Found this on a website
http://www.herbal-treatments.com.au/articles_treating_canine_incontinence.html
I have no idea if it is effective.
Herbal Treatment:
Structural incontinence was another condition common throughout the ages, especially with larger families, and there are very specific herbs which support and improve the muscle tone of the sphincter. There are others which can rehabilitate to some extent, nerve and muscle wastage generally.
All the same herbs traditionally used for human stress incontinence are suitable for dogs even through the cause of the sphincter weakness may be different. A typical mix would include the following herbs;
Couch Grass: Specific for sphincter rehabilitation.
Horsetail: Assists in strengthening wasted or damaged tissue.
Comfrey: Speeds up healing even of old trauma.
Mugwort: Supports repair of nerve fibers along with the herbs above.
Saw Palmetto: Specific for muscle wastage and lack of tone.
An initial course of three months of such a mix will often be enough to reverse completely a structural incontinence problem if identified early. Longer-term maintenance doses may be required to maintain the result in more serious cases.
Canine Incontinence Mix