Ileus

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DEFINITION

Impaired function of the gut in the absence of a mechanical obstruction.
- pseudo-obstruction mainly pertains to colon
Paralytic ileus is not after surgery cf post-operative ileus
Prolonged post-operative ileus lasts 5d+
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EPIDEMIOLOGY

Risk Factors
Electrolyte derangements
Narcotics
Spinal cord injury
Calcium channel blockers
Antidepressants, anticholinergics, calcium channel blockers
Immobility

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AETIOLOGY

See below


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BIOLOGICAL BEHAVIOUR

Pathophysiology
Multifactorial with the principal mediators being:
- immunologic cell activation
- autonomic dysfunction (both primarily and as part of the surgical stress response)
- agonism of exogenous narcotics at gut opioid-receptors
- modulation of gastrointestinal hormone activity
- electrolyte derangements.
A final common pathway for these effectors is impaired contractility and gut wall oedema.


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MANIFESTATIONS

Symptoms
Abdominal pain, nausea, vomiting, diffuse abdominal discomfort / pain, bloating, nil passage of flatus.

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INVESTIGATIONS

Biochemistry
Electrolyte derangements contribute and that should be tested.

FBC
WCC may suggest contributing pathology

Imaging
Plain films usually show gas in segments of both the small bowel and large bowel
CT with contrast is usually helpful but shd be used selectively.
- high sensitivity for differentiating obstruction from ileus
- and contrast may be therapeutic by osmotic properties.
- also exclude intra-abdominal pathology that may be contributing e.g. leaks or abscess.


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MANAGEMENT

Prevention
see below; critical to reducing incidence of ileus.



1. Differentiating post-op ileus and early bowel obstruction
E.g. due to hernia, dense early adhesions or misplaced sutures
Concern for SBO if:
A more dramatic presentation:
- intense pain
- feculent emesis
- rapidly progressive pain and distension

Localized tenderness, fever, peritoneal signs --> consider laparotomy

2. NG tube?
Generally not in routine ileus.
Studies show that morbidity of aspiration and discomfort outweigh benefits

3. Drugs?
Several have been evaluated, e.g. metoclopramide, cisapride and erythromycin.
- may be useful in selected cases where gastric emptying is the problem, but not efficacious in ileus in general
Opioid antagonists are peripherally acting; do not cross the BBB.
- e.g alvimopan, methylnaltrexone
- evidence for use in speeding post op recovery in bowel surgery and hysterectomy.
- however uncertain cardiovascular and neoplastic risks with alvimopam; approved for short term use and not prolonged ileus



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REFERENCES

Cameron 10th

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