What are the grades of vesicoureteral reflux?

I: Reflux limited to the lower ureter
II: Reflux extended to the renal pelvis
III: Reflux with mild hydronephrosis and hydroureter
IV: Reflux with moderate hydronephrosis and hydroureter blunting of calyces
V: Reflux with severe hydronephrosis, tortuous ureter, absent papillary impressions in the calyces