Utility of technetium-99m-MAG3 diuretic renography in the neonatal period.

UNLABELLED

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 units were reviewed; a renal unit being defined as comprising a kidney and its ureter. All were referred following perinatal ultrasound diagnosis of hydronephrosis or hydroureteronephrosis. The neonates had standard diuretic renography using MAG3 with a frusemide dose of 1 mg/kg followed by another image obtained after gravity-assisted drainage.

RESULTS

There were 17 normal undilated renal units showing excellent diuretic responses with clearance half-times of 0.6-7.7 min. Eighteen renal units were diagnosed as having pelvi-ureteric junction (PUJ) obstruction, with surgical confirmation in all. Eight were diagnosed as unobstructed and of these seven were confirmed nonobstructed by serial imaging using ultrasound and MAG3, but one subsequently had pyeloplasty performed for PUJ obstruction. One unit was indeterminate for PUJ obstruction but had good clearance with gravity-assisted drainage and was shown to be unobstructed on repeat studies. Of nine units diagnosed as having vesico-ureteric junction (VUJ) obstruction, eight had surgical confirmation and one remains of uncertain final diagnosis. Co-existing VUJ obstruction could not be diagnosed in two units with PUJ obstruction because of insufficient radiotracer drainage through the tight stenosis into the ureter.

CONCLUSION

An adequate diuretic response is present in the neonatal period using MAG3 and this allows for reliable diagnosis of obstruction. An unobstructed or indeterminate result necessitates follow-up imaging to ensure obstruction does not develop. Co-existing VUJ obstruction may be missed in a scan showing PUJ obstruction.