Value of supranormal function on 99m Tc-mercaptoacetyltriglycine renal scan in paediatric patients with obstructive hydronephrosis.

Supranormal function is related to large hydronephrosis where geometrical features are modified. A preoperative APD ≥30 mm is a reliable predictive factor of supranormal function. Preoperative renal function is overestimated either in supranormal patients or severe hydronephrotic kidneys. DRF should be interpreted with caution in kidneys with large hydronephrosis with or without supranormal function. Surgical indication should not entirely rely upon DRF.