Shear wave elastography for the identification of intra-abdominal testes in cryptorchid cats

Cryptorchidism is one of the congenital reproductive system disorders encountered in cats, and ultrasonography is commonly used for the preoperative localization of undescended testes. However, the standard ultrasonographic appearance of intraabdominal testes, especially small or deeply situated ones, can resemble surrounding lymph nodes and other soft tissue structures, making identification based solely on morphological B-mode features difficult. Since the difficulties in accurately localizing and characterizing the intraabdominal testis can complicate surgical planning, additional imaging methods that can complement B-mode ultrasonography are needed. Although shear wave elastography (SWE) can quantitatively assess tissue stiffness, the elastographic characteristics of intraabdominal cryptorchid testes in cats have not yet been elucidated. This study aimed to quantitatively characterize the intraabdominal testes of cats with unilateral cryptorchidism using shear wave elastography (SWE) and to compare their stiffness with that of the contralateral scrotal testes and the testes of healthy cats. Seventeen male cats with unilateral intraabdominal cryptorchidism and seventeen healthy male cats were included in the study. Intraabdominal testes were localized using B-mode ultrasonography and then evaluated with SWE. Shear wave velocity (SWV, m/s) and Young's modulus (kPa) were recorded. In cats with cryptorchidism, intraabdominal and contralateral scrotal testes were compared using paired analyses. In healthy cats, the mean values of the right and left testes were used for intergroup comparisons. The mean SWV values were 1.59 ± 0.11, 1.63 ± 0.14, and 1.68 ± 0.14 m/s in the healthy control, cryptorchid scrotal, and intra-abdominal testes, respectively. The corresponding Young's modulus values were 7.68 ± 1.12, 7.97 ± 1.39, and 8.54 ± 1.38 kPa, respectively. No significant differences were detected between the intra-abdominal and contralateral scrotal testes (SWV, P = 0.394; Young's modulus, P = 0.311) or in any of the other testicular comparisons (P > 0.05). In cats, intra-abdominal cryptorchid testes can be quantitatively assessed using SWE and have similar stiffness characteristics to scrotal testes. Therefore, SWE, when used in conjunction with B-mode ultrasonography, may provide complementary quantitative information for the characterization of suspected intra-abdominal testes. However, its ability to differentiate intra-abdominal testes from other abdominal structures with a similar ultrasonographic appearance remains to be determined.