Reproduction System Anomalies in Dogs and Cats

Although generally rare, abnormalities of the reproductive system of dogs and cats occur. Many of these anomalies are found during routine sterilization procedures. Other abnormalities are obvious when examining the animal. These conditions must be considered when making the decision to sterilize your pet, as well as the method of sterilization. In this blog we discuss the most common anomalies affecting sterilized and intact dogs and cats.

  1. Cryptorchidism is the failure of one or both testicles to descend into the scrotum. This condition is seen in all domestic animals and is the most common sexual development disorder in dogs (13%). Unilateral cryptorchidism, where one of the two testicles is retained in the abdomen, is more common. In these cases, the male may still be fertile and can exhibit mating behavior. Bilateral cryptorchidism (both testicles fail to descend) results in sterility. Neutering is the recommended course of treatment for animals with this condition, even with bilateral cryptorchidism, because of the suspected genetic link to the condition and the predisposition to testicular tumors. Animals in this condition should be removed from the breeding pool. The risk of developing testicular cancer is estimated to be at least 10 times greater in animals with this condition. Cryptorchidism occurs in all breeds but toy breeds, including toy Poodles, Pomeranians, and Yorkshire Terriers may be at higher risk. Cryptorchidism is diagnosed with ultrasound and an hCG or GnRH response blood test to determine the level of male hormone. Delaying neutering until 1 year of age is typically recommended for puppies diagnosed with cryptorchidism to give the testicle time to descend into the scrotum. Even if both testicles descend, neutering is still recommended because of the genetic link to the condition.[1] Treatment options to try include adding the herbal formula Epimedium, deer antler velvet, and acupuncture. Jing Tonic foods (eggs, small fish, nuts and seeds, algae, seaweed, Royal jelly, bones and bone marrow) can also help. I have had many cases where the testicle(s) will drop using this protocol for twelve months.


  1. Hermaphroditism, also known as testicular or ovotesticular disorder, is a chromosomal abnormality which results in a puppy developing both testes and ovaries. There are two types of this condition. True hermaphrodites are rare and have both ovarian and testicular tissue and exhibit anomalies of the external genitalia. The most common intersex condition, the male pseudohermaphrodite, has testicular tissue in the abdominal cavity or beneath the skin in the scrotal region, and external genital organs that resemble those of females.[2]  Female pseudohermaphrodites have XX chromosomes and ovaries but the internal and external genitals appear masculine due to excess amounts of testosterone. In mild cases, the pet may just have an enlarged clitoris and otherwise appear normal. In more severe cases, the pet may have a normal appearing penis and even a prostate gland. Ovariohysterectomy, including removing the abdominal testes, is recommended to eliminate the risk of uterine, ovarian, and testicular disease. These dogs are often sterile but should not be bred, even if fertile.


  1. Urogenital anomalies are congenital anomalies that predominantly affect dogs, cats and horses. They are more common in males than females. A urethrorectal fistula is a connection between the lower urinary tract and part of the rectum.  A rectovaginal fistula occurs when a hole forms between the vagina and the rectum. Fluids and feces may pass between these two areas spreading bacteria and preventing your dog from having normal bowel movements. Urinary tract infections are common in animals with these conditions. Both fistulas are classified as congenital. Surgical correction is necessary. Urogenital anomalies were twice as common in cats as in dogs. Ipsilateral renal agenesis is a defect in the development of the kidneys in utero. This condition is linked to developmental deficiencies of the sex organs, and often occurs on the same side of the body as the sex organ deficiency. Ipsilateral renal agenesis was present in 29.4% (10/34) of cats and 50.0% (6/12) of dogs with uterine anomalies in which kidneys were evaluated.[3] Identification of uterine developmental anomalies in dogs and cats should trigger evaluation of both kidneys and both ovaries because ipsilateral renal agenesis is common, but both ovaries are likely to be present and should be removed during ovariohysterectomy.


  1. Abnormalities of the uterus: A 2007 study conducted in the US and Canada looked retrospectively at the records of 53,258 cats and 32,600 dogs undergoing elective ovariohysterectomy at 26 clinics. The study showed prevalence of congenital uterine abnormalities estimated to be about .05% in dogs and almost twice that for cats at .09%[4] Many factors are involved in uterine abnormalities, including genetic, hormonal, environmental and blood flow. Unfortunately, there are no definitive studies that link genetics to congenital uterine abnormalities.

The uterus is Y-shaped, with the arms of the “Y” being longer than the stem. The long arms of the uterus are called the horns (or oviducts), and the short stem is called the body. The uterine horns extend from each ovary and join to form the body of the uterus.  Uterus unicornis (absence of a uterine horn), segmental aplasia (obstruction) of a uterine horn, and uterine horn hypoplasia (underdevelopment) are defects in the development of the uterus. Pregnancy can still occur if sterilization has not been performed.  An ovariohysterectomy (traditional spay) is performed to eliminate the risk of progression of the anomaly (tumors). Malignant endometrial adenocarcinoma is the most common uterine tumor, and prognosis for this condition is guarded. In addition to adenocarcinoma, there are several other types of both benign and malignant tumors that can form. Most dogs and cats affected with tumors are intact and are middle aged or older.[5]

  1. Abnormalities of the ovaries: The most common congenital abnormality of the ovary is ovarian hypoplasia or underdevelopment of the ovary. Ovarian agenesis is a condition in which one or both ovaries are absent. Ovarian cysts are common and their frequency increases with age.  Ovarian cysts are often detected during sterilization surgery; larger cysts can be detected by ultrasound. Ovarian remnant syndrome is detected when a sterilized female starts showing signs of a heat cycle. It is possible that the ovarian tissue was not completely removed during sterilization or ovarian tissue was dropped in the surgical field and that tissue can become functional when not removed. In the past, it was recommended to repeat surgery to remove the ovarian remnant. Knowing what we do now about the protective effects of reproductive hormones, perhaps the ovarian remnant should be left in place to protect against cancers and endocrine disorders.

While reproductive abnormalities are rare, they can occur. Most animals are sterile, but some will need corrective surgery to enjoy a long lifespan.






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