EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014


543


Review Article


Rethinking equine gastric ulcer syndrome: Part1–Terminology, clinical signs and diagnosis


B. W. Sykes* and J. M. Jokisalo† BW Sykes Consultancy, Upper Orara, New South Wales, Australia; and †Animagi Equine Hospital Hyvinkää, Hyvinkää, Finland. *Corresponding author email: bensykes21@hotmail.com


Keywords: horse; EGUS; stomach; gastroscopy


Summary Equine gastric ulcer syndrome (EGUS) is a common condition in the horse. A series of recent articles highlighting differences in healing of squamous and glandular ulceration have reinvigorated interest in the condition. The purpose of this series of articles is to review the current thinking on EGUS with particular emphasis on the differences between diseases of the squamous and glandular mucosae. This article, the first will review the terminology, clinical signs and diagnosis of EGUS in the horse.


Introduction


Gastric ulceration is the most common disease condition of the equine stomach with a high prevalence of both squamous and glandular disease reported in various populations (Luthersson et al. 2009a; Tamzali et al. 2011; Habershon- Butcher et al. 2012). Significant confusion exists surrounding the terminology used to describe disease in various regions of the stomach. A flow-on effect of this is that factors such as pathophysiology and risk factors from one specific region of the stomach, in particular the squamous mucosa, which is the best studied, are often inappropriately extrapolated to other regions of the stomach, namely the glandular body and pyloric antrum. The objectives of this series of articles are to: 1) clarify the distinction between diseases in different regions of the stomach; and 2) carry this distinction through into separate reviews of disease of the squamous and glandular mucosa.


Terminology


The term equine gastric ulcer syndrome (EGUS) was first adopted by the EGUS Council in 1999 to describe gastric ulceration in the horse (Andrews et al. 1999). However, numerous disease entities exist under the umbrella of the term EGUS, and recently an attempt has been made to clarify the terminology to recognise this distinction (Merritt 2009). The development of a clear distinction between diseases of different anatomical regions is essential in furthering an understanding of gastric ulceration in the horse and in the clinical treatment of affected horses. Reported differences between the squamous and glandular mucosae include differences in risk factors (Habershon-Butcher et al. 2012) and in the response to treatment with omeprazole (Sykes et al. 2014a,b,c). Further, the prevalence of squamous and glandular disease within a population differ (Murray et al. 2001; Begg and O’Sullivan 2003; Luthersson et al. 2009a; Tamzali et al. 2011; Habershon-Butcher et al. 2012) and the presence of squamous and glandular ulceration within an individual are


unrelated (Murray et al. 2001; Begg and O’Sullivan 2003; Luthersson et al. 2009a). As such, the direct extrapolation of findings from the squamous mucosa to the glandular mucosa is inappropriate and instead, disease of the squamous mucosa should be considered as a distinct entity to disease of the glandular mucosa. It is likely that disease of the glandular body differs from that of the pyloric antrum, although at present little work has been done to distinguish the two. Further complicating the terminology of EGUS is that true


ulceration of the glandular mucosa is rare with the majority of lesions more appropriately graded as erosions based on histological examination (Hepburn 2012). Similar to the term EGUS in horses, the termpeptic ulcer disease is used in man to describe a wide variety of diseases under a single umbrella term (Malfertheiner et al. 2009). It is recognised in human medicine that many of the lesions described clinically as ulceration are in fact erosions by the true histopathological definition, but the term peptic ulcer disease is maintained for its ease of use (Malfertheiner et al. 2009). Consensus surrounding the terminology used to describe ulcerative and erosive disease in the stomach of the horse is needed. However, for the purpose of this series of articles a distinction is made between disease of the squamous mucosa and disease of the glandular mucosa. Accordingly, the term equine squamous gastric ulcer syndrome (ESGUS) will be used to discuss diseases of the squamous mucosa, while the term equine glandular gastric ulcer syndrome (EGGUS) will be used to discuss diseases of the glandular mucosa as proposed recently (Sykes et al. 2014a).


Anatomy of the stomach


The equine stomach consists of a single large compartment that can be divided into 3 regions approximately equal in size. The dorsal third of the stomach is covered with a stratified squamous epithelium and is otherwise referred to as the nonglandular region of the stomach. Entry to the stomach via the cardia is within the squamous mucosa. The remaining two-thirds of the stomach is covered with glandular mucosa which can be further divided into the glandular fundus (body), which occupies the mid third of the stomach, and the pyloric antrum, which occupies the most distal third (Hepburn 2011). The delineation between the squamous and glandular regions of the stomach is termed the margo plicatus.


Clinical signs


Clinical signs of EGUS are wide and varied, but include recurrent colic, poor appetite, weight loss, hair coat changes, poor performance, behavioural changes and pain on


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