What is the most likely diagnosis for an adult female spayed dog with blood vulvar discharge and degenerative neutrophils on cytology?

The most likely diagnosis for the condition described is stump pyometra. This occurs in spayed females when there is a remnant of ovarian tissue left behind after an ovariohysterectomy (i.e., spaying). This residual ovarian tissue can produce hormones, particularly estrogen, which stimulates the endometrial tissue in the uterus to grow and can lead to a condition that mimics a pyometra, characterized by accumulation of pus and inflammation.

The presence of blood vulvar discharge and degenerative neutrophils on cytology supports this diagnosis. The degenerative neutrophils indicate an inflammatory process, likely due to infection or irritation in the uterus, consistent with stump pyometra. Blood vulvar discharge is also symptomatic of a uterine issue, confirming the likelihood of this diagnosis.

In contrast, other conditions such as ovarian remnant syndrome, while related to retained ovarian tissue, are less likely to present with the significant clinical signs of discharge and systemic illness that accompany stump pyometra. Uterine infection could initially seem plausible, but in the context of a spayed dog, stump pyometra is a clearer cause, especially when the dog has a history of surgery. Vaginal neoplasia might cause discharge but would not typically