Quit Your Bellyaching: Colic in the Equine Neonate

May 2, 2023  |  Blog

Introduction

Abdominal pain is a relatively common problem encountered in the foal. Accurate and prompt diagnosis is critical to successful management, but it comes with unique challenges. Colic in a foal may look like the classic cockroach on its back or might present as dull and obtunded. To complicate evaluation, some routine diagnostics performed in an adult are not feasible in foals and, unlike adult horses, the degree of pain exhibited by a foal does not often correlate to the severity of the underlying lesion. Ultimately, similar decision-making criteria is required to determine the need for exploratory surgery in the neonate versus the adult horse. Common differentials, diagnostic techniques, and treatment options will be discussed further in this article.

Evaluation

Signalment and history are invaluable when narrowing differentials for colic in the neonatal foal. For example, complications due to congenital abnormalities are often observed within the first few hours of life, while colic secondary to meconium retention or uroperitoneum usually presents within 24-48 hours of life. A thorough foaling history can raise suspicion of foaling injuries which may present like colic pain, and a complete farm history may suggest infectious enterocolitis.

Physical examination is helpful to further differentiate causes of abdominal pain in the foal. Observation of the colicky foal can be extremely important as certain types of colic in the foal have a more typical outward appearance. Foas with gastric ulcers commonly lay on their back with their legs in the air, while a hunched-up position may indicate a caudal impaction. Foals which park out and appear straining could be trying to urinate or indicate an urge to urinate associated with omphalitis or to relieve the weight of sand impaction. A complete physical examination includes vital parameters as well as auscultation of the thorax for typical “clicks” of a rib fracture or murmur of congenital cardiac abnormalities. Rib fractures can also be identified via palpation or imaging. As heart rate is influenced by several parameters, its value as a prognostic indicator is not as great in the foal compared to the adult. Nasogastric intubation can provide important information as in adult horses, but severe gastric distension can make intubation more challenging. Digital rectal examinations will replace the abdominal palpation per rectum and can provide information about meconium retention or the presence of diarrhea.

Occasionally meconium impactions may be palpated externally via deep abdominal palpation. Complete blood count, serum biochemistry, and immunoglobulin G concentrations should be performed to help identify the cause of abdominal pain and help rule out comorbidities.

As the equine neonate tends to be more demonstrative about pain than its adult counterpart, the vast majority of equine colic is non-surgical despite the severity of discomfort they may display. Ultrasound of the foal’s abdomen provides information regarding gastrointestinal distension and motility, but may also identify the presence of fluid, gas or meconium within the gastrointestinal tract, increased free abdominal fluid (with or without evidence of a ruptured bladder) as well as parasitism (older foals). Radiographs can be beneficial in determining gas distension and the presence of meconium impactions. Contrast studies using barium enemas delivered by gravity can be diagnostic for atresia coli or meconium impaction in the small colon, while barium administered by nasogastric tube can identify pyloric or duodenal strictures. Abdominocentesis is slightly more challenging in the foal and should be performed with caution. Due to the relatively thin bowel wall, enterocentesis is more likely and can result in septic peritonitis, especially in the face of bowel distension. When performed, a blunt cannula should be used, and the fluid obtained submitted for testing which may include cytology, culture, and creatinine analysis.

Specific conditions that cause acute abdominal pain in the neonate are widespread and encompass some of the same differentials that are seen in the adult. Disorders of the stomach, small intestine, and large colon are all seen in foals, but more unique disorders include meconium impactions, gastroduodenal ulcer syndrome, and uroperitoneum. A brief discussion of common conditions and field therapy, where appropriate, follows.

Congenital Conditions

Atresia ani, atresia coli, and congenital intestinal aganglionosis generally present early in life. Atresia ani is confirmed through physical examination of the perineum, atresia coli may be confirmed through contrast radiography and congenital aganglionosis suspected based on breed and phenotype.

Enterocolitis

Enterocolitis accounts for approximately 40% of colic in foals presenting to referral institutions. As enterocolitis may appear similar to strangulating intestinal lesions depending on the individual’s pain response and is in a gray zone on diagnostic evaluation, we often initiate a period of therapy and assess response rather than moving immediately to surgery. Ideal therapy includes a period of gastrointestinal rest, antimicrobials, and supportive care. The identification of gas within the intestinal walls on ultrasound is a poor prognostic indicator.

