Practical Matters: Vaginal cytology: Its value in detecting the cause of vulvar discharge

Jul 01, 2008

Margaret V. Root Kustritz, DVM, PhD, DACT
Vulvar discharge can be a diagnostic challenge because the inciting problem may arise from the urinary tract, uterus or uterine stump, or vagina. As a general rule, mucoid discharge is associated with vaginitis; mucopurulent to purulent discharge is associated with vaginitis, metritis (postpartum), pyometra (during or after diestrus) or uterine stump pyometra, and, occasionally, brucellosis; and hemorrhagic discharge is associated with the subinvolution of placental sites (postpartum), neoplasia of the genitourinary tract, coagulopathy, the presence of blood parasites (ehrlichiosis or babesiosis), or physiologic estrus (vaginal epithelial cells cornified).

Microscopically assessing the discharge to determine its character often leads to further appropriate diagnostic tests. More information is gathered by collecting a vaginal cytology specimen than by looking at the discharge only. To collect a specimen, moisten a nonsterile cotton-tipped applicator, insert it at the dorsal commissure of the vulva, advance it at a 45-degree angle for one-third to one-half its length, roll it on the epithelial surface, and pull it straight out. Then roll the swab several times onto a glass slide and stain the slide. Stains commonly used include new methylene blue and Romanowsky stain (triple stain).

Mucoid discharge is characterized by proteinaceous streaming and an absence of a significant number of polymorphonuclear cells. Purulent discharge is characterized by a large number of polymorphonuclear cells (2 to 4+). Hemorrhagic discharge is characterized by the presence of red blood cells.

Margaret V. Root Kustritz, DVM, PhD, DACT
Department of Veterinary Clinical Sciences
College of Veterinary Medicine
University of Minnesota
St. Paul, MN 55108