Cryptorchidism In Dogs And Cats
Cryptorchidism occurs when testicles fail to enter the scrotum and instead are retained in the abdomen. Equivalent terms are “retained testicle(s)” and “undescended testicle(s).”
Crypto, from the Greek kryptos, means “hidden.” The Greek word orkhis means “testicle.”
In mammalian embryos (people, dogs, cats, cattle, horses, etc.), gonads of both genders begin life immediately below each kidney.
In the female dog and cat, ovaries never move far, residing between the caudal pole of the kidney and the Fallopian tube attached to the uterus.
Testicles, or the other hand, don’t belong inside the abdomen. Rather, they need to be securely anchored in the cooler environment of the scrotum. To get there, the gubernaculum (a ligament-like structure also called the epididymal ligament) exerts a tug by shortening itself during development. Meanwhile, the spermatic cord, consisting of the spermatic artery and vein, and the vas deferens, lengthen to accommodate the new position.
To leave the abdomen, all of these structures must pass through a natural opening called the inguinal canal. In some individuals the inguinal canal, and its termination, the inguinal ring, present a tight fit, and one or both testicles may not pass through. Other factors, including failure of the gubernaculum to shorten sufficiently, may cause testicle(s) to fail to reach the scrotum.
A retained testicle may reside in its original, embryonic position near the kidney, just inside the inguinal ring, just outside the inguinal ring (under the skin between the inguinal ring and scrotum) or anywhere else along this path.
Retained testicles are predisposed to two types of cancer and torsion of the testicle. Testicular torsion, or twisting, results in a painful, potentially life-threatening condition that requires immediate emergency surgery.
Sertoli cell tumor is an abnormal growth of the “nurse,” or “mother” cells of the testes. Their normal function is to help sperm cells through their maturation process. This cancer is especially dangerous because of its tendency to metastasize, or spread.
Another tumor type is the seminoma, a tumor of undifferentiated germ cells, cells that would, in a healthy pet, have turned into sperm cells. While a seminoma may sometimes grow quite large, the likelihood of metastasis is low in most patients.
Regardless of where a retained testicle resides, it must be surgically removed. The only exception would be a patient for whom anesthesia and surgery would be life-threatening. Otherwise, risking cancer and/or torsion of the testicle is not an option.
In my opinion, removing a retained testicle while leaving another testicle in the scrotum is also not an option. Research evidence points to a very strong likelihood that cryptorchidism is inheritable. Therefore, any offspring such a surgically altered male pet might sire would pass on the gene for cryptorchidism, and perpetuating the cryptorchidism cycle.
In patients with retained testicles between the inguinal ring and the scrotum, surgical removal consists of little more than a skin incision over the organ, a ligature on each side, followed by removal.
Testicles inside the abdomen, however, present a much larger surgical challenge. Far and away the vast majority of them will be just inside the inguinal ring. However, surgery there is challenging because of the large pudendal artery and vein, which pass near.
For testicles not found there, a search ensues. As stated above, these testicles can be anywhere along the prescribed path. I once performed surgery on a toy poodle with both testicles still residing in their embryonic location, right against the kidneys.
If either testicle has an abnormal appearance, it should be submitted for histopathology.
It is imperative that these pets have a surgical tattoo, indicating that both testicles have been surgically removed.
See you tomorrow, Dr. Randolph.