UTILITY OF TECHNETIUM-99M-MAG3 DIURETIC RENOGRAPHY IN THE NEONATAL-PERIOD

Diuretic renography performed in the neonatal period has been reported to be unreliable in diagnosing obstruction. Methods: The scans of 27 neonates (age up to 28 days; mean 17 days) with a total of 53 renal un its were reviewed; a renal unit being defined as comprising a kidney a nd its ureter. All were referred following perinatal ultrasound diagno sis of hydronephrosis or hydroureteronephrosis. The neonates had stand ard diuretic renography using MAG3 with a frusemide dose of 1 mg/kg fo llowed by another image obtained after gravity-assisted drainage, Resu lts: There were 17 normal undilated renal units showing excellent diur etic responses with clearance half-times of 0.6-7.7 min. Eighteen rena l units were diagnosed as having pelvi-ureteric junction (PUJ) obstruc tion, with surgical confirmation in all, Eight were diagnosed as unobs tructed and of these seven were confirmed nonobstructed by serial imag ing using ultrasound and MAG3, but one subsequently had pyeloplasty pe rformed for PUJ obstruction. One unit was indeterminate for PUJ obstru ction but had good clearance with gravity-assisted drainage and was sh own to be unobstructed on repeat studies. Of nine units diagnosed as h aving vesico-ureteric junction (VUJ) obstruction, eight had surgical c onfirmation and one remains of uncertain final diagnosis. Co-existing VUJ obstruction could not be diagnosed in two units with PUJ obstructi on because of insufficient radiotracer drainage through the tight sten osis into the ureter. Conclusion: An adequate diuretic response is pre sent in the neonatal period using MAG3 and this allows for reliable di agnosis of obstruction. An unobstructed or indeterminate result necess itates follow-up imaging to ensure obstruction does not develop. Co-ex isting VUJ obstruction may be missed in a scan showing PUJ obstruction .