Pseudo-obstruction

Question 1

What is pseudo-obstruction?

Answer 1

disorder characterised by dilatation of the colon due to an adynamic bowel, in the absence of mechanical obstruction.

Question 2

What location within the bowel does pseudo-obstruction usually occur?

Answer 2

Caecum & Ascending colon

But can affect anywhere along the bowel

Question 3

How common is pseudo-obstruction?

Answer 3

Rare

Question 4

Who does pseudo-obstruction most commonly affect?

Answer 4

Older patients

Question 5

What is the pathophysiology of pseudo-obstruction?

Answer 5

Exact mechanism unknown but thought to be due to an interruption of the autonomic nervous supply to the colon resulting in the absence of smooth muscle action in the bowel wall.

Question 6

What are causes of pseudo-obstruction?

Answer 6

• Electrolyte imbalance / Endocrine disorders
  
  • e.g. hypercalcaemia, hypothyroidism, hypomagnesaemia
• Medication
  
  • e.g. opioids, Ca channel blockers, anti-depressants
• Recent surgery / Trauma / Severe illness
• Neurological disease
  
  • e.g. Parkinson’s, Multiple Sclerosis, Hirschsprung’s disease

Question 7

What are the symptoms of pseudo-obstruction?

Answer 7

Same as mechanical obstruction:

• Abdominal pain
• Abdominal distension
• Constipation
  
  • Often patients may have paradoxical diarrhoea
• Vomiting
  
  • Typically late feature as colon is most distal structure of the GI tract

Question 8

What are the signs seen on examination of a patient with pseudo-obstruction?

Answer 8

Abdomen typically distended & tympanic but soft and non-tender

Question 9

Why should presence of focal abdominal tenderness be assessed in a patient with suspected pseudo-obstruction?

Answer 9

Focal tenderness is a red flag for ischaemia.

Bowel obstruction may be uncomfortable on palpation but there should be no focal tenderness, guarding, or rebound tenderness unless ischaemia is developing

Question 10

What are your differentials for pseudo-obstruction?

Answer 10

• Mechanical obstruction
• Paralytic ileus
• Toxic megacolon

Question 11

What investigations would you order for a suspected case of pseudo-obstruction?

Answer 11

1. Routing blood tests (FBC, LFTs, etc.)

• inc. U&Es, Ca, Mg, TFTs
  
  • To assess for biochemical / endocrine causes of pseudo-obstructio

2. Abdominal XR (AXR)
   * To show bowel distension, however this will be much the same as mechanical obstruction, hence has limited use in definitive diagnosis of the condition.
3. CT abdo-pelvis with IV contrast
   * Will show dilatation of the colon, as well as definitively excluding a mechanical obstruction and assessing for any complications (e.g. perforation).
4. Motility studies
   * Often required in the long-term

Question 12

How do you manage pseudo-obstruction conservatively?

Answer 12

1. NBM & IV fluids w/ a fluid balance chart started
2. NG tube
   * If the patient is vomiting to aid decompression
3. Endoscopic decompression

• In most cases of pseudo-obstruction that do not resolve within 24-48 hours
• Insertion of flatus tube allows the region to decompress

4. IV Neostigmine
   * An anticholinesterase may also be trialled if suitable & condition not relieved by previous measures.
5. Nutritional support & Regular review

Question 13

What is the surgical management of pseudo-obstruction?

Answer 13

1. Segmental resection +/- anastomosis

• For non-responsive cases w no perforation or ischaemia
• NOT a curative measure unless ALL the affected bowel is removed.

2. Caecostomy / Ileostomy
   * Alternative procedures used to decompress the bowel in the long-term