An 8 year old male is brought in by his mother with weakness, problems walking, excessive thirst and urination. The child has not had any gastrointestinal problems and is on no medications. Blood pressure and physical exam is normal. Laboratories show sodium 140 meq/L, potassium 2.4 meq/L, bicarbonate 31 meq/L, and chloride 102 meq/L. 24 hour urine collection shows sodium 210 mmol, potassium 52 mmol, and chloride 32 mmol. There is bilateral symmetrical enlargement of the kidneys but no hydronephrosis on ultrasound. Plasma renin is elevated. Select the most likely diagnosis.