What tests are needed to further define hydronephrosis?

In most cases, ultrasound imaging is used to discover kidneys that are hydronephrotic. Once a kidney has been determined to be hydronephrotic, depending on the age and gender of the baby, a bladder X ray should be performed to look for backwash of urine up to the kidney (vesicoureteral reflux) or blockage in the urethra if the child is male.

In other instances where the condition is quite severe, a nuclear medicine renal scan should be performed to rule out obstruction of the kidney. An obstruction might require surgical intervention to preserve the kidney.

If the hydronephrosis involves both kidneys, then further evaluation with a standard blood test should be performed in the hospital or office to make sure that kidney function is normal.