<prompt> In hydronephrosis from pelvi-ureteric junction PUJ obstruction idiopathic or congenital hydronephrosis, which of the following statements are false?The condition may be asymptomaticIt can be diagnosed in uteroUltrasound scanning is the least invasive method of imagingIf there is more than 5 per cent of function in the obstructed kidney, a procedure to preserve the kidney is carried out  <response>: 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. 