History
An 8-month-old spayed female Wheaten Terrier was evaluated because of a mass protruding from the urogenital tract. The owners associated the mass with the dog's reluctance to maintain a sitting posture. Three months prior to evaluation, the dog was neutered. At that time, the reproductive tract appeared abnormal and was submitted for histologic evaluation. Results indicated that the uterus was normal; however, the gonads were identified as testes. The testes were devoid of germ cells; ovarian structures were absent. On the basis of those findings, the dog was considered as a male pseudohermaphrodite.
On physical examination, a fleshy protuberance extending caudally between the labia of the vulva was detected. A small elliptical slit at the tip of the protuberance resembled the external urethral orifice. When voiding, urine exited the vulva normally. Radiographs of the perineal area were obtained (Figure 1).
Right lateral (A) and ventrodorsal (B) radiographic views of an 8-month-old dog evaluated because of a mass protruding from the urogenital tract.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Right lateral (A) and ventrodorsal (B) radiographic views of an 8-month-old dog evaluated because of a mass protruding from the urogenital tract.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Right lateral (A) and ventrodorsal (B) radiographic views of an 8-month-old dog evaluated because of a mass protruding from the urogenital tract.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Radiographic Findings and Interpretation
A curvilinear mineral opacity can be seen extending caudally within the sagittal plane of the perineal region (Figure 2). Differential diagnoses for the mineral opacity in the perineal region included os clitoris, os of a rudimentary or malformed penis, foreign body, dystrophic mineralization of perineal structures, urethral calculi, or radiographic artifact. Considering that the dog was phenotypically female with the gonads of a male, radiographic findings were most consistent with an os clitoris or os penis in a dog with ambiguous genitalia.
Same lateral radiographic view as in Figure 1. Notice the linear mineralized opacity (arrow). 1384 Vet Med Today: What Is Your Diagnosis?
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Same lateral radiographic view as in Figure 1. Notice the linear mineralized opacity (arrow). 1384 Vet Med Today: What Is Your Diagnosis?
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Same lateral radiographic view as in Figure 1. Notice the linear mineralized opacity (arrow). 1384 Vet Med Today: What Is Your Diagnosis?
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Comments
Contrast urethrography was performed during anesthesia to identify the location and integrity of the urethra prior to removal of the mass. Initially, the slit at the end of the protuberance was catheterized; however, it ended blindly 0.5 cm proximal to its opening. Because the mass obscured localization of the external urethral orifice, contrast agent was injected into the urinary bladder transabdominally by use of a needle and syringe. The urethra appeared normal and contrast material was evident in the vagina (Figure 3). The mass was surgically removed and submitted for histologic evaluation. Microscopically, the mass had features of both a clitoris and a penis. An os penis or os clitoris was also identified.
Positive contrast cystourethrogram obtained from the dog in Figure 1. Notice the urethral opening (arrow). Contrast material can also be seen in the vagina. Because the mass obscured localization of the external urethral orifice, contrast agent was injected into the urinary bladder transabdominally by use of a needle and syringe.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Positive contrast cystourethrogram obtained from the dog in Figure 1. Notice the urethral opening (arrow). Contrast material can also be seen in the vagina. Because the mass obscured localization of the external urethral orifice, contrast agent was injected into the urinary bladder transabdominally by use of a needle and syringe.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
Positive contrast cystourethrogram obtained from the dog in Figure 1. Notice the urethral opening (arrow). Contrast material can also be seen in the vagina. Because the mass obscured localization of the external urethral orifice, contrast agent was injected into the urinary bladder transabdominally by use of a needle and syringe.
Citation: Journal of the American Veterinary Medical Association 229, 9; 10.2460/javma.229.9.1383
An individual's genotype determines gonadal differentiation. Gonadal differentiation, in turn, determines the phenotype of external genitalia. Intersex conditions develop when there is a discrepancy at any of these levels.1
Pseudohermphroditism results when chromosomal and gonadal sex are identical, but the phenotype is characteristic of the opposite sex. Male pseudohermophroditism has been described in Miniature Schnauzers2 with a 78, XY genotype and testes. For reasons that are not known, the testes fail to produce sufficient amounts of androgens to masculinize the undifferentiated reproductive tract in the embryo, resulting in persistence of the female phenotype. Female pseudohermaphroditism can occur if excessive amounts of androgens are present during the development of a female fetus. This results in masculinization of the external, but not the internal, genitalia.3
True hermaphrodites and sex reversals result from discrepancies between genotype and gonadal differentiation. The presence of both ovarian and testicular tissue is the hallmark of a true hermaphrodite. Histologically, dogs may have 1 testis and 1 ovary or ovotestes.
Sex reversal occurs when the gonadal and phenotypic sex agree, but chromosomal sex corresponds to the opposite gender. In some cases, 1 or more genes responsible for masculanization translocate onto an autosomal chromosome.4 Although the SRY gene is often implicated, SRY-negative XX–sex reversal dogs have been reported.5–7 Affected individuals have testes, epididymes, and ductus deferens of the male with an XX genotype and a uterus. These dogs are considered female, but may have abnormal male external genitalia such as a vestigial penis and hypospadias. Sex reversal has been identified in Cocker Spaniels, Beagles, German Shorthair Pointers, Kerry Blue Terriers, Pugs, and Weimeraners.2,4 In the dog reported here, chromosomal analysis of peripheral blood leukocytes revealed a 78, XX karyotype, indicating that the dog was genetically female and, therefore, an XX sex reversal, not a male pseudohermaphrodite.
- 1↑
Meyers-Wallen VN, Patterson DF. Disorders of sexual development in the dog. In: Morrow D, ed.Current therapy in theriogenology. Philadelphia: WB Saunders Co, 1986;567–574.
- 2↑
Sommer MM, Meyers-Wallen VN. XX true hermaphro-ditism in a dog. J Am Vet Med Assoc 1991;198:435–438.
- 3↑
Roberts SJ. Veterinary obstetrics and genital diseases. 3rd ed. North Pomfret, Vt: Edwards Brothers, 1986;709–710.
- 4↑
Meyers-Wallen VN, Patterson DF. XX sex reversal in the American Cocker Spaniel dog: phenotypic expression and inheritance. Hum Genet 1988;80:23–30.
- 5
Kothapelli KSD, Kirkness E, Natale LJ, et al. Exclusion of P1SRTi as a candidate locus for canine SRY-neg XX sex reversal. Anim Genet 2003;34:467–476.
- 6
Meyers-Wallen VN, Bowman L, Acland GM, et al. Sry-negative XX sex reversal in the German Shorthair Pointer dog. J Hered 1995;86:369–375.
- 7
Selden JR, Wachtel SS, Koo GC, et al. Genetic basis of XX male syndrome and XX true hermaphroditism: evidence in the dog. Science 1978;201:18.
