Introduction
Background
Sigmoid volvulus is the most common form of volvulus of the gastrointestinal tract, and this condition is responsible for 8% of all intestinal obstructions. Sigmoid volvulus is particularly common in elderly persons. Patients present with abdominal pain, distention, and absolute constipation.1,2 Predisposing factors to sigmoid volvulus include chronic constipation, megacolon, and an excessively mobile colon. Plain abdominal radiograph findings are usually diagnostic. Decompression may be achieved with the introduction of a stiff tube per the rectum, aided by endoscopy or fluoroscopy. Early radiographic recognition is important to prevent the mortality related to sigmoid volvulus.1,2,3,4,5,6
This radiograph demonstrates a greatly dilated sigmoid that almost fills the entire abdomen (same patient in Images 1-3). Note the coffee bean sign. The remainder of the large bowel is not dilated, presumably because the proximal point of the twist is not causing obstruction and thus allows drainage into the sigmoid.
Erect abdominal radiograph (same patient in Images 1-3). This image shows fluid levels in the distended sigmoid loop.
This radiograph shows decompression of the sigmoid loop following retrograde passage of a flatus tube (same patient in Images 1-3).
Recent studies
Larkin et al studied 27 patients treated for acute sigmoid volvulus between 1996 and 2006, 11 of whom were managed with colonoscopic decompression alone. Fifteen patients underwent operative management (5 semielective after decompression; 10 emergency). Mortality associated with nonoperative management was 36.4% (4 of 11 patients), and there was 1 mortality in the emergency surgery group and none in the semielective group. The patients who died had established bowel gangrene. There was a 71.4% recurrence rate among patients managed with colonoscopic decompression who survived. The authors noted that good outcomes can be achieved with early surgical intervention before the onset of gangrene, even in patients apparently unsuitable for elective surgery.
Larken and coauthors concluded that all patients should be considered for definitive surgery after initial colonoscopic decompression because of the high rate of recurrence of sigmoid volvulus after successfulnonoperativemanagement and the risks of mortality from gangrenous bowel with subsequent volvulus.7
Jumbi and Kuremu studied patients in Kenya who underwent emergency resection of sigmoid volvulus between 2000 and 2005. Sigmoid volvulus accounted for 14.1% of all cases of intestinal obstruction and 80% of large gut obstruction. They found that emergency resection in cases with a viable colon had a similar outcome to standard treatment by emergency endoscopic derotation followed by resection. Overall outcome was comparable to global standards, and inadequate postoperative intravenous fluid therapy significantly affected outcome.8
For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles, Abdominal Pain in Adults, Constipation in Adults, Barium Enema, and Gastrointestinal Endoscopy.
Pathophysiology
An unusually narrow attachment of the root of the sigmoid mesentery to the posterior abdominal wall permits close approximation of the 2 limbs of the sigmoid colon. This, in turn, may predispose patients to a twisting in the sigmoid colon around its mesenteric axis. The anatomic defect may be complicated by predisposing factors, including a high-roughage diet, chronic constipation, and lead poisoning. Sigmoid volvulus is common in elderly persons, in individuals with neurologic conditions, and in patients in nursing homes or mental health facilities. The common factor is chronic constipation. Megacolon and sigmoid volvulus are common lower GI disorders in high-altitude inhabitants.9
Frequency
United States
Sigmoid volvulus is the most common colonic volvulus, and this condition is responsible for approximately 8% of all intestinal obstructions.
International
The worldwide frequency is not known, but sigmoid volvulus occurs frequently in young people in geographic areas that have a high incidence of roundworm infestation. In Brazil, the condition occurs in 10% of patients with a megacolon secondary to Chagas disease. A rare form of volvulus may occur in school-aged children in whom pathologic elongation of the sigmoid colon occurs. In this form, the symptoms are less acute and can spontaneously disappear.
