eMedicine Specialties > Radiology > Gastrointestinal

Sigmoid Volvulus

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK
Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute; John MT Howat, MB, BCh, MD, FRCS, Consultant General and Colorectal Surgeon, North Manchester General Hospital, UK

Updated: Aug 20, 2009

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).

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

Radiography

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).

Supine abdominal radiograph in a 6-year-old child from an area in which roundworms are endemic. This image shows a sigmoid volvulus. The sigmoid loop is dilated and associated with mild proximal large-bowel dilatation.

This erect radiograph shows fluid levels in the sigmoid loop and in the transverse colon (same patient as in Image 4).

Erect abdominal radiograph demonstrating a giant sigmoid diverticulum. This image shows a dilated loop of bowel with air-fluid levels and intraluminal feces. This appearance mimics that of an enlarged cecum or sigmoid loop.

Radiograph from an enema examination with water-soluble contrast material in an unprepared bowel (same patient as in Image 6). This image shows a giant sigmoid diverticulum that contains feces.

Findings

• Plain radiographs show a markedly distended sigmoid loop, which assumes a bent inner tube or inverted U -shaped appearance, with the limbs of the sigmoid loop directed toward the pelvis.
• The colonic haustra are lost, and progressive distention elevates the sigmoid loop under one side of the diaphragm.
• An upright radiograph shows a greatly distended sigmoid loop with air-fluid levels mainly on the left side of the abdomen and extending toward the right hemidiaphragm.
• The involved bowel walls are edematous, and the contiguous walls form a dense white line on radiographs. This line is surrounded by the curved and dilated gas-filled lumen, resulting in a coffee bean-shaped structure; this is the coffee bean sign.¹¹
• If more fluid than air is in the obstructed loop of the sigmoid, the volvulus may be demonstrable by a soft-tissue mass or a pseudotumor sign.
• A single-contrast barium enema examination is adequate because the barium readily enters the empty rectum and usually encounters a complete stenosis, which is likened to a beak, the so-called bird's beak or bird-of-prey sign.
• If barium can enter the obstructed segment, spiraling of the mucosal folds may be seen. Signs of bowel ischemia, such as thumbprinting, transverse ridging, and mucosal ulceration, may be observed.
• A dilated sigmoid colon that ascends to the transverse colon (northern exposure sign) is said to be a reliable sign of a sigmoid volvulus on a supine abdominal radiograph.¹²

Degree of Confidence

In 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/Negatives

Other 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.

Computed Tomography

Findings

• CT scan findings of sigmoid volvulus include the whirl sign, which represents tension on the tightly twisted mesocolon by the afferent and efferent limbs of the dilated colon.^13,14
• CT scanning may be useful in identifying the etiology and site of the obstruction that result from other pathologies, as well as in demonstrating ischemia that results from strangulation.
• CT scan signs of ischemia include a serrated beak at the site of the obstruction, mesenteric edema or engrossment, and moderate to severe thickening of the bowel wall.
• Intramural gas or portal venous gas may be seen (grave prognostic signs), and in patients in whom a perforation has occurred, a large amount of free intraperitoneal gas or fluid may be noted.

Degree of Confidence

CT 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/Negatives

False-positive findings may involve other forms of volvulus or obstruction and causes of large-bowel ischemia.

Magnetic Resonance Imaging

Findings

MRI 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 Confidence

With 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/Negatives

With the present experience, the limitations of MRI regarding false-positive findings of sigmoid volvulus are not known.

Ultrasonography

Findings

Ultrasonography might occasionally be useful in assessing large-bowel obstruction.^15,16

Degree of Confidence

The confidence level of ultrasonography is low in the diagnosis of sigmoid volvulus.

False Positives/Negatives

In the limited experience in diagnosing sigmoid volvulus by ultrasonography, the images fail to depict the cause in most patients.

Intervention

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.

Safioleas et al performed a retrospective review of the clinical presentation and imaging characteristics of 33 sigmoid volvulus patients. The authors determined from the study findings that although sigmoid volvulus causing intestinal obstruction is frequently successfully encountered by endoscopic decompression, the principal therapy remains surgery and that only occasionally in patients with advanced age, lack of bowel symptoms, and multiple comorbidities might surgical repair not be considered.¹⁷

Oren et al reviewed the outcomes of emergent treatment of sigmoid volvulus in 827 patients. Nonoperative reduction was used in 575 patients (barium enema in 13, rigid sigmoidoscopy in 351, and flexible sigmoidoscopy in 211, with rectal tube placement in all patients), with a success rate of 78.1%; mortality, 0.9%; complication rate, 3%; and early recurrence rate, 3.3%. Surgical treatment was performed in 393 patients, with a mortality of 15.8%; complication rate, 37.2%; early recurrence rate, 0.8%; and late recurrence rate, 6.7%. 

