Pseudo-Obstruction

Pseudo-obstruction, also known as Oglivie’s 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.

In this article, we shall look at the causes, key clinical features, investigations and management of acute colonic pseudo-obstruction.


Pathophysiology

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.

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
  • Recent cardiac event
  • Parkinson’s disease
  • Hirschsprung’s disease
By Blausen gallery 2014 [CC BY 3.0] and OpenStax College [CC BY 3.0], via Wikimedia Commons

Figure 1 – (A) the anatomy of the large bowel (B) the macroscopic features of the large intestine


Clinical Features

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, due to this being colonic-specific pathology, bowel sounds are often present. The abdomen will be tympanic due to the distension and you should palpate for focal tenderness*

*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.


 Differential Diagnosis

  • Mechanical obstruction
  • Paralytic ileus
  • Toxic megacolon

Investigations

Figure 2 – Coronal view from CT abdo-pelvis scan showing acute pseudo-obstruction

A wide range of initial blood tests should be performed to assess for infective or electrolyte causes of pseudo-obstruction, including FBC, CRP, U&Es, LFTs, 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.


Management

Most cases can be managed conservatively and do not require surgical intervention. Treatment of the underlying acute illness will be required.

Patients should be made NBM and started on IV fluids, with a fluid balance chart started; if the patient is vomiting, an NG tube should be inserted to aid decompression*.

Any underlying cause should be identified and managed accordingly. Ensure appropriate analgesics and prokinetic anti-emetics are also prescribed.

*As pseudo-obstruction affects the distal part of the GI tract, vomiting is a late-stage of the disease progression hence may not always be warranted

 

In most cases of pseudo-obstruction that do not resolve within 24hours, endoscopic decompression will be the mainstay of treatment. This involves the insertion of a flatus tube and allowing the region to decompress.

Patient should be reviewed regularly to assess the condition’s progression. If there is limited resolution, use of IV neostigmine (an anticholinesterase) may also be trialled

Nutritional support should be considered in these patients, particularly if recurrent, as this may lead to weight loss and malnutrition. Regular small soft or liquid meals may be easier to digest.

Surgical Management

In cases with suspected ischaemia or perforation, or those not responding to conservative management, surgery may be indicated.

In the absence of perforation, segmental resection +/- anastomosis will often be performed, however unless a unless affected areas are removed this will not be curative.

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

Key Points

  • Pseudo-obstruction is a disorder characterised by acute dilatation of the colon in the absence of a mechanical obstruction
  • Causes include electrolyte imbalance, medication, and trauma
  • It is important to differentiate from mechanical bowel obstruction, most often warranting CT imaging
  • Management includes supportive measures, selective use of neostigmine and endoscopic decompression
  • Surgical decompression should be reserved for patients with peritonitis or perforation and for those failing endoscopic and medical therapy

Quiz

Question 1 / 3
Which of the following drug classes is not associated with pseudo-obstruction?

Quiz

Question 2 / 3
What investigation option is not routinely indicated for a patient with suspected pseudo-obstruction?

Quiz

Question 3 / 3
What is the best initial management for a patient with clinically and radiographically confirmed pseudo-obstruction, who is otherwise clinically stable?

Results

Further Reading

Acute colonic pseudo-obstruction
Saunders MD, Gastrointest Endosc Clin N Am

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