Colic in horses is defined as abdominal pain, but it is a clinical sign rather than a diagnosis. The term colic can encompass all forms of gastrointestinal conditions which cause pain as well as other causes of abdominal pain not involving the gastrointestinal tract. The most common forms of colic are gastrointestinal in nature and are most often related to colonic disturbance. There are a variety of different causes of colic, some of which can prove fatal without surgical intervention. Colic surgery is usually an expensive procedure as it is major abdominal surgery, often with intensive aftercare. Among domesticated horses, colic is the leading cause of premature death. The incidence of colic in the general horse population has been estimated between four and ten percent over the course of their lifetime. Clinical signs of colic generally require treatment by a veterinarian..
- 1 Types
- 1.1 Gas and Spasmodic colic
- 1.2 Pelvic flexure impaction
- 1.3 Ileal impaction
- 1.4 Sand impaction
- 1.5 Cecal impaction
- 1.6 Gastric impaction
- 1.7 Small colon impaction
- 1.8 Large colon impaction
- 1.9 Enteroliths and Fecaliths
- 1.10 Meconium Impactions and Foal Colic
- 1.11 Ascarids (Roundworms)
- 1.12 Tapeworms
- 1.13 Cyathostomes
- 1.14 Large strongyles
- 1.15 Left dorsal displacement (Nephrosplenic entrapment)
- 1.16 Right dorsal displacement
- 1.17 Proximal enteritis
- 1.18 Torsion and Volvulus
- 1.19 Intussusception
- 1.20 Epiploic foramen entrapment
- 1.21 Mesenteric rent entrapment
- 1.22 Strangulating pedunculated lipoma
- 1.23 Other cancers
- 1.24 Gastric ulceration
- 1.25 Right dorsal colitis
- 1.26 Ileus
- 1.27 Uterine tears and torsions
- 1.28 Toxins
- 1.29 Herniation
- 1.30 Other causes that may show clinical symptoms of colic
- 2 Pathophysiology of equine colic
- 3 Diagnosis
- 4 Clinical signs
- 5 Management and Complications of Colic
- 6 Prevention
- 7 Further reading
- 8 External links
- 9 References
This list of types of colic is not exhaustive but details some of the types which may be encountered.
Gas and Spasmodic colic
Gas colic, also known as tympanic colic, is the result of gas buildup within the horse's digestive tract due to excessive fermentation within the intestines or a decreased ability to move gas through it. It is usually the result of a change in diet, but can also occur due to low dietary roughage levels, parasites (22% of spasmodic colics are associated with tapeworms), and anthelminthic administration. This gas buildup causes distention and increases pressure in the intestines, causing pain. Additionally, it usually causes an increase in peristaltic waves, which can lead to painful spasms of the intestine, producing subsequent spasmodic colic. The clinical signs of these forms of colic are generally mild, transient, and respond well to spasmolytic medications, such as buscopan, and analgesics. Gas colics usually self-correct, but there is the risk of subsequent torsion (volvulus) or displacement of the bowel due to gas distention, which causes this affected piece of bowel to rise upward in the abdomen.
Abdominal distention may occasionally be seen in adult horses in the flank region, if the cecum or large colon is affected. Foals, however, may show signs of gas within the small intestines with severe abdominal distention.
Pelvic flexure impaction
This is caused by an impaction of food material (Water, Grass, Hay, Grain) at a part of the large bowel known as the pelvic flexure of the left colon where the intestine takes a 180 degree turn and narrows. Impaction generally responds well to medical treatment, usually requiring a few days of fluids and laxatives such as mineral oil, but more severe cases may not recover without surgery. If left untreated, severe impaction colic can be fatal. The most common cause is when the horse is on box rest and/or consumes large volumes of concentrated feed, or the horse has dental disease and is unable to masticate properly. This condition could be diagnosed on rectal examination by a veterinarian. Impactions are often associated with the winter months because horses do not drink as much water and eat drier material (hay instead of grass), producing drier intestinal contents that are more likely to get stuck.
The ileum is the last part of the small intestine that ends in the cecum. Ileal impaction can be caused by obstruction of ingesta. Coastal bermuda hay is associated with impactions in this most aborad segment of the small intestine. Other causes can be obstruction by ascarids (Parascaris equorum), usually occurring at 3–5 months of age right after deworming, and tapeworms (Anoplocephala Perfoliata), which have been associated with up to 81% of ileal impactions (See below). Horses show intermittent colic, and it is usually mild but occasionally severe. Although most ileal impactions will pass without intervention, those present for 8–12 hours will cause fluid to back up, leading to gastric reflux. Diagnosis is usually made based on clinical signs, presence of reflux, rectal exam, and ultrasound. Those impactions that are unresponsive to medical management, which include IV fluids and removal of reflux, may be treated using a single injection into the ileum with 1 liter of carboxymethylcellulose, and then massaging the ileum. This allows the impaction to be treated without actually cutting into the ileus.
This is most likely to occur in horses that graze sandy or heavily grazed pastures leaving only dirt to ingest. Foals, weanlings, and yearlings are most likely to ingest sand, and are therefore most commonly seen with sand colic. The term sand also encompasses dirt. The ingested sand or dirt most commonly accumulates in the pelvic flexure, but may also occur in the right dorsal colon and the cecum of the large intestines. The sand can cause colic signs similar to other impactions of the large colon, and often causes abdominal distention As the sand or dirt irritates the lining of the bowel it can cause diarrhea. The weight and abrasion of the sand or dirt causes the bowel wall to become inflamed and can cause a reduction in colonic motility and, in severe cases, leads to peritonitis.
Diagnosis is usually made by history, environmental conditions, auscultation of the ventral abdomen, radiographs, ultrasound, or fecal examination (See Diagnosis). Historically, medical treatment of the problem is with laxatives such as liquid paraffin or oil and psyllium husk. More recently veterinarians treat cases with specific synbiotic (pro and prebiotic) and psyllium combinations. Psyllium is the most effective treatment. It works by binding to the sand to help remove it, although multiple treatments may be required. Mineral oil is mostly ineffective since it floats on the surface of the impaction, rather than penetrating it. Horses with sand or dirt impaction are predisposed to Salmonella infection and other Gi bacteria, so antibiotics are often added to help prevent infection. Medical management usually resolves the colic, but if improvement doesn't occur within a few hours then surgery must be performed to flush the colon of any sand, which procedure that has a 60-65% survival rate. Horses that are not treated, or treated too late after after the onset of clinical signs, are at risk of death.
Horses should not be fed directly on the ground in areas where sand, dirt and silt are prevalent, although small amounts of sand or dirt may still be ingested by grazing. Management to reduce sand intake and prophylactic treatments with sand removal products are recommended by most veterinarians. Such prophylaxis includes feeding a pelleted psyllium for one week every 4–5 weeks. Longer duration of treatment will result in gastrointestinal flora changes and the psyllium to be broken down and ineffective for sand clearance. Other methods include feeding the horse before turnout, and turning the horses out in the middle of the day so they are more likely to stand in the shade rather than graze.
