Hydronephrosis is not a disease but a condition that makes kidney swell because of damage to the urinating collecting system of the body. Normally urine flows through the urinary tract but when there is a blockage in the urinary tract, the patient needs to put an extra effort in order to allow the urine to pass.
Hydronephrosis is a condition that typically happens when a kidney swells as pee fail to genuinely run down from the kidney to the bladder. This swelling most normally impacts only a solitary kidney; it can incorporate both kidneys.