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Posts Tagged ‘colonic impaction’

There are other special circumstances affecting the gastrointestinal (GI) system that can result in impaction of the small or large colon. The formation of fecaliths (a dehydrating and hardening of feces to the extent that it becomes stone-like), enteroliths (a mineral concretion) and meconium-induced impaction (early accumulation of fetal feces in newborns). Horses that have a recent and significant decrease in exercise, usually from an injury, can develop large colon impactions. Twice-daily feedings of grain can result in a measurable increase (up to 15%) in fluids secreted into the bowl from the cardiovascular system which can result in hypotension (reduction of circulating blood volume). This causes the renin-angiotensin-aldosterone regulatory to be activated resulting in the reabsorption of more fluid from the GI tract. This results in a dehydration of the feces and can also result in an impaction.

Four types of displacement colic are described in horses. Displacement occurs because most of the bowel is not anchored to the body wall but suspended from the dorsal abdominal wall in the mesentery. It is therefore relatively easy for a portion to move out of its normal position. Left dorsal displacementoccurs when the pelvic flexure moves toward the space found between the spleen, the left kidney and the nephrosplenic ligament the structure that attaches the spleen and kidneys to the body wall. Right dorsal displacement occurs when the colon lodges between the cecum and the body wall. The pelvic flexure can move to a position closer to the diaphragm resulting in a volvulus, a 180-degree twist along the longitudinal axis. Torsion (a twist along the axis of the mesentery) can also occur. The mesentery is the diaphanous tissue supporting the bowel through which veins, arteries and nerves are carried from the dorsal abdominal wall to the intestine.

Any type of displacement can result in an occlusion of the blood supply (partial or complete) to the involved portion of the GI tract.

Left dorsal displacement will often resolve itself following conservative medical treatment. In recalcitrant cases your veterinarian may elect to anesthetize the horse, put it on its left side, then quickly roll it to its right side while repeatedly pushing on the abdomen. Obviously, this is not a maneuver to be attempted by only one person.

An intussusception of the bowel occurs when a section of intestine “telescopes” into an adjacent section. This most often occurs at the ileocecal junction. When this happens, surgical correction is the only effective treatment. This condition is most common in horses about one year old and is almost always associated with tapeworms, other parasites, small masses and foreign bodies or severe diarrhea.

Epiploic foramen entrapment occurs when a portion of the small intestine (rarely the colon) becomes lodged in the epiploic foramen, also known at the foramen of Winslow. This opening is the communication between the abdominal cavity and the omental bursa. Entrapment of a loop of bowel can also occur through a rent (tear) in the mesentery.

Proximal enteritis (inflammation of the gut lining) is usually the result of infectious organisms, particularly Salmonella and/orClostridium species. Fusarium(a large genus of filamentous fungi) can also be the cause of enteritis. Fusariuminfections occur most commonly in the Southeastern U.S. Overfeeding a high concentrate diet can also result in enteritis. Horses suffering from enteritis have an increased risk of laminitis and thrombophlebitis. Colitis (inflammation of the lining of the colon) is most often associated with infectious caused by Salmonella species, Clostridium difficileand/or Neorickettsia risticii. This last organism is the cause of Potomac Horse Fever. Ingestion of toxic agents such as arsenic or cantharidin, as well as several plant toxins can result in colitis as well.

Gastric ulceration is associated with confinement (lack of adequate exercise), infrequent feeding, a high concentrate diet, over-use of non-steroidal anti-inflammatory (NSAID) drugs, and from the stress associated with shipping and/or performing.

Tumors that can affect the GI tract and result in colic include lipomas (fatty tumors) that form on the mesentery and stretch the connective tissue into a stalk as it enlarges. The stalk can wrap around a section of bowel, usually the small intestine. Neoplastic growths of the GI tract can also include lymphosarcoma, leiomyomas, adenocarcinomas and squamous cell carcinomas. The last of these usually involves the stomach.

Ileus is characterized by no, or very low, movement of the intestines. Between ten and fifty percent of horses will develop ileus following abdominal surgery, with over 80% of those animals having been operated on for correction of a strangulating obstruction. Diagnosis is made using ultrasound when more than three loops of intestine lack peristaltic waves.

Hernias can result in incorporation of a loop of bowel and signs of colic. Standardbred and Tennessee Walker stallions are prone to a large inguinal ring and inguinal hernias. Umbilical and diaphragmatic hernias are rare but can occur in any breed of horses.

Non-bowel related colic include the ingestion of toxins, uterine tears and torsions, disease of the liver, ovaries, spleen, urinary system, or testicular torsion. Inflammatory conditions of the pleura (lining of the lungs and thorax), uterine contractions, laminitis and rhabdomyolysis can all present with signs resembling colic.

Parasitic infestations with Parascaris equorum(roundworms), Anoplocephala perfoliate(tapeworms), cyathostomes(Strongylus-type roundworms) and Strongylus vulgariscan all result in colic. The larvae of Strongylusspecies migrate out of the GI system and find their way into the arterial system. They are sometimes found in the cranial mesenteric artery where they can cause vasospasm as well as blockage. The regular use of modern anthelminthics has reduced the incidence of this problem.

