HI Bob ! Sentinel piles are formed in chronic fissure by the natural defensive mechanism of the body to cover the fissure. You may try some short term steroid
cream for the itching. If it does not help, I would suggest you to consult a surgeon for removal of the sentinel piles along with a curative surgery for the fissure so that you are not troubled later for the fissure again.
The surgery is a simple one though under anaesthesia, and the recovery time is around seven days maximum although you may be allowed home in the afternoon of operation or the next day.
You are also suggested to modify your dietary habits towards more of vegetables, fruits for roughage and plenty of water as well to avoid constipation
Wishing you an early recovery.