A 50-year old man with recurrent history of unable to pass stools for 3 days’ duration with abdominal distension. Otherwise he appears comfortable. On examination, abdomen is distended, but soft and non-tender on palpation. Bowel sounds were diminished. He had multiple admissions for similar complaints for the last two years. The abdominal x-ray for the current admission is as below:
And the abdominal x-ray taken 9 months ago when he was admitted similarly is as below:
Further history revealed that when he presented for the first time, the surgical team performed an exploratory laparatomy and found no abnormality. He has history of schizophrenia and is on antipsychotics.
What diagnosis should you consider in this case?
Ans: recurrent colonic pseudo-obstruction also known as Ogilvie Syndrome.
Pathophysiology:
1. When Ogilvie first described these cases, he hypothesized that the etiology was due to sympathetic deprivation to the colon, leading to unopposed parasympathetic tone, resulting in regional contraction, and thus functional obstruction.
2. However, the current understanding is, unlike the hypothesis Ogilvie proposed, is because of parasympathetic suppression (in this case, sacral parasympathetic outflow), or excessive sympathetic stimulation (Maloney & Vargas, 2005)
RECALL that:
the parasympathetic nervous system increases gut motility and
the sympathetic nervous system decreases gut motility
Thus, in the presence of disruption of the parasympathetic stimulation, results in reduced gut motility or adynamic of distal gut segment, resulting in functional dilatation. This hypothesis is supported by the use of neostigmine in the treatment of this condition.
3. Neostigmine is an acetycholinesterase inhibitor (Ponec et al, 1999).
Acetycholinesterase results in the breakdown of acetylcholine into acetate and choline.
Thus, neostigmine, by inhibiting the action of this acetylcholinesterase, inhibits the breakdown of acetylcholine (by the same token, neostigmine can be used to treat myastenia gravis by increasing the concentration of acetycholine)
4. The cecum is the usual site of the largest dilatation in Ogilvie syndrome and, thus, is more prone to the risk of perforation. This is because cecum has a large diameter. Laplace law states that the intraluminal pressure needed to stretch the wall of a hollow tube is inversely proportional to its diameter. Thus, because of its large diameter, it is easier to overcome the wall tension of cecum with a small amount of pressure than with other parts of the gut (Click here to access the article in emedicine)
5. Of course, this syndrome has to be a diagnosis of exclusion. Mechanical obstruction has to be ruled out. In this patient, exploratory laparatomy was first performed and the gut was found to be normal.
6. The patient is on anti-psychotic drugs. Many of these anti-psychotics such as phenothiazines have anticholinergic properties; thus aggravate this patient's condition.
Click here for a chapter on Ogilvie Syndrome
One should also differentiate toxic megacolon from Ogilvie syndrome. However, the clinical features in toxic megacolon are quite different from this syndrome. Patient with toxic megacolon is rather sick looking. Jalan criteria for toxic megacolon are:
- Radiographic evidence of colonic dilatation - The classic finding is more than 6cm in the transverse colon PLUS
- Any 3 out of 4 of the following
- Fever (>38.6C)
- Tachycardia (>120/min)
- Leukocytosis (>10.5 x 103/µL) or
- anemia PLUS
- Any 1 of the following - Dehydration, altered mental status, electrolyte abnormality, or hypotension
References:
1. Maloney N, Vargas HD. Acute intestinal pseudo-obstruction (Ogilvie's syndrome). Clin Colon Rectal Surg. 2005 May;18(2):96-101. Click here for free full text in pdf
2. Ponec RJ, Saunders MD, Kimmey MB. Neostigmine for the treatment of acute colonic pseudo-obstruction. N Engl J Med. 1999 Jul 15;341(3):137-41. Click here for free full text.
