Small Intestine Volvulus in Horses: Risk Factors, Causes & Treatment

Small intestine volvulus or torsion is a serious condition in horses, characterized by twisting of the small intestine around itself and the root of the mesentery.

Volvulus is life-threatening to horses because it can cause an intestinal blockage, restricting blood flow and leading to severe damage to the intestinal tissues. The main symptoms of small intestine volvulus are colic and a distended abdomen. Horses with these signs require prompt veterinary attention.

Small intestine volvulus primarily affects the jejunum and ileum, sections of the small intestine that are particularly mobile. Horses with other conditions such as lipoma, mesenteric rents, and impactions are at greater risk.

Diagnosis often requires exploratory surgery due to the non-specific nature of the symptoms. While surgical intervention can save the horse’s life, the prognosis depends heavily on the extent of the intestinal damage.

The severity of volvulus combined with its lack of specific symptoms underscores the importance of seeking veterinary attention at the first signs of colic.

Small Intestine Volvulus in Horses

Small intestine volvulus or torsion describes cases where the intestine twists around itself and the root of the mesentery, the tissue that suspends the bowels from the abdominal wall. ^[1][2][3][4]

Other names for small intestine volvulus include:

• Twisted bowel/small intestine
• Strangulated intestine
• Small intestine torsion

Once the twist has occurred, the intestine forms a sort of “lasso shape” that prevents ingesta from passing through the trapped section of the intestinal tract to the lower intestines.

Small intestine volvulus usually occurs in the lower half of the small intestine, and involves at least a 180-degree, and sometimes as much as a 360-degree rotation. ^[3][4]

As the intestine rotates, the mesentery also becomes twisted. This can interrupt the blood and oxygen flow through the mesentery, leading to tissue death in the intestine. ^[1][2][3]

In severe cases, a loop of intestine can get trapped in the lasso as well, forming a sort of noose. If this happens, the structures can strangle each other, blocking the flow of blood to the area and food through the gastrointestinal system. ^[3][4]

Small Intestine Anatomy

To fully understand the nature of small intestine volvulus, it is useful for horse owners and caretakers to familiarize themselves with the anatomy and function of the small intestine itself.

The small intestine in horses is a long, coiled tube made up of a double layer of muscle. ^[5] It is connected to the stomach on one end, and the large intestine on the other. Its length, flexibility, and mobility increase the risk of it becoming twisted. ^[5]

The equine small intestine comprises three contiguous parts: ^[5]

• The duodenum: The short first section, which is relatively fixed in position.
• The jejunum: The middle section, which is long and very mobile. This section is most commonly affected by volvulus.
• The ileum: The final section which is also long and is highly folded. Some cases of volvulus involve this section.

Two layers of muscle that make up the small intestine walls contract and relax in coordinated movement, referred to as peristalsis or gut motility. The ingesta moves through the small intestine with the help of these peristaltic waves. ^[5]

Once the food has passed through the small intestine, it passes the ingesta along to the structures of the hindgut for further digestion. ^[5]

The small intestine is attached to the mesentery. The mesentery is a thin, fan shaped tissue that loosely holds the structures of the digestive tract in place and attaches them to the abdominal wall. ^[5] It contains the blood vessels and nerves that supply the necessary nutrients and information to the small intestine and other organs of digestion. ^[5]

Intro to Equine Nutrition

Gain a deeper understanding of your horse's nutrition needs. This free introductory course provides a foundation for horse owners to learn how to balance your horse's diet.

Enroll Now

Risk Factors

Horses of any gender, breed, or age can develop small intestine volvulus. ^[1][2] While there is no age predisposition for volvulus, it is the most common reason for intestinal surgery in foals. ^[3]

Horses involved in endurance sports are at greater risk of this condition, particularly just after a race. ^[2] Horses who have recently been swimming are also at greater risk. ^[3]

Horses that have undergone gastroscopy are also more likely to develop small intestine volvulus. ^[2][6][8]

In addition to physical risk factors, there are some management practices that can impact gut motility, which may indirectly contribute to development of volvulus. Specifically, dehydration and feeding large grain-based meals can disrupt peristalsis and intestinal function.

Symptoms

The symptoms of small intestine volvulus or torsion are variable and non-specific. This means that no one symptom is present in every single case of this condition, and all of the symptoms point to several different possible causes.

The main symptoms of small intestine volvulus are a distended abdomen and moderate to severe colic. ^[1][2]

Colic is a broad term for pain in the horse’s abdomen, the signs of which include: ^{[9][10][11][12]}

• Lethargy
• Lack of appetite
• Biting or staring at the flanks
• Restlessness including shifting weight, circling, pacing, biting, repositioning the body, or nibbling non-food items
• Lying down
• Rolling
• Decreased stomach noises
• Rapid breathing
• Rapid heartbeat
• Sweating
• Bloating
• Teeth grinding
• Unusual postures including stretching, dog-sitting, crouching, or lying on the back
• Kicking at the abdomen
• Curling the upper lip (Flehmen Response)
• Tensing the abdomen
• Changes in gum color

Causes

The horse has an exceptionally long digestive tract housed in an expansive abdominal cavity. Their ability to run at high speeds is aided in part by the ability of their internal organs to accommodate movement, allowing the digestive tract to shift within the abdomen during exercise.

As a result, the horse is prone to various intestinal conditions related to displacement and movement of parts of the gastrointestinal tract, including small intestine volvulus.

