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Basics ⬇

Outline

BASICS

Definition!!navigator!!

Accumulation of excessive amounts of gas, fluid, or solid material in the stomach, resulting in dilation.

Pathophysiology!!navigator!!

  • The position of the stomach as well as the high resting tone of the esophageal sphincter result in the inability of the horse to regurgitate or vomit. Furthermore, if this occurs, the horse will be at risk of aspiration pneumonia owing to its upper airway anatomy. For this reason, horses are predisposed to excessive distention of the stomach followed by possible rupture
  • Causes of gastric dilation can be primary, secondary, or idiopathic
  • Primary causes of gastric dilation include diseases of the stomach, aerophagia, feed engorgement, and rapid intake of water. The dilation results in decreased motility and a failure to discharge the stomach contents into the proximal duodenum. Overeating of easily fermentable food such as grain, fresh grass, beets, or beet pulp can lead to production of lactic acid and volatile fatty acids by the gastric flora. Gastric emptying is inhibited by increased concentrations of volatile fatty acids, resulting in further fermentation and production of gas. Primary gastric dilation may also result from local infestation of Gasterophilus larvae or habronemiasis, especially in the area of the pylorus. Primary gastric distention can also be caused iatrogenically following passage of a nasogastric tube and overloading the stomach with liquids
  • Gastric dilation can be secondary to an obstructive lesion of the small intestine, resulting in retrograde movement of intestinal fluid and bile, or nonobstructive small intestinal ileus (e.g. proximal duodenojejunitis). The time of development of gastric reflux is proportional to the distance to the obstructed small intestine segment. It may also be secondary to colonic displacement (left and right dorsal displacement), which most likely obstructs duodenal outflow. Improper mastication, poorly digestible ingested material, and eating behaviors may result in gastric impaction
  • Gastric dilation may lead to gastric rupture, usually along its greater curvature. Gastric rupture may be secondary to mechanical obstruction, gastric ulceration, ileus, as well as overload and idiopathic causes

Systems Affected!!navigator!!

  • Gastrointestinal
  • Cardiovascular—affected if horse is dehydrated. Gastric rupture results in endotoxemia, shock, and death
  • Respiratory—abdominal distention and pressure on the diaphragm may affect breathing

Incidence/Prevalence!!navigator!!

Not common.

Signalment!!navigator!!

No sex or breed disposition, but the age might assist in the identification of a primary cause. For example, foals are more predisposed to gastric ulceration.

Signs!!navigator!!

General Comments

A gastric dilation/distention can lead to gastric rupture.

Historical Findings

Depend on the severity of the dilation/distention. Signs of abdominal pain may occur abruptly following excessive or rapid consumption of a large amount of liquid or food. There may be a history of ingestion of highly fermentable food. If secondary to a distal obstruction, the clinical signs are initially related to the primary problem. Mild to severe signs of abdominal pain may be observed. The animal may assume a dog sitting position and present with retching or gurgling sounds. Gastric rupture results in relief, depression, and eventually a reluctance to move.

Physical Examination Findings

Increase in heart and respiratory rates, may have sour smell to the breath, and possibly some ingesta at the nares. Cyanosis and pale mucous membranes may be present, likely due to the local increase in gastric space occupation, thus reducing venous return. There may be dehydration or toxic shock as the disease progresses. Rectal examination may reveal the spleen to be displaced caudally. If the condition is secondary to an aboral obstruction, other abnormalities such as distention of the small intestines may be palpated. On nasogastric intubation, large amounts of gas, fluid, or ingesta may escape. Net gastric reflux of more than 2 L is significant. Spontaneous reflux may also be present in severe cases. Passage of the nasogastric tube may be difficult due to distortion of the cardia. If gastric rupture occurs, the signs of colic will initially subside. Depression, tachycardia, tachypnea, sweating, muscle fasciculations, blue or purple mucous membranes, and severe signs of shock will quickly develop; colic may return.

Causes!!navigator!!

See Pathophysiology.

Risk Factors!!navigator!!

  • Overeating
  • Poor mastication
  • Intestinal obstructions
  • Ingestion of fermentable food

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Any other cause of colic.

CBC/Biochemistry/Urinalysis!!navigator!!

  • May have an elevated packed cell volume and total protein due to dehydration or endotoxic shock. Horses with severe dehydration may have prerenal azotemia
  • Hypoproteinemia if protein loss
  • Hypochloremia if gastric reflux is present, resulting in metabolic alkalosis
  • Metabolic acidosis secondary to severe endotoxemic shock and progressive dehydration possible
  • If gastric rupture occurs, a moderate to severe leukopenia will be noticed secondary to the acute peritonitis

Other Laboratory Tests!!navigator!!

pH

pH of reflux might assist to determine the origin of the problem. Normal gastric pH varies between 3 and 6. pH of fluid originating from the small intestine is between 5 and 7 and has a bilious color.

Abdominocentesis

  • Abdominocentesis is usually normal if there is a primary gastric dilation without rupture
  • There may be an increase in protein concentrations and leukocytes with devitalized bowel (stomach or small intestine)
  • Sanguineous fluid may be indicative of a strangulated obstructive lesion of the small intestine or devitalization of the stomach
  • Plant material in the sample in the absence of an enterocentesis suggests intestinal rupture
  • No leukocytes or cells should be present if an enterocentesis was performed

Imaging!!navigator!!

