Gastric Impaction - Horse

Description

Gastric impaction is rare in the horse.(Edwards) It can occur spontaneously as a primary condition but is often secondary to other disturbances in the intestinal tract of the stomach such as ucleration of fibrosis at the pylorus.(Mair) The condition typically causes mild to moderate colic that does not resolve with routine medical treatment.(Bliks)

Aetiology

The specific cause of the impaction is not always apparent(Sanchez) but the obstruction typically consists of excessive dry, coarse ingesta such as straw bedding or poor quality forage.(Sanchez) It may also be composed of foreign bodies, ingested materials that form a mass (such as persimmon seeds or mesquite beans.1-3 in Bliks) or feeds that tend to swell after ingestion.(151-4 in Sanchez) Gastric impaction may be the result of an gastric atony or defective secretion.(Edwards)

Predisposing factors

• Ingestion of certain feedstuffs including sugar beet pulp, bran, straw, wheat and barley. Beet pulp and bran can become dessicated within the stomach and may not become rehydrated by water or gastric secretions.(Mair)
• Dental disorders - roughage may be only partially masticated.(Mair)
• Feeding a horse that has signs of colic - there may be poor gastric emptying associated with generalised decreased gastrointestinal motility
• Rapid consumption of feedstuffs.(Sanchezz)
• Inadequate water consumption.(Sanchez)

• Secondary gastric impaction has been related to ragwort poisoning(Milne)

Clinical signs

The colic associated with gastric impaction varies from mild and chronic to acute and severe.(Bliks) Other signs reported include (Bliks):

• Anorexia
• Lethargy
• Prolonged recumbency
• Dysphagia
• Dropping of feed
• Bruxism
• Salivation (Edwards)
• Insidious weight loss (if chronic)(Edwards)
• Spontaenous reflux with gastric contents visible at the nares (in severe cases)(Sanchez)

In mild cases where signs resolve spontaneously or with analgesics, owners my continue to feed the horse, which only serves to worsen the impaction.(Mair)

Diagnosis

Suspected if cannot pass NGT, with gastric distension the gastoroesophageal junction can become distorted making it difficult to pass an NGT If poorly macerated or digested feed material is recovered from the NGT when the horse has been starved for several hrs On rectal, spleen may be displaced caudally and medially (not specific) Endoscopy (not diagnostic for impaction and difficult to assess gastric distension) Rads may help, will show diaphragm displaced cranially

However, the diagnosis of stomach impaction is usually made at surgery on horses that have had uncontrollable colic or poor response to medicaltherapy. However, endoscopy will reveal gastric impaction, and may provide information on the specific nature of the impaction. Although this would nottypically be performed on an acute colic case, it would be indicated in a horse with chronic colic. (Bliks)

Alateral radiograph of the cranial abdomen showedthe stomach extending caudally from the diaphragm to the level of the 13th or14th intercostal space in several cases.The sonographic appearance is of a markedly enlarged gastric echo extendingover six or more intercostal spaces onthe left side of theabdomen. A marked increase in the thickness of the wall of the stomach may alsobe imaged. (Edwards)

If the horse sufferes from acute severe colic, a diagnosis os often made during exploratory celiotomoy. If signs do not warrant surgical intervnetion, endocosocpy showing a full stomahc after a norally adeqaute fast of 18-24hrs can often confirm the diagnosis. Abdominal rads are resrved for smaller horses and ponies.

Treatment

If suspected, horse should be tranferred with NGT in place to a faciltiy where surgery can be perfomed if necessary Medical tx can include gastric lavage to remove as much impacted material as possible - may need to be done repeatedly 100-200ml 8%DSS may facilitate hydration of dessicated ingesta IV fluid and anlagesics should also be given, although unlikely that IV fluids will resolve the impaction Gastric motility stimulants should be avoided if the extent of the impaction is unkown to prevent gastric rupture Those diagnosed at sx may be treated with bethanecol at 0.2mg/kg SC every 8hrs Medical treatment includes nasogastric intubation, and frequent attempts at softening the ingesta with water, followed by refluxing the fluid contents. (BLiks)

Surgery Direct infusion of balanced polyionic fluids into the impaction through the stomach wall Stomach massaged to break down impaction and facilitate movement of fluid into the ingesta Or fluid may be infused via NGT followed by massage of the stomach Post-op starve for 48-72hrs Gastroscopy indicated to confirm resolution of impaction and identify any underlying causes in stomach

At surgery, the impaction can be massaged and infused, most commonly via insertion of a needle adjacent to the greater curvature, followed by infusionof a balanced polyionic fluid such as saline. There is also a report including the details of a pony and a horse in which a gastrotomy was performed to removethe impacted stomach contents.5 However, there are major risks with this procedure, and infusion followed up by postoperative lavage by stomach tube isusually successful. (Bliks) Withthe horse in dorsal recumbency, the impacted stomach can be

feltextending back to midway between the xiphisternum and the umbilicus and istherefore readily accessible via a midline celiotomy.As much as 30 - 40 kg have been removed via a gastrotomy but postoperativelynormal gastric motility was not restoredand impaction recurred (Edwards 1997). Reduction of stomach volume by partialresection of its flaccid wall was similarlyunsuccessful (Huskamp et al 2000). At post mortem examination there is markedtransmural hypertrophy of the non-glandularregion of the stomach particularly near the cardia, and large chronic ulcersalong the margo plicatus. The contentsof the body and fundic area are foetid and fermenting, and clearly have beenretained for several weeks or longer. Themost recently ingested food passes directly from the cardia to the pylorus. (Edwards)

In addition to analgesia, gastrric lavage via NGT or massage and injection of fluid to soften the impaction during laparotomy (151-3 in Sanchez)

References

Mair, T.S, Divers, T.J, Ducharme, N.G (2002) Manual of Equine Gastroenterology, WB Saunders.