Gastric Impaction - Horse

Also known as:

Colic Impaction Simple Obstruction

Description

Gastric impaction is rare in the horse. 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. The condition typically causes mild to moderate colic that does not resolve with routine medical treatment.

Aetiology

The specific cause of the impaction is not always apparent but the obstruction typically consists of excessive dry, coarse ingesta such as straw bedding or poor quality forage. 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.

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.
• Dental disorders - roughage may be only partially masticated.
• Feeding a horse that has signs of colic - there may be poor gastric emptying associated with generalised decreased gastrointestinal motility
• Rapid consumption of feedstuffs.
• Inadequate water consumption.

• Secondary gastric impaction has been related to ragwort poisoning

Clinical signs

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

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

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

Diagnosis

• Gastric impaction is suspected if a nasogastric tube cannot be passed or if poorly macerated or digested feed material is recovered from the tube when the horse has been starved for several hours. With gastric distension, the gastoroesophageal junction can become distorted making it difficult to pass the tube.
• On rectal examination, the spleen may be displaced caudally and medially (but this is not specific for gastric impaction).
• Endoscopy would be indicated in a chronic case and may show a full stomach after a fast of 18-24hrs. However it is not diagnostic for impaction as it is difficult to assess gastric distension by endoscopy.
• In a small horse or pony, a lateral radiograph of the cranial abdomen may show the diaphragm displaced cranially
• Ultrasonography may reveal a markedly enlarged gastric echo extending over six or more intercostal spaces on the left side of the abdomen. A marked increase in the thickness of the wall of the stomach may also be imaged.

However, if the horse suffers from acute severe colic, a diagnosis is often made at surgery.

Treatment

If gastric impaction is suspected, the horse should be transported with a nasogastric tube in place to a clinic with surgical facilities. Medical treatment might include gastric lavage with water to remove as much impacted ingesta as possible, which may take several attempts. 100-200ml of an 8% solution of dioctyl sodium sulfosuccinate (DSS) may help to hydrate the dessicated material. IV fluid therapy and analgesia should be commenced, although IV fluids are unlikely to resolve the impaction. Owing to the risk of gastric rupture, gastric motility stimulants should be avoided if the extent of the impaction is undetermined. At surgery the following should be performed:

• In dorsal recumbency, the impacted stomach can be felt extending back midway between the xiphisternum and the umbilicus, so it is easily accessed via a midline celiotomy.
• Infusion of balanced polyionic fluids such as saline either directly into the impaction through the gastric wall (adjacent to the greater curvature) or via a nasogastric tube
• Massage of the stomach to reduce the impaction and aid movement of fluid into the ingesta
• Impactions diagnosed at surgery may benefit from bethanechol at 0.2mg/kg SC every 8 hours to stimulate gastric motility.
• The stomach should be lavaged by nasogastric tube post-operatively and the horse starved for 48-72 hours.
• Gastroscopy is indicated to confirm resolution of the impaction and to identify any underlying causes in the stomach.

Gastrotomy has been attempted to remove impacted stomach contents but this has largely been unsuccessful (Huskamp 2000 in Edwards) and carries major risk including poor gastric motility and recurrence of the impaction.(Edwards 1997)

Prognosis

Infusion followed by postoperative gastric lavage by stomach tube is usually successful. Chronic cases carry a poorer prognosis.