In hydronephrosis from pelvi-ureteric junction (PUJ) obstruction (idiopathic or congenital hydronephrosis), which of the following statements are false?

Isotope renography is the best test to establish that dilatation is caused by obstruction. It would also determine the percentage function of the kidney. A procedure to preserve the kidney is carried out when a renogram shows that there is more than 20 per cent of renal function. The operation of choice is Anderson-Hynes pyeloplasty, a procedure which is now being carried out laparoscopically.