Hi Pamela,
My first guess would have been SRT, too. Any other cause for the diarrhea? It is the number one formula for abnormal micturition due to disc disease.
The incontinence patterns suggest a neurogenic cause to the incontinence. As to how SRT and SFZYT could both create adverse effects (in different areas), the only common link to them is that they are both relatively drying. If that is the issue, we would see signs of Yin or Blood deficiency, and the small pulse fits with that.
So, considering the breed (Dachshund), the chief complaint (IVDD), and the pulse, I would suggest Du Huo Ji Sheng Tang as the alternative. We've had rare cases of IBD and lymphangiectasia resolve on it, and it supports Kidney function to concentrate urine
Hope that helps,
Steve