Ultrasound Evaluation of the Reproductive Tract of Three Female Lowland Gorillas (Gorilla gorilla)
Numerous reports describe the reproductive behavior of lowland gorillas (Gorilla gorilla) and the attempts to promote assisted reproductive techniques. Fundamental to any of these techniques is a basic gynecologic exam. Sonography is an essential part of that evaluation which may be overlooked for various reasons, perhaps most notably the lack of familiarity with anatomical differences between human and gorilla females. Sonography has been described in pregnancy confirmation3,4 or utilized for oocyte retrieval1-3. Little has been reported about the use of sonography in the routine examination of female gorillas.
Three female lowland gorillas were each subjected to a reproductive exam as part of a routine health care program and to specifically evaluate infertility in the troop at Busch Gardens, Tampa, Florida (BGT). Each female was immobilized with 2.0–2.3 mg/kg tiletamine-zolazepam (Telazol, Ft. Dodge Animal Health, Ft. Dodge, IA, USA), 0.5–0.8 mg/kg xylazine (Xylazine-100, Ben Venue Laboratories, Inc., Bedford, OH, USA) and 1.5 mg atropine (Atropine LA, AmVet Scientic Products, Yaphawk, NY, USA). Ketamine (Ketaset, Ft. Dodge Animal Health, Ft. Dodge, IA, USA) was given at 2 mg/kg IV as needed to allow intubation with a 10 mm tracheal tube and each were maintained on 0.5–2.0% isoflurane (IsoFlo, Abbott Laboratories, North Chicago, IL, USA) and 6.0 L/minutes of oxygen for the duration of the examination. The first two animals were injected by hand syringe with the induction dose while the third required darting. The anesthesia was unremarkable in the first two animals but the third female developed fatal complications.
Initial evaluation of the external genitalia of the first gorilla revealed a normal appearing labia majora with a clitoris and a patent vaginal introitus with a somewhat internal urethra meatus. This urethral meatus was ultimately catheterized with a 3 Fr straight catheter, which was then replaced with a 5 Fr straight catheter and the bladder drained. Examination revealed a palpable cervix at the apex of the vagina. Further bimanual manipulation was unable to delineate any other significant findings. Vaginal probe sonography was then performed revealing normal appearing ovaries bilaterally and an apparently normal uterus in somewhat of a retroverted position. The speculum examination was then performed using a small disposable Pederson speculum and after some manipulation, the posterior lip of the cervix was visualized and grasped with a single-toothed tenaculum. Using the single-tooth tenaculum, the cervix could be displaced into somewhat of a posterior position, bringing the cervical os into the field of vision. The os was swabbed with an iodine swab and a Soule’s catheter placed within the uterine cavity. Saline infusion sonography was performed transrectally with a standard 5 mHz transvaginal probe designed for use in human females. Intracavitary abnormalities were absent and the endometrial cavity appeared smooth. After installation of the saline, fluid was noted within the cul-de-sac, indicative of a patent tube. The Soule’s catheter was removed and a Prah dilator utilized to dilate the cervix. Initially a 7 Fr dilator was passed through the cervical os without difficulty. A 9–10 Fr dilator followed this. The 11–12 Fr dilator was not easily passed due to limited vaginal space, making manipulation of this dilator difficult and potentially requiring a more forceful dilatation. The decision was made to discontinue further dilatation at this point since it appeared that the cervical os was freely open to at least a 9–10 Fr dilator. Progressing to a larger dilator would require increased force that may have resulted in a more traumatic dilatation than desired. An alternative method of visualizing the reproductive tract by sonography was employed in this gorilla as well during a previous exam. The urethra was catheterized and 300 ml of warm saline was infused into the urinary bladder. A 3.5 mHz abdominal probe was used to visualize both the ovaries and uterus using the bladder as an acoustic window. Ovarian measurements were taken and an assessment of the uterus was possible. The imaging in this manner was not as comprehensive as that obtained from transvaginal or transrectal sonography, although it may provide valuable information when special probes and machines are not available or in smaller apes and other primates.
A 31-year-old nulliparous gorilla was found to have a tight vaginal introitus, most likely due to her nulliparity. This female had a history of chronic mycoplasmal-rheumatoid arthritis and was specifically being examined for chronic endometritis. The gorilla had a normal appearing cervix high in the vaginal vault. After grasping the cervix with a tenaculum and manipulating the cervix into position, it was possible to perform an endometrial Pipelle biopsy. A pap smear was also performed. Attempts were then made to perform a vaginal ultrasound. However, due to the narrow nature of the introitus the standard probe could not be inserted. A rectal ultrasound was, therefore, performed which revealed a normal shaped uterus in a normal anteverted, anteflexed position. The ovaries were visualized completely and appeared to be normal in appearance with one developing follicle. A catheter was placed within the uterine cavity and saline was infused in order to perform a sonohysterosalpingogram. The uterine cavity appeared to be normal and fluid was noted external to the uterus, suggestive of at least one tube being patent.
The third gorilla was a nulliparous 21-year-old female suspected as having pituitary-dependent hyperadrenalcorticism. Other possible explanations for this animal’s overall condition included polycystic ovarian syndrome. This female was grossly obese and upon examination revealed a vaginal mucosal without rugae and prominent, thin vascularity somewhat suspicious for adenosis versus atrophy. The cervix also demonstrated this prominent vascular appearance. A pap smear was performed A Soule’s catheter was placed within the uterine cavity. Transrectal sonography revealed a normal appearing uterus and fluid collecting outside the uterine cavity after saline injection, indicating a tubal patency. The ovaries were thought to be normal in size although the left did have a ring of small follicles along the outer margin of the ovaries suspicious for polycystic ovarian disease.
The exam in these three animals demonstrates that routine evaluation of reproductive health in female gorillas can be easily obtained. Consultation with a gynecologist is an ideal situation but much information can still be gathered without specialized training or equipment.
1. Hatasaka HH, Schaffer NE, Chenette PE, Kowalski W, Hecht BR, Meehan TP, et al. Strategies for ovulation induction and oocyte retrieval in the lowland gorilla. J Assist Repro Genet. 1997;14:102–110.
2. Lanzendorf SE, Holmgren WJ, Schaffer N, Hatasaka H, Wentz AC, Jeyendran RS. In vitro fertilization and gamete micromanipulation in the lowland gorilla. J Assist Repro Genet. 1992;9:358–364.
3. Pope CE, Dresser BL, Chin NW, Liu JH, Loskutoff NM, Behnke EJ, et al. Birth of a western lowland gorilla (Gorilla gorilla gorilla) following in vitro fertilization and embryo transfer. Am J Primatol.1997;41:247–260.
4. Yeager CH, O’Grady JP, Esra G, Thomas W, Kramer L, Gardner H. Ultrasonic estimation of gestational age in the lowland gorilla: a biparietal diameter growth curve. J Am Vet Med Assoc. 1981;179:1309–1310.