Abstract: Background - Nephrolithiasis in horses is poorly documented. Objectives - The objectives are to describe the clinical findings, alterations in renal function and short term survival rate of horses with nephrolithiasis. Animals - 25 horses with nephrolithiasis presented to the Centre Hospitalier Universitaire Vétérinaire (CHUV). Methods - Medical files from 2007 to 2021 with “nephrolithiasis” as a primary or secondary diagnosis based on ultrasonography were reviewed. Creatinine concentration was determined for 24 out of 25 cases. Results - 25 horses (14 females, 11 males) with a wide age range (4-30 years) were included. The most common breeds were QH (5 cases) and Standarbred (4 cases). The short term survival rate was 88% (22/25 cases) and one horse was euthanized 8 months after hospitalization for poor quality of life. Three of these four euthanized horses had grade 3 Acute Kidney Injury (AKI). Hypercreatinemia (highest value during hospitalisation) were observed in 16/24 cases (67%) and grades 2 or 3 AKI were detected in 7/24 cases (29%). Nephrolithiasis was diagnosed bilaterally (56% cases) or unilaterally (44% cases), affecting the left and right kidney almost equally. Grade 2 to 3 AKI was observed in horses with unilateral (10%) and bilateral (43%) nephrolithiasis. Conclusion and clinical importance - Nephrolithiasis can affect a variety of breeds, a wide range of ages and both sexes of horses. It can be uni- or bilateral, with or without altered renal parameters, or ultrasonographic changes in the renal parenchyma. In some horses, nephrolithiasis may even be an incidental clinical findings.
