Use of transabdominal ultrasonography to determine the location of cryptorchid testes in the horse

REASONS FOR PERFORMING STUDY: Transrectal ultrasonography is a reliable technique to identify intra-abdominal testes, but can be hazardous or impractical in fractious, juvenile or small equids. The transabdominal approach therefore requires validation. OBJECTIVES: To evaluate the sensitivity and specificity of transabdominal ultrasonography to localise cryptorchid testes. METHODS: Thirty-eight horses admitted for cryptorchidism underwent transabdominal ultrasonography to locate errant testes. Location of the testes was confirmed during surgery (n = 37) or necropsy (n = 1). RESULTS: Horses weighed 175-760 kg. Twenty-two testes were located within the abdomen, 19 in the inguinal space and 3 in a subcutaneous location. In 2 horses, a thick winter coat prevented adequate contact between the probe and the skin, and visualisation of their inguinal testis and one abdominal testis was missed during transabdominal ultrasonography. Excluding the 2 horses with excessive hair, the sensitivity of transabdominal ultrasonography to locate errant testes was 97.6% (93.2% when all horses were included), and its specificity 100%. CONCLUSIONS: Transabdominal ultrasonography is a reliable, safe and immediate technique to diagnose cryptorchidism precisely in horses of all ages, sizes and temperaments. POTENTIAL RELEVANCE: Transabdominal ultrasonography provides an immediate definitive diagnosis of adominal cryptorchidism and should enhance selection of an appropriate surgical approach for their removal.