Pseudo-Obstruction

Question 1

What is a pseudo-obstruction?

Answer 1

Pseudo-obstruction, also known as Ogilvie syndrome in the acute setting, is a disorder characterised by dilatation of the colon due to an adynamic bowel, in the absence of mechanical obstruction.

The disorder most commonly affects the caecum and ascending colon, however can affect the whole bowel. It is a rare condition, yet is most common in the elderly.

Question 2

Briefly describe the pathophysiology of pseudo-obstruction

Answer 2

The exact mechanism is unknown, yet it is 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.

As with mechanical obstruction, untreated cases can result in an increasing colonic diameter, leading to an increased risk of toxic megacolon, bowel ischaemia and perforation.

Question 3

What can cause pseudo-obstruction?

Answer 3

There are a variety of causes of pseudo-obstruction, including:

• Electrolyte imbalance or endocrine disorders
  
  • Including hypercalcaemia, hypothyroidism or hypomagnesaemia
• Medication
  
  • Including opioids, calcium channel blockers or anti-depressants
• Recent surgery, severe illness, or trauma
  
  • Includes cardiac ischaemia
• Neurological disease
  
  • Includes Parkinson’s disease, Multiple Sclerosis and Hirschsprung’s disease

Question 4

What are the clinical features of pseudo-obstruction?

Answer 4

Most patient’s will present with the clinical features of mechanical bowel obstruction:

• Abdominal pain
• Abdominal distension
• Constipation
  
  • Due to an adynamic bowel, whilst not passing ‘normal’ stool, often patients may have paradoxical diarrhoea
• Vomiting
  
  • Typically a late feature due to the colon being most distal in the GI tract

On examination, the abdomen will be distended and tympanic; whilst often soft and non-tender, the presence of focal abdominal tenderness should be assessed.

Question 5

What does focal tenderness indicate in pseudo-obstruction?

Answer 5

Focal tenderness indicates ischaemia and is a key warning sign; patients with bowel obstruction may be uncomfortable on palpation due to the discomfort from pressing on a distended abdomen, but there should be no focal tenderness, guarding, or rebound tenderness unless ischaemia is developing.

Question 6

What investigations should be ordered for pseudo-obstruction?

Answer 6

A wide range of initial blood tests should be performed to assess for biochemical or endocrine causes of pseudo-obstruction, including U&Es, Ca²⁺, Mg²⁺ and TFTs.

Plain abdominal films (AXR) will show bowel distension, however this will be much the same as mechanical obstruction, hence has limited use in definitive diagnosis of the condition.

Patients presenting with features of pseudo-obstruction should undergo an abdominal-pelvis CT scan with IV contrast. This will show dilatation of the colon, as well as definitively excluding a mechanical obstruction and assessing for any complications (e.g. perforation).

Motility studies will often be required in the long-term and potential biopsy of the colon at colonoscopy.

Question 7

Briefly describe the management of pseudo-obstruction

Answer 7

Most cases can be managed conservatively and do not require surgical intervention. Treatment of the underlying cause will be required, where applicable.

Patients should be made nil-by-mouth and started on intravenous fluids, with a fluid balance chart started; if the patient is vomiting, an nasogastric tube should be inserted to aid decompression.

In most cases of pseudo-obstruction that do not resolve within 24-48 hours, endoscopic decompression will be the mainstay of treatment. This involves the insertion of a flatus tube and allowing the region to decompress. If there is limited resolution, use of intravenous neostigmine (an anticholinesterase) may also be trialled if suitable.

Patient should be reviewed regularly to assess the condition’s progression. Nutritional support should be considered early in these patients, particularly if recurrent, as this may lead to weight loss and malnutrition.

Question 8

Briefly describe the surgical management of pseudo-obstruction

Answer 8

In the absence of perforation or ischaemia, non-responding cases may require segmental resection +/- anastomosis, however unless all the affected areas are removed, this will not be curative.

Alternative procedures can also be performed to decompress the bowel in the long-term, such as caecostomy or ileostomy.

Question 9

What differentials should be considered for psudeo-obstruction?

Answer 9

• Mechanical obstruction
• Paralytic ileus
• Toxic megacolon