DES or Diethylstilbestrol is a synthetic female hormone. It was once a money maker for Ely Lilly back in the 50s and 60s. Eventually it was link to cancer in the female offspring of women who took the drug, and was taken off the market for human use. At one point it had become extremely difficult to obtain, but apparently it's still available, and used in Veterinary medicine.

The idea of DES is that in some female dogs spayed too early the muscle and surrounding estrogen sensitive tissues did not get a chance to fully develop. Thus there is not enough pressure on the urethra to keep urine from seeping out. In the younger dog where they have good muscle tone, they can compensate for it, but as they age and the muscle tone is lost then you end up with incontinence. What the DES does is to cause swelling of the Estrogen sensitive tissue, giving the muscle something to push against, claimping down on the urethra.

If it were my dog I would question the Vet about the idea of giving one of the estrogen analogs, rather than a synthetic estrogen such as DES which has been linked to cancer. You would be trying to use the absolute minimum needed for short periods of time. The danger is possible stimulation of the mammary tissue leading to cancer if too high a dose is used. Hopefully you can minimize that danger while getting enough tissue developed or barely swelled to help give the dog better control.

If you have noticed your dog drinking more water, panting, or gaining weight then you should ask your Vet about the possibiity of Cushings disease being present.- see Cushings thread. For example when a dog is placed on high doses of prednisone (i.e. mimics high levels of corticosteroids as seen with Cushings) it's not too unusual for their water consumption to increase, and for them to have wee-wee accidents in their sleep. Just another possibility to ask the Vet about.