<prompt> A child presented with intermittent episodes of left sided flank pain. Ultrasonography reveals large hydronephrosis with dilated renal pelvis and cortical thinning with a normal ureter. Kidney differential function was observed to he 19 which of the following is the best managementNephrectomyPyeloplastyExternal drainageEndopylostomy  <response>: Pelvi-ureteral junction PUSureteropelvic IUPJ UPJ obstruction is the most common obstructive lesion in childhood and is the most common cause of hydronephrosis found on prenatal and early postnatal ultrasonography. It is most commonly caused by intrinsic stenosis of a segment of ureter which is usually localized to the region of pelviureteric junction. Other causes include ureteric folds extrinsic obstruction by crossing lower pole vessels.PresentationHydronephrois revealed by maternal USG Dilated renal pelvis but normal ureter.Palpable renal mass in new horns or infants.Abdominal flank or back pain typically exacerbated by drinking large volumes of liquid.UTUHaemanuia after minimal trauma.EpidemiologyLeft side more commonly involved than right Bilateral 10.Male more commonly involved than females M : F 2 : 1. Initial iagnosis by UltrasonographyHydronephrosis with dilated renal pelvis.Ureter if visualized is of normal caliber not dilated.Renal Differential functionNuclear Renography is used to determine Renal Differential functionA differential function of 40 is considered significant and often an indication for surgical management. ManagementManagement depends on the differential renal function and AP diameter of PUJ :-Differential renal function 40 especially when AP diameter ofPILI 30 min -3 Conservative treatment.Differential renal function 40 especially when AP diameter of PUI 30 MM 4 Surgical treatment is indicated. Pyeloplasty is the surgical procedure of choice. Other surgical procedures used are external drainage nephrostomy, endopyelotomy and nephrectomy.Differential function of 10 is often considered as an arbitary cut off for nephrectomy. 