Vaginitis is an inflammation and/or infection of the vagina, (the vagina is the tube leading from the outer genitals to the cervix). It is more commonly seen in dogs than cats. When cats are affected, it is most commonly seen in young cats.
There are several possible causes of vaginitis in cats including:
Bacterial infection – The vagina has a natural fauna of bacteria, predominantly lactobacillus, which helps to maintain normal vaginal pH, which protects against unhealthy bacteria. The use of antibiotics could possibly wipe out the normal vaginal bacteria, creating an opportunity for opportunistic bacteria to take hold. The postpartum queen is at a higher risk of bacteria taking hold in the vagina also.
Viral infection – Although possible, this is a rare cause of vaginitis in cats.
Yeast infection – Candida albicans is the most common type of yeast infection.
Foreign body – Any foreign body that enters the vagina has the potential to cause irritation and infection.
Trauma – Usually the result of rough intercourse with a tom.
Urinary tract infection which spreads to the vagina.
Vaginitis may appear as a sole entity or part of an upper genital tract infection. 
Bacterial infection of the vagina may spread to the bladder or uterus if left untreated.
The most common symptom of vaginitis is a discharge from the vulva. It may vary in colour from cloudy white to green or yellow. Other common symptoms include the following:
Licking the genital area.
Scooting the anal area along the floor.
Toms are sometimes attracted to a cat with vaginitis.
Pain when urinating, your cat may cry, or urinate outside the litter tray (cats often do this because they associate the pain they are experiencing with the litter tray).
Mild irritation of the skin around the vulva.
Your veterinarian will perform a complete physical examination, and he will obtain a medical history from you including symptoms and how long they have been present. Tests he may wish to perform include:
Digital vaginal examination to check for vaginal masses, foreign object, and vaginal structure.
Vaginal culture to determine the pathogen involved.
Complete blood count and biochemical profile to assess the overall health of your cat. These typically come back normal.
Urinalysis which may reveal inflammation or infection.
Endoscopic examination of the vagina.
If an obvious cause isn’t determined, your veterinarian may recommend X-Rays or ultrasound to check for vaginal masses or foreign body.
The goal of treatment is to find and address the underlying cause, this may include:
Removal of the foreign body or cancer.
Mild vaginitis may only require douches.
Antibiotics to treat a bacterial infection. It is advisable to perform a bacterial culture to select the most suitable antibiotic.
Prepubertal vaginitis usually resolves itself upon the first estrus.
Do not breed with a queen who has vaginitis until she has recovered.