Sigmoid volvulus is a condition where the sigmoid colon, the S-shaped section of the large intestine just above the rectum, twists around itself and the tissue that anchors it in place. This twisting creates a blockage that traps stool and gas, and if the twist is tight enough, it cuts off blood flow to that segment of bowel. It’s the most common type of colon volvulus and can become life-threatening if the blood supply is compromised for too long.
How the Twisting Happens
The sigmoid colon naturally has some mobility. It hangs from a fold of tissue called the mesentery, which connects it to the back wall of the abdomen and carries its blood vessels. In some people, the sigmoid is unusually long (a condition called dolichosigmoid) or has an especially narrow base where the mesentery attaches. Both of these features give the colon more freedom to rotate.
When the sigmoid becomes heavy and dilated, typically from a buildup of stool or gas, it can rotate counterclockwise around that narrow mesenteric base. A partial twist may block the passage of stool and gas but still allow some blood flow. A complete twist pinches off the blood vessels running through the mesentery, starving the bowel wall of oxygen. Without intervention, the tissue dies (becomes gangrenous), and the bowel can perforate, spilling contents into the abdominal cavity.
Who Is Most at Risk
Sigmoid volvulus predominantly affects men. In developed countries, the average age at diagnosis is around 70, while in lower-income countries, particularly in sub-Saharan Africa and parts of Asia, it strikes much younger, with average ages between 40 and 60. In parts of Eastern Europe, India, and Africa, sometimes called the “volvulus belt,” sigmoid volvulus accounts for roughly half of all intestinal obstruction cases.
The main trigger factors include:
- Chronic constipation: A persistently full, heavy sigmoid colon is more prone to rotating.
- High-fiber diet: In regions where diets are very high in fiber, the sigmoid becomes chronically distended, which increases susceptibility.
- Neuropsychiatric conditions: People with conditions like Parkinson’s disease, dementia, or schizophrenia have higher rates, likely because of reduced bowel motility and medication side effects.
- Diabetes: Nerve damage from diabetes can slow gut motility.
- Chagas disease: Common in Latin America, this parasitic infection damages the nerves of the colon, causing chronic dilation.
- Prior abdominal surgery: Adhesions from previous operations can create fixed points around which the bowel twists.
- Laxative overuse: Long-term laxative use can alter bowel motility patterns.
Symptoms to Recognize
The classic triad is abdominal pain, abdominal distention (a visibly swollen belly), and constipation. In an acute episode, these come on relatively suddenly, though most people don’t seek care right away. The typical delay between symptom onset and hospital presentation is one to four days.
Some people experience a subacute or recurrent pattern, where the sigmoid partially twists and then untwists on its own, causing episodes of cramping, bloating, and difficulty passing stool that resolve spontaneously. Over time, these episodes tend to become more frequent and more severe until a complete twist occurs. Nausea and vomiting can develop as the obstruction worsens. If the bowel loses its blood supply, the pain intensifies and may be accompanied by fever, rapid heart rate, and signs of shock.
How It’s Diagnosed
A plain abdominal X-ray is often the first imaging study, and in sigmoid volvulus it can show a distinctive pattern called the “coffee bean sign.” The two halves of the massively dilated, gas-filled sigmoid loop form the sides of a bean shape, while the crease down the middle represents the two walls of the bowel pressed together at the twist point. This sign is considered unmistakable for sigmoid volvulus when present.
CT scans provide more detail and are especially useful when the X-ray is inconclusive or when doctors need to assess whether the bowel wall is still healthy. Air within the bowel wall itself (called parietal pneumatosis) suggests the tissue is dying from lack of blood flow. Free air outside the bowel, in the abdominal cavity, signals perforation, which is a surgical emergency.
Initial Treatment: Endoscopic Detorsion
For uncomplicated cases where the bowel still has adequate blood flow, the first-line treatment is endoscopic detorsion. A flexible or rigid scope is passed through the rectum and into the twisted segment, and the pressure of the scope and the release of trapped gas allow the colon to untwist. This works in 80 to 90% of cases with viable bowel. A flexible scope has a slightly higher success rate (about 85%) compared to a rigid one (about 82%).
The procedure converts what could be a dangerous emergency into a controlled situation, buying time for the patient to be stabilized and prepared for a planned surgical procedure. However, endoscopic detorsion is not attempted when there are signs that the bowel has already died or perforated, since passing a scope through compromised tissue risks making things worse.
Why Surgery Is Usually Necessary
Endoscopic untwisting solves the immediate crisis, but it does nothing to prevent the next episode. Recurrence rates without surgery are striking. Studies report that 55 to 90% of patients managed with decompression alone will be readmitted with another episode of sigmoid volvulus. One series found that 87% of patients initially treated non-surgically were later readmitted with a recurrence, and more than half of those ultimately needed emergency surgery anyway.
For this reason, the standard approach is to use endoscopic detorsion as a bridge to a planned (semi-elective) surgical procedure, ideally during the same hospital stay. The goal is to remove the redundant sigmoid colon so it can no longer twist.
When the bowel is healthy, the surgeon removes the sigmoid segment and reconnects the two remaining ends directly. This single-stage approach avoids the need for a temporary colostomy bag. When the bowel is gangrenous or perforated, or the patient is hemodynamically unstable, a two-stage approach is used instead: the affected colon is removed, the upstream end is brought out through the abdominal wall as a stoma (colostomy), and the downstream end is closed off. Reconnection happens in a second operation months later, once the patient has recovered.
Mortality and Prognosis
The stakes of sigmoid volvulus depend almost entirely on whether the bowel is still alive at the time of treatment. When the bowel is viable, mortality ranges from 0 to 40%, depending on the patient’s age and overall health. When gangrene has set in, that range jumps to 3.7 to 80%. The wide ranges reflect the enormous difference between a relatively healthy person treated promptly and a frail, elderly patient presenting late with sepsis and perforation.
Early recognition is the single most important factor in outcomes. A sigmoid volvulus caught before the blood supply is compromised can usually be decompressed safely and then treated with planned surgery that carries far lower risk than emergency operation on dead bowel. For people who have experienced one episode, elective removal of the sigmoid colon dramatically reduces the chance of facing a future emergency.
Conditions That Can Look Similar
Several other conditions cause a dramatically distended abdomen and share symptoms with sigmoid volvulus. Cecal volvulus involves twisting of a different part of the colon and produces a similar obstruction pattern but in a different location. Acute megacolon and toxic megacolon cause massive colon dilation without a mechanical twist, often in the setting of inflammatory bowel disease or severe infection. Colon cancer or strictures can also cause obstruction that mimics volvulus on initial assessment. Imaging, particularly CT, is what distinguishes these from one another.