Pathology beyond the stomach

Emma Hardy, PhD

Until very recently, the equine industry has afforded little clinical attention to conditions of the equine large colon or intestine. Perhaps under-diagnosis of hindgut pathologies has been a result of a long-standing assumption amongst the veterinary community that these conditions do not indeed exist. However, the work of a research team at Glasgow Veterinary School, led by Professor Derek Knottenbelt, is shedding new light on hindgut pathology, and revealing that these conditions are more prevalent than once thought – even in ostensibly normal horses. The team are working hard to further understand aberrations in intestinal pathology, improve methods of diagnosis and explore its clinical significance.  

 

Shifting the spotlight  

Diagnostic limitations for conditions beyond the stomach have undoubtedly been a barrier for veterinary professionals, with the wide scope in aetiology, pathogenesis and severity of “large bowel disease” also a compounding factor.  

Knottenbelt remarks that areas of ceacal or colonic pathology are not easily recognized by current means. The main issues are associated with a lack of sensitivity, non-specificity, subjectivity of images and data, and limitations in the physical reach and access to areas of interest. Currently, post mortem analysis remains the only way to comprehensively examine the entire equine gastrointestinal tract and effectively identify all aberrations, but this is obviously not helpful for diagnosing conditions in practice. 

Knottenbelt et al. (2015) describes the findings from his preliminary post-mortem studies at Glasgow as very enlightening. “In horses which demonstrated no gastrointestinal disease symptoms anti-mortem, and lacked confounding factors such as nonsteroidal anti-inflammatory administration, more than 60-70% were found to have significant large colon pathology.” These prevalence rates agree with the original post-mortem studies of this nature, first carried out by Pellegrini (2005), and they support Knottenbelt’s opinion that “subclinical hindgut pathology does exist in a high proportion of horses”. He believes that this is very likely to be of clinical significance and work needs to be continued to identify the pathological mechanisms at an earlier stage and ascribe definitive clinical syndromes to these signs. 

Investigating and defining pathology of the large intestine

Aside from the obvious major infectious and parasitic conditions of the large intestine, infiltrative bowel disease has become an umbrella term for a number of idiopathic conditions. Knottenbelt admits that previous research has explored the concept of large bowel disease from a surgical basis, and that developing methods for definitive diagnosis without surgical intervention to enable earlier detection is key in promoting rapid recovery. He notes: “Just because we have no current specific and sensitive pre-surgical diagnostic tests for any of the so-called idiopathic disorders, does it mean that we do not have to investigate them?” 

Knottenbelt further explains that there is likely a large range of diseases that affect the large colon, and within that will be a spectrum of severity and extent. However, he believes that most of these issues will be chronic, thereby affording the practitioner some scale of time in which to identify the problem, implement early intervention and prevent disease progression. 

The need for early detection

Knottenbelt points out that “the sooner we can detect something, the earlier we can focus treatment and limit the possibility of significant long term effects”. Whilst he remarks that the current methods of identifying intestinal pathology are generally “not bad, but not good”, the SUCCEED® Equine Fecal Blood Test (FBT), which detects equine occult haemoglobin and albumin in a faecal sample, can be useful as a sensitive but non-specific screening test to indicate an anomaly within the gastrointestinal tract. He stresses that veterinary professionals need to view the FBT as akin to a thermometer or a stethoscope and encourages the clinician to explore intestinal health and, if necessary, further diagnostic possibilities.  

 “The range of pathological disorders in the ceacum and colon is seemingly much wider than we first thought,” Knottenbelt says. Whilst some work has been undertaken to characterise infiltrative disease pathologically, little is fully understood and the concept of specific focal disease is still making headway among professionals. Knottenbelt cautions “just because we do not yet have a method of visualising the entire intestinal tract, we can’t assume there are only two or three pathologies that affect it. Clearly subclinical colonic disease does exist, and we can much better understand the clinical significance of these conditions once we have better methods of detection and diagnosis.”

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