Only 5% of large intestinal impactions at referral hospital are involve the cecum. Often the cecum contains feed material, and the horse shows minor colic for 1–7 days, and diagnosis is made via rectal palpation. Cecal impactions may also occur post-surgery, orthopedic or otherwise, and the cecum does not function properly. Horses usually show clinical signs 3–5 days post general anesthesia, including decreased appetite, decreased manure production, and gas in the cecum which can be auscultated. The cecum quickly distends due to fluid and gas accumulation, often leading to rupture within 24–48 hours if not corrected. Surgery has a fair to good prognosis. Often incision into the cecum (typhlotomy) results in complications such as a second impaction occurring post-surgery, and cecal bypass surgery is often recommended. The cause of cecal impactions are not known.
Gastric impactions are relatively rare, and occur when food is not cleared at the appropriate rate. It is most commonly associated with ingestion of foods that swell after eating or feeds that are coarse (bedding or poor quality roughage), poor dental care, poor mastication, inadequate drinking, ingestion of a foreign object, and alterations in the normal function of the stomach. Persimmons, which form a sticky gel in the stomach, and haylage, have both been associated with it, as has wheat, barley, mesquite beans, and beet pulp. Horses usually show signs of mild colic that is chronic, unresponsive to analgesics, and may include signs such as dysphagia, ptyalism, bruxism, fever, and lethargy, although severe colic signs may occur. Signs of shock may be seen if gastric rupture has occurred. Usually, the impaction must be quite large before it presents symptoms, and may be diagnosed via gastroscopy or ultrasound, although rectal examinations are unhelpful. Persimmon impaction is treated with infusions of Coca-Cola. Other gastric impactions are often resolves with enteral fluids. Quick treatment generally produces a favorable prognosis.
Small colon impaction
Small colon impactions represent a small number of colics in the horse, and are usually caused by obstruction from fecaliths, enteroliths, and meconium. Horses usually present with standard colic signs (pawing, flank watching, rolling) in 82% of horses, and occasionally with diarrhea (31%), anorexia (30%), straining (12%), and depression (11%), and rectal examination will reveal firm loops of small colon or actually palpable obstruction in the rectum. Impactions are most common in miniature horses, possibly because they do not masticate their feed as well, and during the fall and winter. Medical management includes the aggressive use of fluids, laxatives and lubricants, and enemas, as well as analgesics and anti-inflammatories. However, these impactions often require surgical intervention, and the surgeon will empty the colon either by enterotomy or by lubricants and massage. Surgical intervention usually results in longer recovery time at the hospital. Prognosis is very good, and horses treated with surgical treatment had a survival with return to athletic function rate of 91%, while 89% of the medically managed horses returned to previous use.
Large colon impaction
Large colon impactions typically occur at the pelvic flexure and right dorsal colon, two areas where the lumen of the intestine narrows. Large colon impactions are frequently seen in horses that have recently had a sudden decrease in exercise, such as after a musculoskeletal injury. They are also associated in the practice of twice daily feeding of grain meals, which causes a short-lived but significant secretion of fluid into the lumen of the intestine, resulting in a 15% decrease in plasma volume (hypovolemia of the circulatory system) and the subsequent activation of the renin-angiotensin-aldosterone system. Aldosterone secretion activates absorption of fluid from the colon, decreasing the water content of the ingesta and increasing risk of impaction. Horses with a large colon impaction usually have mild signs that slowly get worse if the impaction does not resolve, and can produce severe signs. Diagnosis is often made by rectal palpation of the mass, although this is not always accurate since a portion of the colon is not palpable on rectal. Additional sections of intestines may be distended if there is fluid backup. Horses are treated with analgesics, fluid therapy, mineral oil, DSS, or epsom salts. Horses that do not improve or become very painful, or those that have large amounts of gas distention, are recommended to undergo surgery to remove the impaction via enterotomy. Approximately 95% of horses that undergo medical management, and 58% of surgical cases, survive.
Enteroliths and Fecaliths
Enteroliths in horses are round 'stones' of mineral deposits, usually of ammonium magnesium phosphate (or struvite), that develop within the horse's gastrointestinal tract. They can form around a piece of ingested foreign material, such as a small nidus of wire or sand (similar to how an oyster forms a pearl). When they move from their original site they can obstruct the intestine, usually in the right dorsal and transverse colon, but rarely in the small colon. They may also cause mucosal irritation, or pain when they move within the gastrointestinal tract. Enteroliths are not a common cause of colic, but are known to have a higher prevalence in states with a sandy soil and where an abundance of alfalfa hay is fed, such as California. They may be more common in horses with diets high in magnesium, and are also seen more often in Arabians, Morgans, American Saddlebreds, and donkeys, and usually occur in horses older than four years of age. Horses with enteroliths typically have chronic, low-grade, recurring colic signs, which may lead to acute colic and distention of the large colon after occlusion of the lumen occurs. These horse may also have had a history of passing enteroliths in their manure. Abdominal radiographs can confirm the diagnosis, but smaller enteroliths may not be visible. In rare instances, enteroliths may be palpated on rectal examination, usually if they are present in the small colon. Once a horse is diagnosed with colic due to an enterolith, surgery is necessary to remove it and fully resolve the signs of colic. Horses will usually present a round enterolith if it is the only one present, while multiple entheroliths will usually have flat sides, a clue to the surgeon to look for more stones. The main risk of surgery is rupture of the colon (15% of cases), and 92% of horses that are recovered survive to at least 1 year from their surgery date.
Meconium Impactions and Foal Colic
Meconium, or the first feces produced by the foal, is a hard pelleted substance. It is normally passed within the first 24 hours of the foal's life, but may become impacted in the distal colon or rectum. Meconium impaction is most commonly is seen in foals 1–5 days of age, and is more common in miniature foals and in colts more than fillies (possibly because fillies have a wider pelvis). Foals will stop suckling, strain to defecate (presents as an arched back and lifted tail), and may start showing overt signs of colic such as rolling and getting up and down. In later stages, the abdomen will distend as it continues to fill with gas and feces. Meconium impactions are often diagnosed by clinical signs, but digital examination to feel for impacted meconium, radiographs, and ultrasound may also be used.
Treatment for meconium impaction typically involves the use of enemas, although persistent cases may require mineral oil or IV fluids. It is possible to tell that the meconium has passed when the foal begins to produce a softer, more yellow manure. Although meconium impactions rarely cause perforation, and are usually not life-threatening, foals are at risk of dehydration and may not get adequate levels of IgG due to decreased suckling and not enough ingestion of colostrum. Additionally, the foals will eventually bloat, and will require surgical intervention. Surgery in a foal can be especially risky due to immature immune system and low levels of ingested colostrum.
Lethal white syndrome, or ileocolonic aganglionosis, can lead to meconium impaction since the foal does not have adequate nerve innervation to the large intestine. Foals, usually of overo to over0 breeding or of Paint horse heritage, are most at-risk. They present with signs of colic within the first 12 hours after birth, and die within 48 hours due to constipation. This syndrome is not treatable.
Atresia coli and atresia ani can also present as meconium impaction. The foal is missing the lumen of its distal colon or anus, respectively, and usually show signs of colic within 12–24 hours. Atresia coli is usually diagnosed with barium contrast studies, in which foals are given barium, and then radiographed to see if and where the barium is trapped. Atresia ani is simply diagnosed with digital examination by a veterinarian. Both situations requires emergency surgery to prevent death, and often still has a poor prognosis for survival with surgical correction.
