Acute Intestinal Pseudo Obstruction

Acute colonic pseudo obstruction, or Ogilvie syndrome, is acute colonic dilatation without a mechanical obstruction.

It occurs particularly in severely ill, postoperative, trauma, neurological, cardiac and metabolically disturbed patients. Drugs including opioids and anticholinergic agents may precipitate or worsen it.

The caecum is at greatest risk of ischaemia and perforation because wall tension rises as diameter increases.

• Progressive abdominal distension is dominant. Pain is usually mild to moderate unless ischaemia or perforation develops.
• Nausea, vomiting and altered bowel function may occur. Some patients continue to pass stool or flatus, so continued bowel output does not exclude the diagnosis.
• Increasing pain, focal tenderness, fever, leukocytosis or peritonism suggests ischaemia or perforation.

Check potassium, magnesium, calcium, renal function and markers of systemic illness. Correctable metabolic causes should be actively sought.

CT abdomen and pelvis with IV contrast: confirms colonic dilatation without a mechanical transition point and excludes volvulus or obstructing tumour.

A caecal diameter approaching or exceeding 12 cm, prolonged distension and worsening symptoms increase perforation risk. ASGE defines uncomplicated disease as absence of ischaemia, peritonitis and perforation with caecal diameter below 12 cm.

For uncomplicated disease, initially correct the precipitating factors for up to about 48 to 72 hours:

• Keep fasting initially if markedly distended
• Correct potassium, magnesium and fluid abnormalities
• Stop opioids and anticholinergic drugs where possible
• Mobilise and reposition frequently
• Treat sepsis, cardiac, respiratory or neurological triggers
• Use nasogastric decompression when significant upper gastrointestinal distension or vomiting is present

If significant distension persists despite conservative treatment and there is no contraindication, give:

Neostigmine 2 mg IV over 3 to 5 minutes with continuous cardiac monitoring and immediate availability of atropine because clinically important bradycardia can occur. A second 2 mg dose may be given if the first dose fails and the patient remains an appropriate candidate.

Avoid neostigmine in mechanical obstruction or perforation. Significant bradyarrhythmia and severe active bronchospasm are important contraindications or cautions.

Colonoscopic decompression with placement of a decompression tube is appropriate when neostigmine is contraindicated or unsuccessful.

Peritonitis, perforation or bowel ischaemia requires surgery. Surgical options depend on bowel viability and may include caecostomy or colectomy, but operative mortality is substantial in these often critically ill patients.