My cat’s vulva is bleeding and smells bad; she is almost 1 year old. What is wrong?

Bleeding from the rear can have many causes. In a female it may be a reproductive issue such as pyometra, uterine fluid, vaginitis or miscarriage; in a male it is usually bloody urine from the urinary system. First take the temperature; fever points to infection.

Red discharge with a foul smell and pus in a female strongly suggests pyometra and endometritis; if urination is normal, urinary causes are ruled out. Have a vet do an ultrasound and bloodwork, then treat accordingly, and use an Elizabethan collar during treatment.