Page 115 - January 2021

EQUINE HEALTH
A study that looked at more than 5,000 cryptorchid horses found the highest number in:
Percherons
Quarter Horses
Saddlebreds
Ponies
a grapefruit-size mass of fetal material) forms in the abdominal cavity where the testicles origi- nally develop. This type of tumor starts early, in the fetus, and may continue to grow during the life of the horse. The tumor may become life-threatening if it becomes large and puts pressure on other organs or becomes malig- nant. “Normally, testicular cancer in horses is not malignant, but there have been cases where these tumors have metastasized,” says Tibary.
Yarbrough says another concern with cryptorchids is the possibility of testicular tor- sions, because the testicle is not tethered down. “It can become twisted or become the focus
of entrapment for a section of small intestine. These are the possible long-term health risks for the abdominal cryptorchid,” he says. The horse owner needs to be aware of these risks.
Tibary says the cause of this type of colic may not be discovered until the horse goes to surgery to correct the colic problem. “Most of the time this would be an incidental finding, when the horse is opened up for colic surgery. You would not suspect this, unless you know the horse is a cryptorchid,” he says.
DIAGNOSIS
If you are uncertain about whether a horse
is a cryptorchid (a young colt that has only one testicle in the scrotum, or you’ve purchased a gelding that shows stallion-like behavior) he can be checked by a veterinarian. Careful palpation of the scrotum and the tissues above it, and rectal palpation to check the pelvic area can give a clue. But a retained testicle is sometimes hard to pal- pate in the standing horse. If it’s in the abdomen, it is usually suspended by a fold of peritoneum (the membrane that lines the abdominal cavity).
According to Tibary, rectal ultrasound can often help locate it, but not in all cases. The tes- ticle is somewhat mobile within the abdomen and may be hard to spot if it has become mixed up with coils of intestine or lies beside the blad- der. In some cases, it adheres to the wall of the abdomen or to an internal organ, such as the spleen, and can be hard to identify. A retained testicle within the abdomen is usually small, flabby and undeveloped, but in some cases, it can be very large if it becomes tumorous.
“There is a test that can be used to differ- entiate between a completely gelded horse and one that has a retained testicle in the abdomen. What you look for in the test is the response
of the horse to an injection of HCG (human chorionic gonadotropin), to know if he still
has some testicular tissue. Blood samples are taken before administration of HCG and again one to two hours after. If you see a 2 to 3-fold increase in testosterone, you are dealing with a horse that has a retained testicle,” says Tibary.
“There are other hormonal tests, but I like this one because it is very simple and works well. If interpretation of the testosterone level is not clear enough with the HCG, then the other tests can be done,” he says. Some fully castrated males still have some stallion-like behavior. If you buy a gelding and wonder if he is truly a gelding or a cryptorchid, the hormone tests are useful.
Yarbrough says that any time we are faced with a case where there’s questionable history on the horse - if we don’t know if he was com- pletely gelded or not, or whether both testicles were actually removed - we can run a hormone profile. “If the hormone profile comes back indicating there’s a testicle present, we go in with a laparoscope to explore for it.”
If only one testicle was removed in an earlier castration, you probably don’t know which side it was on. Using a laparoscope makes it easier
to find the missing one. And if a stallion has only one testicle in the scrotum, you don’t know whether this might be a rare case of monorchi- dism (in which the horse had only one testicle to begin with). A hormone assay can tell you whether to go looking, or not, says Yarbrough.
SURGICAL REMOVAL
Most owners of a cryptorchid opt to have the retained testicle removed. A testicle caught in the inguinal canal is easiest. The veterinar- ian reaches into that canal to search for the missing testicle and works it out through the canal. “These can often be palpated or located using ultrasound, placing the ultrasound on the scrotal area,” says Tibary.
Yarbrough says the standard inguinal approach to search for the missing testicle is the oldest method. The horse is on its back, anesthetized. “Most practitioners will cut very close to or immediately over the external in- guinal ring and go down the canal looking for the inguinal extension of the gubernaculum
- that little cord. They follow it to the internal ring. If the horse is a high flanker you encoun- ter the testicle before you get to the abdomen, but otherwise you’d follow the canal right
on into the abdomen to the internal inguinal ring. Once you have identified that structure, you can nip the internal sheath and tease the testicle out,” says Yarbrough.
Even if the one descended testicle has been removed, the horse will still act like a stallion.
SPEEDHORSE January 2021 113