Vaginal cytology as a diagnostic tool (Proceedings)


The normal physiologic and pathologic vaginal conditions.

Normal physiologic conditions

Proestrus / estrus

History = Time is correct for onset of estrous cycle.

Physical examination findings = Turgid vulvar swelling is present in proestrus. Classically, the vulva softens in estrus (standing heat).

Gross appearance of discharge = The discharge is serosanguinous in proestrus and classically changes to a straw color during estrus. At no time should it have a foul odor.

Microscopic appearance of discharge = Over the period of proestrus, there will be an increase in percentage of the vaginal epithelial cells that are cornified and a decrease in number of PMNs. The classic definition of estrus by cytology is complete cornification with greater than 50% of the cells being anuclear squames, and an absence of PMNs.

Miscellaneous = Male dogs may be attracted but the bitch is not interested in proestrus. Estrus is defined by the bitch's behavior, as she allows the male to mount and breed.

Diagnostic tests to confirm = None usually are needed. Serial vaginal swabs and measurement of concentration of progesterone in serum may be needed to differentiate proestrus from diestrus.

Late pregnancy / parturition

History = The bitch is due to whelp soon or is at term. Remember that gestation length from breeding date can vary from 58 to 71 days.

Physical examination findings = Mammary development may be present and milk may be expressed. This occurs in some bitches up to a week before whelping; conversely, some primiparous bitches have no discernible mammary development at the time of parturition.

Gross appearance of discharge = Scant mucoid discharge of variable amounts may be exuded intermittently in the week before whelping. At the time of parturition, passage of clear, slightly blood-tinged or slightly brown fluid is normal. Green coloration indicates placental separation has occurred. Frank hemorrhage never is normal. Vulvar discharge at the time of parturition never should be foul-smelling.

Microscopic appearance of discharge = This is a non-inflammatory discharge. Red blood cells and occasional healthy PMNs may be present.

Miscellaneous = Bitches in labor should be showing other clinical signs, including restlessness, panting, vomiting and overt abdominal contractions as they enter Stage II labor. Monitoring systems (WhelpWise, for example) may be required to determine if uterine contractions are occurring.

Diagnostic tests to confirm = Serum progesterone concentration must fall to less than 2 ng/ml for a bitch to have effective uterine contractions. Measurement of progesterone may help set the mind of a worried owner at rest in the week prior to parturition, especially if the bitch is carrying a large litter and is uncomfortable. Patency of the cervix cannot routinely be determined by digital vaginal examination. Determination of gestational age of the pups is possible with radiography; if teeth are visible, the bitch is within 4 days of whelping.


History = Lochia is the normal postpartum discharge of the bitch. It may be present for up to 3 weeks after parturition.

Physical examination findings = Mammary development is present and milk can be expressed from the mammary glands.

Gross appearance of discharge = The discharge varies in color from green to black to red. It should not be frankly hemorrhagic, should not be foul-smelling and should decrease in volume over time.

Microscopic appearance of discharge = The discharge is non-inflammatory.

Pathologic conditions

Ovarian follicular cysts

History = This is most common in young bitches. Combined length of proestrus and estrus is greater than 6 weeks.

Physical examination findings = The bitch has the clinical appearance of proestrus or estrus.

Gross appearance of discharge = The discharge usually is serosanguinous and has no foul odor.

Microscopic appearance of discharge = The vaginal epithelial cells are completely cornified and may appear ragged. PMNs are not present; bacteria may be visible, adhered to the surface of the epithelial cells.

Miscellaneous = This condition obviously only occurs in intact bitches. Young bitches with follicular cysts and subsequent anovulation on one cycle often cycle normally the next time. Follicular cysts are hereditary in cattle; hereditary basis in dogs is not known. Bitches under the influence of estrogen for a long time that then are induced to ovulate may be predisposed to cystic endometrial hyperplasia and pyometra (see below).

Diagnostic tests to confirm = Serial vaginal cytology is unchanging. The only rule-out for prolonged estrus in bitches is a functional granulosa cell tumor; these usually arise from the ovaries of older bitches and often are so large as to be palpable per abdomen or visible on radiographs or ultrasound. Often, response to treatment is used for diagnosis.

Treatment = Ovulation induction with gonadotropin releasing hormone (GnRH; 50 mcg IM).


History = The classical presentation of canine brucellosis is late term abortion. Bitches also may present with persistent vulvar discharge.

Physical examination findings = There are no specific associated clinical signs in bitches.

Gross appearance of discharge = The discharge will vary from mucopurulent to purulent and may be blood-tinged.

Microscopic appearance of discharge = This is an inflammatory discharge. All vaginal epithelial cells are non-cornified.

Miscellaneous = Brucellosis is uncommon but is reported to occur, usually in kennel situations, with enough regularity to necessitate continued testing for the disease. Brucellosis is reportable and has zoonotic potential.

