Right flank pain in 17 yo son with dark urine?

If he is dehydrated, give him water immediately. Your liver is on the right side of your body, and if there are problems with it, some symptoms can be dark urine. If the urine lacks a bad smell and he is feeling fine other than that (no chills, fever, nausea) then go to the doctor and order a comprehensive metabolic panel or complete blood count. This will rule out any problems other than urinary. Good luck.