The two could be quite unrelated. Most people have the urge to empty their bladder when they wake up. The pain may be caused by the position you lay in bed or the mattress may be to soft. The walk to the loo excercises the back/hip muscles and the pain is soon gone. As always... "If the pain persists, see a doctor".
Morningwood Rise; right guys.. there's a medical reason for that; it keeps you from wee-ing the bed; maybe the backache serves a similar purpose for women, to wake them up. oops does that sound unfair? sorry, women..
I have a related problem when I have back ache I usually have to wee more and my theory is that because my back muscles go into a spasm my bladder is squashed because its just an empty bag so it can't fill up like it normally can pregnant women usually go to the loo lots more than they normally do.Its worth going to the doctor just to make sure theres nothing else wrong though .