Equine Idiopathic Hemorrhagic Cystitis: Is It Idiopathic or More Likely to Be Exercise-Associated?

Recently, a syndrome called "equine idiopathic hemorrhagic cystitis" was described and clinical features compared with bladder neoplasia. In this case report, we describe a case of hemorrhagic cystitis with a favorable outcome in a high-performance dressage horse, in which exercise intensity might be the etiologic factor for the development of bladder-wall hyperplasia and hematuria. A 14-year-old Warmblood gelding was presented with a history of hematuria of 2-day duration. The high-level dressage horse had performed on the previous 3 weekends and was trained at least three times a week at performance intensity level. Sonographically, the dorsal bladder wall was about 1.5 cm thick and the different layers of the bladder wall could not be differentiated. Endoscopy revealed that the bladder was highly edematous and showed diffuse submucosal bleeding. Histopathological differential diagnoses were severe reactive hyperplasia or a low-grade transitional cell carcinoma. Four months later, bladder wall thickness had decreased to 1.0 cm and the different layers of the bladder wall were easily visible sonographically. Endoscopy showed a normal bladder mucosa. On histopathology, hyperplasia of the epithelium was significantly decreased. A diet low in calcium was recommended after the checkup, and the owners started working the horse very lightly for 2 days a week. Over the following 2 months, hematuria had not recurred. In conclusion, it seems likely that hemorrhagic cystitis in this horse was exercise-associated, but as repeated provocation by high exercise intensity was not performed in this case, this remains an assumption.