When a horse’s gut twists on itself, the condition is called a volvulus, and specifically in horses it most commonly involves the large colon rather than the stomach. You’ll also hear it called a “torsion” or simply a “twisted gut.” Large colon volvulus is one of the most dangerous forms of colic in horses, and without emergency surgery, it can be fatal within 24 hours.
Why It’s the Colon, Not the Stomach
Horses have an enormous large colon, roughly 3 to 4 meters long, and unlike most of their other organs, it isn’t firmly anchored in place by connective tissue. Its weight, length, and lack of extensive attachments allow it to shift and rotate. When it twists, typically at the point where the colon connects to the cecum, the rotation strangles the blood vessels feeding the intestinal wall. That’s what makes the condition so urgent: without blood flow, the tissue starts to die.
A true stomach twist (gastric volvulus) is extremely rare in horses. When horse owners or veterinarians talk about a “twisted stomach,” they’re almost always referring to this large colon volvulus. Small intestinal volvulus also occurs but is a separate condition with its own characteristics.
What Causes the Colon to Twist
The exact trigger isn’t fully understood, but several risk factors make a twist more likely. Anything that causes the colon to slow down, fill with gas, and become heavy enough to shift out of position increases the risk. Known contributors include:
- Recent foaling. Broodmares in the days and weeks after giving birth are at significantly higher risk. The theory is that after the foal is delivered, the sudden increase in abdominal space gives the colon room to move into abnormal positions. Geographic areas with high concentrations of broodmares see more cases.
- Dietary changes. Switching feed suddenly, or giving a horse access to lush pasture it isn’t accustomed to, can disrupt normal gut motility and lead to gas buildup.
- Stress and electrolyte imbalances. Both can slow the colon’s normal contractions, allowing gas to accumulate and the heavy, distended organ to rotate.
Signs That a Twist May Be Happening
A colon volvulus produces severe, unrelenting colic pain. Horses will paw at the ground, roll repeatedly, stare at their flanks, sweat heavily, and become increasingly restless. What distinguishes a twist from milder forms of colic is the intensity and the fact that the pain doesn’t let up. A horse with a simple gas colic might settle down between episodes; a horse with a volvulus rarely does.
Heart rate is one of the most telling indicators. A normal resting heart rate for an adult horse is 24 to 44 beats per minute. In horses with serious colic requiring surgery, the heart rate often climbs well above 44. In one study of 111 colic cases, a heart rate above 44 was strongly associated with a worse outcome, making it roughly 7.5 times more likely the case was life-threatening. The color of the gums also matters: healthy horses have bright pink gums, while horses with compromised blood flow develop pale or bluish (cyanotic) gums, a sign that circulation is failing.
How Veterinarians Confirm It
A veterinarian will typically start with a rectal exam, feeling for displacement or distension of the colon. Abdominal ultrasound can reveal thickened intestinal walls and free fluid in the abdomen, both signs of tissue in distress. But the definitive diagnosis often comes during surgery itself. Because every hour counts with a volvulus, veterinarians frequently recommend going to surgery based on the severity of pain, heart rate, and rectal findings rather than waiting for perfect diagnostic certainty.
What Happens During Surgery
Emergency surgery for a colon volvulus is performed at a referral hospital. The horse is placed under general anesthesia, lying on its back. The surgeon opens the abdomen along the midline below the navel, then uses needles attached to suction to decompress the gas-filled colon so it can be partially brought outside the body. The twist is then manually corrected by rotating the colon back into its normal position.
Once untwisted, the surgical team watches the tissue for around 15 minutes, checking whether color returns and whether blood flow through the vessels resumes. If the tissue looks healthy and pulses are strong, the colon goes back into the abdomen. If sections have died from too long without blood flow, the surgeon removes the damaged portion and reconnects the healthy ends, a procedure called resection and anastomosis. That’s a more complex operation with a longer recovery.
One particularly dangerous aspect of this condition is something called ischemia-reperfusion injury. When blood flow is restored to tissue that’s been starved of oxygen, the sudden return of oxygenated blood actually triggers an intense inflammatory response. White blood cells flood into the intestinal wall, and the resulting damage can sometimes be worse than the original loss of blood flow. This is a major reason why outcomes depend so heavily on how quickly the horse reaches surgery.
Survival Rates and Recovery
The prognosis depends heavily on how long the colon has been twisted and how much tissue damage has occurred. Twists greater than 270 degrees cause more severe blood vessel compression and faster tissue death. Without surgery, a horse with a true volvulus will typically die within 24 hours as the intestinal wall breaks down and infection spreads into the abdomen.
With surgery, the numbers improve considerably. In a study of 73 horses that underwent large colon resection for strangulating volvulus, 74% survived to leave the hospital. At one year, 67.8% were still alive, and at three years, 63.5%. Diarrhea was the most common complication after surgery, but it typically resolved on its own. Horses that survived past the first year returned to their intended use, whether as broodmares, racehorses, or show horses, with no chronic problems from the procedure.
The critical variable is time. The onset of the twist, the horse’s heart rate at admission, and the degree of tissue damage all influence whether a horse survives. Four of the horses in that study died of colic in the first year after surgery, suggesting that some horses may have underlying risk factors that predispose them to repeated episodes. For horses that clear that first year, though, the long-term outlook is genuinely good.