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Help, My Dog Has Only One Testicle

Dog Has Only One Testicle

If your dog has only one testicle, you may be concerned about it. Whether your dog is for breeding or you just plan on having a companion and will be getting him neutered one day, you might have been keeping an eye on your dog's growth rate and whether both of his testicles have descended. You are rightfully concerned if you notice your dog has only one testicle. There are several potential consequences that may result, but the good news is that in many cases, the other testicle will descend soon, given the allotted time. Following is some information from veterinarian Dr. Fernandez about dogs with only one testicle.


When do Dog Testicles Descend?

By Dr. Joanne Fernandez

Help! My dog has only ONE testicle! Not to worry. Testes typically descend into the scrotum by 6 to 16 weeks of age in puppies. In dogs, descent can occur as late as 10 months of age, but that time frame is abnormal. Typically, late testicular descent and undescended testes are heritable defects.

The condition is called cryptorchidism. This is a common congenital genital defect in male dogs. It is diagnosed if either or both testes are not present in the scrotum at puberty.

But what causes cryptorchidism in dogs in the first place? Cryptorchidism is caused by incomplete migration of the testicle as outlined below.

Why My Dog Has Only One Testicle?

Cryptorchidism is caused by incomplete migration of the testicle at one of the following pathways. It may happen that testicular hormone insulin-like factor 3, produced by Leydig cells, which mediate testicular descent from the caudal pole of the kidney to the inguinal canal (the area located close to the pelvis) will cause a retained testicle in the abdominal area.

The migration of fetal testes is independent of androgen presence, but the one from the inguinal canal to the scrotum is mediated by testosterone. When there is a defect in this pathway, the testicle will stay in the inguinal canal. During a physical examination, the doctor will be able to palpate it in this location.

Now, what goes wrong exactly in the pathway? Risk factors include the use of drugs with anti-androgenic effects during pregnancy like cimetidine, flutamide, finasteride, progestagens, diethylstilbestrol, estradiol cypionate.

There may be also genetic factors at play like an autosomal recessive trait causing the defect. Breed predisposition: mixed breeds 3.9%, purebred dogs 8.7% (toy and miniature breeds have higher rate of occurrence), cats 1.3%

Diagnosis of Dog Cyptorchidism

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How is cryptorchidism diagnosed when both testes do not descend or when we are not sure if the affected dogs were neutered in the past?

Localization of one or both cryptorchid testes on ultrasonography can confirm the condition in pediatric patients with unilateral or bilateral involvement and can assist the surgeon in planning the approach if testes are present.

This is important since the veterinarian needs to determine if he needs to perform a pre-scrotal (cryptorchid that is in the inguinal area) versus a cranial abdominal incision (cryptorchid inside the abdomen).

However, there is still the possibility that ultrasound of the abdomen alone can miss cryptorchid testes in the inguinal canal because of interference from the bony pelvis. Remember, retained testes can be positioned anywhere between the caudal kidney and the scrotum.

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Treatment for Undescended Testicles in Dogs

My dog has only one testicle how is this treated? Unfortunately, surgery is the only way to treat this condition. Consequences of not neutering a cryptorchid male dog are perpetuation of the hereditary defect to the following generations. They can still reproduce as usual.

I typically perform neuters at 6 months of age. By this time, testes are supposed to have descended already. If not, I discuss the need for diagnosing through ultrasound if is not felt during the physical exam and the need for cryptorchid surgery.

At all clinics, this will incur in an additional fee due to the increased in surgery time, anesthesia and suture material compared to a routine standard neuter. If castration is not an option for the owner, the cryptorchid males should be isolated from receptive females to prevent unwanted pregnancies.

If left untreated, the retained testicle may develop complications such as neoplasia (dog testicular cancer) and/or an enlarged prostate.

"Dogs who are 'cryptorchid' (meaning those that only drop one testicle) have this trait within their genes, meaning if it were possible to breed from them then they would pass this trait on to puppies they father."~Dr M D Edwards


  • Canine Cryptorchidism. Davidson, Autumn. Clinician’s Brief, January. 2014. Web. 09 September. 2017.
  • Clinical conditions of the dog and tom. Davidson AP. In Nelson RW, Couto CG (eds): Small Animal Internal Medicine, 5th ed—Mosby, 2013 (in press).
  • Origin of alkaline phosphatase of canine seminal plasma. Frenette G, Dubé JY, Tremblay RR. Arch Androl 16:235-241, 1986.

About the author 

Dr. Joanne Fernandez-Lopez is an emergency veterinarian on staff in the Emergency and Critical Care Department at Florida veterinary Referral Center (FVRC).

joanne fernandez

Originally from Puerto Rico, Dr. Joanne Fernandez-Lopez graduated from North Carolina State University – College of Veterinary Medicine in Raleigh, NC. Prior to joining FVRC, Dr. Fernandez-Lopez worked in small animal general practice and as a relief doctor in South East Florida. Her professional interests include dermatology, surgery, internal medicine, preventive medicine, reptile medicine and practice management.

In her free time, Dr. Fernandez-Lopez enjoys relaxing at the beach, paddle boarding, kayaking, and surfing. She has a small Tibetan spaniel mix named Carlitos.

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