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 retrieval.1-3 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 tiletomine-zolazepam (Telazol, Ft. Dodge Animal Health, Ft. Dodge, IA 50501 USA),
0.5-0.8mg/kg xylazine (Xylazine-100, Ben Venue Laboratories, Inc., Bedford, OH 44146 USA) and 1.5 mg atropine (Atropine
LA, AmVet Scientic Products, Yaphawk, NY 11980 USA). Ketamine (Ketaset, Ft. Dodge Animal Health, Ft. Dodge, IA 50501 USA)
was given at 2 mg/kg i.v 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 60064 USA) and 6.0 L/min 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
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-yr-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-yr-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, NE Schaffer, PE Chenette, W Kowalski, BR Hecht, TP Meehan, AC Wentz, RF
Valle, RT Chatterton, RS Jeyendran. 1997. Strategies for ovulation induction and oocyte retrieval in the lowland gorilla.
J. Assist. Repro. Genet. 14:102-110.
2. Lanzendorf SE, WJ Holmgren, N Schaffer, H Hatasaka, AC Wentz, RS Jeyendran. 1992. In
vitro fertilization and gamete micromanipulation in the lowland gorilla. J. Assist. Repro. Genet. 9:358-364.
3. Pope CE, BL Dresser, NW Chin, JH Liu, NM Loskutoff, EJ Behnke, C Brown, MA McRae, CE
Sinoway, MK Campbell, KN Cameron, OM Owens, CA Johnson, RR Evans, MI Cedars. 1997. Birth of a western lowland gorilla
(Gorilla gorilla gorilla) following in vitro fertilization and embryo transfer. Am. J. Primatol.
4. Yeager CH, JP O'Grady, G Esra, W Thomas, L Kramer, H Gardner. 1981. Ultrasonic estimation
of gestational age in the lowland gorilla: a biparietal diameter growth curve. J. Am. Vet. Med. Assoc.