History

A 6.5-year-old sexually intact female English Springer Spaniel was examined to determine the cause of postestral vulvar discharge. The bitch had begun exuding odorless, green vulvar discharge 19 days after the onset of proestrus. Prior to that date, vulvar discharge was as expected during proestrus and estrus.

The bitch had been tested for brucellosis approximately 1 year before admission; results for that test were negative. The bitch had successfully given birth to puppies in the past, but she was not bred during this estrus. The owner also described signs of a depressed attitude, which was considered typical for this bitch at this stage of estrus. The bitch had no changes in thirst or appetite, and all additional history was unremarkable. The owner intended to use this dog for breeding 1 more time and was concerned about possible pyometra because of the age of the bitch.

The referring veterinarian had evaluated the dog 2 days prior to referral to and admission at the author's facility. At that time, the referring veterinarian recorded that rectal temperature, pulse rate, and respiratory rate were within respective reference ranges, and the bitch was not clinically dehydrated. A moderate amount of odorless, brownish-green discharge was exuding from the vulva. All other results of that physical examination were considered unremarkable. Vaginal cytologic examination was performed on a swab specimen; approximately 50% of the visible epithelial cells were cornified, and few neutrophils and many cocci were detected. A sample was collected from the vagina for microbial culture and susceptibility testing, and treatment with amoxicillinclavulanate (dosage and frequency of administration not known) was instituted. Microbial culture revealed a mixture of numerous organisms indigenous to the canine vagina with no predominant organism. A CBC was performed, and the hemoglobin concentration was slightly increased (18.8 g/dL; reference range, 12 to 18 g/dL). However, all additional CBC results (including WBC number and a differential count) were within reference ranges. The bitch was referred for further assessment and possible abdominal ultrasonographic evaluation.

Initial examination at the author's facility revealed that rectal temperature, pulse rate, and respiratory rate were within the respective reference ranges. The attitude of the bitch was considered normal. A small amount of odorless, tan discharge was detected in the perivulvar hair. The bitch was sufficiently relaxed such that abdominal palpation could readily be used to identify abdominal structures. All structures were considered palpably normal, except the uterus, which was not palpable. A sample was obtained from the vagina and submitted for cytologic examination by use of a Romanowski stain^a (Figure 1).

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Photomicrograph of a swab specimen obtained from the vagina of 6.5-year-old English Springer Spaniel with a green, odorless vulvar discharge first detected 19 days after onset of proestrus. Romanowski stain; bar = 100 μm.

Citation: Journal of the American Veterinary Medical Association 232, 6; 10.2460/javma.232.6.841

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Question

What are the 3 most likely differential diagnoses for a bitch with this type of cytologic pattern?

Answer

Early diestrus, pyometra, and vaginitis. For the bitch reported here, early diestrus is the most likely diagnosis on the basis of the medical history, results of physical examination, and supporting results of laboratory tests.

Results

The bitch was considered to be in early diestrus. Abdominal ultrasonography was not performed because of a lack of palpable uterine enlargement, healthy appearance of the bitch, unremarkable results of physical examination, and results consistent with early diestrus for cytologic examination of a vaginal swab specimen.

Discussion

Results of cytologic examination of specimens obtained from the vagina during proestrus in bitches are characterized by an increase in the population of cornified epithelial cells. The classic definition of cytologic estrus is that 100% of cells will have cornification, with > 50% of those cells appearing anuclear. Neutrophils are evident during early proestrus, then gradually decrease until they become undetectable during estrus. Onset of cytologic diestrus is abrupt, with sloughing of most of the cornified epithelial cells during approximately 1 day. Sloughing of the vaginal epithelium is a physiologically inflammatory event, and thinning of the vaginal epithelium allows greater movement of neutrophils into the vaginal lumen via diapedesis. Therefore, it is not uncommon to see a substantial number of neutrophils during cytologic examination of specimens collected from the vagina during the first 3 or 4 days of diestrus in bitches; appearance of neutrophils may precede or lag behind changes in epithelial cell types.¹

Typically, bitches ovulate approximately 11 days after the onset of proestrus and reach diestrus 6 days after ovulation.^1,2 Early diestrus was the most likely differential in the bitch reported here on the basis of the medical history (ie, onset of proestrus approx 20 days prior to examination), unremarkable results for the physical examination, and WBC and differential cell counts within reference ranges. Mucoid vulvar discharge may be detected early during diestrus. The green color described for the vulvar discharge of this bitch was unusual and could not be explained on the basis of results for the diagnostic tests conducted.

