Introduction

A 1-year-old 50.8-kg (111.8-lb) apparently sexually intact and externally female Great Dane was referred for further evaluation of abnormal and underdeveloped internal reproductive organs. At 18 weeks of age, results of presurgical testing, including a CBC, serum biochemical panel, and assessments of prothrombin time and partial thromboplastin time, were unremarkable. A laparotomy was performed by the referring veterinarian for an elective incisional gastropexy and ovariohysterectomy. On gross examination, the reproductive tract was reportedly underdeveloped. Structures resembling uterine horns and ovaries were identified and described as small, discolored, and firmly attached to the body wall. Because of these abnormalities, the incisional gastropexy was completed but gonadectomy was not performed.

At the referral evaluation, the owner reported that the dog had had no signs of estrus. Physical examination revealed that the vulva was cranioventrally displaced (Figure 1). A grade 2/6 left apical systolic murmur was ausculted. Abdominal ultrasonography was performed, but no uterus or ovaries were identified. The dog underwent CT with retrograde positive-contrast vaginourethrography, which revealed an underdeveloped uterus (Figure 2) and a suspected left intra-abdominal gonad at the level of the sixth lumbar vertebra (Figure 3); no gonadal structure was evident on the right side. A whole blood sample was collected and submitted for karyotyping by means of cytogenic and PCR-based analyses. Karyotyping revealed a normal chromosome number and morphology with an abnormal mix of male and female sex chromosomes. The lymphocytes were noted to carry 2 cell lines: genetically male cells (70%) and genetically female cells (30%). A diagnosis of 78,XX/78,XY chimerism was made. Sex hormone analyses were performed. Analysis of a serum sample yielded positive results for anti-Müllerian hormone. Serum estradiol concentration was 48.2 pg/mL (reference intervals, 31.5 to 65.4 pg/mL for sexually intact females; 30.8 to 69.9 pg/mL for spayed females; 30.5 to 66.6 pg/mL for sexually intact males; and 23.1 to 65.1 pg/mL for neutered males). Serum progesterone concentration was < 0.2 ng/mL (reference intervals, < 1.0 ng/mL for anestrous females; 2.0 to 3.0 ng/mL for females undergoing a luteinizing hormone surge; and 5.0 to 12.0 ng/mL for ovulating females). Serum testosterone concentration was < 20 ng/dL (reference intervals, < 20 ng/dL for neutered males; 20 to 100 ng/dL for cryptorchid males; and > 40 ng/dL for sexually intact males). Results of an echocardiographic examination indicated that the dog had apparently normal cardiac structure and function. The ausculted murmur was suspected to be a physiologic flow murmur.

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Photographs of the caudal (A) and ventral abdominal (B) aspects of a 1-year-old apparently sexually intact Great Dane with a ventrally and cranially displaced vulva. The dog was referred for further evaluation of previously identified abnormal and underdeveloped internal reproductive organs.

Citation: Journal of the American Veterinary Medical Association 258, 1; 10.2460/javma.258.1.80

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Computed tomographic views of the dog in Figure 1 obtained with positive-contrast retrograde vaginourethrography in a soft tissue algorithm and transverse plane. A—The urethra (dashed arrow) and cervix and uterine body (solid arrow) at a level dorsal to the pubis and just caudal to the left and right acetabulae are filled with contrast material. B—This view is of the urethra (dashed arrow) and cervix and uterine body remnant (solid arrow) at a level just cranial to the pubis; notice the minuscule size of the uterine body and lack of contrast medium in its lumen.

Citation: Journal of the American Veterinary Medical Association 258, 1; 10.2460/javma.258.1.80

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Computed tomographic views of the dog's abdomen obtained with a soft tissue algorithm and in the sagittal plane (A) and with a soft tissue algorithm and in the transverse plane (B). In panel A, the presumed gonad (arrow) and its location are evident. In panel B, notice the left-sided intra-abdominal soft tissue structure consistent with a gonad (solid arrow) and a right-sided intra-abdominal soft tissue structure consistent with a gonad (dashed arrow). Asterisks denote nearby loops of the small intestine. In panel A, the distance between the caudal pole of the left kidney and the left gonad (double-headed arrow) is 14.5 cm.

