HYPOTHESIS / AIMS OF STUDY The Gold standard surgical treatment for uretro-pelvic junction obstruction (UPJO) is Anderson Hynes (AH) dismembered pyeloplasty resulting in a dependent tension free anastomosis that relieves obstruction and helps functional improvement. The available ultrasound parameters that reflects functional improvement after AH are only the supportive parameters in form of decrease in the antero-posterior diameter (APD) of renal pelvis and increase in parenchymal thickness in a growing kidney. Measurement of APD is too limited in evaluating pyeloplasty as it is a 1 dimensional measurement. So, renal parenchymal thickness to hydronephrosis area (PHAR) including renal pelvis and renal calyces in different dimensions may provide a more accurate estimate of the renal size, amount of pelvicaliectasis and possibly the renal function for prediction of pyeloplasty outcome. STUDY DESIGN, MATERIALS AND METHODS The study included 30 children having UPJO and scheduled for open Anderson-Hynes pyeloplasty between April and October 2019. All included patients did an abdominal ultrasound to assess parenchymal thickness, PHAR, renal echogenicity. PHAR was done preoperatively and postoperatively at 3 and 6 months. Following the outline of the kidney to obtain the whole surface area of the kidney including the parenchymal (RPA) and the hydronephrosis areas. The following equations were used: RPA= total renal area - hydronephrosis area. PHAR = Hydronephrosis area / RPA RESULTS The median age of study was 9.5 years. Improvement rate after pyeloplasty was 83.3% according to clinical and radiological improvement by ultrasound and renal isotope scan. Pelvic APD and half time (T/2) postoperatively were significantly lower among improved cases, parenchymal thickness, glomerular filtration rate (GFR) and split function postoperatively was significantly higher among improved cases, and PHAR postoperatively was significantly higher among improved cases. INTERPRETATION OF RESULTS Pelvic APD and T ½ postoperatively showed significantly negative correlation with PHAR postoperatively while parenchymal thickness, split function, GFR total pre and postoperatively showed significantly positive correlation with PHAR postoperatively. When a cutoff value for PHAR of 1.89 is assigned to a ROC curve it showed sensitivity 84% specificity 80% for improvement. CONCLUDING MESSAGE PHAR can be used as a good indicator of success of pyeloplasty and improvement of renal function postoperatively with a positive correlation with renal isotope. The cutoff value of PHAR post-operatively is 1.89 with PHAR above it indicates improvement and can omitting radioisotope scans of those patients.