Diuresis renography and ultrasonography in children with antenatally detected hydronephrosis can support diagnoses and suggest related surgery treatment.

OBJECTIVE: Prenatal ultrasound (US) screening detects the hydronephrosis (HN)-dilatation of fetal renal collecting system in 1%-5% of all pregnancies. In most children, HN is detected by prenatal US screening between 18-20 gestational week. Pelvi- ureteric junction (PUJ) stenosis is the most common etiological factor of prenatal HN and requires postnatal follow-up. Diuresis renography plays important role in the follow-up by complementing morphological information obtained by US with the data about differential renal function (DRF) and drainage. We studied the association between ultrasound parameters and results of diuresis renography in first diagnosed PUJ stenosis and the predictive factors of pyeloplasty in order to evaluate the usefulness of diuresis renography in these children postnatally.

PATIENTS AND METHODS: Children with antenatally detected HN attributed to presumed PUJ stenosis were investigated with mercapto-acetyltriglycine (MAG3 ) diuresis renography. Parents gave informed consent for the procedure. The inclusion criteria were: age up to 4 years, diagnosis of prenatal HN determined by US during pregnancy based on the antero-posterior diameter (APD) of renal pyelon and at least one post-natal US which confirmed diagnosis. Exclusion criteria were: APD of pyelon <10mm, previous surgical treatment of HN, vesicoureteral reflux excluded by micturating cystourethrography, and patients having any anomaly of the contralateral kidney. Sixty two patients 43 boys, 19 girls, median age 16 months were selected. They were divided into three groups based on the size of pyelon, three groups based on the calyceal size and two groups according to thickness of parenchyma. Renography was performed for 24 minutes after the iv. application of 99m Tc MAG3 , 144 ten-sec images were applied. Furosemide was administered after 2 min. (F+2). Post-void static images were acquired at 60min. The non-commercial software developed by International Atomic Energy Agency was applied to process the studies. The criteria for pathological findings (poor or no drainage) were the renographic curve maintaining a plateau, Normalized Residual Activity (NORA) at 20. min.>1.62, Output efficiency (OE) at 20. min.<71%, postmicturating NORA >0.11. The DRF was considered normal within the range of 45%-55%.

RESULTS: Good drainage had 74% of children, partial drainage 11%, and poor 15%. There was a clear association between the size of pyelon, calyces, parenchyma thickness and drainage. There was also a clear association between the calyceal size, parenchyma thickness and DRF. Differential renal function was <45% in 18% of children. A relation between the type of drainage and DRF was not determined. Thus, 66.7% of those with poor drainage had preserved DRF. Seven out of nine children with poor drainage underwent pyeloplasty. The threshold for pyeloplasty was the pyelon of 18mm and calyces of 10mm. The model of the multivariate logistic regression which included ultrasound parameters (APD of pyelon, calyces size and parenchymal thickness), drainage and DRF, which were significant predictors in univariate analysis, showed that only drainage was an independent predictor for the need of pyeloplasty.

CONCLUSION: Antero-posterior diameter of the pyelon <15mm indicates a favorable course of congenital HN in most children. Pattern of drainage obtained by diuresis renography was the only independent predictor for the need of pyeloplasty.