![]() Cox J E, Redhead P H & Dawson F E (1986) Comparison of the measurement of plasma testosterone and plasma estrogens for the diagnosis of cryptorchidism in the horse.Vet Clin North Am Equine Pract 4 (3) 493-513 PubMed. Trotter G W (1988) Normal and cryptorchid castration.Parks A H, Scott E A, Cox J E & Stick J A (1989) Monorchidism in the horse.Equine Vet Educ 13 (1), 32-35 VetMedResource. Mariën T et al (2001) Laparoscopic testis-sparing herniorrhaphy: A new approach for congenital inguinal hernia repair in the foal.Equine Vet Educ 18 (2), 88-89 VetMedResource. Rakestraw P (2006) The value of laparoscopy in equine cryptorchidism and monorchidism.Barakzai S & Perkins J (2006) Equine cryptorchidism.Equine Vet Educ 23 (8), 391-395 VetMedResource. Brommer H, Grinwis G C M, Van Loon V & Ensink J M (2011) Laparoscopic-assisted diagnosis of anomalous unilateral abdominal cryptorchidism.Recent references from PubMed and VetMedResource.Some resolve spontaneously by the age of 3 years others permanent.įurther Reading Publications Refereed papers.Testicular descent after 6 months of age is rare.But descent into the scrotum may not be complete until 1 month (up to 4 years).By 2 weeks after birth, the vaginal ring contracts preventing retraction of testicle into abdomen.At birth about 50% of foals have descended testes.Left testicle slightly larger than right on average with possibilities of increased left sided abdominal retention (75%) and right sided inguinal retention (60%).This gradually reduces allowing complete descent of the testicle into the scrotum. ![]() ![]() The gubernaculum is within the scrotum and can be mistaken at birth for a testicle.Increased fetal abdominal pressure helps push the testicle through the vaginal ring.Epididymis enters the canal first as the gubernaculum grows and dilates the vaginal ring and canal.Descent begins at 270-300 days gestation.From 6 weeks of gestation the testicle increases rapidly in size and by 8 months is as large as an adult testicle.Attached to body wall by mesenchyme which becomes gubernaculum, which guides descent through the inguinal canal and then becomes the epididymal ligament.Suspended by mesorchium (fold of peritoneum) from the dorsal abdominal wall.Testes develop at the caudal pole of the kidney at approximately 5.5 weeks of gestation.Usually unilateral (5-20 (15)% bilateral).Note that the epididymis does not produce testosterone, and retention of epididymal tissue cannot account for persistence of stallion-like behavior.Cause uncertain, may be genetic, hormonal or multifactorial.Failure of one or both testes to descend to scrotal position.Other congenital or developmental defects.History of cryptorchidism in lineage of either parent.Failure of testicle to regress to a sufficiently small size to transverse the vaginal ring including testicular teratoma Teratoma.Persistence of suspensory ligament of testis preventing migration.Combined with other congenital abnormalities such as intersexuality Reproduction: gonadal dysgenesis.Abnormal fetal and/or maternal hormones.Genetic predisposition - complex and involves multiple genes.Improper function of the gubernaculum particularly regression.
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