Vaginal discharge will still be present, and classically attains a straw color at this point, although in many dogs it will remain serosanguinous. With vaginoscopy, the vaginal mucosa will shrink and become angulated and wrinkled with subsequent blanching to a pale pink-white color. This stage lasts an average of nine days with a range from 3-21 days. There will be virtually no RBCs, PMNs or debris present. We cannot prospectively predict ovulation time from looking at vaginal cytology.
Progesterone rises abruptly early in estrus, and estrogen declines.
The bitch enters diestrus when she will no longer stand to be bred. The vulva will gradually decline in size through this stage. Some dogs will continue to exhibit vaginal discharge. The discharge may be serosanguinous for a time, but is most characteristically mucoid. Most dogs will have no vaginal discharge during this stage.