A twisted bowel, known medically as volvulus, happens when a section of intestine rotates around the tissue that anchors it in place, cutting off blood flow and blocking the passage of food and stool. The causes range from anatomy you’re born with to lifestyle factors that develop over decades, and the specific trigger depends on which part of the bowel is affected and your age.
How the Bowel Twists
Your intestines are held in position by a fan-shaped tissue called the mesentery, which connects the bowel to the back wall of your abdomen and carries blood vessels to and from the gut. When a loop of bowel rotates along the axis of this mesentery, it pinches off its own blood supply and seals the intestine shut in both directions, trapping gas and fluid inside.
Two anatomical features make this possible: a long mesentery that gives a section of bowel too much freedom to move, and a narrow point of attachment where the mesentery connects to the abdominal wall. Think of it like a swing hanging from a single hook rather than a fixed bar. The longer the rope and the narrower the anchor, the easier it is for the seat to spin. Cadaver studies have found that 10 to 25 percent of the general population have a mesentery long enough to make the beginning of the large intestine prone to twisting, even if most of those people never develop a problem.
Sigmoid Volvulus: The Most Common Type
The sigmoid colon, the S-shaped curve of large intestine just above the rectum, is the most frequent site of twisting in adults. It’s particularly vulnerable because it sits on a mesentery that varies widely in length from person to person. In U.S. cadaver studies, the average sigmoid mesentery measured about 8 centimeters long and 5.6 centimeters wide. In Middle Eastern populations, the average width was nearly three times that, at over 15 centimeters, which helps explain why sigmoid volvulus rates differ dramatically across regions.
Several factors cause the sigmoid colon to elongate and become more mobile over time:
- Chronic constipation. Years of straining and retaining stool stretch the sigmoid colon, making it longer and more redundant. The typical patient is an elderly person in a care facility with a long history of constipation or laxative use.
- High-fiber diets in certain populations. In parts of Africa, where traditional diets are extremely high in fiber, fermentation of carbohydrates in the colon produces large volumes of gas and bulky stool. This chronically distends the sigmoid, increasing its weight and making it more likely to swing and twist on its mesentery.
- Repeated partial twisting. The sigmoid can twist partway and then untwist on its own, sometimes causing only mild cramping. But each episode creates low-grade inflammation at the base of the mesentery. Over time, scar tissue locks the two limbs of the sigmoid loop into a paddle-like shape that actually makes full twisting more likely to happen again.
Sigmoid volvulus is more common in elderly men, particularly those over 70, and occurs at higher rates in African Americans and in people with diabetes or neuropsychiatric conditions. The connection with neuropsychiatric disorders likely reflects the chronic constipation that many psychiatric medications cause, combined with reduced physical activity in institutional settings.
Cecal Volvulus: A Different Location, Different Profile
The cecum is the pouch at the beginning of the large intestine, in the lower right side of the abdomen. In most people it’s fixed firmly to the back wall of the abdomen, but developmental variations during fetal growth leave some people with a cecum that’s unusually mobile. When the ascending colon has a longer-than-normal mesentery, the cecum can fold upward (a movement called bascule) or rotate, producing a volvulus.
Unlike sigmoid volvulus, cecal volvulus tends to affect younger women rather than elderly men. It’s less common overall but can be just as dangerous because it also strangles the blood supply to the affected bowel.
Malrotation and Midgut Volvulus in Children
In babies and young children, a twisted bowel is usually caused by a condition called intestinal malrotation, which originates before birth. During normal fetal development, the intestines temporarily push out of the abdominal cavity, rotate 270 degrees counterclockwise around the main blood vessel supplying the gut, and then settle back into place. This rotation is what positions the small intestine in the center of the abdomen and fixes the large intestine along its familiar frame around the edges.
If that rotation is interrupted or incomplete, the intestines end up in the wrong position with an abnormally narrow base of mesentery. Instead of a broad, stable fan of tissue anchoring the bowel, the entire midgut hangs from a thin stalk. This narrow stalk is prone to clockwise twisting, which can cut off blood flow to most of the small intestine at once.
The stage at which rotation stops determines the specific problem. A complete failure of rotation leaves the small bowel on the right side and the large bowel on the left, all dangling from a narrow mesenteric base. A partial rotation can leave the cecum in an abnormal position where fibrous bands stretch across the duodenum, compressing it and causing obstruction even without twisting. Most cases of malrotation that cause midgut volvulus present in the first year of life, often within the first month, though some go undetected into adulthood.
Adhesions and Internal Hernias
Previous abdominal surgery creates scar tissue called adhesions, which can form bands or pockets inside the abdomen. A loop of bowel can slide through a gap between these adhesions and the abdominal wall, then twist around the band like a jump rope caught on a fence post. Internal hernias, where bowel pushes through an opening in the mesentery or between the mesentery and the abdominal wall, work the same way. One surgical review found this type of internal herniation with subsequent twisting occurred in about 1 percent of major abdominal reconstructions, rare but potentially devastating when it happens.
Any condition that creates a new pivot point inside the abdomen, whether from surgical scarring, a tumor, or even pregnancy shifting the position of the intestines, can set the stage for a section of bowel to rotate.
Why Speed Matters
The danger of a twisted bowel isn’t just the blockage itself. When the mesentery twists, it strangles the blood vessels running through it. Without blood flow, the trapped section of intestine begins to die. The difference in outcomes between a viable bowel and one that has already lost its blood supply is stark: mortality in cases where the bowel is still alive ranges from 3 to 30 percent, while gangrenous bowel carries a mortality rate of 17 to 80 percent depending on the extent of damage and how quickly treatment begins.
This is why a twisted bowel is treated as a surgical emergency. The symptoms, which typically include sudden severe abdominal pain, bloating, vomiting, and the inability to pass gas or stool, escalate quickly. In sigmoid volvulus, doctors can sometimes untwist the bowel using a flexible tube passed through the rectum, buying time before definitive surgery. Cecal volvulus and midgut volvulus almost always require an operation.