The diagnosis of all forms of RTA ultimately rests on finding an elevated urine pH or decreased urinary ammonium excretion in the presence of hyperchloraemic metabolic acidosis. [2] [3] In the case of proximal RTA, the diagnosis requires the demonstration of bicarbonate wasting in a patient presenting with hyperchloraemic, hypokalaemic metabolic acidosis. [2] [3] [5] The confirmatory testing for Fanconi's syndrome addresses two evaluations: