Bilateral hydronephrosis is the distention of the pelvis and calyces (the urine-collecting structures) of both kidneys.   Bilateral (meaning both sides) hydronephrosis develops when the pelvis and calyces of both kidneys become distended because urine is unable to drain from the kidney down the ureters into the bladder.   Hydronephrosis is not itself a disease, but rather a physical result of whatever disease is keeping urine from draining out of the kidneys, ureters, and bladder. The symptoms, treatment, and expected outcome are those of the responsible disease. For more information, see:   Bilateral hydronephrosis  http://www.healthcentral.com/ency/408/000474.html   Best of luck.    - MG