Clostridial enterocolitis due to infection by Clostridium perfringens is most commonly seen in foals under 3 months of age. Clostridial toxins damage the intestine, leading to dehydration and toxemia. Foals usually present with signs of colic, decreased nursing, abdominal distention, and diarrhea which may contain blood. Diagnosis is made with fecal culture, and while some foals do not require serious intervention, others need IV fluids, antibiotics, and aggressive treatment, and may still die. Other bacterial infections that may lead to enterocolitis include Salmonella, Klebsiella, Rhodococcus equi, and Bacteriodes fragilis'.
Parasitic infection, especially with threadworms (Strongyloides westeri) and ascarids (Parascaris equorum) can produce signs of colic in foals (see below). Other conditions that may lead to signs of colic in foals include congenital abnormalities, gastric ulcers (see Gastric Ulcers), which may lead to gastric perforation and peritonitis, small intestine volvulus, and uroabdomen secondary to urinary bladder rupture.
Occasionally there can be an obstruction by large numbers of roundworms. This is most commonly seen in young horses as a result of a very heavy infestation of Parascaris equorum that can subsequently cause a blockage and rupture of the small intestine. Deworming heavily infected horses may cause a severe immune reaction to the dead worms, which can damage the intestinal wall and cause a fatal peritonitis. Veterinarians often treat horses with suspected heavy worm burdens with corticosteroids to reduce the inflammatory response to the dead worms. Blockages of the small intestine, particularly the ileum, can occur with Parascaris equorum and may well require colic surgery. Large roundworm infestations are often the result of a poor deworming program. Horses develop immunity to parascarids between 6 months age and one year and so this condition is rare in adult horses.
Tapeworms at the junction of the cecum have been implicated in causing colic. The most common species of tapeworm in the equine is Anoplocephala perfoliata. However, a 2008 study in Canada indicated that there is no connection between tapeworms and colic, contradicting studies performed in the UK.
Acute diarrhea can be caused by cyathostomes or "small Strongylus type" worms that are encysted as larvae in the bowel wall, particularly if large numbers emerge simultaneously. The disease most frequently occurs in winter time. Pathological changes of the bowel reveal a typical "pepper and salt" color of the large intestines. Animals suffering from cyathostominosis usually have a poor deworming history. There is now a lot of resistance to fenbendazole in the UK.
Large strongyle worms, most commonly Strongylus vulgaris, are implicated in colic secondary to non-strangulating infarction of the cranial mesenteric artery supplying the intestines, most likely due to vasospasm. Usually the distal small intestine and the large colon are affected, but any segment supplied by this artery can be compromised. This type of colic has become relatively rare with the advent of modern anthelminthics. Clinical signs vary based on the degree of vascular compromise and the length of intestine that is affected, and include acute and severe colic seen with other forms of strangulating obstruction, so diagnosis is usually made based on anthelminthic administration history although may be definitively diagnosed during surgical exploratoration. Treatment includes typical management of colic signs and endotoxemia, and the administration of aspirin to reduce the risk of thrombosis, but surgery is usually not helpful since lesions are often patchy and may be located in areas not easily resected.
Left dorsal displacement (Nephrosplenic entrapment)
Left dorsal displacement, also known as a nephrosplenic entrapment, is a form of colic where the left dorsal colon becomes trapped in the nephrosplenic space. This space is found between the spleen, the left kidney, the nephrosplenic ligament (which runs between the spleen and kidney), and the body wall. It accounts for 6-8% of all colics, but has a reoccurrence rate of up to 21%, usually if the horse has a naturally deep space. It may necessitate surgery although often it can be treated with exercise and/or phenylephrine, at times anesthesia and a rolling procedure, in which the horse is placed in left lateral recumbency and rolled to right lateral recumbency while jostling, must be performed to correct the condition medically. This condition can be diagnosed on rectal examination or through ultrasonography by a veterinarian. Reoccurance can be prevented by closing the nephrosplenic space with sutures.
Right dorsal displacement
Right dorsal displacement occurs when the right dorsal colon displaces and traps between the cecum and body wall. Although signs of colic may not be very severe, surgery is usually the only available treatment.
Proximal enteritis, also known as anterior enteritis or duodenitis-proximal jejunitis (DPJ), is inflammation of the duodenum and upper jejunum. It is potentially caused by infectious organisms, such as Salmonella and Clostridial species, but other possible contributing factors include Fusarium infection or high concentrate diets. The inflammation of the intestine leads to large secretions of electrolytes and fluid into its lumen, and thus large amounts of gastric reflux, leading to dehydration and occasionally shock.
Signs include acute onset of moderate to severe pain, large volumes orange-brown and fetid gastric reflux, distended small intestine on rectal examination, fever, depression, increased heart rate and respiratory rate, prolonged CRT, and darkened mucous membranes. Pain level usually improves after gastric decompression. It is important to differentiate DPI from small intestinal obstruction, since obstruction may require surgical intervention. This can be difficult, and often requires a combination of clinical signs, results from the physical examination, laboratory data, and ultrasound to help suggest one diagnosis over the other, but a definitive diagnosis can only be made with surgery or on necropsy.
DPI usually is managed medically with nasogastric intubation every 1–2 hours to relieve gastric pressure secondary to reflux, and aggressive fluid support to maintain hydration and correct electrolyte imbalances. Horses are often withheld food for several days. Use of anti-inflammatory, anti-endotoxin, anti-microbial, and prokinetic drugs are common with this disease. Surgery may be needed to rule out obstruction or strangulation, and in cases that are long-standing to perform a resection and anastomosis of the diseased bowel. Survival rates for DPJ are 25-94%, and horses in the southeast United States appear to be more severely affected.
Torsion and Volvulus
A volvulus is a twist along the axis of the mesentery, a torsion is a twist along the longitudinal axis of the intestine. Various parts of the horse's gastrointestinal tract may twist upon themselves. It is most likely to be either small intestine or part of the colon. Occlusion of the blood supply means that it is a painful condition causing rapid deterioration and requiring emergency surgery.
Volvulus of the large colon usually occurs where the mesentery attaches to the body wall, but may also occur at the diaphragmatic or sternal flexures, with rotations up to 720 degrees reported. It is most commonly seen in postpartum mares, usually presents with severe signs of colic that are refractory to analgesic administration, and horses often lie in dorsal recumbency. Abdominal distention is common due to strangulation and rapid engorgement of the intestine with gas, which then can lead to dyspnea as the growing bowel pushes against the diaphragm and prevents normal ventilation. Additionally, compression can place pressure on the caudal vena cava, leading to pooling of blood and hypovolemia. However, horses may not have a high heart rate, presumably due to increased vagal tone. Rectal palpation will demonstrate a severely gas distended colon, and the examiner may not be able to push beyond the brim of the pelvis due to the obstruction. The colon may be irreversibly damaged in as little as 3-4 hours from the initial time of the volvulus, so immediate surgical correction is required. The surgeon works to correct the volvulus and then removes any damaged colon. 95% of the colon may be resected, but often the volvulus damages more than this amount, requiring euthanasia. Plasma lactate levels can help predict survival rates, with an increased survival seen in horses with a lactate below 6.0 mmol/L. Prognosis is usually poor, with a survival rate of approximately 36% of horses with a 360 degree volvulus, and 74% of those with a 270 degree volvulus, and a reoccurrence rate of 5-50%. Complications post-surgery include hypoproteinemia, endotoxic shock, laminitis, and DIC.
