Swelling in a kidney due to a backup of urine.
Hydronephrosis is caused by a blockage in the tube that connects the kidney to the bladder (ureter). Possible causes include a kidney stone, an infection, an enlarged prostate, a blood clot or a tumor.
Pain in the side, back or groin and trouble urinating are some symptoms.
Treatment may include antibiotics or surgery. In severe cases, the urine may need to be drained from the bladder or kidney.