Mortality/Morbidity
The mortality rates associated with sigmoid volvulus are 20-25%, depending on the interval between when the diagnosis is made and treatment is rendered. Therefore, radiographic recognition of sigmoid volvulus is important.
Race
Sigmoid volvulus is particularly common in South America, Africa, and parts of Asia where the consumption of high-fiber diets results in a long, redundant sigmoid colon. This condition accounted for 79% of all intestinal obstructions at a Bolivian hospital.9
Sex
In one restrospective study of 859 cases over a 40-year period, 83.0% of the patients with sigmoid volvulus were male.1
Age
Sigmoid volvulus is most common in persons older than 50 years, followed by pediatric patients. The mean age of the patients in one large retrospective study was 58.1 years.1
Anatomy
Examination of the base of the sigmoid at the time of surgery for volvulus may show that the 2 limbs of the colon are bound closed, usually by fibrous adhesions within the peritoneum. This scenario, plus the dependent position of a redundant sigmoid loop, predisposes patients to the volvulus.
In acute sigmoid volvulus, the degree of torsion varies from 180º (35% of cases) to 540º (10% of cases). A 360º torsion is seen in 50% of patients, and the torsion is usually counterclockwise. The common form of volvulus around the mesenteric axis is usually situated 15-25 cm from the anus and is therefore accessible to sigmoidoscopic examination.
Presentation
Although a sigmoid volvulus may present insidiously with chronic abdominal distention, constipation, vague lower abdominal discomfort, and vomiting, this condition is seen more often as an abdominal emergency with acute distention, colic, and a failure to pass either flatus or stool. Vomiting occurs in the late stage, and the distention may be gross enough to compromise respiratory and cardiac function. Physical examination reveals a tympanitic abdomen, and a palpable mass may be present. Shock and an elevation of temperature may be present if colonic perforation has occurred. Rectal examination shows only an empty rectal ampulla.
A retrospective review of 859 patients showed sigmoid volvulus is an uncommon cause of mechanical intestinal obstruction.1 Approximately 26% of the patients had a history of previous volvulus episodes, associated disease was found in another 26% of the patients, and a shock state occurred in 13.5% of the patients. The most common symptoms and signs were abdominal pain and tenderness, asymmetrical distention, and absolute constipation. Abdominal x-rays were suggestive of sigmoid volvulus in 65.0% of the patients. When used, computed tomography (CT) scanning, magnetic resonance imaging (MRI), and sigmoidoscopy were diagnostic in all patients.
Typical features of sigmoid volvulus include colicky pain in the left lower abdominal quadrant, distention, and constipation. Barium enema examination demonstrates obstruction at the rectosigmoid junction. The most common and clinically significant twist of the sigmoid occurs in the mesenteric axis, although a less frequent and more benign form of the twist may occur around the longitudinal axis of the sigmoid loop. This longitudinal twist has been variably termed the kink, axial torsion, or physiologic incomplete torsion. Patients with this twist are usually not symptomatic, and it may be an incidental finding on a routine barium enema examination.
Bowel gas may be able to enter the closed sigmoid loop through the twist, but it cannot escape. This condition results in massive dilatation of the sigmoid loop and further tightening of the obstructive twist, leading to complete obstruction. Failure to provide prompt diagnosis and treatment ultimately leads to colonic ischemia, with perforation and peritonitis.
The extent of sigmoid colon ischemic changes must be determined before proceeding with surgical resection to prevent anastomosis of the ischemic colon and subsequent stenosis. The differential diagnosis includes an ileosigmoid knot, a rare but serious abdominal emergency in which the ileum and sigmoid entangle each other to form a knot.2,3,5,6,10 This knot may lead to vascular compromise and gangrene of both the ileum and sigmoid colon. The presentation is acute, with rapid deterioration in the patient's condition, including the development of shock and bowel gangrene. Abdominal cramps, vomiting, and absolute constipation occur in most patients. The patient's pain is said to be out of proportion to the physical signs.
