Sigmoid volvulus occurs when the last part of the large bowel just before the rectum (the sigmoid shaped sigmoid colon) twists on its self.
It is by far the most common type of volvulus, accounting for 75 to 90 % of all volvulus.
Sigmoid volvulus accounts for up to 8 % of all cases of intestinal obstruction. It is commoner in the elderly, patients with chronic illnesses, those in long term institutions like nursing homes, and patients with mental illness.
The use of anti-psychotic medications which often have anti-cholinergic constipatory effect has been blamed for the increased incidence of sigmoid volvulus in the later sets of patients.
It can also been seen in children under the age of ten. Men are more often affected than women.
Common to all patients with this condition is chronic constipation, which leads to a long redundant sigmoid colon with narrowing of the mesentery (the part where blood vessels pass in to reach the gut).
Volvulus of the sigmoid colon is commoner in Africans, Asians, and South Americans. This has been attributed to their consumption of high roughage diet. This in it self offers protection against many bowel disorders including constipation.
There is a common type of sigmoid volvulus almost restricted to those of African descent called ileo-sigmoid knoting, and affects even young adults.
In parts of the world with round worm infestation, a heavy load of worm has been associated with sigmoid volvulus in young persons.
This is also true in South American Countries like Brazil where acquired Mega colon diseases of the large bowel lead to sigmoid volvulus.
Volvulus affecting the sigmoid colon will cause a cramping left lower abdominal pain, with associated distension, complete failure to open the bowel (obstipation), and there may be nausea.
Vomiting is usually a very late sign. Fever may occur, especially if the blood supply to that part of the gut is affected, and there is perforation of the bowel.
Doctors may wish to do a combination of the following investigations to confirm the presence of a sigmoid volvulus:
A normal plain abdominal x-ray will demonstrate a huge air filled distended bowel like the shape of an inverted U, with the convexity of the U facing the right upper abdominal quadrant. This shape has been described as the kidney bean shape, coffee bean shape, bent inner tube shape, ace of spades or ‘Omega loop Sign’. You can see an example down in the resource section.
With a water soluble barium enema, the dilatation in the sigmoid colon can be demonstrated to be due to a twist, as it will show an area of complete obstruction with some twisting in the so called bird beak or bird of prey sign.
Colonoscopy could be done in rare cases, which would help to confirm diagnosis, as well as treating the obstruction.
Once the diagnosis of sigmoid volvulus is confirmed, treatment must be immediate, as delay means more likelihood of bowel wall death and gangrene.
Up to 80% of people with this condition die from gangrene if intervention is delayed.
There are two approaches to treatment. The first step is to free the acute obstruction, and then to fix the redundant part of the bowel in a bid to reduce or defer re-occurrence.
In the UK, a rigid sigmoidoscope is often passed into the sigmoid colon through the anus under direct vision.
Once the junction between the rectum and sigmoid is negotiated and passed, it could open up the obstruction, letting off the trapped wind in the twisted bowel.
This is followed by spontaneous unwinding of the obstruction, with massive explosion of faeces to the exterior. A flatus tube is then left in place.
The patient may need fluid replacement, and resuscitation if severely dehydrated, if signs of infection have set in.
If there is evidence suggestive of perforation, then the abdomen is opened and dealt with.
In up to 90% of patients with sigmoid volvulus, the condition reoccurs after untwisting, without a definitive operation. For this reason, any one with a sigmoid volvulus would need to be operated during the same admission if fit enough, to fix down the excessive bowel length.
Prevention of volvulus is basically a matter of preventing chronic constipation.
A diet too high in high fibre diet would lead to elongation of the bowel, and large redundant sigmoid or mega colon.
Other causes of mega colon include diabetes mellitus, celiac sprue, low potassium levels in the blood for a long time, and excessive use of laxatives.
Please see more resources on sigmoid volvulus below:
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