What Is The Treatment For Vibrating Sensation In The Rectal Area?

I have been experiencing a rectal pulsating sensation for two days, with no pain. I am 68 yrs old, 5ft 2in and weigh 125lbs and am in good health. I was diagnosed two years ago with Celiac Disease, and have been very strict with my diet since then. My labs are fine and all within normal limits. What could be causing this sensation?