The aim of the procedure is to widen the abnormally narrowed part of the PUJ. With the patient under general anaesthesia, a cutting device (which may be a laser or a diathermy probe, or an endoscopic knife) is inserted into the PUJ area endoscopically via the ureter, or via a percutaneous approach in the flank. Under endoscopic visualisation a full-thickness incision is made, through the wall of the ureter, into the periureteric fat. A stent is inserted across the PUJ, with the aim of maintaining patency, and is removed after several weeks.