Anal Orgasm?

[pigsnizzle]

I've read posts in thread about the pleasure of anal, that some people can cum while recieving anal.
I've been having an experience for a while now that feels like an Orgasm in My ass. I Dildo a while and the pleasure builds up till I feel... almost like a pulsating pleasure in my ass and it causes a little bit of urine to squirt from my cock like a water gun. I usually take the dildo out at the climaxing feeling and put it back in when the spasming feeling is done. A few more strokes and I could have another seconds later.
What kind of orgasm is this? Had anyone here ever had a similar experience?