Hydronephrosis describes a condition of urine-filled dilation of the collecting system. Normally, urine flows through the urinary tract with minimal or low pressure. If the build-up of excess fluid in the urinary collecting system continues, there will be an increase in pressure and atrophy of renal cortex. If hydronephrosis is left untreated for a long time, renal damage with permanent loss of function occurs

Inclusion Criteria:

• 1) Patients for whom a percutaneous nephrostomy is indicated provided that the hydronephrosis is advanced ( parenchymal thickness not more than 5 mm ) 2) Patients for whom a nephrectomy is planned for a seemingly poorly functioning kidney along with either

Exclusion Criteria:

1. Target kidney is the only functioning or better functioning kidney or otherwise substantially contributing to the total renal function, so nephrectomy is not likely.
2. Emergency cases where the general condition of the patient cannot withstand the logistics of undergoing a radioisotope study eg
3. Malignancy in the target kidney
4. Patients unlikely to undergo a nephrectomy

Patients will be recruited from out-patient clinics and in-patient sectors of Assiut Urology and Nephrology hospital