You are in: eMedicine Specialties > Radiology > GASTROINTESTINAL Sigmoid VolvulusArticle Last Updated: Jan 3, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, LRCP, Chairman of Medical Imaging, Professor of Radiology, NGHA, King Fahad National Guard Hospital, King Abdulaziz Medical City, Riyadh, Saudi Arabia Ali Nawaz Khan is a member of the following medical societies: American Institute of Ultrasound in Medicine, Radiological Society of North America, Royal College of Physicians, Royal College of Physicians and Surgeons of the United States, Royal College of Radiologists, and Royal College of Surgeons of England Coauthor(s): Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute Editors: Eric P Weinberg, MD, Associate Professor, Department of Radiology, University of Rochester Medical Center, Strong Memorial Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Spencer B Gay, MD, Professor of Radiology, Director of Body Computed Tomography, Department of Radiology, University of Virginia Health Sciences Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: intestinal torsion, gastrointestinal tract, sigmoid colon, large bowel, chronic constipation, roundworm, large bowel obstruction, large-bowel obstruction, pneumoperitoneum INTRODUCTIONSection 2 of 11
  BackgroundSigmoid 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 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. See also the following topics in eMedicine:Obstruction, Large Bowel [in the Emergency Medicine section] Colonic Obstruction, Megacolon, Toxic, and Megacolon, Chronic [in the Gastroenterology section] Toxic Megacolon [in the Radiology section] See also the following topics in Medscape: CME What's New in the Management of IBS and Chronic Constipation? Living Related Segmental Bowel Transplantation: From Experimental to Standardized Procedure Resource Center Colorectal Cancer PathophysiologyAn 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.7 FrequencyUnited StatesSigmoid volvulus is the most common colonic volvulus, and this condition is responsible for approximately 8% of all intestinal obstructions. InternationalThe 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/MorbidityThe 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. RaceSigmoid 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.7 SexIn one restrospective study of 859 cases over a 40-year period, 83.0% of the patients with sigmoid volvulus were male.1 AgeSigmoid 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 AnatomyExamination 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. Clinical DetailsAlthough 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 include 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, 8 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, andabsolute constipation occur in most patients. The patient's pain is said to be out of proportion to the physical signs. Preferred ExaminationPlain 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. Limitations of TechniquesDiagnostic 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. DIFFERENTIALSSection 3 of 11
Other Problems to Be ConsideredOther forms of large-bowel obstruction (especially carcinoma of the sigmoid colon) RADIOGRAPHSection 4 of 11
Findings
Degree of ConfidenceIn 60-70% of patients, the diagnosis of sigmoid volvulus can be made by using plain abdominal radiographic findings. In 20-30% of patients, the 2 limbs of the twisted sigmoid colon may overlap or deviate to the right or left, obscuring the remainder of the colon. In these instances, the findings are those of a nonspecific large-bowel obstruction, and barium enema examination is required for confirmation of the diagnosis. False Positives/NegativesOther forms of large-bowel obstruction, especially those due to sigmoid colon carcinoma, pseudo-obstruction, cecal volvulus, and an ileosigmoid knot, may mimic or be confused with a sigmoid volvulus. At times, emphysematous cystitis and a giant sigmoid diverticulum may also mimic a sigmoid volvulus. (See also the eMedicine article Cecal Volvulus.) CT SCANSection 5 of 11
Findings
Degree of ConfidenceCT scanning is the least invasive imaging technique that allows assessment of mural ischemia. This imaging modality helps in identifying the cause of an acute large-bowel obstruction in 74-86% of cases, although the sensitivity of the investigation is not yet defined. False Positives/NegativesFalse-positive findings may involve other forms of volvulus or obstruction and causes of large-bowel ischemia. MRISection 6 of 11
FindingsMRI has been used successfully in the assessment of large-bowel obstruction (not specifically in sigmoid volvulus). These examinations were performed with the retrograde insufflation of 1000-1200 mL of air through a Foley catheter that was placed in the rectum and with scopolamine to inhibit peristalsis in order to demonstrate the site of bowel obstruction. In addition, MRI has been used in the diagnosis of mural necrosis in infants and, theoretically, this modality can be used in adults. Degree of ConfidenceWith limited experience at the present stage in using this imaging modality to evaluate sigmoid volvulus, assessing the degree of confidence with MRI is not possible. False Positives/NegativesWith the present experience, the limitations of MRI regarding false-positive findings of sigmoid volvulus are not known. ULTRASOUNDSection 7 of 11
FindingsUltrasonography might occasionally be useful in assessing large-bowel obstruction.13, 14 Degree of ConfidenceThe confidence level of ultrasonography is low in the diagnosis of sigmoid volvulus. False Positives/NegativesIn the limited experience in diagnosing sigmoid volvulus by ultrasonography, the images fail to depict the cause in most patients. INTERVENTIONSection 8 of 11
With the patient in the left lateral position, decompression and untwisting of the sigmoid loop may be achieved by the passage of a long, soft tube through the obstruction, per rectum, under fluoroscopic or endoscopic control. This procedure allows for rapid decompression of the distended colon, with the immediate relief of symptoms. The tube may be left in situ for 48 hours to allow for complete emptying of the loop and for the resolution of mural edema. Most patients are elderly persons, and they may be treated conservatively with tube decompression per rectum. However, this form of treatment is controversial because recurrence and mortality rates of sigmoid volvulus are high. If rectal decompression is instituted, the patient should be observed for persistent abdominal pain and blood-stained stools, signs that may herald ischemia and indicate the need for surgical intervention. Surgery is reserved for patients in whom tube decompression fails to alleviate the patient's symptoms or for those in whom signs of ischemia are suggested. Surgery also has a role in an elective situation when the volvulus repeatedly recurs. After conservative treatment, further episodes of volvulus occur in approximately 60% of patients, and elective surgery is frequently required as prophylaxis against recurrence. Medical/Legal Pitfalls
Resource Center Medical Malpractice and Legal Issues ACKNOWLEDGMENTSSection 9 of 11
We would like to gratefully acknowledge Dr. John Howat, MD, FRCS, for his work on this article. MULTIMEDIASection 10 of 11
REFERENCESSection 11 of 11
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