Radiology

Radiography may identify an impacted stomach pushing on the diaphragm. In foals, a contrast study can help in outlining the gastric wall for detection of gastric ulcers and possibly strictures and determining the gastric emptying time.

Gastroscopy

Gastroscopy is useful for identification of impacted stomach, parasites, gastric ulcer, and neoplasm. In small horses, the duodenum also may be inspected for presence of ulceration and strictures.

Abdominal Laparoscopy

Abdominal laparoscopy is useful for visual inspection of the visceral part of the stomach and small intestine for lesions.

Ultrasonography

Stomach outline is usually seen between the 10th and 15th intercostal spaces. The wall thickness is less than 0.75 cm. May be able to evaluate distention if expand to other intercostal spaces. There is a correlation between the volume in the stomach and its height at the level of the 12th intercostal space. May be useful to identify a primary lesion in the small intestine by evaluation of its wall thickness and diameter. Abnormal findings such as intussusception, mass, abscess, and adhesions may sometimes be identified. The evaluation of the amount, quality, and characteristics of abdominal fluid is also possible.

Other Diagnostic Procedures!!navigator!!

Exploratory laparotomy is useful to treat small intestinal lesions and possibly some gastric problems.

Treatment ⬆ ⬇

TREATMENT

Supportive therapy for treatment of shock.

Primary Gastric Dilation/Impaction

Primary gastric dilation consists of deflating the stomach regularly by passage of the nasogastric tube. If impaction is present, lavage of the stomach followed by administration of DSS (10–30 mg/kg of a 10% solution), which acts as a surfactant and allows water to penetrate the impaction to soften it. It may be necessary to repeat this procedure. Care should be taken not to give too much DSS. Following resolution of an impaction the horse should be kept off feed for 48–72 h. Alternatively, repeated intragastric administration of saline carbonated drinks (“soft drinks”) may be useful.

Secondary Gastric Dilation

Treatment consists of leaving the nasogastric tube in place and performing periodic decompression until resolution of the primary problem by medical or surgical treatment. Gastric rupture may occur despite periodic emptying of the stomach. Ultrasonographic monitoring may be useful to monitor the decompression.

Fluidotherapy

May be necessary in the presence of dehydration.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Analgesics may be necessary to control the abdominal pain. They include:

  • NSAIDs—flunixin meglumine (0.5–1.1 mg/kg IV, IM every 8 or 12 h); and α2-blockers, such as xylazine (0.25–0.5 mg/kg IV or IM), detomidine (5–10 μg/kg IV or IM), or romifidine (0.02–0.05 mg/kg IV or IM)
  • Narcotic or narcotic-derivative analgesics such as butorphanol (0.02–0.04 mg/kg IV), which can be given alone or in combination with xylazine. There is potentiation of these 2 drugs. Analgesics should be used judiciously as they may mask clinical signs and may lead to postponement of surgery
  • Parenteral fluid treatments (100–200 mL/kg/day)
  • When cardiovascular shock is present, hypertonic saline IV (in the adult horse 2 L of 7% NaCl; 4 mL/kg) prior to balanced electrolyte solutions (e.g. lactated Ringer's solution)
  • In case of grain overload, secondary endotoxemia may result in laminitis; see chapter Laminitis

Precautions!!navigator!!

The nasogastric tube should be manipulated gently; avoid overloading the stomach.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

The patient should be monitored for any increase in heart rate or discomfort indicating that the stomach may need to be further decompressed. If the condition is secondary to gastric ulcer, the use of NSAIDs may aggravate the problem.

Possible Complications!!navigator!!

  • Gastric rupture
  • Endotoxemic shock

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Primary Condition

  • Gastric ulceration
  • Parasitism
  • Neoplasia

Secondary Condition

  • Small intestinal obstruction (strangulated or nonstrangulated)
  • Proximal duodenojejunitis

Age-Related Factors!!navigator!!

Gastric ulceration is often the primary cause of gastric dilation/distention in young foals.

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Abbreviations!!navigator!!

Suggested Reading ⬆ ⬇

Carter GK. Gastric diseases. In: Robinson NE, ed. Current Therapy in Equine Medicine, 2e. Philadelphia, PA: WB Saunders, 1987:41–44.

Hackett ES. Specific causes of colic. In: Southwood LL, ed. Practical Guide to Equine Colic. Ames, IA: Wiley Blackwell, 2013:204–207.

Kiper ML, Traub-Dargatz J, Curtis CR. Gastric rupture in horses: 50 cases (1979–1987). J Am Vet Med Assoc 1990;196:333–336.

Murray MJ. Diseases of the stomach. In: Mair T, Divers T, Ducharme N, eds. Manual of Equine Gastroenterology. Philadelphia, PA: WB Saunders, 2002:241–248.

Todhunter RJ, Erb HN, Roth L. Gastric rupture in horses: a review of 54 cases. Equine Vet J 1986;18:288–293.

Author(s) ⬆

Author: Nathalie Coté

Consulting Editor: Henry Stämpfli and Olimpo Oliver-Espinosa