Small intestinal volvulus is thought to be caused by a change in local peristalsis, or due to a lesion that the mesentery may twist around (such as an ascarid impaction), and usually involves the distal jejunum and ileum.w It is one of the most common causes of small intestinal obstruction in foals, possibly because of a sudden change to a bulkier foodstuff. Animals present with acute and severe signs of colic, and multiple distended loops of small intestine, usually seen radiographically in a foal. Small intestinal volvulus often occurs secondary to another disease process in adult horses, where small intestinal obstruction causes distention and then rotation around the root of the mesentery. Surgery is required to resect nonviable sections of bowel, and prognosis is correlated to the length of bowel involved, with animals with greater than 50% of small intestinal involvement having a grave prognosis.
Intussusception is a form of colic in which a piece of intestine "telescopes" within a portion of itself because a section is paralyzed, so the motile section pushes itself into the non-motile section. It most commonly occurs at the ileocecal junction and requires urgent surgery. It is almost always associated with parasitic infections, usually tapeworms, although small masses and foreign bodies may also be responsible, and is most common in young horses usually around 1 year of age. Ileocecal intussusception may be acute, involving longer (6–457 cm) segments of bowel, or chronic involving shorter sections (up to 10 cm in length). Horses with the acute form of colic usually have a duration of colic less than 24 hours long, while chronic cases have mild but intermittent colic. Horses with the chronic form tend to have better prognosis.
Rectal examination reveals a mass at the base of the cecum in 50% of cases. Ultrasound reveals a very characteristic "target" pattern on cross-section. Abdominocentesis results can vary, since the strangulated bowel is trapped within the healthy bowel, but there are usually signs of obstruction, including reflux and multiple loops of distended small intestine felt on rectal. Surgery is required for intussusception. Reduction of the area is usually ineffective due to swelling, so jejunojejunal intussusceptions are resected and ileocolic intussusceptions are resected as far distally as possible and a jejunocecal anatomosis is preformed.
Epiploic foramen entrapment
On rare occasions, a piece of small intestine (or rarely colon) can become trapped through the epiploic foramen into the omental bursa. The blood supply to this piece of intestine is immediately occluded and surgery is the only available treatment. This type of colic has been associated with cribbers, possibly due to changes in abdominal pressure, and in older horses, possibly because the foramen enlarges as the right lobe of the liver atrophies with age, although it has been seen in horses as young as 4 months old. Horses usually present with colic signs referable to small intestinal obstruction. During surgery, the foramen can not be enlarged due to the risk of rupture of the vena cava or aorta, which would result in fatal hemorrhage. Survival is 74-79%, and survival is consistently correlated with abdominocentesis findings prior to surgery.
Mesenteric rent entrapment
The mesentery is a thin sheet attached to the entire length of intestine, enclosing blood vessels, lymph nodes, and nerves. Occasionally, a small rent (hole) can form in the mesentery, through which a segment of bowel can occasionally enter. As in epiploic foramen entrapment, the bowel first enlarges, since arteries do not occlude as easily as veins, which causes edema (fluid buildup). As the bowel enlarges, it becomes less and less likely to be able to exit the site of entrapment. Colic signs are referable to those seen with a strangulating lesion, such as moderate to severe abdominal pain, endotoxemia, decrease gut sounds, distended small intestine on rectal, and nasogastric reflux. This problem requires surgical correction. Survival for mesenteric rent entrapment is usually lower than other small intestinal strangulating lesions, possibly due to hemorrhage, difficulty correcting the entrapment, and the length of intestine commonly involved, with <50% of cases surviving until discharge.
Strangulating pedunculated lipoma
Benign fatty tumors known as lipomas can form on the mesentery. As the tumor enlarges, it stretches the connective tissue into a stalk which can wrap around a segment of bowel, typically small intestine, cutting off its blood supply. The tumor forms a button that latches onto the stalk of the tumor, locking it on place, and requiring surgery for resolution. Surgery involves cutting the stalk of the tumor, untwisting the bowel, and removing bowel that is no longer viable. If the colic is identified and taken to surgery quickly, there is a reasonable rate of success of 50-78%. This type of colic is most commonly associated with ponies, and aged geldings, 10 years and older, probably because of fat distribution in this group of animals.
Cancers (neoplasia) other than lipoma are relatively rare causes of colic. Cases have been reported with intestinal cancers including intestinal lymphosarcoma, leiomyoma, and adenocarcinoma, stomach cancers such as squamous cell carcinoma, and splenic lymphosarcoma.
Gastric squamous cell carcinoma is most often found in the non-glandular region of the stomach of horses greater than 5 years of age, and horses often present with weight loss, anorexia, anemia, and ptyalism. Gastric carcinoma is usually diagnosed via gastroscopy, but may sometimes be felt on rectal if they have metastasized to the peritoneal cavity. Additionally, laparoscopy can also diagnose metastasized cancer, as can presence of neoplastic cells on abdominocentesis. Often the signs of intestinal neoplasia are non-specific, and include weight loss and colic, usually only if obstruction of the intestinal lumen occurs.
Horses form ulcers in the stomach fairly commonly, a disease called equine gastric ulcer syndrome. Risk factors include confinement, infrequent feedings, a high proportion of concentrate feeds, such as grains, excessive non-steroidal anti-inflammatory drug use, and the stress of shipping and showing. Gastric ulceration has also been associated with the consumption of cantharidin beetles in alfalfa hay which are very caustic when chewed and ingested. Most ulcers are treatable with medications that inhibit the acid producing cells of the stomach. Antacids are less effective in horses than in humans, because horses produce stomach acid almost constantly, while humans produce acid mainly when eating. Dietary management is critical. Bleeding ulcers leading to stomach rupture are rare.
Right dorsal colitis
Long-term use of NSAIDs can lead to mucosal damage of the colon, secondary to decreased levels of homeostatic prostaglandins. Mucosal injury is usually limited to the right dorsal colon, but can be more generalized. Horses may display acute or chronic intermittent colic, peripheral edema secondary to protein losing enteropathy, decreased appetite, and diarrhea. Treatment involves decreasing the fiber levels of the horse's diet by reducing grass and hay, and placing the horse on an easily digestible pelleted feed until the colon can heal. Additionally, the horse may be given misoprostol, sucralfate, and psyllium to try to improve mucosal healing, as well as metronidazole to reduce inflammation of the colon.
Ileus is the lack of motility of the intestines. It often occurs postoperatively following abdominal surgery, and 10-50% of all cases of surgical colic will develop this complication, including 88% of horses with a strangulating obstructions and 41% of all colics with a large intestinal lesion. The exact cause is unknown, but is suspected to be due to inflammation of the intestine, possibly a result of manipulation by the surgeon, which alters the signals to the gastrointestinal tract from the central nervous system. It has a high fatality rate of 13-86%.
Ileus diagnosed based on several criteria:
- Nasogastric reflux: 4 liters or greater in a single intubation, or greater than 2 liters of reflex over more than one intubation
- A heart rate greater than 40 bpm
- Signs of colic, which may vary from mild to severe
- Distended small intestine, based on rectal or abdominal ultrasound findings. On ultrasound, ileus presents as more than 3 loops of distended small intestine, with a lack of peristaltic waves.