Citation: Journal of the American Veterinary Medical Association 258, 1; 10.2460/javma.258.1.80

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The dog was anesthetized and underwent laparoscopic gonadectomy. By use of a single-port^a technique¹ and a 5-mm, 30° endoscope,^b both the right and left intra-abdominal gonads were easily identified (Figure 4). The right and left gonads were approximately midway between the caudal pole of the respective kidney and the inguinal canal, and these positions were caudal to the normal anatomic locations of ovaries. The gonads each appeared small (approx 5 mm in length) with a large vascular pedicle or plexus (similar to a pampiniform plexus) extending dorsally to the great vessels. Underdeveloped, ligamentous uterine horn–like structures were also present. A gonadectomy was performed in a similar manner as a laparoscopic ovariectomy with a bipolar vessel-sealing device^c and articulating forceps^d to hold and manipulate the gonadal tissue. Both gonads were submitted for histologic examination and were determined to be rudimentary testicles in an ovarian bursa with structures consistent with seminiferous tubules, epididymis, pampiniform plexus, and ovarian tubes (Figure 5). The seminiferous tubules were lined by large numbers of spindleshaped Sertoli cells with scant numbers of spermatogonia and no spermatids within the seminiferous tubules or epididymis. On the basis of the board-certified veterinary pathologist's report, the rudimentary testicles did not have enough elements to be classified as ovotestes. By definition, an ovotestis must contain both seminiferous tubules and oocytes.² In the tissue removed from the dog, no primary, secondary, or antral oocytes were observed.

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Intraoperative images of the dog obtained during laparoscopic gonadectomy. The left gonad (A and B) and right gonad (C and D) are visible, each with a vascular plexus or pedicle. The ligamentous uterine horns are underdeveloped.

Citation: Journal of the American Veterinary Medical Association 258, 1; 10.2460/javma.258.1.80

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Photomicrographs of sections of the left (A, C, and D) and right (B) gonads. There are structures consistent with pampiniform plexuses (A [white arrowhead] and B). Seminiferous tubules with large numbers of Sertoli cells and few spermatogonia are present (C [black arrowhead in panel A]). Other structures are consistent with an epididymis (D). H&E stain; bar = 1,000 μm in panels A and B and 50 μm in panels C and D.

Citation: Journal of the American Veterinary Medical Association 258, 1; 10.2460/javma.258.1.80

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The dog's recovery from anesthesia and surgery was uneventful, and it was discharged from the hospital the following day. At 2 months after hospital discharge, the owner reported that the dog was doing well with no complications or observed signs of estrus. Following surgery, the owner noted reduction in the size of the dog's vulva. The remainder of the dog's physique and demeanor remained unchanged.

Discussion

To the authors’ knowledge, this is the first report describing laparoscopic gonadectomy in an externally female Great Dane with abnormal and underdeveloped internal reproductive organs (evidence of a DSD). Disorders of sexual development are congenital conditions, and development of chromosomal, gonadal, or phenotypic sex in affected animals is atypical. Dogs with DSDs have variable reproductive organ abnormalities, some of which can be easily identified on gross examination and with abdominal imaging techniques.^3,4,5 For the dog of the present report, abdominal ultrasonography did not identify a uterus or gonadal structures, and evaluation of an abdominal CT scan failed to definitively detect gonadal structures. Karyotyping revealed the dog was a 78,XX/78,XY chimera; results of sex hormone analyses were consistent with findings for either a sexually intact female or a neutered male dog.

