The magnitude of fetal renal pelvic dilatation can identify obstructive postnatal hydronephrosis, and direct postnatal evaluation and management

Division of Urology, and Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
The Journal of Urology (Impact Factor: 3.75). 09/2006; 176(2):724-7; discussion 727. DOI: 10.1016/j.juro.2006.03.079
Source: PubMed

ABSTRACT Up to 1% of prenatal ultrasounds will detect fetal renal pelvic dilatation. We sought to evaluate and determine whether fetal renal pelvic measurements may appropriately direct prenatal counseling and postnatal evaluation and management.
We performed a retrospective analysis of prospectively collected measurements of anteroposterior renal pelvic dilatation obtained at a single fetal maternal medicine center between 1990 and 2003. Fetuses with renal pelvic dilatation 4 mm or greater at less than 33 weeks of gestation, or 7 mm or greater at more than 33 weeks of gestation were evaluated postnatally at a single pediatric urology center. Infants with renal pelvic dilatation were evaluated with ultrasound, voiding cystourethrograms and renal scintigraphy. Renal obstruction was the main outcome measure assessed. Obstruction was defined as the need for surgery and was not based on the renal scan drainage time. Indications for surgery included declining function and increasing hydronephrosis.
There were 257 neonates with prenatally detected renal pelvic dilatation. A mean maximum prenatal renal pelvic dilatation of 11.8 mm was seen in 195 patients with nonobstructive dilatation. In the 62 patients with obstruction there was a nearly 2-fold increase in the mean renal pelvic dilatation (22.3 mm), which was statistically significant. Receiver operating characteristic analysis revealed that when 15 mm renal pelvic dilatation is used as a threshold it correctly discriminates obstruction in at least 80% of fetuses with a sensitivity of 73% and a specificity of 82%.
The magnitude of fetal renal pelvic dilatation is predictive of obstruction. Our results suggest that 15 mm renal pelvic dilatation represents a significant threshold. Receiver operating characteristic analysis provides a useful guide for prenatal counseling and may help to direct the postnatal evaluation.

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    ABSTRACT: Introduction and Objective: Hydronephrosis (HN) and obstruction are closely associated, but upper urinary tract dilatation can occur without significant obstruction. Despite some pitfalls, conventional ultrasonography and diuretic renography (DR) are the main modalities in the evaluation of HN in children. Recent reports have demonstrated the usefulness of Color Doppler Ultrasonography (CDUS) as a reliable method to identify the ureteric jets (UJ) in the bladder. The aim of this study was to evaluate CDUS evaluation of the UJ in the bladder as a diagnostic tool to distinguish obstructive from non-obstructive dilatations of the upper tract in pediatric population. Methods: We evaluated 48 patients (35 boys and 13 girls), aged 1 month to 14 years (median = 4 ys.), who presented with unilateral grade III and IV hydronephrosis suspicious of pyeloureteral junction obstruction. All patients underwent DR and evaluation of UJ by transverse CDSG of the bladder within a maximum of 2 weeks. Obstruction was considered in the DR when the hydronephrotic unit showed Differential Renal Function of less than 40%, or when symptomatic intermittent renal colic was present in older children. The number of UJ was counted over a 5 min period and its frequency was calculated for each ureteral orifice. Relative Jet Frequency (RJF) was defined as the UJ frequency of hydronephrotic side divided by total UJ frequency. Receiver-Operating Characteristic (ROC) plots were constructed to determine the best cuttoff for RJF, in order to identify renal units with obstructive hydronephrosis. Results:Twenty-two(45.8%) hydronephrotic units were considered obstructed. The mean RJF differed significantly between obstructive (0.09 ± 0,15) and non-obstructive hydronephrosis (0.41± 0.11)(p<0.001). ROC analysis revealed that RJF< 0.25 was the best threshold and it correctly discriminates obstruction in 91.2% of the childrens with a sensitivity of 86.4% (95%CI=78.6-98.2%) and specificity of 96.15% (95%CI=87,8-99%). The Positive Likelihood Ratio was 22.45 and Diagnostic Odds Ratio was 158.3.The area under the ROC curve was 0.91 (95%CI=0.86-0.98), indicating excellent discrimination power. Conclusions: In this study RJF < 25% was found to be a good indicator of obstruction in children with unilateral hydronephrosis. CDUS evaluation of UJ is an easy and non-invasive method that can be used as an initial diagnostic tool and in follow-up cases, to differentiate obstructed from non-obstructed hydronephrosis in the pediatric population
    08/2007, Degree: PhD, Supervisor: Francisco Tibor Dénes