What does bilateral extrarenal pelves are seen which are prominent more so on right kidney then left mean in a ct scan. also states mild hydronephrosi?

Hydronephrosis: Extrarenal pelvices are of no consequence on a ct; hydronephrosis is an indication of obstruction and additional evaluation is needed.

Likely no problem: Extra-renal pelves are a normal variant. Just meen the kidney funnel for urine leaving the kidney is outside the kidney rather than inside. Most cases of mild hydronephrosis or of little or no consequence unless you have kidney pain suggesting obstruction, most likely from a stone. Also needs furether evaluation if you have a UTI especially if infection has reached the kidneys.