Types of Colic
Pelvic flexure impaction
This is caused by an impaction of food material 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, 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 straw, or the horse has dental disease and is unable to masticate properly. This condition could be diagnosed on rectal examination by a veterinarian.
Spasmodic colic
Spasmodic colic is the result of increased peristaltic contractions in the horse’s gastrointestinal tract. It can be the result of a mild gas buildup within the horse’s digestive tract. The signs of colic are generally mild and respond well to spasmolytic and analgesic medication. Anecdotally, spasmodic colic may be caused by too much fresh grass.
Ileal impaction
The ileum is the last part of the small intestine that ends in the cecum. Ileal impaction can be caused by obstruction of ingesta. other causes can be obstruction by ascarids (Parascaris equorum) or tapeworm (Anaplocephala Perfoliata) as mentioned below.
Sand impaction
This is most likely to occur in horses that graze sandy or heavily grazed pastures leaving only dirt to ingest. The term sand also encompasses dirt. The ingested sand or dirt accumulates in the pelvic flexure, right dorsal colon and the cecum of the large intestines. 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 even peritonitis. Historically medical treatment of the problem is with laxatives such as liquid paraffin or oil and psyllium husk. More recently doctors are treating cases with specific synbiotic (pro and prebiotic) and psyllium combinations. Some cases may need surgery. Horses with sand or dirt impaction are predisposed to Salmonella infection. Horses should not be fed from the ground in areas where sand, dirt and silt are prevalent although small amounts sand or dirt will still be ingested by grazing. Management to reduce sand intake and prophylactic treatments with sand removal products are recommended by most veterinarians.
Enterolith
Enteroliths in horses are round balls of mineral deposits often formed around a piece of ingested foreign material, such as sand or gravel. When they move from their original site they can obstruct the intestine. Enteroliths are not a common cause of colic, but are known to have a higher prevalance in states with a sandy soil and where an abundance of alfalfa hay is fed, this includes California. Once a horse is diagnosed with colic due to enterolith it usually requires surgery to correct the condition.
Colic caused by parasites: Large Roundworms
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 Parascarus equorum that can subsequently cause a blockage and rupture of the small intestine. Deworming heavily infected horses may cause dead worms to puncture the intestinal wall and cause a fatal peritonitis. A blockage of the small intestines by worms may well require colic surgery. A more conservative approach can be to give a horse a laxative (eg liquid paraffin) prior to deworming if a heavy worm infestation is suspected. It is often the result of a poor deworming program. Horses develop immunity to parascaris between 6 months age and one year and so this condition is rare in adult horses.
Colic caused by parasites: Tapeworms
Tapeworms at the junction of the cecum have been implicated in causing colic.
Colic caused by parasites: Cyathostomes
Acute diarrhoea can be caused by cyathostomes or "small Stronglus 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" colour of the large intestines. Animals suffering from cyathostominosis usually have a poor deworming history.
Left dorsal displacement
Left dorsal displacement is a form of colic where the left dorsal colon becomes trapped on the outside of the spleen and against the nephrosplenic ligament. It may necessitate surgery although often it can be treated with exercise and/or phenylephrine, at times anesthesia and a rolling procedure must be performed to correct the condition medically. This condition can be diagnosed on rectal examination by a veterinarian.
Right dorsal displacement
Right dorsal displacement is another displacement of part of the large bowel. Although signs of colic may not be very severe, surgery is usually the only available treatment.
Torsion
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.
Intussusception
Intussusception is a form of colic in which a piece of intestine "telescopes" within a portion of itself. It most commonly happens in the small intestine of young horses and requires urgent surgery.
Epiploic foramen entrapment
On rare occasions, a piece of small intestine can become trapped through the epiploic foramen. The blood supply to this piece of intestine is immediately occluded. The intestine becomes trapped and surgery is the only available treatment.
Other causes that may show clinical symptoms of colic
Stricly spoken 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 kidneys, ovaries, spleen, testicular torsion, pleuritis, pleuropneumonia etc.
