What is the "train track" in the retained equine testis?
Authors: Giorgio S Di, Monti S, Palmieri V, Marino G, Napoli E, Vullo C, Catone G
Journal: Journal of equine veterinary science
Summary
# Editorial Summary A 3-year-old Quarter horse presented with unilateral cryptorchidism (absence of the left testis from the scrotum), and ultrasonographic examination revealed an intratesticular finding that resembled a foreign body: two parallel hyperechogenic lines within a poorly demarcated, non-homogeneous testicular region. Following laparoscopic removal and necropsy of the retained testis, two live adult *Strongylus vulgaris* nematodes were recovered from blood-filled tracks running through the testicular parenchyma, with histopathology confirming lymphoplasmacytic infiltration and haemorrhage surrounding the parasitic migration tunnels. Whilst *S. vulgaris* erratic migration in cryptorchid stallions has been documented, this localisation remains rare in the literature, and this case is notable for characterising the distinctive ultrasonographic appearance of parasitic tracks within retained testicular tissue. Understanding this unusual presentation has clinical relevance for practitioners managing cryptorchid stallions, particularly regarding differential diagnosis of intratesticular lesions and the potential parasitic complications of non-descended testes, though practitioners should recognise this remains an uncommon finding.
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Practical Takeaways
- •Cryptorchid stallions with ultrasonographic evidence of unusual parallel hyperechogenic lines within the retained testis should be evaluated for possible parasitic migration, particularly S. vulgaris
- •Laparoscopic removal remains a viable diagnostic and therapeutic approach for retained testes with suspected parasitic involvement
- •Clinicians should be aware that aberrant S. vulgaris localization in retained testes, while uncommon, is possible and may present with non-homogeneous testicular ultrasound findings
Key Findings
- •A retained abdominal testis in a 3-year-old Quarter horse stallion contained two live adult Strongylus vulgaris nematodes within blood-filled tracks in the testicular parenchyma
- •Ultrasonography revealed two parallel hyperechogenic lines resembling a cylindrical cavitary foreign body within a non-homogeneous testicular area
- •Histologically, the parasite tracks were characterized by lymphoplasmacytic infiltrates with abundant hemorrhage invading surrounding testicular structures
- •This case represents one of the few documented reports of S. vulgaris aberrant migration into a cryptorchid equine testis, confirming the rarity of this localization