Hi, You might be having a stone in left ureter (the tube connecting kidney to bladder). This might have been the cause for your left sided back pain. Usually a stone in ureter is a little difficult to visualize in ultrasound, especially if it is in the middle part of ureter (since intestines block the view). However, there may be some swelling in the kidney (hydronephrosis), if there is a stone blocking the ureter. This can be picked up easily in ultrasound. The other tests for stone are urine analysis (to look for blood in urine), X-ray KUB (Kidney, Ureter and Bladder region) and if in doubt, a CT scan. Ureteric stones less than 10 mm size are treated with medical expulsive therapy, which include some drugs to dilate ureter and reduce local swelling so that stone can be passed. I would advise you to first confirm whether your pain is due to stone (based on the tests suggested) and then start appropriate treatment (medical expulsive therapy) under a Urologist. Pain relief can be achieved by routine pain killers, although it needs to be prescribed by a physician or Urologist. In the meanwhile, drink lot of fluids (3 to 4 liters per day) and take citrus fruits like lemon and orange. I am available to guide your further based on the above reports. Wish you a speedy recovery, Dr. Raguram G MS, MRCS, MCh (Urology), Fellow in Endourology