Diagnostic tests to confirm = Culture is definitive but is difficult; ten negative cultures are required to accurately say an animal is free of brucellosis. Serologic testing is more commonly performed. The rapid slide agglutination test (RSAT) is a good screening test. Animals that test negative are free of infection, provided testing is performed 8 to 12 weeks after exposure and that the suspect animal has not received antibiotics. Animals testing positive with the RSAT should have the result verified with the agarose gel immunodiffusion test (AGID) from Cornell.

Treatment = Combination antibiotic therapy has been described but complete eradication of the organism from the animal generally is considered unlikely. Historically, treatment with a tetracycline-type drug orally, coupled with injectable streptomycin or gentamycin, has been used. More recently, use of fluoroquinolone antibiotics, alone or in combination with the drugs used above, has been described.


History = Metritis occurs in postpartum bitches. Often there is a history of dystocia or retained fetuses or placentas. The bitch often is anorexic and refuses to care for the pups.

Physical examination findings = Mammary development is present and milk can be expressed from the mammary glands. Discharge may be caught in the perivulvar area.

Gross appearance of discharge = The discharge is purulent and foul-smelling.

Microscopic appearance of discharge = This is an overtly inflammatory discharge, with full fields of degenerative PMNs.

Diagnostic tests to confirm = The uterus may or may not be palpably enlarged; ultrasonography or radiography can be used to determine if retained fetuses still are present.

Treatment = Appropriate antibiotic therapy should be instituted, based on culture and sensitivity testing. A good empirical choice, while awaiting culture results, is amoxicillin-clavulanate (14 mg/kg twice daily per os x 10-14 days). If tissues are retained in the uterus or if excessive intrauterine fluid is present, treatment with an ecbolic agent to cause expulsion of uterine content, such as prostaglandin (Lutalyse; 250 mcg/kg once daily SQ) may be indicated. Ovariohysterectomy may be necessary in dogs with systemic signs of disease indicating possible septicemia or peritonitis.


History = Pyometra occurs during or after diestrus and is most common in aged, nulliparous bitches. Dogs with closed-cervix pyometra do not have vulvar discharge and will not be described. Dogs with open-cervix pyometra may show signs of systemic disease (anorexia, PU/PD) or may appear normal.

Physical examination findings = Discharge will be present in the perivulvar area. The dog may be dehydrated. The uterus usually is palpably enlarged.

Gross appearance of discharge = The discharge is purulent and foul-smelling, often with the appearance of cream of tomato soup.

Microscopic appearance of discharge = This is an overtly inflammatory discharge, with full fields of degenerative PMNs.

Miscellaneous = Pyometra is not the same thing as metritis! Pyometra occurs during or after diestrus; metritis occurs postpartum. Pyometritis does not exist!

Diagnostic tests to confirm = White blood cell number is increased in 75% of cases; a left shift usually is present. Animals often are azotemic from dehydration and from secondary renal disease caused by endotoxemia. Uterine enlargement can be identified on radiographs; caution must be employed in differentiating uterine enlargement of pyometra from that of pregnancy in bred bitches. Ultrasound is the preferred imaging technique and is accurate for differentiation of pyometra from pregnancy after 25 days from breeding.

Treatment = The best treatment for pyometra is ovariohysterectomy. If the bitch is of breeding age, valuable in a breeding program and is not azotemic, medical therapy for open-cervix pyometra may be considered. This involves treatment with an appropriate antibiotic, based on culture and sensitivity testing (amoxicillin [10 mg/lb twice daily per os] or amoxicillin-clavulanate [14 mg/kg twice daily per os]) can be instituted while awaiting culture and sensitivity results. Expulsion of the purulent fluid from the uterus is effected with prostaglandin (Lutalyse; 250 mcg/kg twice daily SQ until the uterus nears normal size). Treatment with the progesterone receptor blocker, aglepristone (Alizine) is used to effect in other countries. Bitches with pyometra have underlying cystic endometrial hyperplasia, which cannot be reversed with medical therapy, and will be predisposed to pyometra after every heat cycle. Ovariohysterectomy is the treatment of choice.

Subinvolution of placental sites (SIPS)

History = This is most common in young bitches after whelping their first litter. The bitch appears normal but postpartum discharge continues beyond 3 weeks postpartum.

Physical examination findings = There are no specific clinical signs associated with SIPS.

Gross appearance of discharge = This is an odorless, serosanguinous to sanguinous discharge.

Microscopic appearance of discharge = This is a non-inflammatory discharge. RBCs usually are present. All vaginal epithelial cells are non-cornified.

Diagnostic tests to confirm = Definitive diagnostic testing usually is not performed, as it requires laparotomy and uterine biopsy.

Treatment = Most cases resolve spontaneously. Ovariohysterectomy may be required in bitches with excessive blood loss.


