99MTC-MAG3 RENAL DIURETIC SCINTIGRAPHY IN DIAGNOSIS AND FOLLOW-UP OF PAEDIATRIC DUPLEX KIDNEY

Introduction: Paediatric duplex kidney is usually studied with 99mTc-DMSA scan, which is unable to evaluate the hydronephrosis frequently observed in this condition, nor the wash-out from the contralateral kidney, frequently abnormal on the ultrasound scan. This study evaluates the routinary use of 99mTc-MAG3 diuretic scintigraphy in the diagnosis and follow-up of paediatric duplex kidney. Patients and methods: Seventy-three children were enrolled (sex F=45, M=28, age at first scintigraphy: median=8.6 months) with hydronephrosis and known/suspected duplex kidney. In 14/73 cases the contralateral kidney presented ultrasonographic abnormalities. Micturating cysto-uretreography was performed in all patients and an ureterocele was detected in 28 children. An endoscopic treatment was performed in 10 cases during the follow-up. All patients underwent 99mTc-MAG3 renal diuretic scintigraphy following the guidelines of the Paediatric Group of the EANM: controlled hydration (10 ml/kg/30 min), no sedation, no bladder catheter, F20 protocol, post-void image. Differential renal function (DRF) has been calculated for every renal unit, drawing ROIs on the single moieties. Results: A duplex kidney was observed in 36/73 on the left side, in 18/73 on the right side whereas the remaining 19 children had a bilateral duplex kidney. Vesico-ureteral reflux (VUR) was detected in the lower pole of 21 duplex unit and in the non-affected kidney in 10 cases. DRF in the duplex units resulted only slightly reduced (mean=47%), but a relevant (<35%) loss was already present at the first scan in 11 cases. It has been possible to evaluate the function of the single moieties in every patients in this group and the most severe reduction has been detected in the upper pole (mean=16% relative to total renal function). Absent or negligible function has been observed in 18/73 cases (3 with renographic obstructive pattern). Ureterocele was present in 13/18, but only in 15/55 patients with measurable function (p<0.01 Fisher exact test). Eminephroureterectomy was performed in 9/73 cases, based on the association of markedly reduced DRF and recurrent upper urinary tract infections. The post-operative DRF of the affected kidney remained stable. The diuretic renography excluded obstruction in all hydronephrotic contralateral kidney, supporting a conservative approach, even when pelvic and/or ureteral dilatation was marked. Conclusion: The study demonstrates the usefulness 99mTc-MAG3 diuretic renography in the diagnosis and follow-up of paediatric duplex kidney. The capability to evaluate the diuretic wash-out from the single moieties of the duplex units and from the contralateral kidney is a significant clinical advantage over 99mTc-DMSA.