Accessory Sex Glands in Geldings: Establishing the Norm

A gelding’s gonads are gone, but he’s still susceptible to problems developing in his reproductive tract, particularly abnormal growths in the accessory sex glands. Take, for example, prostatic tumors, which can cause difficulty urinating or blood to show up in the urine. When a gelding has signs of discomfort associated with the urogenital tract, it’s often difficult to determine whether the accessory sex glands are within normal limits of size and “character.” Researchers recently determined and described the ultrasound appearance of a group of “normal” geldings’ accessory sex glands so practitioners can to better detect when something’s amiss.

Maria Schnobrich, VMD, Dipl. ACT, a reproduction specialist at Rood & Riddle Equine Hospital, in Lexington, Ky., completed the research as a resident in the University of Pennsylvania School of Veterinary Medicine’s Department of Clinical Studies. She presented her findings at the 2013 American College of Theriogenology Conference & Symposia, held Aug. 7-10 in Louisville, Ky.

The accessory sex glands (vesicular glands, prostate, ampullae, and bulbourethral glands) are intimately associated with other organs (bladder, urethra, and ureters) and can be evaluated using transrectal ultrasound. Schnobrich and her Penn colleagues used this approach in a group of 12 clinically normal light-breed geldings, ages 2-25 years old, with the goal of establishing a baseline for comparison. “This may help us in looking at geldings when we see them clinically,” she said. Researchers had already characterized normal measurements of stallions’ accessory sex glands (“These measurements come into play when we’re doing breeding soundness exams, or evaluating stallions for pathology,” but as far as she knew, these measurements weren’t available for geldings, though she noted it is generally accepted that geldings' accessory sex glands are smaller than those of mature stallions.)

The team sought to obtain 24 separate measurements of the various components of the internal urogenital tract for each gelding. Some of their findings include:

  • They identified a full complement of accessory glands in each animal and successfully obtained 281 of the 288 (97.6%) measurements.
  • Schnobrich used both a 7.5 MHz linear-array transducer and a 6.0-10 MHz microconvex linear-array transducer, and she found both were effective and obtained similar measurements, but some structures (prostatic isthmus) were easier to identify using the microconvex transducer.
  • Seminal vesicles are collapsible structures, making them difficult to image. “Careful with the (ultrasound transducer) pressure you’re using,” she said.
  • Nine of 12 geldings had luminal contents in the seminal vesicles with no clinical signs; six of those were “hypoechoic to anechoic,” meaning the fluid appears dark to black on the ultrasound screen, and three of nine were “hyperechoic relative to the wall,” meaning the contents were brighter or whiter than the seminal vesicle wall. “In general fluid with low protein and cells appears black on the ultrasound image whereas fluid containing concentions of protein and or cells is brighter or more white on the ultrasound screen,” she explained.
  • The lumen of the ampullae was never larger than 1 mm, and seven of 12 subjects had hyperechoic luminal contents; four of 12 had hypoechoic contents. “The accessory glands are easily imaged in the gelding for one who is familiar with imaging these structures in stallions,” Schnobrich said, “the only caveat being the prostatic isthmus is a little small. There was no difference between the size of the left and right side of the structures imaged, and both transducers worked equally well.”

Veterinarians noting clinical signs such as blood in the urine or abnormal urination should consider prostatic abnormalities. These measurements might help them determine if there is a developing prostatic tumor or other pathology. Other potential problems associated with the accessory sex glands include seminal vesiculitis (inflammation of the vesicles), which has been reported as a cause of colic in stallions, but “is not high on the differential list.”

“We conclude that the accessory sex glands can be reliability imaged in normal geldings,” Schnobrich said. “We have successfully applied these values to the evaluation of geldings presenting to our hospital for clinical signs associated with the internal urogenital tract, thus demonstrating the utility of this data.”

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.