This form of colic is usually managed medically. Because there is no motility, intestinal contents back up into the stomach. Therefore, periodic decompression of the stomach though nasogastric intubation is essential to prevent rupture. The horse is placed on intravenous fluids to maintain hydration and electrolyte balance, since oral hydration is not possible. Motility is encouraged by the use of prokinetic drugs such as erythromycin, metoclopramide, bethanechol and lidocaine, as well as through vigorous walking, which has also been shown to have a beneficial effect on GI motility. Anti-inflammatory drugs are used to decrease inflammation of the GI tract, which is thought to be the underlying cause of the disease.
Decreased intestinal motility can also be the result of drugs such as Amitraz, which is used to kill ticks and mites. Xylazine, detomidine, and butorphanol also reduce motility, but will not cause colic if appropriately administered.
Uterine tears and torsions
Uterine tears often occur a few days post partition. They can lead to peritonitis and require surgical intervention to fix. Uterine torsions can occur in the third trimester, and while some cases may be corrected if the horse in anesthetized and rolled, others require surgical correction.
Ingested toxins are rarely a cause of colic in the horse. Toxins that can produce colic signs include organophosphates, monensin, and cantharidin. Additionally, overuse of certain drugs such as NSAIDs may lead to colic signs (See Gastric ulceration and Right dorsal colitis).
Herniation can cause signs of colic. Inguinal hernias are most commonly seen in Standardbred and Tennessee Walking Horse stallions due, likely due to a breed prevalence of a large inguinal ring, as well as Saddlebred and Warmblood breeds. Inguinal hernias in adult horses are usually strangulating (unlike foals, which are usually non-strangulating). Stallions usually display acute signs of colic, and a cool, enlarged testicle on one side. Hernias are classified as either indirect, in which the bowel remains in the parietal vaginal tunic, or direct, in which case it ruptures through the tunic and goes subcutaneously. Direct hernias are seen most commonly in foals, and usually congenital. Indirect hernias may be treated by repeated manual reduction, but direct hernias often require surgery to correct. The testicle on the side of resection will often require removal due to vascular compromise, although prognosis for survival is good (75%) and the horse may be used for breeding in the future.
Although umbilical hernias are common in foals, strangulation is rare, occurring only 4% of the time and usually involving the small intestine. Rarely, the hernia will only involve part of the intestinal wall (termed a Richter's hernia), which can lead to an enterocutaneous fistula. Strangulating umbilical hernias will present as enlarged, firm, warm, and painful with colic signs. Foals usually survive to discharge.
Diaphragmatic hernias are rare in horses, accounting for 0.3% of colics. Usually the small intestine herniates through a rent in the diaphragm, although any part of the bowel may be involved. Hernias are most commonly acquired, not congenital, with 48% of horses having a history of recent trauma, usually through during parturition, distention of the abdomen, a fall, or strenuous exercise, or direct trauma to the chest. Congenital hernias occur most commonly in the most ventral part of the diaphragm, while acquired hernias are usually seen at the junction of the muscular and tendinous sections of the diaphragm. Clinical signs usually are similar to an obstruction, but occasionally decreased lung sounds may be heard in one section of the chest, although dyspnea is only seen in approximately 18% of horses. Ultrasound and radiography may both be used to diagnose diaphragmatic herniation.
Other causes that may show clinical symptoms of colic
Strictly speaking, colic refers only to signs originating from the gastrointestinal tract of the horse. Signs of colic may be caused by problems other than the GI-tract e.g. problems in the liver, ovaries, spleen, urogenital system, testicular torsion, pleuritis, and pleuropneumonia. Diseases which sometimes cause symptoms which appear similar to colic include uterine contractions, laminitis, and exertional rhabdomyolysis. Colic pain secondary to kidney disease is rare.
Pathophysiology of equine colic
This is characterised by a physical obstruction of the intestine, which can be due to impacted food material, stricture formation, or foreign bodies. The primary pathophysiological abnormality caused by this obstruction is related to the trapping of fluid within the intestine oral to the obstruction. This is due to the large amount of fluid produced in the upper gastro-intestinal tract (around 125l daily[clarification needed]), and the fact that this is primarily re-absorbed in parts of the intestine downstream from the obstruction. The first problem with this degree of fluid loss from circulation is one of decreased plasma volume, leading to a reduced cardiac output, and acid-base disturbances.
There also occur serious effects on the intestine itself, which becomes distended due to the trapped fluid, and by gas production from bacteria. It is this distension, and subsequent activation of stretch receptors within the intestinal wall, that leads to the associated pain. With progressive distension of the intestinal wall, there is occlusion of blood vessels, firstly veins, then arteries. The difference in time to onset of occlusion is due to the relatively more rigid walls of arteries compared with veins. This impairment of blood supply leads firstly to hyperemia and congestion, and ultimately to ischaemic necrosis and cellular death. The poor blood supply also has effects on the vascular endothelium, leading to an increased permeability. This results initially in leakage of plasma, and eventually blood into the intestinal lumen. In the opposite fashion, gram-negative bacteria and endotoxins can enter the bloodstream, leading to further systemic effects.
Strangulating obstructions have all the same pathological features as a simple obstruction, but the blood supply is immediately affected. Both arteries and veins may be affected immediately, or progressively as in simple obstruction. Common causes of strangulating obstruction are intussusceptions, volvulus and displacement of intestine through a hole, such as a hernia, a mesenteric rent, or the epiploic foramen.
In a non-strangulating infarction, blood supply to a section of intestine is occluded, without any obstruction to ingesta present within the intestinal lumen. The most common cause is infection with Strongylus vulgaris larvae, which develop within the (primarily cranial) mesenteric artery.
Many different diagnostic tests are used to diagnose the cause of a particular form of equine colic, which may have greater or lesser value in certain situations. The most important distinction to make is whether the condition is managed medically or surgically. If surgery is indicated, then it must be performed as soon as possible, as delay is a dire prognostic indicator.
A thorough history is always taken, including age, sex, recent activity, diet, any recent dietary changes, and routine anthelmintic treatment. The most important factor is time elapsed since onset of clinical signs, as this has a profound impact on prognosis. Additionally, a veterinarian will need to know any drugs given to the horse, their amount, and the time they were given, as those can help with the assessment of the colic progression and how it is responding to analgesia.
Heart rate rises with progression of colic, in part due to pain, but mainly due to decreased circulating volume due to dehydration, decreased preload, and endotoxemia. The rate is measured over time, and its response to analgesic therapy ascertained. A pulse that continues to rise in the face of adequate analgesia is considered a surgical indication. Mucous membrane color can be assessed to appreciate the severity of haemodynamic compromise. Pale mucous membranes may be caused by decreased perfusion (as with shock), anemia due to chronic blood loss (seen with GI ulceration), and dehydration. Pink or cyanotic (blue) membrane colors are associated with a greater chance of survival (55%). Dark red, or "injected", membranes reflect increased perfusion, and the presence of a "toxic line" (a red ring over the top of the teeth where it meets the gum line, with pale or gray mucous membranes) can indicate endotoxemia. Both injected mucous membranes and the presence of a toxic line correlate to a decreased likelihood of survival, at 44%. Capillary refill time is assessed to determine hydration levels and highly correlates to perfusion of the bowel. A CRT of < 2 seconds has a survival rate of 90%, of 2.5–4 seconds a survival rate of 53%, and > 4 seconds a survival rate of 12%.
