Objective: Pyonephrosis is defined as accumulation of purulent debris in the renal pelvis and urinary collecting system. Urinary diversion through percutaneous nephrostomy (PCN) is the first choice of treatment for pyonephrosis. Even after PCN insertion some patients end up with complete loss of renal function. We aim to determine the proportion of patients undergoing complete loss of renal function after PCN insertion, the factors facilitating renal function recoverability and the complications of the procedure.