Acute colonic pseudo-obstruction

It can be caused by a range of conditions, however post partum, post Caesarean section women are at particular risk. 

The cecum, with its larger diameter, requires less pressure to increase in size and in wall tension, and hence is the most frequent site for perforation. The greater the dilation, the more likely perforation will be, especially ≥ 10 cm.

Acute colonic pseudo-obstruction (ACPO) should be considered in all women with symptoms of ileus after Caesarean Section, who present with progressive abdominal distension 2 – 12 days after caesarean section     

History

Ogilvie syndrome is named for the British surgeon Sir William Heneage Ogilvie (1887-1971), who first described the condition in 1948.

Epidemiology

The true incidence of Ogilvie syndrome is unknown as many mild cases resolve spontaneously.

There is no reliable national or international data for its frequency.

In obstetric cases, caesarean section with spinal anaesthesia seems to be the most common operative procedure associated with this syndrome.

It has, however, also been reported after caesarean hysterectomy and vaginal births.

There is no data on predisposing factors.

Classification

Pseudo-obstruction syndromes can be divided into:

1. Acute (or “Ogilvie syndrome”):
   • In acute colonic pseudo-obstruction the colon may become massively dilated and if it is not decompressed, the patient risks perforation, peritonitis, and death.
2. Chronic forms

Physiology

Colonic motor and secretory functions are mediated by the autonomic nervous system.

The sympathetic nervous system arises from the spinal cord at the level of the thoracic and lumbar spinal cord.

Parasympathetic innervation of the colon is delivered from two sources:

• From the ascending colon to the splenic flexure parasympathetic innervation is supplied by the vagus nerve.
• Distal to the splenic flexure, parasympathetic innervation is via lumbar nerves       from spinal segments S2 to S4

Sympathetic innervation of the colon is via:

• The celiac plexus
• The mesenteric ganglia

In general, the parasympathetic nervous system increases gut motility and the sympathetic system decreases motility.

Abnormalities of the autonomic nervous system, characterized by sympathetic dysfunction, parasympathetic dysfunction, or a combination of both, have been used to explain the etiology of Acute colonic pseudo-obstruction, (ACPO).

In contrast to Sir William Heneage Ogilvie’s initial theory of “sympathetic deprivation”, the benefit of neostigmine suggests that parasympathetic failure is more likely to be the aetiology for Ogilvie syndrome.

Pathophysiology

Physiological ileus is an expected physiological consequence of abdominal surgery and has been defined as:

• Disruption of normal intestinal peristalsis that usually persists for 0 – 24 hours in the small intestine 24 – 48 hours in the stomach, and up to 72 hours in the distal large colon
• This type of ileus generally resolves without serious sequelae.

A pathologic ileus is suspected when return of intestinal function is:

• Delayed
  Or
• Symptoms develop

The aetiology of a small bowel ileus can differ from a large bowel ileus due to local neurological, hormonal and anatomical factors.

Causes

Patients with Ogilvie syndrome have underlying medical or surgical conditions that predispose them to the syndrome.

Pseudo-obstruction appears to related to an autonomic dysfunction with:

• Decreased parasympathetic activity
  And /or
• Sympathetic stimulation

Obstetric related

Caesarean sections are thought to more significantly effect distal large bowel motility due to:

1. Minimal intraoperative small bowel handling
2. Disruption of the sacral plexus through spinal anaesthesia
3. Compression by the gravid uterus
4. Opioid use

Distal large bowel ileus causes proximal accumulation of gas and fluid, with the caecum being most at risk of over-distension and perforation.

This variant of ileus is known as Acute Colonic Pseudo-Obstruction or Ogilvie Syndrome and if unrecognized it  is associated with significant morbidity.

Additionally pregnancy itself predisposes to Ogilvie syndrome.

Pregnant women have:

1. Prolonged gastrointestinal transit time in the third trimester due to mechanical intestinal obstruction by the gravid uterus
2. Increased levels of progesterone reducing gastrointestinal smooth muscle contractility.
3. Reduced physical activity
4. Dietary habits changes such as increased iron supplements.

These factors combined with further insult to distal large bowel motility from Caesarean Section places women at high risk of Acute Colonic Pseudo-Obstruction.

Non-obstetric related:

1. Abdominal – pelvic surgery in general:
2. Trauma
3. Serious sepsis
4. Medications:
   • Opioids
   • Anticholinergic agents.
   • Anaesthetic agents (especially spinal anaesthesia)
5. Electrolyte disturbances
6. Diabetes mellitus
7. Renal failure/ uraemia

Complications

Despite the absence of mechanical obstruction, patients can nonetheless go on to bowel necrosis and perforation (especially if dilatation is severe) which a consequent generalised peritonitis, and ultimately death from septic shock.

The largest dilatations in ACPO patients usually develop in the cecum.

• According to Laplace’s law, the intraluminal pressure needed to stretch the wall of a hollow tube is inversely proportional to its diameter.
• Accordingly, the cecum, with its larger diameter, requires less pressure to increase in size and in wall tension, and hence is the most frequent site for perforation.
• A caecal diameter of > 9 cm is considered dilated
• The greater the dilation, the more likely perforation will be, especially ≥ 10 cm. ³

Rupture or ischemic perforation of the bowel, carries a high mortality rate (> 50% according to some literature ³).

There can also be significant fluid, (“third space”) losses into the distended bowel.

