Gastrointestinal disorders of neonatal foals

Colic in the foal can be difficult to diagnose accurately because one cannot perform an examination per rectum. However, many diagnostic aids, most importantly ultrasonography, are available to help differentiate medical from surgical causes of abdominal discomfort in the foal.

Obstruction

Intestinal accidents of all types described in adult horses, with the possible exception of enteroliths, occur in foals. Intussusception, volvulus, displacement, diaphragmatic hernia, and intra- and extraluminal obstruction have been reported in foals.Abdominal ultrasonographic and radiographic evaluation greatly aids diagnosis. Treatment is primarily surgical.

Meconium Retention/Impaction Meconium retention or impaction is a common cause of abdominal discomfort in newborn foals. Most foals defecate shortly after their first meal. The usual practice for most owners or veterinarians attending the birth of a foal is to administer an enema to aid this process. The best enema is warm soapy water made with a mild soap such as liquid Ivory soap that can be administered through soft rubber tubing using gravity flow. Foals with significant meconium retention become colicky within the first few hours of life as gas accumulates within the bowel. Additional diagnostics can include abdominal ultrasonography and radiography, particularly if one must rule out other, more serious types of colic. One can treat persistent meconium retention resulting in significant abdominal distention by muzzling the foal administering intravenous fluids. Trocharization for the relief of gas can be quite effective and the author uses this approached commonly in severe cases where pain management is difficult. Most cases resolve with medical management and trocharization alone within 12 to 24 hours.

Congenital Defects

Atresia within the gastrointestinal system of the foal occurs infrequently, but clinical signs are characteristic. Acute colic occurs within the first few hours and is accompanied by abdominal distention similar to meconium retention. Antemortem diagnosis of atresia, short of abdominal exploratory surgery, is aided by the lack of meconium staining of the rectum or any administered enema fluids. Additional diagnostic tests may include administration of a barium enema for a radiographic study, colonoscopy, and abdominal ultrasonography. One can make affected foals more comfortable by muzzling them to prevent further milk intake and by supplying them with fluids and nutrition intravenously. If one attempts surgical correction, one first should initiate broad-spectrum antimicrobial therapy and determine passive transfer status. Frequently, these foals are hypoxemic because of the abdominal distention, and oxygen supplementation is desirable.

Lethal White Syndrome Solid white foals born to overo-overo mating of American Paint Horses may suffer from congential aganglionosis of the ileum, cecum, and colon. These foals present similarly to foals with meconium impaction or atresia in that colic develops shortly after birth and involves progressive abdominal distention with feeding. The inherited defect is in the endothelin receptor gene. No effective treatment exists, but the clinician should be aware that not all white foals of this mating are affected, and some simply may have meconium retention, so a short period of treatment may be warranted.

Necrotizing Enterocolitis

Necrotizing enterocolitis is considered the most common acquired gastrointestinal emergency of human infants.The clinical spectrum of necrotizing enterocolitis is multifactoral and ranges from temperature instability, apnea, lethargy, abdominal distention, bilious residuals, septic shock, disseminated intravascular coagulation, and death. In the neonatal foal, necrotizing enterocolitis is probably one of the most underrecognized causes of gastrointestinal dysfunction and in the past has been attributed only to infection with anaerobic organisms including Clostridium perfringens type C and C. difficile. Although a specific form of enteritis in the foal is associated with intestinal infection by these organisms, most necrotizing enterocolitis is associated with prematurity or PAS in the infant and the foal. One should suspect necrotizing enterocolitis in any foal that is having difficulty tolerating oral feeding, demonstrating signs of ileus, or having episodes of colic and in any foal with occult blood, digested blood or frank blood in the stool or reflux.

Gastric Ulcers

Gastric ulcer disease has been recognized in foals, and lesions vary in anatomic distribution, severity, and cause. In clinically normal neonatal foals (<30 days of age), gastric ulcers and mucosal desquamation have been documented. Because of these reports and other early reports of death following ruptured clinically silent ulcers in neonatal foals, for years many clinicians felt it necessary to treat critically ill neonates with antiulcer medication prophylactically. Few specific causes have been found for gastric ulcer disease in foals. Excessive administration of nonsteroidal anti-inflammatory drugs can result in ulceration of the glandular and squamous epithelium because of an inhibition of prostaglandin production, which leads to a decrease in mucosal blood flow and an increase in acid production. Nonsteroidal anti-inflammatory drugs also can impair the healing of lesions and rarely are indicated in neonatal equine medicine. In the sick neonatal foal (<7 days of age) a wide variability in the intragastric pH has been documented depending on the type of disease, severity, and milk intake frequency and volume, suggesting that in the critically ill equine neonate, ulcer prophylaxis using histamine antagonists or proton pump inhibitors is not only unnecessary but unlikely to work.

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