Bulbourethral (Cowper's) gland abnormalities in inbred laboratory mice

Abnormalities of the bulbourethral (Cowper's) glands are rare in most strains of inbred laboratory mice. Since the glands are covered with striated muscle and because of their small size, the bulbourethral glands are often overlooked at necropsy. We review the gross and microscopic anatomy of the bulbourethral glands in laboratory mice and report in SJL/J and RBF/DnJ mice a series of anomalies of this gland that appear to be common in these strains and relatively strain specific. From 14 different inbred strains of mice that had been submitted for necropsy over a period of 4.5 years for various clinical complaints, including enlargement of the perianal region, 23.8% of SJL/J mice (27/113) and 51.2% of RBF/DnJ mice (21/41) had cystic hyperplasia of the bulbourethal glands. Furthermore 7.3% of BALB/cByJ mice (3/41) had cystic glands and 6.7% of DBA/2J mice (4/60) had enlarged bulbourethal glands, three of which (5.0%) were abscessed. All selected mice were active male breeders older than 6 months of age from production colonies at The Jackson Laboratory. Detailed examination of bulbourethral glands of retired SJL/J breeders revealed cystic glands in 83.8% (109/130) of mice. No abnormalities were found in the other inbred strains of mice investigated.