Clinical features

Acute colonic pseudo-obstruction (ACPO) should be considered in all women with symptoms of ileus after Caesarean Section, who present with progressive abdominal distension 2 – 12 days after caesarean section     

The clinical distinction between Ogilvie syndrome and mechanical obstruction is difficult to make, as both groups of patients essentially present with obstructive symptoms

Features of Acute colonic pseudo-obstruction include:

1. Vomiting
2. Abdominal distension / hyper-resonant to percussion.
3. Reduced flatus (but variable).
4. Abdominal pain
5. Abdominal tenderness
6. Bowel sounds: may be hypoactive, high pitched, or absent bowel (diagnostically unhelpful)
7. Sign of possible perforation include:
   • Pyrexia
   • Tachycardia
   • Hypotension
   • Peritonism (i.e. guarding/ rigidity): this is a serious sign and suggests perforation/ peritonitis. 

Pseudo-obstruction may also present with a sudden painless enlargement of the proximal colon accompanied by abdominal distension.

Investigations

Blood tests: FBE, U&ES/ glucose, CRP, LFTs

Plain radiography:

• Findings on plain radiology can be identical to a mechanical large bowel obstruction.
• Plain radiography, however is a good initial screening investigation. 
• Bowel dilation is often limited to the cecum and right colon.
• The concurrent finding of both small and large bowel distension on AXR may be explained by:
  • Large bowel distension with an incompetent ileocaecal valve
  • Adynamic ileus (less likely).

CT Scan:

• Concerning clinical or plain x-ray features warrant further investigated with an abdominal-pelvic CT scan.
• The hallmark of colonic pseudo-obstruction is the presence of dilatation of the large bowel (often marked) without evidence of an abrupt transition point or a mechanically obstructing lesion.
• It is important to note, however, that a gradual transition point may be seen, usually at or near the splenic flexure.
• Caecum diameter can be more accurately determined by CT scan, (compared to plain radiology).  
• CT scan is the investigation of choice if perforation is suspected.

Radiological Differential Diagnoses:

1. Adynamic ileus:
   • No transition point
   • Often history has a cause for the ileus, e.g. surgery
   • Small bowel is also often dilated
2. Mechanical large bowel obstruction:
   • Abrupt transition point often with an identifiable obstructing lesion
3. Toxic megacolon secondary to Clostridium difficile colitis
   • C. difficile infection is usually preceded by antibiotic use or chemotherapy and is therefore usually encountered in unwell, hospitalized patients with significant co-morbidity
   • Bowel wall thickening usually a prominent feature
4. Ischaemic colitis
   • Usually bowel wall is thickened, but can be thinned and dilated
   • Absent/poor wall enhancement
   • Usually involves vascular territories
5. Sigmoid volvulus / caecal volvulus
   • Transition point evident
   • Whirlpool sign of the twisted mesentery 

Management

1. Conservative

• If diagnosed early, conservative management is often successful and morbidity is minimal.
• Conservative management is appropriate for patients with a caecal diameter of ≤ 10 cm and without signs or symptoms of peritonism/ perforation/ sepsis.

Conservative management consists of:

• Bowel rest (nil orally)
• Nasogastric tube insertion
• Intravenous fluids
• Analgesia (minimise opioid use as much as possible)

Important to avoid aperients, antispasmodics.

2.  Medical

Neostigmine: Give 2 mg neostigmine IV over a 3 – 5 minute period

• Criteria for medical management have been defined as patients with a caecal diameter of 10 cm in whom 24 hours of conservative treatment has failed. ²
• There should be no evidence of perforation or peritonism or sepsis
• Patients should be monitored and atropine should be available at the bedside to counter significant symptomatic neostigmine-induced bradycardia, (note however that atropine can worsen the pseudo-obstruction!).
• Neostigmine may be repeated for patients with an incomplete response, patients without a response, or those with a recurrence.
• Success rates of up to 50% have been documented.
• If the second dose of neostigmine fails to resolve the caecal dilatation, the patient should proceed to more aggressive measures of decompression.
• Signs of resolution of ACPO may be observed within 30 minutes of administration

Mechanical intestinal obstruction is a contraindication to the use of neostigmine.

3. Decompression

• Colonoscopic decompression of the colon is effective, causing decreased caecal diameter in a good proportion of cases.
• However, recurrence rates of 10% – 65% have been noted after initial success as documented by increased caecal diameter on radiography.
• Additional benefits of decompression included definitive assessment of the colon to exclude mechanical obstruction.
• A decompression tube may also be placed
• Colonoscopy is contraindicated with evidence of ischemia or perforation as these patients should proceed to surgical intervention.

4. Surgical

Surgical cecostomy is the definitive intervention for patients with ACPO unresponsive to other therapies and without evidence of ischemia or perforation.

Formal laparotomy is reserved for treatment of patients displaying peritoneal signs or perforation.

The actual surgical procedure performed is based on the status of the bowel at the time of operation. Procedures can range from surgical cecostomy to right hemicolectomy to total abdominal colectomy.

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References

FOAMed

• Farkas J. Acute colonic pseudo-obstruction (Oglivie’s syndrome). Emcrit

Publications

• Ogilvie H. Large-intestine colic due to sympathetic deprivation; a new clinical syndrome. Br Med J. 1948 Oct 9;2(4579):671-3.
• Wells CI, O’Grady G, Bissett IP. Acute colonic pseudo-obstruction: A systematic review of aetiology and mechanisms. World J Gastroenterol. 2017 Aug 14;23(30):5634-5644.