Volvulus is strongly associated with conditions that impact the motility of the intestines (peristalsis). ^[1] One proposed mechanism is that a volvulus develops when two adjacent sections of the intestine have a significant differential between their rate or cadence of peristaltic motion. ^[4]

Some cases of small intestine volvulus have no clear underlying cause. Others may be related to other dysfunctions within the gut. ^[2][3][4]

In adult horses, small intestine volvulus is often related to an intestinal obstruction that leads to distention of the intestine. ^[1]

Other conditions associated with volvulus include: ^{[2][3][4][10]}

• Inguinal hernia
• Ileal impaction
• Mesodiverticular band
• Meckel diverticulum
• Vitelloumbilical band
• Strangulation in mesenteric rents
• Adhesions
• Intestinal distention
• Intestinal incarceration
• Lipoma

Some activities are also associated with small intestine volvulus, including: ^[1][2][3][7]

• Endurance racing
• Swimming
• Gastroscopy

The cause of small intestine volvulus in foals is thought to be changing feeding habits, specifically the need to adapt to bulkier foods after weaning. ^[1]

Severity

Any part of the small intestine can be involved in a volvulus, but due to the relative lengths of the structures and their attached mesentery, the ileum and jejunum are most likely to be affected. ^[1]

The severity of the condition depends on how much intestinal tissue is trapped and the extent of tissue damage. ^[1] If significant parts of the intestine have to be surgically removed, the prognosis for recovery declines proportionally. ^[1]

Volvulus Nodosus

A rarer type of volvulus is known as volvulus nodosus. ^[2] This condition develops when the lasso of intestine traps another part of the intestine inside its loop, forming a sort of noose. ^[2]

As the trapped part begins to swell, it pulls more of the intestine and mesentery into the noose, increasing the likelihood and extent of tissue damage. ^[2]

This form of the disease is particularly noted in foals, although on very rare occasions can affect adult horses. ^[2][3]

Diagnosis

Diagnosing small intestine volvulus can be challenging since the symptoms are variable and non-specific.

Horses with moderate to severe colic require prompt veterinary care since some causes of colic are life-threatening.

Diagnostic tools typically used for horses with symptoms of small intestine volvulus include: ^[1][2]

• Physical examination
• Rectal palpation (the insertion of a gloved hand into the rectum to feel for abnormalities in the digestive organs)
• Nasogastric intubation
• Ultrasound

Diagnosis of small intestine volvulus is usually confirmed with exploratory surgery. ^[1]

Treatment

The treatment for volvulus is surgery. During volvulus surgery, the intestine is manually untwisted and explored for tissue damage. ^[1]

In many cases, some part of the intestine needs to be removed because blood and oxygen deprivation causes irreversible tissue death (necrosis). ^[1]

In cases of volvulus nodosus, releasing the trapped portion of intestine is a challenge due to swelling, but in some cases can be achieved. ^[3] Surgery is required to open the abdomen, and then the intestinal contents are massaged through to the next portion of intestine so that the trapped loop may be pulled out of the noose. ^[2][3]

As with more straightforward cases, if the trapped tissues are already dead, that segment will be removed. ^[2]

Prognosis

The prognosis for affected horses depends on the amount of intestine that is affected and the severity of the tissue damage. ^[1]

Horses where more than 50% of the intestine is affected have a grave prognosis. ^[1] Otherwise, the prognosis is more favorable with 50 – 75% of horses surviving this condition. ^[2][3] Survival rates are higher for horses that receive surgical intervention. ^[2]

Prevention

There are no proven preventative measures to avoid small intestine volvulus in horses. Preventing this condition centers on maintaining a healthy digestive system through balanced nutrition, adequate hydration, and appropriate feeding practices.

A forage-first diet is recommended, as horses are adapted to consume small amounts of fibrous material throughout the day. Providing continuous access to appropriate-quality forage, such as hay or pasture, helps keep the digestive system functioning smoothly and reduces the risk of intestinal disruptions that could lead to volvulus.

In addition to a forage-based diet, horses should be offered frequent, small meals. This trickle-feeding approach mimics their natural grazing behavior, ensuring a steady flow of ingesta through the intestines and reducing the chances of large, indigestible masses forming, which can contribute to twisting and other forms of intestinal disturbance.

Adequate water intake is equally important, as dehydration can lead to impaction and reduced peristalsis, both of which increase the risk of volvulus. Horses should have constant access to fresh, clean water, especially after exercise or in hot weather, to maintain proper hydration levels and support normal digestive function.

If you are unsure how to switch your horse to a forage-based diet, work with a qualified equine nutritionist who can give you personalized guidance for your individual horse’s needs and lifestyle.

Summary

Small intestine volvulus in horses occurs when a section of the small intestine and its attached mesentery become twisted, cutting off the blood supply to intestinal tissue and preventing passage of ingesta through the digestive tract.

• The main symptoms of intestinal volvulus in horses are a distended abdomen and colic.
• Horses of any breed, gender, or age can develop this condition but it is particularly noted as a cause of colic in foals.
• Some horses develop small intestine volvulus on its own, and some develop it alongside other associated conditions such as impaction, inguinal hernia, adhesions, and lipomas.
• The severity of this condition depends on how much of the intestine is trapped and whether the blood and oxygen supply are completely cut off. In some severe cases, a loop of intestine can get trapped in the lasso as well and begin to swell.
• Diagnosis is based on physical examination, rectal palpation, ultrasound, and nasogastric intubation and confirmed during exploratory surgery. Treatment is surgical.
• The prognosis is favorable in cases where not too much intestine needs to be surgically removed. Otherwise, the prognosis is more guarded.