The first step in screening a bitch is to perform a vaginal examination, inserting a gloved finger or using a scope to assess the vaginal lining. The most common vaginal abnormality is a persistent hymen-- a membrane found part-way in the vagina. The hymen normally ruptures as a bitch matures, but sometimes it doesn’t. If part or all of the membrane persists and it’s present when the bitch is first mated, copulation can be painful. Simple finger pressure is sometimes enough to break down a hymen. If this is too painful, or if large segments of the membrane are present, surgical resection under anesthesia is required.
Vaginal tumors, though rare, do occur. These range from benign polyps that plug the vagina to malignant growths in the vaginal wall. Because tumors are more common in older individuals, any mature bitch who has a vaginal discharge or suddenly shows pain during mating should have a vaginal examination.
The uterus can sometimes be malformed, but abnormalities are more commonly caused by scarring after a difficult whelping or cesarean section. Veterinarians diagnose these conditions by examining the reproductive tract during exploratory surgery or by ultrasound examination. Some defects are surgically correctable.
Bitches can also suffer from uterine infections. Chronic infections deep in the uterine wall are called an endometritis and can cause loss of fertility. A long-standing infection can turn into a life-threatening pyometra and end a breeding career.