The vagina of the mouse is closed at birth and does not open until the animal is 24 to 28 days of age, around the onset of sexual maturity.2 Defects in development of the caudal sections of the Mullerian duct can result in a variety of abnormalities of the vagina including septa formation1 or imperforate vagina.4 The latter can have dramatic complications due to accumulation of secretions resulting in marked distention and atony of the vagina, cervix and uterus.4 Pyometra may develop as a result of fortuitous implantation of bacteria into the uterine contents.4 Imperforate vagina in the mouse is believed to be inherited in a complex recessive manner.3
Mice with imperforate vaginas are submitted to The Jackson Laboratory Animal Health Diagnostic Laboratory because of marked distention of their abdomens due to mucometra. Differential diagnoses include abdominal (umbilical) abscessation, macerated fetuses, or neoplasia in these animals. A hypoplastic vagina opening can be observed on the affected animals. When the abdomen is opened, the uterine horns are markedly distended, thin walled and translucent . Clear to slightly cloudy mucous is obtained when the walls are cut.
From 1987 to 1989, 44 cases of imperforate vagina and mucometra were submitted for evaluation to the diagnostic laboratory. Affected mice of 14 different strains were examined from production colonies at The Jackson Laboratory.
This represents a relatively rare, sporadic abnormality affecting female mice. The age at the time of submission ranged from 27 to 258 days with a mean of 100 days. Animals submitted exhibited extreme distention of the abdomen. Three additional cases of mucometra were associated with partial uterine prolapse (CBA/J), uterine fibroma (C57BL/6J), and various abnormalities in a true hermaphrodite (BALB/cByJ).
1. Cunliffe-Beamer TL, Feldman DB: Vaginal septa in mice: incidence, inheritance, and effect on reproductive performance. Lab Anim Sci 26:895-898, 1976.
2. Green EL: Biology of the Laboratory Mouse, Dover Publications, New York, 1975.
3. Gruneberg H: Genetics of the Mouse. 2nd ed., Nijhoff, The Hague, 1952.
4. Jubb KVF, Kennedy PC, Palmer N: Pathology of Domestic Animals. 3rd ed., Academic Press, Orlando, 1985.