing meds.
Consider broad spectrum antibiotics.
- No level 1 evidence but supported in animal studies; reduced translocation and mortality in animals.
Watch carefully with serial abdo exams and bloods, ABG and imaging as necessary.
Outcome:
--> no improvement or deterioration in 20% (acidosis, oliguria, SIRS, peritonitis): operate
--> improvement: resume diet, rpt endoscopy in 6 weeks; stricture or ongoing colitis may need surgery

2. Fulminant gangrenous
Operate
Resect all compromised bowel, wash.
- serosa can be deceptive; look at full thickness of resected ends, and for bleeding.
- nb: palpable pulses do not rule out colonic ischaemia.
Stoma.
- Right colon: R hemi, end ileostomy, long Hartmann's pouch or mucus fistula.
- Splenic: left hemi, take transverse and up to proximal rectum. End colostomy and Hartmann's pouch.
Consider a second look if SB concerning.

Late stricture:
Can be more conservative, limited resections and primary anastomosis possible.

D E A B M I M

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REFERENCES
Cameron 10th

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