Bilateral renal hypoplasia in four young horses

Three horses less than or equal to 3 years old were evaluated because of stunted growth, weight loss, anorexia, depression, and lethargy of at least 1 month's duration. A neonatal foal was examined after its death. In each case, gross and microscopic renal lesions were compatible with bilateral renal hypoplasia (ie, cortical hypoplasia with severe medullary hypoplasia). In young horses with renal failure, bilateral renal hypoplasia should be considered in the differential diagnosis, and may represent a congenital lesion.