South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
Pre-renal azotaemia may be present if the horse is clinically dehydrated; evaluate in conjunction
with the hydration status, including urinalysis and following rehydration therapy, if required.
Hypercalcaemia of malignancy (part of the paraneoplastic syndrome) develops due to the
production of parathyroid hormone-related protein (PTHrP) by both neoplastic cells and normal
cells stimulated by neoplasia.
Rectal biopsy
This is easy to perform in the standing horse, preferably restrained in stocks and with sedation. It
can be performed using mare uterine biopsy instrument, a „bottle top‟ or skin punch biopsy
instrument. Using a gloved, lubricated hand, the uterine biopsy instrument is introduced into the
rectum to the level of the wrist and a mucosal fold is palpated and fed into the jaws of the
instrument.
Avoid the dorsal blood vessels (usually a fold at 10 or 2 o‟clock is sampled). Carefully remove
the sample by „peeling‟ the mucosa away and place into formalin.
Rectal biopsy has been shown to be diagnostic in up to 40% of inflammatory bowel
diseases/lymphosarcoma, therefore a normal biopsy does not rule out the absence of large
intestinal lesions. Eosinophilic proctitis is a common, normal finding in the rectum of the horse
and should not be over-interpreted as eosinophilic enteritis.
Paracentesis
Paracentesis is generally low yield for diagnosing the cause of chronic diarrhoea. Intestinal
neoplasia rarely exfoliates into the peritoneal cavity and therefore a normal tap does not rule out
neoplasia. Transudate is common in horses with hypoalbuminaemia.
Oral glucose absorption test
OGAT is rarely useful for the investigation of large intestinal pathology, but can be helpful in
detection of small intestinal pathology/diffuse malabsorption syndromes.
Glucose is a normal body metabolite and is absorbed in the small intestine by specific transport
processes. Plasma concentration is affected not only by absorption but also by metabolic
processes, thus limiting sensitivity. False positive results are also possible with the OGAT. DXylose is a more specific alternative and is not affected by hormonal effects, stress or mucosal
metabolism. Reduced appetite, altered intestinal motility, intraluminal bacterial overgrowth and
renal clearance can affect both xylose and glucose absorption.
Complete malabsorption is generally consistently associated with severe infiltrative small
intestinal disease and normal glucose absorption consistently associated with the absence of small
intestinal pathology (based on comparing overnight glucose tolerance test with histopathological
examination of the small intestine). Partial malabsorption does not always correlate with small
intestinal lesions; some conditions in the horse have been associated with partial malabsorption
curves in the absence of histopathological changes in the small intestine, eg equine motor neuron
disease and larval cyathostominosis. Delayed gastric emptying, such as gastric impaction, can also
result in abnormal glucose absorption curve.
The OGAT is simple and easy to perform. Fast the horse overnight and collect a resting blood
sample for glucose prior to administration of 1g glucose/kg bodyweight as a 20% solution via
nasogastric intubation.
Do not sedate the horse as alpha-2 agonists may &