History = This can occur in prepubertal bitches ("puppy" vaginitis) or in spayed, adult bitches. Dogs may present for excessive vulvar licking or vulvar discharge may be an incidental finding on physical examination.

Physical examination findings = Puppies rarely show any evidence of vaginitis, other than sticky discharge gluing together their vulvar lips. Adult dogs may show evidence of vulvar licking and perivulvar dermatitis; the occasional bitch will have traumatized her perivulvar region to a great extent.

Gross appearance of discharge = The discharge may be scant, mucoid and sticky (puppy vaginitis) or may vary from mucoid to purulent with tremendous variation in amount present (adult-onset vaginitis). The discharge rarely is bloody.

Microscopic appearance of discharge = Cytology varies as above. Vaginal epithelial cells all are non-cornified. If cornified cells are present, especially if the discharge appears bloody, ovarian remnant syndrome should be considered.

Miscellaneous = The most common underlying causes of vaginitis are vaginal anatomic abnormalities and chronic urinary tract disease.

Diagnostic tests to confirm = Localization of disease requires concurrent urinalysis and urine culture on a sample collected by cystocentesis and culture and sensitivity of a vaginal culture specimen, collected from as far forward in the vagina as possible. Remember that the vagina is not sterile; moderate to heavy growth of any single organism is significant. Vaginoscopy must be performed and inflammation of the vaginal mucosa identified to diagnose vaginitis. Lymphoid follicles are a non-specific indicator of inflammation.

Treatment = Puppy vaginitis usually clears spontaneously. Affected bitches (vulvar licking, excessive discharge) can be treated with antibiotics. Some bitches clear puppy vaginitis more readily after being allowed to go through one heat cycle; whether this is due to estrogen exposure or simply to age is not known. For dogs with adult-onset vaginitis, any underlying causes should be corrected. Symptomatic treatment includes antibiotic therapy, either systemically or topically and concurrent treatment with estrogen (DES, 1 mg x 5 days, then 1 mg every 4-7 days as needed). Glucocorticoids may be beneficial in some cases but should not be used in bitches with urinary incontinence. The author does not like douching as a treatment for vaginitis in dogs; douching with chlorhexidine products can cause desquamation of the vaginal mucosa and should be avoided in all cases. Dogs with signs of atopy may benefit from treatment with diphenhydramine (2-4 mg/kg orally three times daily or as needed) or hydroxyzine (1-2 mg/kg orally two to three times daily, taper dose if needed) as for allergies.

Neoplasia of the uterus, vagina or urinary tract

Transmissible venereal tumor or leiomyoma may be present.

History = Neoplasia of the reproductive tract is uncommon; leiomyoma is the most common tumor type and occurs in aged intact or spayed bitches. Transitional cell carcinoma of the urinary tract may be associated with vulvar discharge.

Physical examination findings = Masses may be visible or may be concealed within the vaginal vault or urinary tract. Perineal swelling may be present.

Gross appearance of discharge = The discharge associated with neoplasia most commonly is hemorrhagic with no foul odor.

Microscopic appearance of discharge = Many RBCs and occasional PMNs are present. All vaginal epithelial cells are non-cornified.

Diagnostic tests to confirm = Vaginoscopy can be used to locate vaginal tumors. Ultrasound is required for identification of uterine tumors. Retrograde cystourethrography may be required to localize a tumor to the urinary tract.

Treatment = Surgical removal is curative for leiomyoma. Ovariohysterectomy is the treatment of choice for uterine tumors. Treatment of transitional cell carcinoma with radiation or chemotherapy including peroxicam may prolong life with acceptable quality.

Coagulopathy or presence of blood parasites

History = Vulvar discharge associated with coagulopathy may occur in intact or spayed bitches of any age. Reported causes include hereditary coagulopathy (for example, von Willebrand's disease) and acquired coagulopathy (anticoagulant rodenticide toxicity). Babesiosis and ehrlichiosis have been reported to be associated with sanguinous vulvar discharge.

Physical examination findings = Signs of anemia and hemorrhage may be present, depending on chronicity and extent of bleeding. These include pale mucous membranes, petechial hemorrhages, icterus and lethargy.

Gross appearance of discharge = This is a frankly hemorrhage discharge that often waxes and wanes in volume.

Microscopic appearance of discharge = The microscopic appearance is as of peripheral blood.

Diagnostic tests to confirm = Tests that may be performed, depending on the history of rodenticide exposure, breed of the dog, etc. include complete blood count, coagulation profile, VWD test and assay for specific rodenticides, if the product ingested is not known. Babesia may be seen on RBCs and Ehrlichia in WBCs and PCR testing is available for both.

Treatment = Transfusions of whole blood or blood components should be provided as necessary. Vitamin K therapy is used for anticoagulant rodenticide toxicity. Doxycycline and imidocarb are treatments for ehrlichiosis and babesiosis, respectively.

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