This is a small plastic tube that is placed into the urinary system using a cystoscope.
The procedure is carried out under general anaesthetic and the tube is sited from the bladder into the kidney. It will allow drainage of urine from the kidney into the bladder.
It is used to relieve obstruction if, for instance, a stone is blocking the ureter. It is called a J-J stent because of its curled shape at each end.