A volvulus is the twisting of a loop of intestine* around its mesenteric attachment, resulting in a closed loop bowel obstruction. The affected bowel can often become ischaemic due to a compromised blood supply, rapidly leading to bowel necrosis and perforation.
Most volvuli occur at the sigmoid colon and are the leading cause of bowel obstruction in many developing countries (the third most common in UK, USA, and Australia, after malignancy and diverticular disease). They can also occur at the stomach, small intestine, caecum, and transverse colon, but are much rarer.
The long mesentery of the sigmoid colon means that this segment bowel is prone to twisting on its mesenteric base to form a volvulus more than any other region. As such, this article will mainly focus on the risk factors, clinical presentation and management of a sigmoid volvulus.
*Interestingly, the word volvulus derives from the Latin ‘to twist’
The risk factors for developing a volvulus include:
- Neuropsychiatric disorders
- Resident in a nursing home or advanced age
- Chronic constipation or laxative
- Male gender
- Previous abdominal surgeries
- Diabetes mellitus
Patients with a volvulus will present with the clinical features of bowel obstruction. Due to its recurring nature, the patient may have a previous history of volvulus formation.
The sigmoid colon is located distally in the GI tract and so vomiting is usually a late sign, whilst the colicky pain, abdominal distension, and absolute constipation occur earlier on in the clinical course. The abdomen is markedly distended with increased bowel sounds and tympanic percussion.
Ensure to examine for signs of perforation or generalised peritonism, as this is a surgical emergency.
The main differential diagnoses to consider are the alternative causes for bowel obstruction, as well as severe constipation, pseudo-obstruction, and severe sigmoid diverticular disease.
All patients presenting with clinical features of bowel obstruction should be investigated accordingly. Routine bloods should be taken, including electrolytes, Ca2+, and TFTs to exclude any potential pseudo-obstruction.
The most decisive initial investigation ordered for a suspected sigmoid volvulus is an abdominal X-ray (AXR). This will classically show (present in around 60-75% cases) a “coffee-bean sign” arising from the left iliac fossa (Fig. 2); if the ileocaecal valve is incompetent, the AXR will also show signs of small bowel dilatation.
If the diagnosis remains unclear or clinical features suggest potential bowel ischaemia developing, a CT scan may be warranted; CT imaging classically will document a ‘whirl sign’, from the twisting mesentary around its base. Barium enema can aid in any unclear diagnosis, yet are rarely performed in modern practice.
All patients admitted with suspected sigmoid volvulus should be managed initially as per any bowel obstruction.
Most patients with sigmoid volvulus are treated conservatively initially, requiring decompression with a sigmoidoscope and insertion of a flatus tube.
In sigmoidoscope decompression, the patient is placed in the left lateral position and a lubricated sigmoidoscope gently guided into the rectum. It is maneuvered to locate the twisted bowel and once the sigmoidoscope is in the correct position, there will be a rush of air and liquid faeces as the obstruction is relieved.
A flatus tube is often left in situ for a period of time (up to 24 hours) after initial decompression to allow for the continued passage of contents and aid recovery of the affected area. Up to 24% of sigmoidoscopic approaches may not be able to adequately locate the lead point for the twisting and so this may result in a colonoscopic approach being required.
The indications for surgical involvement (typically either a primary anastomosis or Hartmann’s procedure) are:
- Repeated failed attempts at decompression
- Necrotic bowel noted at endoscopy
- Suspected (or proven) perforation or peritonitis
The decision on which operation to perform will depend on the patient’s nutritional status, adequacy of blood supply, haemodynamic stability, and the presence of any perforation or peritonitis. Patients with recurrent volvulus who are otherwise healthy may choose to have an elective procedure (most commonly sigmoidectomy with primary anastomosis) to prevent further recurrence.
The main immediate complication of a sigmoid volvulus is of bowel ischaemia and perforation. Longer term complications are mainly the risk of recurrence (occurring in up to 90% of patients) and complications arising from any stoma placed (if surgical intervention was required).
Overall mortality is reported at less than 5%, for those going to theatre without decompression, but rising to 11% if gangrenous bowel is present. If there is significant delay in diagnosis and treatment, the mortality rate may be as high as 25%.
The second most common site for a volvulus to occur is at the caecum, accounting for around 25-40% of all colonic volvulus.
The ages of those affected appear to occur in two peaks, once in the 10-29 year group and then again in the 60-79 year group. Those in the younger group may have intestinal malformation or excessive exercise as the predisposing cause, whilst in older patients it is more associated with chronic constipation, distal obstruction, or dementia.
Diagnosis once again may be made initially via abdominal X-ray, showing the coffee bean sign with a lead point from the right lower quadrant. Barium enema can also help to aid an unclear diagnosis.
The management of a caecal volvulus can be achieved via endoscopic decompression, (although only with a 30% success rate) or surgical intervention via detorsion and caecostomy. Due to the higher chance of ischaemia in caecal volvulus, surgical management is normally the primary treatment option. Recurrence following surgery is rare.
- Sigmoid volvulus are common in those from a nursing home, have dementia, or suffer with chronic constipation
- Patients will present with features of bowel obstruction, yet vomiting is often a very late sign
- AXR will classically show a ‘coffee-bean’
- Most patients can be treated with flatus tube decompression, however some cases may need further surgical intervention