Hi Welcome to Healthcare Magic Forum The condition is k nown as UNILATERAL RENAL AGENESIS. Yes they can lead a fairly normal life , as that kidney tried to compensate. But there are chances that he/she may have other congenital problems/defects, which if present must have been revealed by now. Also chances of developing hypertension (high blood pressure ) are there , for which medication is available.. One has to be regular with check ups (blood pressure, urine tests ) and always be vigilant. Dietary modifications are needed for some, low salt, low- moderate protein intake, avoiding alcohol/coffee/beverages in excess. Most people find out later in life, and accidently that they have had only one kidney for most of there lives. Hope for the best Takecare