LP, they put the catheter in because the bladder has to be completely empty otherwise (if it's full) it sits right over the area where the surgeon makes the incision. Keeping the bladder empty deflates it and keeps it out of the way. Also removes the need to go to the toilet for the first few hours afterwards before you get out of bed.

At our hospital, you can either choose to have the catheter put in in the privacy of a pre-surgical room (just you and a nurse) which is more private but you feel it (uncomfortable, I imagine). Or you can elect to wait until after the spinal has gone in (in theatre) which means you won't feel it but there will be more ppl in the room by then.

I'm opting to have it put in after the spinal, I'd rather be comfortable and I figure they'll all get a good look at my bottom end anyway!