A mucus like discharge from the vulva is an indication of a potentially deadly condition called cystic endometrial hyperplasia. This can lead quickly to the life threatening disease called pyometra. This is where the uterus enlarges and fills up with a purulent exudates (pus). These dogs need to have the uterus and ovaries removed surgically as soon as possible. This is basically a spay surgery but is more complicated due to the enlarged uterus and the potential for uterine rupture which would spill the pus into the abdomen. Other signs of this disease are anorexia (not eating or drinking), lethargy, weakness, vomiting, abdominal distension and sometimes excessive thirst and urination. Pyometras typically occur 1-12 weeks following a heat cycle. Most dogs recover well following surgery if there has been no uterine rupture. This disease can largely be avoided by spaying your dog at an early age. If a dog is used for breeding then she should be spayed as soon as she retires from breeding.