Pain at waist

I had surgery the same day as you and actually ended up going to the ER last night because pain in my left side at my waistline got so bad.  It. felt like a pressure pain and would intermittently "grab".  The grabbing pain would take my breath.  I ended up being in surgery I think almost ten hours because there were some problems with my liver and I ended up needing my gallbladder removed also.  I had an ultrasound of the painful area last night and found out that my spleen is slightly enlarged and irritated and my ribs are bruised from being on the OR table so long and from the surgical instruments moving around so much for so long.  I was assured that in time it would go away.  If it were not for this pain, I would be ready to get out and do things within moderation.  This may not be the same problem you are having, but it is possible for our internal organs to become irritated when they get jostled around.