Diethylstilbestrol is a type of estrogen. It is used for the treatment of urinary incontinence in dogs. It may also be used to treat prostate hypertrophy (enlargement), certain types of cancers, and reproductive conditions. Most dogs being treated with DES for urinary incontinence need to be treated long term, but some dogs may need to be treated seasonally or for several months. Side effects are less common with dosages used to treat estrogen responsive urinary incontinence. At higher doses or long-term use, contact your veterinarian if your pet experiences signs of estrus (female dog coming into heat), feminization in males, lack of appetite, vomiting, diarrhea, vaginal discharge, pyometra (infection in the uterus), lethargy, increased thirst or urination, bruising, bleeding, or anemia while being treated with DES. Prolonged use may cause ovarian cancer. Prolonged use in cats may cause damage to the heart, liver, and pancreas. CAUTION: Pregnant women, or women trying to become pregnant, should avoid contact with DES or any estrogen-containing drug.