Laboratory tests can be performed to assess the cardiovascular status of the patient. Packed Cell Volume (PCV) is a measure of hydration status, with a value 45% being considered significant. Increasing values over repeated examination are also considered significant. The total protein (TP) of blood may also be measured, as an aid in estimating the amount of protein loss into the intestine. Its value must be interpreted along with the PCV, to take into account the hydration status. When laboratory tests are not available, hydration can be crudely assessed by tenting the skin of the neck or eyelid,looking for sunken eyes, depression, high heart rate, and feeling for tackiness of the gums. Jugular filling and quality of the peripheral pulses can be used to approximate blood pressure.
|Percent Dehydration||Heart rate||Mucous membrane quality||CRT||Time skin tent holds||Other|
|5%||Normal||Moist to slightly tacky||< 2 seconds||1–3 seconds||Decrease in urine production|
|8%||40-60 bpm||Tacky||Usually 2–3 seconds||3–5 seconds||Decrease in blood pressure|
|10-12%||60+ bpm||Dry||Usually > 4 seconds||5+ seconds||Decrease in jugular fill and quality of peripheral pulses; sunken eyes present|
Weight and body condition score (BCS) is important when evaluating a horse with chronic colic, and a poor BCS in the face of good quality nutrition can indicate malabsorptive and maldigestive disorders.
Rectal temperature can help ascertain if an infectious or inflammatory cause is to blame for the colic, which is suspected if the temperature if >103F. Temperature should be taken prior to rectal examination, as the introduction of air will falsely lower rectal temperature.
Coolness of extremities can indicate decreased perfusion secondary to endotoxemia. Elevated respiratory rate can indicate pain as well as acid-base disturbances.
A rectal examination and auscultation of the abdomen (See below) should always occur in addition to the basic physical exam.
Rectal examinations are a cornerstone of colic diagnosis, as many large intestinal conditions can be definitively diagnosed by this method alone. Due to the risk of harm to the horse, a rectal examination is performed by a veterinarian. Approximately 40% of the gastrointestinal tract can be examined by rectal palpation, although this can vary based on the size of the horse and the length of the examiner's arm. Structures that can be identified include the aorta, caudal pole of the left kidney, nephrosplenic ligament, caudal border of the spleen, ascending colon (left dorsal and ventral, pelvic flexure), the small intestine if distended (it is not normally palpable on rectal), the mesenteric root, the base of the cecum and the medial cecal band, and rarely the inguinal rings. The location within the colon is identified based on size, presence of sacculations, number of bands, and if fecal balls are present.
Displacements, torsions, strangulations, and impactions may be identified on rectal examination. Other non-specific findings, such as dilated small intestinal loops, may also be detected, and can play a major part in determining if surgery is necessary. Thickness of the intestinal walls may indicate infiltrative disease or abnormal muscular enlargement. Roughening of the serosal surface of the intestine can occur secondary to peritonitis. Horses that have had gastrointestinal rupture may have gritty feeling and free gas in the abdominal cavity. Surgery is usually suggested if rectal examination finds severe distention of any part of the GI tract, a tight cecum or multiple tight loops of small intestine, or inguinal hernia. However, even if the exact cause can not be determined on rectal, significant abnormal findings without specific diagnosis can indicate the need for surgery. Rectal examinations are often repeated over the course of a colic to monitor the GI tract for signs of change.
Rectals are a risk to the practitioner, and the horse is ideally examined either in stocks or over a stall door to prevent kicking, with the horse twitched, and possibly sedated if extremely painful and likely to try to go down. Buscopan is sometimes used to facilitate rectal examination and reduce the risk of tears, because it decreases the smooth muscle tone of the gastrointestinal tract, but can be contraindicated and will produce a very rapid heart rate. Because the rectum is relatively fragile, the risk of rectal tears is always present whenever an examination is performed. Severe rectal tears often result in death or euthanasia. However, the diagnostic benefits of a rectal examination almost always outweigh these risks.
Passing a nasogastric tube (NGT) is useful both diagnostically and therapeutically. Fluid is refluxed from the stomach, and any more than 2 litres of fluid is considered to be significant. Increased fluid is generally as a result of backing up of fluid through the intestinal tract, due to a downstream obstruction, ileus, or proximal enteritis, and its presence usually indicates a small intestinal disease. Generally, the closer the obstruction is to the stomach, the greater amount of gastric reflux will be present. Approximately 50% of horses with gastric reflux require surgery. Therapeutically, gastric decompression is important, as if fluid build up occurs, gastric rupture may occur, which is inevitably fatal.
Abdominocentesis (belly tap)
Abdominocentesis, or the extraction of fluid from the peritoneum, can be useful in assessing the state of the intestines. Normal peritoneal fluid is clear, straw-colored, and of serous consistency, with a total nucleated cell count of less than 5000 cells/microliter (24-60% which are neutrophils) and a total protein of 2.5 g/dL.
Abdominocentesis allows for the evaluation of red and white blood cells, hemoglobin concentration, protein levels, and lactate levels. A high lactate in abdominal fluid suggests intestinal death and necrosis, usually due to strangulating lesion, and often indicates the need for surgical intervention. A strangulating lesion may produce high levels of red blood cells, and a serosangionous fluid containing blood and serum. White blood cell levels may increase if there is death of intestine that leads to leakage of intestinal contents, which includes high levels of bacteria, and a neutrophil to monocyte ratio greater than or equal to 90% is suggestive of a need for surgery. "High" nucleated cell counts (15,000-800,000 cells/microliter depending on the disease present) occur with horses with peritonitis or abdominal abscesses. The protein level of abdominal fluid can give information as to the integrity of intestinal blood vessels. High protein (> 2.5 mg/dL) suggests increased capillary permeability associated with peritonitis, intestinal compromise, or blood contamination. Horses with gastrointestinal rupture will have elevated protein the majority of the time (86.4%) and 95.7% will have bacteria present. Occasionally, with sand colic, it is possible to feel the sand with the tip of the needle.
Clinical analysis is not necessarily required to analyze the fluid. Simple observation of color and turbidity can be useful in the field.
- sanguinous fluid indicates an excess of red blood cells or hemoglobin, and may be due to leakage of the cells through a damaged intestinal wall, splenic puncture during abdominocentesis, laceration of abdominal viscera, or contamination from a skin capillary.
- Cloudy fluid is suggestive of an increased number of cells or protein.
- White fluid indicates chylous effusion.
- Green fluid indicates either gastrointestinal rupture or enterocentesis, and a second sample should be drawn to rule out the latter. Gastrointestinal rupture produces a color change in peritoneal fluid in 85.5% of cases.
- Colorless (dilute) peritoneal fluid, especially in large quantities, can indicate ascites or uroperitoneum.
- Large amount of fluid can indicate acute peritonitis.
Any degree of abdominal distension is usually indicative of a condition affecting the large intestines, as distension of structures upstream of here would not be large enough to be visible externally. Abdominal distention may indicate the need for surgical intervention, especially if present with severe signs of colic, high heart rate, congested mucous membranes, or absent gut sounds.
