surgery in these cases can be a matter of clinical judgment. in the minority of cases with bilaterally nonpalpable testes, further testing to locate the testes, assess their function, and exclude additional problems is often useful. scrotal ultrasound or magnetic resonance imaging performed and interpreted by a radiologist can often locate the testes while confirming absence of a uterus. at ultrasound, the undescended testis usually appears small, less echogenic than the contralateral normal testis and usually located in the inguinal region. with color doppler ultrasonography, the vascularity of the undescended testis is poor. a karyotype can confirm or exclude forms of dysgenetic primary hypogonadism, such as klinefelter syndrome or mixed gonadal dysgenesis. hormone levels (especially gonadotropins and amh) can help confirm that hormonally functional testes are worth attempting to rescue, as can stimulation with a few injections of human chorionic gonadotropin to elicit a rise of the testosterone level. occasionally, these tests reveal an unsuspected and more complicated intersex condition. in the even smaller minority of cryptorchid infants who have other obvious birth defects of the genitalia, further testing is crucial and has a high likelihood of detecting an intersex condition or other anatomic anomalies. ambiguity can indicate either impaired androgen synthesis or reduced sensitivity. the presence of a uterus by pelvic ultrasound suggests either persistent müllerian duct syndrome (amh deficiency or insensitivity) or a severely virilized genetic female with congenital adrenal hyperplasia. an unambiguous micropenis, especially accompanied by hypoglycemia or jaundice, suggests congenital hypopituitarism. treatment the primary management of cryptorchidism is watchful waiting, due to the high likelihood of self-resolution. where this fails, orchiopexy is effective if inguinal testes have not descended after 4–6 months. surgery is often performed by a pediatric urologist or pediatric surgeon, but in many communities still by a general urologist or surgeon. when the undescended testis is in the inguinal canal, hormonal therapy is sometimes attempted and very occasionally successful. the most commonly used hormone therapy is human chorionic gonadotropin (hcg). a series of hcg injections (10 injections over five weeks is common) is given and the status of the testis/testes is reassessed at the end. although many trials have been published, the reported success rates range widely, from roughly 5% to 50%, probably reflecting the varying criteria for distinguishing retractile testes from low inguinal testes. hormone treatment does have the occasional incidental benefits of allowing confirmation of leydig cell responsiveness (proven by a rise of the testosterone by the end of the injections) or inducing additional growth of a small penis (via the testosterone rise). some surgeons have reported facilitation of surgery, perhaps by enhancing the size, vascularity, or healing of the tissue. a newer hormonal intervention used in europe is the use of gnrh analogs such as nafarelin or buserelin; the success rates and putative mechanism of action are similar to hcg, but some surgeons have combined the two treatments and reported higher descent rates. limited evidence suggests that germ cell count is slightly better after hormone treatment; whether this translates into better sperm counts and fertility rates at maturity has not been established. the cost of either type of hormone treatment is less than that of surgery and the chance of complications at appropriate doses is minimal. nevertheless, despite the potential advantages of a trial of hormonal therapy, many surgeons do not consider the success rates high enough to be worth the trouble, since the surgery itself is usually simple and uncomplicated. in cases where the testes are identified preoperatively in the inguinal canal, orchiopexy is often performed as an outpatient and has a very low complication rate. an incision is made over the inguinal canal. the testis with accompanying cord structure and blood supply is exposed, partially separated from the surrounding tissues ("mobilized"), and brought into the scrotum. it is sutured to the scrotal tissue or enclosed in a "subdartos pouch". the associated passage back into the inguinal canal, an inguinal hernia, is closed to prevent reascent. in patients with intra-abdominal maldescended testis, laparoscopy is useful to see for oneself the pelvic structures, position of the testis and decide upon surgery (single or staged procedure ). surgery becomes more complicated if the blood supply is not ample and elastic enough to be stretched into the scrotum. in these cases, the supply may be divided, some vessels sacrificed with expectation of adequate collateral circulation. in the worst case, the testis must be "autotransplanted" into the scrotum, with all connecting blood vessels cut and reconnected (anastomosed). when the testis is in the abdomen, the first stage of surgery is exploration to locate it, assess its viability, and determine the safest way to maintain or establish the blood supply. multistage surgeries, or autotransplantation and anastomosis, are more often necessary in these situations. just as often, intra-abdominal exploration discovers that the testis is nonexistent ("vanished"), or dysplastic and not salvageable. the principal major complication of all types of orchiopexy is a loss of the blood supply to the testis, resulting in loss of the testis due to ischemic atrophy or fibrosis. other animals cryptorchidism is seen in all domestic animals, most commonly in stallions, boars, and canines. the prevalence of this condition can vary depending on species and breed. evidence of this condition is more likely in companion animals and swine than ruminants. the cause of this condition can vary from a combination of genetics, environment, and epigenetics. dogs inguinal cryptorchidism in a chihuahua cryptorchidism is common in male dogs, occurring at a rate up to 10%. this condition is one of the most common congenital defects in purebred dogs (11%), with 14% reported in siberian huskies. although the genetics are not fully understood, it is thought to be a recessive, and probably polygenetic, trait. some have speculated that it is a sex-limited autosomal recessive trait; however, it is unlikely to be simple recessive. dog testes usually descend by 10 days of age and it is considered to be cryptorchidism if they do not descend by the age of eight weeks. cryptorchidism can be either bilateral (causing sterility) or unilateral, and inguinal or abdominal (or both). because it is an inherited trait, affected dogs should not be bred and should be castrated. the parents should be considered carriers of the defect and a breeder should thoughtfully consider whether to breed the carrier parent or not. littermates may be normal, carriers, or cryptorchid. castration of the undescended teste(s) should be considered for cryptorchid dogs due to the high rate of testicular cancer, especially sertoli cell tumors. the incidence of testicular cancer is 13.6 times higher in dogs with abdominally retained testicles compared with normal dogs. testicular torsion is also more likely in retained testicles. surgical correction is by palpation of the retained testicle and subsequent exploration of the inguinal canal or abdomen, but showing altered dogs is against akc rules, making this correction pointless for breeding stock. orchiopexy is an option for pet dogs that will not be used for breeding. commonly affected breeds include: a retained testicle with cancer removed during necropsy of a dog alaskan klee kai boxer chihuahua dachshund (miniature) bulldog maltese miniature schnauzer pekingese pomeranian poodle (toy and miniature) pug shetland sheepdog siberian husky whippet yorkshire terrier cats cryptorchidism is rarer in cats than it is in dogs. in one study, 1.9% of intact male cats were cryptorchid. persians are predisposed. normally, the testicles are in the scrotum by the age of six to eight weeks. male cats with one cryptorchid testicle may still be fertile; however, male cats with two cryptorchid testicles are most likely to be sterile. urine spraying is one indication that a cat with no observable testicles may not be neutered; other signs are the presence of enlarged jowls, thickened facial and neck skin, and spines on the penis (which usually regress within six weeks after castration). most cryptorchid cats present with an inguinal testicle. testicular tumors and testicular torsion are rare in cryptorchid cats, but castration is usually performed due to unwanted behavior such as urine spraying. horses in horses, cryptorchidism is sufficiently common that affected males (ridglings) are routinely gelded. rarely, cryptorchidism is due to the presence of a congenital testicular tumor such as a teratoma, which has a tendency to grow large.