Ovarian Remnant Syndrome

Ovarian remnant syndrome describes a situation in which a female dog or cat who has been spayed continues to show signs associated with an active ovary. This typically happens when a small piece of ovarian tissue—sometimes only a few millimetres—is unintentionally left behind during the spay procedure and remains functional, continuing to produce hormones. Owners often notice behaviours or physical changes they associate with being in season: a female dog may attract male dogs, show vulval swelling, or display behavioural changes, while a female cat may call, adopt mating postures, or show restlessness. These signs can appear weeks, months, or occasionally years after the spay, and the timing often surprises owners who assumed the surgery was complete. This page explores what these signals can look like in practice, the biological mechanism that allows remnant tissue to function, how the condition is investigated when suspected, and the range of approaches that exist once a remnant is identified.