Count me amongst the skeptics, but...
Apparently (after spending some time on Google) external sphincter dilation is a known medical procedure. It's used as an alternative to, and for the same indications as, sphincterectomy...
I still have a hard time making the leap to finding a doc willing to do this given the relatively benign symptoms given... Sphincterectomy, stents, and apparently dilation, are usually only used to protect the kidneys from extreme urinary retention.