SYMPTOM
Green vaginal discharge
Owners may observe green vaginal discharge in their pet, which can present in various ways depending on the underlying cause.
Reproductive tract infection
Green discharge often reflects bacterial infection within the uterus (pyometra) or vagina, where tissue inflammation and white blood cell accumulation produce purulent material. The colour typically signals the presence of neutrophils and bacterial byproducts.
Pregnancy or parturition complications
During late pregnancy or after whelping, green discharge can indicate placental separation or foetal distress, as the breakdown of placental pigments produces a characteristic dark green fluid. In some cases, retained foetal membranes or developing uterine infection may also present this way.
Foreign material or trauma
Introduction of foreign material into the reproductive tract, or trauma following mating or medical procedures, can trigger localised inflammation and secondary infection. The resulting discharge may appear green as tissue debris and inflammatory cells accumulate.
Hormonal influence and cycle-related changes
Hormonal fluctuations during the oestrous cycle can alter the uterine and vaginal environment, sometimes predisposing to bacterial overgrowth or infection. In some animals, these changes coincide with the appearance of abnormal discharge.
Vaginal or vestibular conditions
Inflammation of the vagina or vestibule, whether from infection, anatomical variation, or other irritation, can produce discharge that appears green when bacterial activity and cellular debris are present. These conditions may occur independently of uterine involvement.
Why timing matters
Early observation
When green discharge first appears, it may represent the early stages of infection or inflammation, often before systemic signs such as fever or malaise become apparent. In pregnant animals, the timing in relation to the expected whelping date can help narrow the range of possible explanations. The initial volume, consistency, and any accompanying odour can offer context, though these features alone do not confirm a specific cause.
Later presentation
If discharge persists or recurs over days to weeks, it may indicate an ongoing infectious process or a condition that has not resolved spontaneously. Animals with untreated uterine infection can develop systemic illness, including lethargy, reduced appetite, or increased thirst, as the infection progresses. Recurrent episodes may also suggest underlying hormonal or anatomical factors that predispose to repeated inflammation.
The pattern of change over time varies widely between individuals. Some animals may show transient discharge that resolves as the reproductive cycle advances, while others may experience worsening signs if infection spreads or tissue damage accumulates. The interplay between immune response, bacterial load, and hormonal environment shapes the trajectory, and what appears stable one day may shift if the underlying balance changes.
When to explore further
If the discharge appears shortly before or after an expected whelping date, or if the animal is known to be pregnant, the timing may warrant closer attention.
If the discharge is accompanied by changes in behaviour, appetite, water intake, or general demeanour, this may suggest that the process involves more than the reproductive tract alone.
If the discharge persists beyond a few days, increases in volume, or develops a strong odour, the pattern may indicate ongoing infection or inflammation.
If the animal has recently been in season or has a history of reproductive tract conditions, the context may help inform whether the discharge reflects a recurring or familiar pattern.
Green vaginal discharge gains meaning when considered alongside the animal's reproductive history, recent cycle activity, and any accompanying changes in behaviour or well-being. Observations about the discharge itself—its onset, volume, and evolution—can form part of a broader picture. These details can be useful in conversations that explore the range of possibilities and the role, if any, of further examination or testing.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS