Diagnostic approach to chronic diarrhoea in adult horses

Summary Chronic diarrhoea presents a diagnostic challenge for both human physicians and equine veterinarians. There is currently no consensus in the equine veterinary literature on the definition of chronic diarrhoea. The differential list is extensive and identifying diarrhoea by pathophysiologic mechanism can help remove less likely diagnoses. Achieving a definitive antemortem diagnosis is also challenging. Results from non‐invasive diagnostics may only lead to the conclusion that inflammation is present. Cellular infiltrate, if present, may not be representative of the underlying disease. Invasive diagnostics resulting in acquisition of full‐thickness biopsies may result in a diagnosis when other methods have failed. However, there is currently minimal data correlating these findings with those from full post‐mortem examination. This article discusses the various diagnostic options and reviews the available literature on their value in evaluating currently available patients with chronic diarrhoea.