Hello,thanks for writing to HCM. Hydronephrosis can occur due to a number of reasons- most common is an obstruction to the outflow of urine due to a stone. However the ureter and cause of the blockage may not be always seen on an ultrasound due to shadowing by bowel gases. Other modalities available are a plain X-ray-though it may not always detect the stone. You can discuss with your doctor about your monetary concerns, and get the X-ray and also if he can recommend a trial of medication and fluids to flush it out. However size and location of obstructing lesion are important in deciding treatment plan. Hope this is helpful. Take care.