Stefano Spada, Daniela De Felice, Alfonso Calabria, Francesca Carletti, Luiz Paulo Nogueira Aires, Massimo Vignoli, Martina Rosto, Marco Russo
Background
Cryptorchidism, the incomplete descent of one or both testes into the scrotum, affects approximately 6.8% of male dogs and is clinically significant due to its association with testicular neoplasia and torsion. Diagnosing and localizing retained testes can be challenging with ultrasonography, especially in cases with deep abdominal or ectopic testicular positions. This study aimed to assess the utility of computed tomography (CT) as a diagnostic tool to evaluate and localize undescended testicles and characterize their anatomical and radiologic features in dogs.
Methods
A retrospective, multicenter study was conducted analyzing 19 dogs diagnosed with cryptorchidism through CT scans obtained between 2014 and 2024. CT scans included both pre- and post-contrast series. Testes were assessed for size, location, shape, margins, parenchymal homogeneity, and Hounsfield unit (HU) density. Dogs were categorized based on unilateral or bilateral cryptorchidism. Comparative analyses between undescended testes (UT) and scrotal testes (ST) included size ratios and density evaluations. Statistical analyses employed Mann–Whitney and Spearman tests.
Results
CT effectively localized all retained testes, which exhibited significant variability in position. UTs were approximately 30% smaller than STs in all dimensions. They also demonstrated higher density (HU) values in both pre- and post-contrast scans, suggesting histological or structural differences such as reduced spermatogenesis. No HU differences were observed in the pampiniform plexus enhancement between groups. One excluded case revealed an ectopic perineal testis, potentially representing the first such report in dogs. CT enabled clear identification of testicular and associated structures, aiding in differentiating testicular tissue from similarly appearing lymph nodes or other abdominal contents.
Limitations
The retrospective design, small sample size, and absence of histopathological confirmation limit the findings. No direct comparison with ultrasonography was possible. Radiation exposure and the need for general anesthesia are inherent limitations of CT as a diagnostic tool.
Conclusions
CT provides reliable, detailed anatomical assessment of retained testicles in dogs, offering advantages over ultrasonography, particularly in complex or ambiguous cases. The ability to determine testicular size, location, and tissue characteristics may enhance surgical planning and diagnostic precision. CT is recommended as a second-line imaging tool when ultrasonography is inconclusive. Future prospective studies comparing CT with other modalities and incorporating histologic validation are warranted.
A — Post-contrast sagittal and B — Post-contrast dorsal, multiplanar reconstruction computed tomography
images of the left caudal abdomen acquired in a soft-tissue algorithm (soft-tissue window, WW-WL 281-22 HU). The
retained left testis (white arrows) was caudal to the left kidney (LK) and was enlarged, ovoid, and soft tissue attenuating
with a thin, mildly contrast enhancing peripheral rim (top images). Bottom images demonstrate an ill-defined, partial whirl
sign, characterized by tortuous, rotated testis and spermatic cord surrounded by a partial whirl of fat and soft tissue.
Fat contiguous with the mesentery extended centrally along the testicular parenchyma and spermatic cord in a crescentic
to triangular pattern (arrowheads). The spleen (SP) and urinary bladder (UB) are annotated. A small volume of iodinated
positive contrast material was within the urinary bladder.
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