I am 31 years old and 22 weeks pregnant. Last week I was admitted to the hospital with extreme pain in the right side of my lower back and a possible bladder or kidney infection including an inability to empty my bladder. Since my urine was totally clear, UTI and kidney infection as well as kidney stones were ruled out. I ended up having my appendix removed (which later appeared to be clear of infection) and still couldn't empty my bladder. A renal ultrasound revealed that my bladder and right kidney were completely full of fluid. After having a catheter for 4 days, I am able to empty my bladder (as shown on another ultrasound) but my right kidney is still full of fluid and no one can tell me why. The doctor said that inactivity can result in the ureter being squished and fluid backing up, but I am a first grade teacher on my feet and moving all day. I participate in STEP aerobics classes and have a 3 year old that I keep up with. I don't think I can possibly be called inactive. So, what could cause this and what can be done? I am due for another renal ultrasound and a visit to my urologist in 3-4 weeks, but have to return to school next week still in pain when I move too much. Thank you for any information you are able to provide. I feel that it is greatly important for me to be actively involved in my own medical care.