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Impaction colic is most commonly found in the pelvic flexure of the colon. It usually consists of poorly digested food lodged where the colon turns back on itself and narrows (the pelvic flexure). This condition is easily diagnoses via rectal examination, an indispensable part of the physical exam when called on a colic case. This condition is most commonly seen when the horse is confined in a small space, not receiving enough exercise and is being fed a large volume of concentrated feed, pellets and/or grain. It can also occur if the animal’s teeth need floating or if there are other dental issues preventing normal chewing (mastication). It can also occur if the animal cannot take in adequate water.

Colonic impaction will almost always respond to medical treatment. Sometimes high enemas will resolve the issue when mineral oil pumped into the stomach is not sufficient to move the blockage.

In the Southeastern U.S. coastal Bermuda hay is commonly available and used to feed horses. This type of hay can result in an impaction of the terminal ilium, the portion of the small intestine where it joins with the cecum (a large blind sac where fermentation aids digestion of roughage) and the entrance into the colon (large intestine). Obstruction of the ilium can also be the result of ascarids (intestinal parasites) after the horse has been treated for the infestation and is passing large numbers of the dead parasites. It is most commonly seen in young horses following their first deworming. When equine tapeworms are an issue treatment can result from a blockage of these dead or stunned parasites in the small intestine. When this condition occurs, the animal will usually exhibit intermittent moderate to severe abdominal pain. Distended loops of small intestine can sometimes be found on rectal exam. Ultrasound diagnosis may be necessary to identify this type of colic. Severe cases may result in gastric reflux. This usually responds to nasogastric intubation and the release of the accumulated gases from the stomach. Cases that are non-responsive to routine treatment may respond to warm soapy water or carboxymethylcellulose enemas providing the site of impaction can be located and reached rectally.

Less commonly encountered is hypertrophy of the longitudinal and/or circumferential smooth muscle layers of the small intestine (ilium or jejunum). The condition may be idiopathic (of unknown cause), or neuronal dysfunction usually associated with parasitic migration, particularly of the larval stage of ascarids. It may also be the result of increased tone of the ileocecal valve. This leads to hypertrophy of the smooth muscle of the ilium because it has to push ingesta through a smaller orifice. This diagnosis is usually made during surgery and can occur following the removal of a portion of intestine and the anastomosis (rejoining of the bowel) resulting in stricture.

Sand colic can occur when horses are pastured on sandy or heavily over-grazed pastures or fed on the ground. When I practiced in Arizona (back in the 1960’s) it was relatively common for backyard horses kept in small corrals to be fed on the ground on loose dirt. The ingested dirt or sand mostly accumulates in the pelvic flexure but may also be found in the right dorsal colon or in the cecum. The sand or dirt will irritate the mucosa (lining) and can result in diarrhea. Examination of the manure will often reveal the presence of sand and/or dirt. Accumulation and the resulting weight and abrasion on the mucosa can also result in a lack of colonic motility rather than hypermotility and diarrhea and in severe cases, rupture and peritonitis.

The diagnosis is the result of careful observation of the conditions in which the animal is kept and fed, abdominal auscultation for the sounds of hyper or hypo motility (too much or too little) and gas accumulation. Radiographs or ultrasound may be required to make the diagnosis. Medical treatment with laxatives is often effective especially with the addition of psylliumhusk. Psylliumis the common name for several members of the plant genus Plantago. Commonly marketed products of this include; Metamucil, Pinch, Fybogel, Kansyl and Luelax. Mineral oil treatment alone is less effective since it will usually float on the surface of the accumulation without penetrating. Psylliumbinds to the sand and helps to remove it. Animals with this condition may also suffer from rapid overgrowth of Salmonellaor other bacteria so antibiotic added to the treatment may be indicated. If signs of severe colic do not respond to medical treatment within a few hours surgery is indicated. Where grazing or feeding on the ground cannot be avoided prophylactic treatment feeding a pelleted psylliumproduct may be recommended by your veterinarian.

Impactions of the cecum are uncommon. They can occur when horses ingest bedding or as a result of post-operative or other pain therapy involving the use of opioids resulting in GI stasis and constipation. Because of its function as a fermentation vat gas and fluid accumulation is rapid and can lead to rupture within a day or two, if not corrected surgically. The condition can usually be diagnosed on rectal exam but rupture can occur early in the progression of the condition.

Gastric impactions are rare. It can occur following ingestion of foods that swell after eating, ingestion of bedding or poor-quality roughage, dental problems, ingestion of a foreign object or disease that interferes with normal gastric function. Ingestion of persimmons form a sticky gel in the stomach and feeding haylage can be problematic. When I practiced in Arizona ingestion or feeding of mesquite beans was a problem. Feeding sugar beet pulp can also be problematic. Diagnosis using gastroscopy or ultrasound may be necessary. Gastric impactions will often respond to treatment with water or other fluids via nasogastric intubation.

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