Auscultation of the abdomen is subjective and non-specific, but can be useful. The gut is listened to in the four-quadrant approach: at the upper flank area and the caudolateral abdomen ventrally, on both sides, and each quadrant should ideally be listened to for 2 minutes. Gut sounds (borborygmi) correlate to motility of the bowel, and care should be taken to note intensity, frequency, and location. Increased gut sounds (hyper-motility) are not usually found with major changes, and may be indicative of spasmodic colic. A decreased amount of sound, or no sound, may be suggestive of serious changes, and persistence of hypomotile bowel often suggests the need for surgical intervention.
Sand may sometimes be heard on the ventral midline, presenting a typical "waves on the beach" sound in a horse with sand colic after the lower abdomen is forcefully pushed with a fist. Abdominal percussion ("pinging") can sometimes be used to determine if there is gas distention in the bowel.
The amount of feces produced, and its character can be helpful, although as changes often occur relatively distant to the anus, changes may not be seen for some time. In areas where sand colic is known to be common, or if the history suggests it may be a possibility, faeces can be examined for the presence of sand, often by mixing it in water and allowing the sand to settle out over 20 minutes. However, sand is sometimes present in a normal horse's feces, so the quantity of sand present must be assessed. Testing the feces for parasite load may also help diagnose colic secondary to parasitic infection.
Ultrasound provides visualization of the thoracic and abdominal structures, and can sometimes rule out or narrow down a diagnosis. It may show the presence of sand, give information on distention, entrapment, strangulation, intussusception, and wall thickening of intestinal loops, as well as diagnose nephrosplenic entrapment, peritonitis, abdominal tumors, and inguinal or scrotal hernias. Abdominal ultrasound requires an experienced operator to accurately diagnose the cause of colic.
Sand presents as a homogenous gray and allows the ultrasound waves to penetrate deep. It is distinguishable from feces, which is less homogenous, and gas colic, which does not allow the operator to see pass the gas. Additionally, the sand usually "sparkles" on ultrasound if it moves. Sand is best diagnosed using a 3.5 megahertz probe. Horses with gastrointestinal rupture will have peritoneal fluid accumulation, sometimes with debris, visible on ultrasound.
Differentiation between proximal enteritis and small intestinal obstruction is important to ensure correct treatment. Horses with small intestinal obstruction will usually have an intestinal diameter of -10 cm with a wall thickness of 3-5mm. Horses with proximal enteritis usually have an intestinal diameter that is narrower, but wall thickness is often greater than 6mm, containing a hyperechoic or anechoic fluid, with normal, increased, or decreased peristalsis. However, obstructions that have been present for some time may present with thickened walls and distention of the intestine.
Radiographs are sometimes used to look for sand and enteroliths. Due to the size of the adult horse's abdomen, it requires a powerful machine that is not available to all practitioners. Additionally, the quality of these images is sometimes poor.
Gastroscopy, or endoscopic evaluation of the stomach, is useful in chronic cases of colic suspected to be caused by gastric ulcers, gastric impactions, and gastric masses. A 3 meter scope is required to visualize the stomach of most horses, and the horse must be fasted prior to scoping.
Rectal biopsy is rarely performed due to its risks of abscess formation, rectal perforation and peritonitis, and because it requires a skilled clinical to perform. However, it can be useful in cases of suspected intestinal cancer, as well as some inflammatory diseases (such as IBD) and infiltrative diseases, like granulomatous enteritis.
Laparoscopy involves inserting a telescoping camera approximately 1 cm in diameter into the horse's abdomen, through a small incision, to visualize the gastrointestinal tract. It may be performed standing or under general anesthesia, and is less invasive than an exploratory celiotomy (abdominal exploratory surgery).
Clinical signs are generally referable to pain, although in some cases, such as if there is tissue death, inflammation of the intestines, endotoxemia, and dehydration, the horse may appear depressed. Pain levels are often used to determine the need for surgical intervention. Usually, severe signs that can not be controlled with analgesics or sedatives, or persistent signs that can be controlled but require multiple administrations of such drugs, are much more likely to require surgery. However, pain tolerance of the individual horse must also be taken into account, and very stoic animals with surgical colic may not show adequate levels of pain. Heart rate may not always be a good indicator of the need for surgical intervention, since early disease may present with a low heart rate despite other signs suggestive of severe pain. High heart rates (>60 bpm), prolonged capillary refill time, and congested mucous membranes suggest cardiovascular compromise and the need for more intense management.
A horse showing severe signs, followed by rapid improvement, may have experienced relief due to perforation and rupture of the stomach or small intestine, which releases the painful pressure. This usually results in non-treatable peritonitis and requires euthanasia. These horses will later display signs of shock, including increased heart rate and CRT, rapid shallow breathing, and change in mucous membrane color, and may also be pyretic, act depressed, and at times extremely painful.
Gas distention usually produces mild clinical signs, but may also cause severe signs due to pressure and tension on the mesentery. Impaction colics also usually produce mild clinical signs. Strangulating obstructions are usually extremely painful, and the horse may have abdominal distention, congested mucous membranes, altered capillary refill time, and other signs of endotoxemia. Simple obstructions often present with a slightly elevated heart rate (<60 bpm) but normal CRT and mucous membrane color.
- Increase in body temperature: most commonly associate with medically managed colics such as enteritis, colitis, peritonitis, and intestinal rupture
- Pawing and/or scraping
- Stretching or standing abnormally
- Frequent attempts to urinate
- Flank watching: turning of the head to watch the stomach and/or hind quarters
- Biting/nipping or kicking at the abdomen
- Change in activity: pacing, decreased activity, or constant shifting of weight when standing
- Repeated flehmen response
- Repeated lying down and rising, which may become violent when colic is severe
- Rolling when laying down, which may become violent when colic is severe (thrashing)
- Excess salivation (ptyalism)
- Excessive yawning
- Loss of appetite
- Change in feces: Decreased fecal output or change in consistency
- Increased heart rate: heart rate >60 bpm is more likely to require surgery
- Increased respiratory rate
- Sweating: generally indicates severe colic
- Change in color of mucous membranes from its normal pink color: this includes pale or injected (red) gums, and the presence of a "toxic line"
- Increased capillary refill time
- Abdominal distention 
- Change in gut sounds (increased, decreased, or absent): Decreased or absent gut sounds often suggests the need for surgical intervention if prolonged
- Dorsal recumbency in foals
- In chronic cases, poor coat or weight loss
Management and Complications of Colic
Colic may be managed medically or surgically. Severe signs often suggest the need for surgery, especially if they can not be controlled with analgesics. Immediate surgical intervention may be required, but surgery may be counter-indicated in some cases of colic, so diagnostic tests are used to help determine the cause of the colic which can guide the practitioner in determining the need for surgery. The majority of colics (approximately 90%) can be successfully managed medically.
The intensity of medical management varies based on the severity and cause of the colic, and the financial capabilities of the owner. At the most basic level, analgesia and at times sedation will be administered to the horse. If reflux is present, it must be removed periodically to prevent the distention and possible rupture of the stomach. Monitoring reflux will also help the practitioner determine the progression of the colic. Generally, food and water will be withheld. Anti-spasmodics may also be administered. Fluids are often administered, either by nasogastric intubation or intravenous catheter, to restore proper hydration and electrolyte balance.
