Have you thought about a chiro adjustment? I know it doesn't sound like they could be connected... but with my girl Tegan she was spayed at about 2.5 years old and was incontinent at about 3.5 years old. She was put on medication and that seemed to help (but not 100% perfect). Life went on like this for another year or so when we started chiro with her. After a while we started to wean her off her meds and she was never leaked again... She lived to be 8.
The chiro and the vet can't say for sure that the chiro cured her incontinence, but it sure seems likely to me!
Tegan 8/23/96-7/30/04 CH. CGC, THD, VADC, VAADC
Owen 5/9/99 ADC
Payton 7/18/04 AGN.J, AGN, SGDC, ADC, AADC