Ha! Those nerve endings must of woken up after all this time. Weird though that it would actually coincide with a full k-pouch. Maybe the general fullness in your abdomen puts pressure in the rectal area still and stimulates those nerves.
A shame though. You'd think that at least you'd be forever free of that sense of urgency... Hopefully, it is like phantom limb syndrome and will fade with time. I know itseems strange to appear this long after surgery, but it can take up to a year for nerve trauma to resolve.