Acute bowel obstruction

Theory

Small bowel obstruction (SBO) is a common condition with a number of causes. The majority of patients settle with conservative treatment.

Large bowel obstruction (LBO) is less common and more sinister.

A true large bowel obstruction is a surgical emergency and often requires major surgery.

Bowel dilatation results in regional hypoperfusion to the wall of the bowel causing regional ischaemia and inhibiting peristalsis. Management is focused on resuscitation and decompression, which allows an improvement in regional wall blood flow and may result in resolution of the obstruction.

Immediate intern management

Targeted history and examination

Obtain IV access and commence IV fluid resuscitation.
- Aim to replace estimated fluid lost and maintenance fluids.

Basic set bloods (FBE, U&E, INR, G&H).
Nil orally.
Anti-emetics (Maxalon 10–20 mg IV QID / Ondansetron 2–4 mg IV bd).
Basic definitive investigations – plain X-rays.
Insert NGT if patient vomiting (place on free drainage and four hourly aspirations).
Contact surgical registrar and unit registrar.

Clinical features

History

General patient features
Colicky central abdominal pain
Abdominal distension
Absolute constipation (flatus and faeces)
Vomiting
PHx abdominal surgery

Examination

Hydration status
Distended abdomen
Abdominal tenderness
High pitched tinkling bowel sounds
Hernia

Causes SBO

Common

Adhesions
Incarcerated hernia
Ileus

Rare

IBD
SB tumour

Causes LBO

Common

Colorectal carcinoma
Diverticular disease
Volvulus (caecal/sigmoid)
Pseudo-obstruction

Uncommon

IBD
Hernia

Investigations

First line

AXR (erect and supine), erect CXR
- Dilated loops of small bowel (central) with air fluid level
- Dilated large bowel (peripheral) with air fluid levels
- Air under diaphragm

Second line

CT scan
Contrast studies
- Enema/follow through

Definitive management

SBO

Initial treatment – trial conservative management

NGT
IV fluid therapy
Nil orally

If NGT drainage becomes faeculent or ongoing obstruction:

Surgical exploration and repair

Note: An SBO in the setting of a hernia is a surgical emergency requiring urgent operative repair.

LBO

‘Never let the sun set twice on an acute large bowel obstruction.’

IV fluid therapy
Nil orally
First line imaging

The key to management of LBO is to establish a likely diagnosis and then decompress the large bowel

Second line imaging
Surgical decompression and bowel resection
Rigid sigmoidoscopic decompression (if sigmoid volvulus)
Limited period of observation if suspecting pseudo-obstruction

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