Difference between revisions of "Category:Medical Colic in the Horse"

Impaction, Colonic - Horse

Stomach

Food engorgement

This is a life threatening condition, with a great risk of gastric rupture, and also of secondary laminitis. It is caused by excess food intake, for example, a horse that has broken into a food store.

Gastric/pyloric spasm

This commonly affects racehorses, immediately after racing, and is known colloquially as 'racehorse colic'. Typically, the animal will have had access to cold water, but this is not always the case. Although the signs of colic seen may be very violent, this condition is not associated with any risk of gastric rupture. Spasmolytic drugs are ineffective in treatment, however, naso-gastric intubation is immediately curative.

Inappropriate feed/poor mastication

Either of these may lead to a condition where the stomach is unable to efficiently empty. A common example is feeding of unsoaked sugar beet, which then expands within the stomach.

Neurological atony

A chronic motility dysfunction, leading to a slow filling of the stomach with ingesta. Inhibition of gastric outflow is not normally a feature, and therefore gastric rupture is not a risk. A mild colic may be seen, but far more common is poor condition and reduced performance. Warmblood horses are more commonly affected than other breeds, leading to the suggestion that there may be a genetic component to the disorder.

Ulceration

Equine Gastric Ulcer Syndrome (EGUS) is a common cause of mild to moderate colic, and is more prevalent than had been appreciated. In racehorses, the prevalence is as high as 90%. In other performance horses, prevalence ranges from 40-60%. In foals, prevalence is approximately 25%, and probably higher in those being hospitalized for other reasons.

In adult horses, ulceration commonly occurs in the non-glandular portion of the stomach, unlike in humans, where peptic ulcers are far more common. While the bacterium Helicobacter pylori is a common cause of ulcers in humans, equine gastric ulcers are not typically infectious in origin. It is thought that EGUS is often stress-related, such as after travelling or confinement, and gastric ulceration is a known potential side-effect of treatment with non-steroidal anti-inflammatory drugs. A diet consisting of a high proportion of concentrates is also considered a risk factor. In affected horses, pain is often associated with eating, and the horse typically takes one or two bites of food, then no more. A definitive diagnosis requires endoscopy. Treatment is usually effected using H₂ receptor antagonists, such as Cimetidine, or proton pump inhibitors, such as Omeprazole.

Neoplasia

A malignant squamous carcinoma can effect the cardia and upper squamous regions of the stomach, resulting in a persistent mild colic, commonly seen soon after feeding. Weight loss and general ill health are usually seen, and the prognosis is very poor, due to the high risk of metastasis.

Small Intestine

Spasmodic colic

Spasmodic colic accounts for a large proportion of colic cases seen in first-opinion practice, however, little is known about its causes. It generally produces a mild colic, due to increased peristaltic activity in the gastro-intestinal tract. Cases are usually easily resolved by treating with a spasmolytic such as Buscopan, and a mild analgesic such as phenylbutazone.

Grass sickness

Equine grass sickness, or equine dysautonomia causes a paralysis of the gastro-intestinal tract, by disruption of the autonomic nervous system. This leads to a pooling of ingesta throughout all parts of the gastro-intestinal tract. The condition may occur acutely, or progress chronically over several weeks, but all cases will eventually die. A definitive diagnosis is obtained by taking an ileal biopsy, and inspecting the intrinsic myenteric plexus. There is no effective treatment, although in the short to medium term, horses can be successfully managed by informed and attentive owners.

Caecum

Flatulent colic

Flatulent, or gas colic, occurs when caecal gases are produced faster than they can be removed by the caecum and colon, leading to a distension of the caecum. A diagnosis is strongly confirmed by a right sided abdominal distension, and auscultation/percussion of tympanitic sounds. Treatment involves withdrawal of fluid, and intra-venous fluid therapy. The distension can be relieved by trocharisation of the caecal head, via the right sub-lumbar fossa, which is ideally performed using ultrasound guidance.

Large Colon

Pelvic flexure impaction

A relatively common form of colic, that is often associated with a recent change in diet, management or exercise levels. Pain is moderate, and often persists despite adequate analgesia, a sign more commonly associated with colic of a surgical nature. However, rectal examination provides a definitive diagnosis, with a large, doughy structure occupying much of the pelvis. Treatment involves encouraging fluid output into the large colon, to help soften the impaction, firstly by ensuring adequate hydration with intra-venous fluids, and sometimes by administration of sodium chloride and sodium sulphate orally, to create an osmotic gradient. Large volumes of water, sometimes with Magnesium Sulfate with or without liquid paraffin (Mineral oil) are also given by naso-gastric tube, to help soften the impaction and encourage its movement.

Left dorsal displacement

Left dorsal displacement, or nephrosplenic entrapment, is a frequent cause of colic, where the left dorsal and ventral colon become displaced, and then trapped by the spleen laterally, the kidney medially, and the nephrosplenic ligament ventrally. It can be diagnosed by rectal examination. The first line of treatment is intra-venous phenylephrine injection, which acts to contract the spleen, so helping release the trapped colon. This is often combined with gentle exercise to encourage movement of the abdominal contents. Circling on the left rein is considered particularly helpful, as it increases the potential space between the spleen and the body wall, allowing more room for the colon to return to its normal location. If this fails, then general anaesthesia is needed. Replacement of the colon is then attempted by rolling of the horse. If this also fails then surgery is needed to correct the displacement.

Small Colon

Pelvic masses

A persistent mild colic may be found when intra-pelvic masses impinge upon the gastro-intestinal tract. Most commonly these are haematomas. Peri-anal lesions, such as melanomas may also produce these signs.

Neurological deficits

A complete or partial paralysis of the small colon and rectum may occur with polyneuritis equi, resulting in a lack of faecal expulsion, and consequent obstruction. A diagnosis is made via a neurological examination. Treatment is palliative only, although the condition can be managed for many years by manual emptying of the rectum.