Impaction colics are usually managed with the use of fluids, either oral or IV, to help soften the impaction. Nasogastric intubation is often used to administer various medications directly into the stomach. This includes softening agents such as mineral oil, epsom salts which act as an osmotic agent to increase fluid in the GI tract and has a laxative effect, or the detergent dioctyl sodium sulfosuccinate (DDS), which helps break down the impaction and stimulate intestinal motility. Mineral oil has the added benefit of telling the practitioner the transit time for GI tract, and thus motility, which should normally take around 18 hours.
Endotoxemia is a serious complication of colic, and aggressive treatment is often warranted. Endotoxin (lipopolysaccharide) is released from the cell well of gram-negative bacteria when they die. Normally, endotoxin is prevented from entering systemic circulation by the barrier function of the mucosa of the intestine, antibodies and enzymes which bind to it, and removal of the small amount which enters the blood stream by Kupffer cells in the liver. Endotoxemia occurs when there is an overgrowth and secondary die-off of gram negative bacteria, releasing mass quantities of endotoxin. This is especially common when the mucosal barrier is damaged, as with ischemia of the GI tract secondary to a strangulating lesion or displacement. This produces systemic effects such as cardiovascular shock and insulin resistance. Endotoxemia is often managed with fluid support to maintain blood pressure, often by administering colloids or hypertonic saline, NSAIDs to reduce systemic inflammation, and drugs that bind endotoxin such as IV polymyxin B and Bio-Sponge. NSAIDs decrease the levels of those prostaglandins that promote healing of the intestinal mucosa, and therefore increases the amount of endotoxin absorbed. It is therefore sometimes administer with a lidocaine drip, which appears to reduce the negative effects of NSAIDs.
Laminitis is a major concern in horses suffering from endotoxemia, and often prophylactic treatment to help prevent it, including the use of NSAIDs, DMSO, icing of the feet, and frog support. Horses are also sometimes administered heparin, which is thought to decrease the risk of laminitis by decreasing the coagulability of blood and thus the risk of blood clots in the capillaries of the foot.
Surgery poses significant expense and risks, including peritonitis, the formation of adhesions, complications secondary to general anesthesia, injury upon recovery of the horse which may require euthanasia, and dehiscence or infection of the incisional site. Additionally, surgical cases may develop post-operative ileus which requires further medical management. However, surgery may be required to save the life of the horse, and 1-2% of all colics require surgical intervention.
If significant damage is done to a section of intestine, it may need to be removed (resected) and the healthy parts reattached together (anastomosis). Horses may have up to 80% of their intestines removed and function normally, without needing a special diet.
In the case of colics requiring surgery, survival rates are best improved by quick recognition of colic and immediate surgical referral, rather than waiting to see if the horse improves, which only increases the extent of intestinal compromise. Survival rates are higher in surgical cases that do not require resection and anastomosis. 90% of large intestinal colic surgeries that are not due to volvulus, and 20-80% of large colon volvuluses, are discharged; while 85-90% of non strangulating small intestinal lesions, and 65-75% of strangulating intestinal lesions are discharged. 10-20% of small intestinal surgical cases require a second surgery, while only 5% of large intestinal cases do so. Horses that survive colic surgery have a high rate of return to athletic function. Of these horses discharged, approximately 86% return to work, and 83.5% return to same or better performance.
Adhesions (scar tissue) between various organs that are not normally attached within the abdomen may occur whenever an abdominal surgery is preformed, and is often seen secondary to reperfusion injury where there is ischemic bowel. Because the gastrointestinal tract is not as free to move, adhesions may encourage future colics, including intestinal obstruction or strangulation, requiring further surgery and risk of adhesion. Several drugs and substances are used to try to prevent adhesion formation. Preoperative use of DMSO, a free radical scavenger, potassium penicillin, and flunixin meglumine may be given. The thick intestinal lubricant carboxymethylcellulose is often applied to the GI tract intraoperatively, to decrease trauma from handling by the surgeon and provide a physical barrier between intestine and adjacent intestinal loops or abdominal organs. It has been shown to double the survival rate of horses, and its use is now a standard practice. Intraperitoneal unfractionated heparin is sometimes used, since it decreases fibrin formation, and thus may decrease fibrinous adhesions. Omentectomy (removal of the omentum) is a quick, simple procedure that also greatly decreases the risk of adhesions, since the omentum is one organ that commonly adheres to the intestines. The abdomen is usually lavaged copiously before the horse is sutured up, and anti-inflammatories are given postoperatively to help reduce their formation. A laparoscope may be used post-surgery to look for and break down adhesions, however there is risk of additional adhesions forming post-proceedure.
Small amounts of food is usually introduced as soon as possible after surgery, usually within 18–36 hours, to encourage motility and reduce the risk of ileus and the formation of adhesions. Often horses are stall rested with short bouts of hand walking to encourage intestinal motility. The incision site is carefully monitored for dehiscence, or complete failure of the incision leading to spillage of the abdominal contents out of the incision site, and the horse is not allowed turn-out until the incision has healed, usually after 30 days of stall rest. Abdominal bandages are sometimes used to help prevent the risk of dehiscence. Incisional infection doubles the time required for postoperative care, and dehiscence may lead to intestinal herniation, which reduces the likelihood of return to athletic function. Therefore, antibiotics are given 2–3 days after surgery, and temperature is constantly monitored, to help assess if an infection is present. Antibiotics are not used long-term due to the risk of antimicrobial resistance. The incision usually takes 6 months to reach 80% strength, while intestinal healing following resection and anastomosis is much faster, at a rate to 100% strength in 3 weeks. After the incision has healed adequately, the horse is turned out in a small area for another 2–3 months, and light exercise is added to improve the tone and strength of the abdominal musculature.
Weight loss of 75-100 pounds is common after colic surgery, secondary to the decreased function of the gastrointestinal tract and from muscle atrophy that occurs while the horse is rested. This weight is often rapidly replaced.
Draft horses tend to have a more difficulty time post-surgery, because they are often under anesthesia for a longer period of time (since they have a greater amount of gastrointestinal tract to evaluate) and their increased size places more pressure on their musculature, which can lead to muscle damage. Miniature horses and fat ponies are at increased risk for hepatic lipidosis post-surgery due to being anorexic or held off feed.
The incidence of colic can be reduced by restricted access to simple carbohydrates including sugars from feeds with excessive molasses, providing clean feed and drinking water, preventing the ingestion of dirt or sand by using an elevated feeding surface, a regular feeding schedule, regular deworming, regular dental care, a regular diet that does not change substantially in content or proportion and prevention of heatstroke. Horses that bolt their feed are at risk of colic, and several management techniques may be used to slow down the rate of feed consumption.
Supplementing with previously mentioned form of pysllium fiber will greatly reduce risk. Most supplement forms are given one week a month and available wherever equine feed is purchased.
Turnout is thought to reduce the likelihood of colic, although this has not been proven. It is recommended that a horse receive ideally 18 hours of grazing time each day, as in the wild. However, many times this is difficult to manage with competition horses and those that are boarded, as well as for animals that are easy keepers with access to lush pasture and hence at risk of laminitis. Turnout on a dry lot with lower-quality fodder may have similar beneficial effects.
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