Health advice. Observation pls clarify!

Baby age 3rd day weight 3.5kg normal delevery . Before delevry while in pregnency on 8th month itself mother scan  report shows left hydronephrosis . But baby feeding well and passing urine today we went for pediatrician 1st checkup and shows old report of mother scan profile . But  just doctor said need to observe urine position direction hint given later after month scaning required said to rule out . My concern is how can we consider any clue pls reply to rule out hydronephrosis problem how can we find in baby at home . What to observe like symptoms pls tell .. Urine speed it goes to upper position or lowr position pls tell Baby mother said his private part looks like standing upper direction showing and getting hard little observation Pls clarify