This study will be conducted to compare early (seven days) versus delayed (14-21 days) definitive ureteroscopic lithotripsy after initial drainage for obstructing ureteral or renal stones associated with infection.

All the study participants will be monitored during the early post-operative period for post-operative pain and complications. The rate and grade of reported complications will be determined according to modified Dindo-Clavian grading system. After ensuring safe status for discharge, all patients will be reassessed at the outpatient department after 4 weeks by NCCT to assess stone free status.

Inclusion Criteria:

1. Obstructing ureteral or renal stone <20 mm.
2. Associated clinical evidence of acute upper urinary tract infection based on systemic inflammatory response syndrome (SIRS).

Exclusion Criteria:

1. History of endoscopic instrumentation to the urinary tract in the last 4 weeks prior to presentation.
2. Bilateral obstructed kidneys necessitating bilateral drainage.
3. Associated emphysematous pyelonephritis or perinephric abscess.