Oren and coauthors noted that nonoperative reduction is the initial treatment, and flexible sigmoidoscopy with rectal tube placement can be used successfully. However, emergency surgery is necessary in patients in whom bowel gangrene or peritonitis is present or nonoperative treatment is unsuccessful. In surgical treatment, resection with primary anastomosis is the first choice and can be performed with acceptable mortality and morbidity rates in stable patients in whom a tension-free anastomosis is possible.¹⁸

Medicolegal Pitfalls

• Take care not to perform a barium enema examination in patients with suspected gangrenous bowel, a pneumoperitoneum (as seen on plain abdominal radiographs), or clinical signs of peritonitis.

Multimedia

Media file 1: 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.

Media file 2: Erect abdominal radiograph (same patient in Images 1-3). This image shows fluid levels in the distended sigmoid loop.

Media file 3: This radiograph shows decompression of the sigmoid loop following retrograde passage of a flatus tube (same patient in Images 1-3).

Media file 4: Supine abdominal radiograph in a 6-year-old child from an area in which roundworms are endemic. This image shows a sigmoid volvulus. The sigmoid loop is dilated and associated with mild proximal large-bowel dilatation.

Media file 5: This erect radiograph shows fluid levels in the sigmoid loop and in the transverse colon (same patient as in Image 4).

Media file 6: Erect abdominal radiograph demonstrating a giant sigmoid diverticulum. This image shows a dilated loop of bowel with air-fluid levels and intraluminal feces. This appearance mimics that of an enlarged cecum or sigmoid loop.

Media file 7: Radiograph from an enema examination with water-soluble contrast material in an unprepared bowel (same patient as in Image 6). This image shows a giant sigmoid diverticulum that contains feces.

References

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17. Safioleas M, Chatziconstantinou C, Felekouras E, Stamatakos M, Papaconstantinou I, Smirnis A, et al. Clinical considerations and therapeutic strategy for sigmoid volvulus in the elderly: a study of 33 cases. World J Gastroenterol. Feb 14 2007;13(6):921-4. [Medline].

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Keywords

sigmoid volvulus, intestinal torsion, gastrointestinal tract, sigmoid colon, large bowel, chronic constipation, roundworm, large bowel obstruction, large-bowel obstruction, pneumoperitoneum

Contributor Information and Disclosures

Author

Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR, Consultant Radiologist and Honorary Professor, North Manchester General Hospital Pennine Acute NHS Trust, UK
Ali Nawaz Khan, MBBS, FRCS, FRCP, FRCR is a member of the following medical societies: American Association for the Advancement of Science, American Institute of Ultrasound in Medicine, British Medical Association, British Society of Interventional Radiology, 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
Disclosure: Nothing to disclose.

Coauthor(s)

Sumaira MacDonald, MBChB, PhD, MRCP, FRCR, Lecturer, Sheffield University Medical School; Endovascular Fellow, Sheffield Vascular Institute
Sumaira MacDonald, MBChB, PhD, MRCP, FRCR is a member of the following medical societies: British Medical Association, Royal College of Physicians, and Royal College of Radiologists
Disclosure: Nothing to disclose.

John MT Howat, MB, BCh, MD, FRCS, Consultant General and Colorectal Surgeon, North Manchester General Hospital, UK
John MT Howat, MB, BCh, MD, FRCS is a member of the following medical societies: Royal College of Surgeons of England
Disclosure: Nothing to disclose.

Medical Editor

Eric P Weinberg, MD, Associate Professor, Department of Radiology, University of Rochester Medical Center, Strong Memorial Hospital
Eric P Weinberg, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, and Radiological Society of North America
Disclosure: Nothing to disclose.

Pharmacy Editor

Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand
Disclosure: Nothing to disclose.

Managing Editor

Spencer B Gay, MD, Professor of Radiology, Director of Body Computed Tomography, Department of Radiology, University of Virginia Health Sciences Center
Disclosure: Nothing to disclose.

CME Editor

Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute
Robert M Krasny, MD is a member of the following medical societies: American Roentgen Ray Society and Radiological Society of North America
Disclosure: Nothing to disclose.

Chief Editor

Eugene C Lin, MD, Consulting Radiologist, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine
Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine
Disclosure: Nothing to disclose.

We would like to gratefully acknowledge Dr. John Howat, MD, FRCS, for his work on this article.

Related eMedicine topics

Obstruction, Large Bowel [Emergency Medicine]
 
Colonic Obstruction [Gastroenterology]

Megacolon, Toxic [Gastroenterology]

Megacolon, Chronic [Gastroenterology]
 
Toxic Megacolon [Radiology]

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