In the case described in the present report, laparoscopic surgery provided detailed visualization of internal organs, which in turn facilitated accurate identification of the gonads for subsequent removal. The use of an open surgical approach was not favored, possibly as a consequence of the perception that visualization of the gonadal structures would be impaired because of the short incision length or the surgeons’ limited experience with gonadectomy in dogs with DSDs. General advantages of laparoscopic surgery over open surgery include small incisions without compromise of the visual field and illumination and magnification for augmented visualization of organs of interest. In the dog of the present report, the suspected left gonad located at the level of the sixth lumbar vertebra on CT images was sought first for removal. The gonad was present just caudal to the region in which the left ovary would typically be located and was confirmed to be a gonad on the basis of its vascular anatomy and ligamentous uterine structure. The right gonad was also easily identified in the region caudal to the expected location of a right ovary. With a laparoscopic approach, evaluation of the abdominal gutter on either side of the body from an area caudal to the kidney to the inguinal ring is easily achieved with appropriate lateral rotation of the patient during the procedure. Laparoscopic procedures have been described as useful for the identification and removal of ovarian remnants, which can be difficult to detect with abdominal imaging techniques or during standard exploratory laparotomy because of the small size of the tissues in some cases.^6,7,8 In human medicine, traditional and laparoscopic surgery are the gold standards for identification and removal of undescended testicles and treatment of people with DSDs.^9,10 Laparoscopy is used for identification and visualization of intra-abdominal gonads to facilitate biopsies, gonadopexies, and excisions.¹⁰

Among diagnostic imaging techniques, CT is the most sensitive for diagnosis of cryptorchidism in people.⁹ During retrospective review of the abdominal CT images obtained from the dog of the present report, the intra-abdominal left gonad was evident 14.5 cm caudal to the left kidney, which is caudal to the area on which sonographers typically focus for imaging of ovaries. The more caudal locations of both gonads in the dog's abdomen may have also contributed to the negative results of abdominal ultrasonography. In addition, a soft tissue structure, which possibly correlated with the right gonadal structure, was identified at the level of the sixth lumbar vertebra, caudal to the right kidney, just caudal to the cecum, and adjacent to several small intestinal loops. Although vaginourethrography was helpful in identifying the uterus, CT angiography would have likely been helpful in identifying the gonads through detection of the gonadal arteries originating from the caudal portion of the aorta. In reports^11,12 of 2 dogs with abdominal masses, the origin of the mass could not be determined with abdominal ultrasonography in 1 dog; however, CT angiography was useful in identifying the masses as testicles on the basis of their vascular characteristics in both dogs.

Reliable methods for identification and proper removal of gonadal tissue are important not only for treatment of DSDs, but also for prevention of pyometra, testicular or ovarian neoplasia, mammary neoplasia, vaginal neoplasia, and unwanted behaviors. For example, on the basis of survival rates calculated from animal insurance claims in Sweden, it is estimated that 23% to 24% of sexually intact female dogs require treatment for pyometra by the age of 10 years.¹³ Even with small amounts of active ovarian tissue, such as that associated with ovarian remnant syndrome, there is an increased risk for unwanted behaviors and development of pyometra and ovarian, mammary, or vaginal neoplasia.¹⁴ In male dogs, undescended testicles have a high incidence of neoplasia (9.2% to 13.6%).¹⁵ In addition, the biological behavior of neoplasms in undescended testicles may be more aggressive than that of neoplasms in testicles located in the scrotum.¹⁶ Similarly, in humans with DSD, testicular dysgenesis and undescended testicles have a higher incidence of neoplasia.¹⁷ Testicular neoplasia in at least 2 male pseudohermaphrodites has been reported.^18,19

The prevalence of histologic malignant features of gonads excised from humans with complete androgen insensitivity syndrome (ie, phenotypic females with an XY genotype and testicular tissue) is reportedly low. In 1 study²⁰ of 133 patients with complete androgen insensitivity syndrome who had undergone gonadectomy, the combined prevalence of premalignant and malignant histologic features was 6% and the prevalence of malignant histologic features was 1.5%. The recommendation for these patients is monitoring rather than early gonadal excision,²⁰ and regular monitoring with imaging techniques such as MRI or abdominal ultrasonography has been suggested.²¹ Assessment of biomarkers and use of microRNA-based blood tests are currently being investigated for detection of early malignancy changes in humans.^22,23,24,25 The case described in the present report involved a 1-year-old externally female Great Dane with 78,XX/78,XY chimerism and has highlighted that laparoscopic surgery appears to be ideal for both confirmation of the diagnosis of abnormal and underdeveloped reproductive organs and gonadectomy in dogs with this type of DSD.