Retrospective Evaluation of the Most Frequently Observed Histological Changes in Duodenal and Rectal Mucosal Biopsies in Horses with Recurrent Colic

SIMPLE SUMMARY: Colic, a condition affecting the digestive tract of horses, manifests itself in severe pain and may be life-threatening. Recurrent colic is usually caused by ongoing, chronic inflammatory process (and may be defied as: ≥3 episodes of colic within a 6-month period, with at least 48 h between colic episodes), associated with a chronic process, often of an inflammatory nature. Multiple causes of recurrent colic may exist, including, for an improper diet, management changes, stress, or parasites infestation. During the diagnostic process, a noninvasive test in the form of taking a biopsy of the duodenal or rectal mucosa proves to be useful, but its usefulness is limited only to diffuse processes. The study presented here depicts a retrospective analysis of the histopathological findings of samples taken from 77 horses with recurrent colic, focusing on cellular infiltration, fibrosis, and erosions. All samples from the duodenum showed the presence of leukocytes infiltrates in the mucosal lamina propria, of which almost 70% were diffuse infiltrates. The most frequently observed cellular infiltration was a moderate infiltration consisting of lymphocytes and plasma cells. More than one-fourth of the horses were also found to have shortened intestinal villi. Similarly, in biopsies from the rectum, cellular infiltration was observed in all horses in this section, which consisted of a mixed population of plasma cells, lymphocytes, and eosinophilia. Analysis of the inflammatory lesions present may help in understanding the pathogenesis of chronic colic in horses. ABSTRACT: Colic, a condition affecting the gastrointestinal tract of horses, manifests as severe pain and may be a life-threatening condition. It is possible to distinguish between an acute, disposable process, as well as recurrent colic symptoms (abdominal pain) caused by an ongoing chronic inflammatory process. This paper presents a retrospective analysis of the histopathological findings of duodenal and rectal samples taken from horses with recurrent colic, with the aim to determine the frequency and extent of inflammation. The samples, i.e., duodenal biopsy (60 samples) and rectal biopsy (17 samples), were taken from 77 horses showing recurrent colic symptoms. Histopathological examination included staining with hematoxylin and eosin. The examination included evaluation of the superficial epithelium, mucosal lamina propria, and submucosa. All samples from the duodenum and rectum showed the presence of leukocyte infiltration in the mucosal lamina propria. The most frequently observed cellular infiltration was a moderate infiltration consisting of lymphocytes and plasma cells in duodenum and mixed populations of plasma cells, lymphocytes, and eosinophilia in the rectum. Mott cells were also noted among the inflammatory infiltrates. More than one-fourth of the horses were found to have shortened intestinal villi. The results presented here showed the involvement of inflammation in the course of recurrent colic, which can be both its cause (by impairing motility and absorption) and its effect (as a result of obstruction or ischemia).