Expert Q & A

Tips for diagnosis and management of IBD

By Adam Marcus

Although it does not get as much attention as colic, inflammatory bowel disease (IBD) is a common and potentially serious gastrointestinal disorder in equines. One study found as many as one-third of horses that lost weight despite showing a strong appetite had some form of IBD. But diagnosing the condition can be challenging. For tips, the Modern Equine Vet spoke with Kathryn J. Timko, DVM, MS, DACVIM, an assistant clinical professor at The Ohio State University College of Veterinary Medicine, in Columbus.

MEV: How can equine veterinarians effectively differentiate between IBD and other conditions, such as alimentary lymphoma, in a clinical setting? As the paper above noted, the clinical signs for both are similar.

Dr. Timko: The clinical signs for both IBD and lymphoma are similar and include weight loss, diarrhea, chronic colic and lethargy. Other conditions, such as dental disease and parasitism, can cause similar clinical signs and will require further diagnostics, such as an oral examination and fecal diagnostic testing, to diagnose.

IBD can be differentiated from lymphoma only through examination of biopsy samples. Biopsies can be obtained in sedated horses through gastroscopy and duodenal (the first part of the small intestine) or rectal mucosal biopsies. If a horse is presented for colic and goes to colic surgery, full-thickness biopsies should be obtained at that time to help aid in a diagnosis. Other diagnostics that are helpful but that will not differentiate between IBD and lymphoma include ultrasonography, rectal palpation and carbohydrate absorption tests.

MEV: Given the risk for malabsorption, what is the preferred initial route for corticosteroid administration?
Dr. Timko: Initially, horses can receive corticosteroids parenterally (intravenously or intramuscularly) to help bypass the gastrointestinal tract and ensure appropriate absorption has been achieved. However, many horses may still receive oral corticosteroid therapy (prednisolone or dexamethasone) as well, but the dosage may differ to account for possible malabsorption.

Dr. Timko: Initially, horses can receive corticosteroids parenterally (intravenously or intramuscularly) to help bypass the gastrointestinal tract and ensure appropriate absorption has been achieved. However, many horses may still receive oral corticosteroid therapy (prednisolone or dexamethasone) as well, but the dosage may differ to account for possible malabsorption.

MEV: What are the specific ultrasonographic criteria that should increase the suspicion of IBD?

Dr. Timko: Ultrasound examination may reveal an increase in free peritoneal fluid, likely secondary to protein loss through the gastrointestinal tract. The small intestinal and colonic walls should be measured for mural thickening. Intestinal wall thickening can be seen with other disorders such as lymphoma, enteritis and colitis, but it may also be appreciated in horses with IBD.

MEV: How reliable is a rectal mucosal biopsy, and what are its diagnostic limitations?

Dr. Timko: Rectal mucosal biopsies are helpful because they can be obtained in the standing, sedated horse, and they are relatively easy to perform. However, interpretation of the biopsies can be challenging because there is a lot of variation in normal rectal mucosa, and there is no standardized histopathologic interpretation protocol. Additionally, not all cases of IBD will have infiltration of abnormal cells within the rectal mucosa, so abnormal cells may not be identified, and the diagnosis can be missed.

MEV: When should a veterinarian choose the D-xylose absorption test over the more common oral glucose absorption test?

Dr. Timko: The oral glucose absorption test is performed more often because most practitioners have ready access to a glucometer. The D-xylose absorption test requires the bloodwork to be sent out to a reference laboratory for evaluation of D-xylose, which is more time-consuming and expensive for the owner. However, the concentration of D-xylose will not be affected by the horse’s environment, whereas glucose concentrations can be affected by the horse’s anxiety over the procedure and sedation.

MEV: What is the prognosis for a horse diagnosed with idiopathic focal eosinophilic enterocolitis (IFEE) compared with other forms of IBD?

Dr. Timko: Horses with IFEE often have the best prognosis because they tend to respond favorably to surgical intervention. The prognosis for other forms of IBD depends on the horse’s initial response to treatment with dietary management, anthelmintic administration and corticosteroids, if necessary. MeV

FOR MORE INFORMATION
Metcalfe LVA, More SJ, Duggan V, Katz LM. A retrospective study of horses investigated for weight loss despite a good appetite (2002–2011). Equine Vet J. 2013;45(3):340-345.
https://beva.onlinelibrary.wiley.com/doi/abs/10.1111/j.2042-3306.2012.00624.x