466
EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2018) 30 (9) 466-471 doi: 10.1111/eve.12700
Case Report
Idiopathic eosinophilic colitis lesions of the equine small (descending) colon
M. P. de Bont†*, A. J. Malbon‡, R. Blundell§ and D. C. Archer¶ †Dubai Equine Hospital, Zabeel, Dubai, UAE; ‡Institute of Veterinary Pathology, Vetsuisse Faculty, University of Zurich, Switzerland; §Department of Pathology, University of Liverpool, Neston, UK; and ¶The Philip Leverhulme Equine Hospital, University of Liverpool, Neston, UK. *Corresponding author email:
t_debont@yahoo.co.uk
Keywords: horse; colic; small (descending) colon; eosinophilic; colitis
Summary Five horses with a primary surgical lesion of the small (descending) colon were diagnosed with eosinophilic colitis based on visual and histopathological examination. These were evident as visibly striking, hyperaemic, focal lesions of the small colon, with serosal petechiation, oedema and marked thickening of the intestinal wall at the site. Areas of focal necrosis were also evident. The gross appearance of the lesions were considered to be sufficiently severe in all cases to merit resection, due to concerns about intestinal necrosis and septic peritonitis. An inability to fully exteriorise the affected portion of intestine to perform a resection and anastomosis necessitated intraoperative euthanasia of one horse. A total of three horses survived to hospital discharge. Eosinophilic colitis lesions are a rare cause of severe small colon disease, but should be considered in cases with similar visual characteristics.
Introduction
Focal and multifocal idiopathic eosinophilic lesions are an uncommon but important cause of gastrointestinal disease in the horse. They have been previously described as causes of acute abdominal pain (colic) as a result of either lesions in the large colon, described as segmental eosinophilic colitis lesions (Bertone et al. 1986; Edwards et al. 2000) and as idiopathic focal eosinophilic enteritis (IFEE) lesions of the small intestine (Scott et al. 1999; Southwood et al. 2000; Stanar et al. 2002; Swain et al. 2003; Archer et al. 2006; Perez Olmos et al. 2006). Focal eosinophilic infiltration of the small colon has been briefly reported in the literature (M€
akinen et al. 2008; de Bont et al. 2013), but
there have not been any detailed reports of the clinical and histopathological features, nor of the outcome in these cases. Primary lesions of the small (descending) colon account for a relatively small percentage (2.8–4.2%) of colic cases requiring surgical treatment (Edwards 1992; Mair and Smith 2005). Eosinophilic colitis lesions affecting the small colon represent a small proportion of these, having been identified in 6% (5/84) of horses undergoing exploratory laparotomy for treatment of colic which was due to a primary lesion of the small colon in one study (de Bont et al. 2013). The aim of this study was to detail the clinical and histopathological features of focal, idiopathic eosinophilic colitis of the small colon.
© 2016 EVJ Ltd Case details
Signalment A total of five horses, where a surgical and histopathological diagnosis of eosinophilic colitis of the small colon as the primary cause of colic was made, were identified in case records at the Philip Leverhulme Equine Hospital, between August 2004 and August 2010. The signalment, clinical and clinicopathological findings of all horses are summarised in Table 1. There was no evidence of age, breed or sex predisposition when compared with the general hospital population. None of the horses had a history of previous colic signs and there did not appear to be any characteristic presurgical findings indicative of an eosinophilic colitis lesion. The median age was 11 years (range 7–21 years). The decision to perform an exploratory laparotomy was based on abnormal rectal and ultrasonographic findings, clinical parameters and/or persistent pain despite the administration of analgesics. Abdominocentesis was not performed in any of the cases prior to surgery, due to other clinical findings indicating that exploratory laparotomy was required.
Surgical findings At exploratory laparotomy the lesions were evident as visibly striking, hyperaemic, focal lesions of the small colon with serosal petechiation (Fig 1) and considered to be the primary cause of abdominal pain. There was evidence of oedema
and marked thickening of the intestinal wall at the site. Other findings included gaseous distention of the small colon, oedema of the mesocolon and impaction of ingesta orad to the lesion. Due to the degree of mural thickening and evidence of focal necrosis already developing at the site, leaving the affected portion of colon in situ was considered likely to result in a poor prognosis for survival, due to the risk of developing septic peritonitis. Resection was therefore undertaken in four horses and a two layer hand sewn end-to- end anastomosis performed (Rakestraw and Hardy 2012). Examination of the resected portions of intestine revealed a green appearance to the mucosa and submucosa, consistent with tissue necrosis. The length of resection ranged from 15 to 180 cm. One horse (Horse 5) was subjected to euthanasia intraoperatively due to the extent of the lesion and an inability to sufficiently exteriorise the affected portions in order to expose healthy tissue margins.
Histopathology The lesions represented a focal severe eosinophilic and granulomatous colitis. Mucosal regions were characterised by
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