What causes hydronephrosis?
There are many causes of hydronephrosis, including: • A blockage, which can occur between the kidney and the ureter (pelviureteric junction or PUJ), between the bladder and the ureter (vesicoureteric junction or VUJ) or in the urethra (posterior urethral valve). • Vesico-ureteric reflux (VUR) occurs when the valve between the ureter and the bladder does not work properly and urine can travel back up to the kidney. For more information, please see our Vesico-ureteric reflux leaflet. • Ureteric duplication, which affects about 1 per cent of all people. Children with ureteric duplication have two ureters leading from a kidney to the bladder, instead of one. Occasionally, they have a blockage at the lower end of one of the two ureters called an ureterocele. • A multicystic dysplastic kidney (MCDK) is a non-functioning kidney made up of many cysts. Sometimes these shrivel up and disappear, but some need to be removed at a later stage. For more information about this, please see our Nephrect