Meconium Impactions

Meconium impactions are one of the most common causes of colic in the equine neonate and are typically seen within the first 24 hours post-foaling. Normal passage of meconium should occur within the first few hours and may continue for 24-48 hours post-foaling. The administration of phosphate “Fleet” enemas within the first 12 hours can help prevent meconium impactions of the small colon. Meconium retention occurs in the rectum, small colon, transverse colon, or large colon. Medical treatment is generally successful, but surgical intervention should be considered in cases of uncontrollable pain, peritoneal fluid abnormalities, and/or signs of bowel inflammation.

Medical management of impactions includes the administration of warm soapy water enemas by gravity feed using very soft tubing; however, clients must know not to administer serial enemas without consulting their veterinarian. Repeated enemas can result in mucosal irritation and associated “straining” in the absence of persistent impaction. I recommend not exceeding two enemas within 24 hours without veterinary intervention. If additional enemas are required, acetylcysteine is recommended.

Enemas with acetylcysteine can be effective in breaking up impactions but can also cause tissue inflammation. Liquid acetylcysteine is available commercially as a 20% can be mixed with 160 ml of water and 20g of NaHCO3 to obtain a concentration of 4% and a pH of 7.6. Foals typically require sedation with midazolam, butorphanol, and/or xylazine for proper positioning in lateral recumbency.Elevation of the hind quarters can also help maintain fluid retention. The procedure requires the introduction of a 30 Fr. Foley catheter with a 30 ml bulb approximately 2.5-5 cm into the rectum. The balloon is gently inflated until the anus and rectum are occluded. One hundred to 200 ml of 4% acetylcysteine is then administered by gravity flow and retained for approximately 30-45 minutes. The procedure can be repeated up to three times (one every 12-24 hours). Retrospective studies have shown this procedure to reduce the requirement for surgery in almost all cases.

Gastroduodenal Ulcer Syndrome

The prevalence of equine gastric ulcer syndrome (EGUS) in neonatal foals is estimated to be approximately 25% to 50%. The four clinical syndromes seen in foals are subclinical, clinical, perforating, and outflow obstruction with a pyloric stricture. Clinical signs include lethargy, colic, bruxism, ptyalism, unthriftiness, frequent recumbency, and rolling into dorsal recumbency. Affected foals are typically two to six months of age; however, gastric ulceration is common in neonates presenting for concurrent disease (e.g., gastrointestinal, sepsis, maladjustment). The pathophysiology of gastric ulceration in foals includes physiologic stress, hypoxia, delayed gastric emptying, prolonged time between feedings, small meal size, and prolonged recumbency. NSAIDs inhibit the production of protective prostaglandins and therefore predispose the equine neonate to glandular ulceration. In addition, illness increases the risk of ulceration by decreasing gastric mucosal defenses secondary to decreased blood flow.

Omeprazole is not recommended for use in neonates as ill neonates often have increased gastric pH; sucralfate administration is recommended instead.

Uroperitoneum

Foals may develop uroperitoneum secondary to traumatic bladder rupture, septic necrosis of the bladder wall, leakage or rupture from the internal urachus, congenital abnormalities of the ureters, or urethral rupture. Foals may present with frequent posturing to urinate, abdominal distension, or obtundation depending upon the severity of electrolyte derangements. Diagnosis may be suspected based upon identification of free peritoneal fluid on ultrasound and confirmed by laboratory analysis of blood and peritoneal fluid. Surgery is often recommended; however, some foals may be managed medically with an indwelling urinary catheter

Sand Ingestion

In Florida, it is not uncommon to see neonates and older foals present for colic or diarrhea associated with pica, particularly ingestion of sand. These foals often display signs of colic through posturing as if to urinate and occasionally have significant abdominal distension. Diagnosis is confirmed via radiography and treatment involves supportive care and prolonged psyllium administration. Oral administration of psyllium may be accomplished by mixing a concoction of psyllium, yogurt, and applesauce. Surgery is rarely required, and recurrence is prevented through controlled management of the environment. Foals will often grow out of this habit within the first few months of age.

Conclusion

Neonatal colic is common, and the degree of pain demonstrated is often not indicative of the severity of the underlying cause. Both gastrointestinal and extra GI causes must be considered, – possible in many cases; however, consideration of owner capabilities and the proclivity of foals to decline rapidly should be taken into account. Indicators for referral include the presence of gastrointestinal reflux, lack of nursing, moderate abdominal distension, refractory pain, intestinal distention, or free fluid on ultrasonography, and/or altered mentation.

References

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This post was written by FVMA Communications.