Ileal hypertrophy in a horse.
A 10 year old Paso fino mare presented for recurrent colic for several months duration. The mare had a long history of being a "hard keeper" but in the past 3-4 months had begun to colic after each feeding. The mare was fed a diet of senior feed plus free-choice coastal bermuda grass hay. The mare was referred to PHD Veterinary services for a gastroscopy (stomach scope). The mare presented with a body condition score of 3 out of 9. The client reported that the mare had a good appetite yet shortly after eating, the mare would develop signs consistent with abdominal discomfort! The gastroscopy was normal therefore we opted to ultrasound the mare's abdomen. In Figure 1 there is a cross-sectional image of a loop of intestine (black circle) that is grossly abnormal. The lumen (center) is completely filled in with soft tissue(grey area). The filled in center in Figure 1 corresponds to thickening of the small intestine which likely results in delayed passage of ingesta. Interestingly, there was only 1 very distinct area of the small intestine that scanned abnormally thick. However, there were several loops of small intestine that were dilated and had diminished peristalsis (Large black circles in Figure 2).
The ultrasound findings were consistent with a focal area of thickened small intestine and a large area of dilated small intestine. The dilated small intestine were likely "up stream" from the thickened small intestine and were as a result of partial obstruction of the thickened small intestine. Based on these findings, the mare was referred for abdominal exploratory surgery. During the abdominal exploration, a very thick region of the small intestine was identified. This region corresponded to the ileum which is the very final section of the small intestine. Approximately 12 inches of ileum were grossly thickened resulting in minimal lumen formation for passage of ingesta (Figure 3). Normally, the ileum is a wide-open tube as depicted in Figure 4!! Unfortunately, due to the severity of the condition, poor prognosis, and financial limitations, the mare was euthanized on the surgical table. Ileal hypertrophy has been reported in horses consuming coastal bermuda grass hay and it is theorized that some horses develop an "allergic" response to coastal hay resulting inflammation of the ileum and ultimately gross thickening. More commonly, colic symptoms associated with coastal hay is due to poor quality hay rather than ileal hypertrophy. However, any horse with chronic colic symptoms that is consuming coastal bermuda grass hay should be evaluated for this condition.