Preferred Examination
Plain abdominal radiographic findings are usually diagnostic of sigmoid volvulus. Decompression may be achieved by the introduction of a stiff tube per rectum, aided by endoscopy or fluoroscopy. A single-contrast barium enema examination is usually adequate if it is required, as in cases when the diagnosis is in doubt. CT scanning is the least invasive imaging technique that allows assessment of mural ischemia. Unlike barium enema examination, CT scanning has a high likelihood of revealing other causes of abdominal pain if the source of the patient's symptoms is not sigmoid volvulus. Results of conventional mesenteric angiography with intravenously administered contrast material or magnetic resonance angiography (MRA) may be more definitive in the diagnosis of mesenteric ischemia.
The key radiologic features are those of a double-loop obstruction, which has been reported in approximately 50% of patients. The key finding consists of a dilated loop of pelvic colon, associated with features of small-bowel obstruction and retention of feces in an undistended proximal colon. The dilated loop usually lies in the right side of the abdomen, and the limbs taper inferiorly into the right lower quadrant. Medial deviation of the distal descending colon is a rare but highly specific finding.
Plain radiographs readily permit the distinction of sigmoid volvulus from primary volvulus of the small intestine and from other nonobstructive surgical emergencies. However, volvulus of the right colon, closed-loop small intestinal obstruction, and sigmoid volvulus complicated by peritonitis may simulate sigmoid volvulus on radiographs. Sigmoidoscopy, rather than barium enema examination, is the procedure of choice if an ileosigmoid knot is suspected.
Limitations of Techniques
Diagnostic difficulties may occur with plain abdominal radiographs if the degree of proximal dilatation is so marked that the sigmoid loop may not be recognized as such. Similar difficulties may be encountered when a large amount of fluid is associated with a small amount of air. This situation causes poor definition of the sigmoid colon on a supine radiograph, and the high air-fluid levels demonstrated on erect images may be inadequate to define the sigmoid loop accurately.
Barium enema examination is contraindicated in patients in whom a gangrenous bowel is suspected or when a pneumoperitoneum is noted on a plain abdominal radiograph or erect chest radiograph. Barium enema examination is also contraindicated in patients who have clinical signs of peritonitis.
Differential Diagnoses
Other Problems to Be Considered
Other forms of large-bowel obstruction (especially carcinoma of the sigmoid colon)
Giant sigmoid diverticulum
Ileosigmoid knot
Pseudo-obstruction
See also the following topics in eMedicine:
Constipation (in the Gastroenterology section)
Constipation [in the Pediatrics section]
Constipation [in the Emergency Medicine section]
Constipation and Bowel Management [in the Pediatrics General Surgery section]
Intestinal Pseudo-obstruction: Surgical Perspective
See also the following topics in Medscape:
Resource Center Colorectal Cancer
Resource Center IBS and Chronic Constipation Resource Center
Cumulative Incidence of Chronic Constipation: A Population-Based Study 1988-2003
CME Update on the Diagnosis and Treatment of Chronic Constipation and Irritable Bowel Syndrome
CME Upper GI Functional and Motility Disorders
CME ACG 2007: Functional Gastrointestinal Disorders
Obstructing Giant Colonic Diverticulum
Clinical Application Prospects of Gastric Pacing for Treating Postoperative Gastric Motility Disorders
Post-Infectious Gastroparesis: Clinical and Electerogastrographic Aspects
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References
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Further Reading
Related eMedicine topics
Obstruction, Large Bowel [Emergency Medicine]
Colonic Obstruction [Gastroenterology]
Megacolon, Toxic [Gastroenterology]
Megacolon, Chronic [Gastroenterology]
Toxic Megacolon [Radiology]
Keywords
sigmoid volvulus, intestinal torsion, gastrointestinal tract, sigmoid colon, large bowel, chronic constipation, roundworm, large bowel obstruction, large-bowel obstruction, pneumoperitoneum