Pyometra is an acute manifestation of a chronic disease, with the reported mean age for clinical appearance of disease of 7.25 years.³ Nulliparous bitches are more commonly affected than multiparous bitches. The primary pathologic change in pyometra is cystic endometrial hyperplasia, which develops with repeated estrous cycles in bitches. The secondary pathologic change is infection. Clinical signs of pyometra are most commonly evident 4 weeks to 4 months after estrus.⁴ During proestrus and estrus, bacteria ascend from the vagina into the uterus. In a bitch with cystic endometrial hyperplasia, those bacteria are not expelled before the onset of diestrus. During the progesteronedominated phase of the cycle, the cervix closes; uterine contractions are inhibited; and endometrial secretions are increased, which facilitate growth of bacteria within the uterus. Bitches may develop open-cervix pyometra (most commonly evidenced by exudation of sanguinopurulent, foul-smelling vulvar discharge) or closed-cervix pyometra (associated with abdominal distention). Other clinical signs commonly evident include polyuria and polydipsia, signs of a depressed attitude, and hypothermia or hyperthermia. Laboratory results supportive of pyometra include neutrophilia with a left shift and growth of a substantial amount of a single organism from a sample of the vulvar discharge or a sample obtained from the cranial vagina. Pyometra was an unlikely differential diagnosis in the bitch described here because of the medical history, clinical findings, lack of a palpably enlarged uterus, WBC and differential cell counts within reference ranges, and lack of growth of a predominant organism during microbial culture of a sample obtained from the vagina.

Vaginitis is a condition for which female dogs most commonly are referred to the author for evaluation and is the third most common topic of telephone calls from practitioners to the author. Adult-onset vaginitis is equally common in spayed and sexually intact female dogs.⁵ Clinical signs most commonly include vulvar licking and exudation of mucoid or purulent vulvar discharge. Primary causes of vaginitis include vaginal anatomic anomalies and urinary tract disease, with overlying opportunistic infection causing the clinical signs. Many cases of vaginitis in female dogs are idiopathic.⁶ Vaginitis was an unlikely differential diagnosis in the bitch reported here because of the medical history, clinical findings, and lack of substantial growth of a predominant organism during microbial culture of a sample obtained from the vagina.

Other causes of vulvar discharge in bitches include brucellosis, metritis, urinary tract infection, vaginal foreign body, vaginal trauma, neoplasia of the genitourinary tract, congenital or acquired coagulopathy, and hematologic parasites.^6,7 Brucellosis classically causes late-term abortion in bitches but may be associated with persistent mucopurulent vulvar discharge.⁸ The bitch reported here had negative results when tested for brucellosis in the past. To be complete, serologic testing for brucellosis could have been performed at the time of admission to rule out infection acquired since the time of the last negative test.

Metritis develops during the postpartum period. Thus, it was ruled out in this bitch because of the timing of her admission with these clinical signs.

Neoplasms of the genital tract are most commonly benign, with leiomyoma the most common tumor type reported. Vulvar discharge associated with neoplasia most commonly is sanguineous, rather than mucopurulent.⁶ Neoplasia of the genitourinary tract can typically be ruled out by use of vaginoscopy or cystoscopy in combination with vaginography or cystourethrography.

Urinary tract disease may be associated with vulvar discharge. However, vulvar discharge is rarely evident without concurrent signs of urinary tract disease, such as pollakiuria or hematuria.

Vaginal foreign body and vaginal trauma are uncommon causes of vulvar discharge. Vaginoscopy is required to rule out these disorders.

Congenital coagulopathies, such as vonWillebrand's disease, and acquired coagulopathies, such as anticoagulant rodenticide toxicosis, usually are associated with sanguineous vulvar discharge and bleeding from other mucosal surfaces or with the formation of ecchymotic or petechial hemorrhages. Examination of a coagulation profile and testing for specific disorders can be used to rule out these disorders.

Similarly, hematologic parasites usually are associated with sanguineous vulvar discharge and abnormalities of the CBC. Babesiosis and ehrlichiosis are described as causes of vulvar discharge in bitches that live in the tropics; however, these conditions are much less common in dogs that live in the northern United States.

Outcome

Vulvar discharge resolved in the bitch within 1 to 2 days after admission to the veterinary medical teaching hospital. The bitch was discharged to the owner with the intent that the bitch will be bred during her next estrus.