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361: Fetal hydronefrosis (HY): a contribution to a challenging diagnosis

      Objective

      To evaluate the postnatal course of fetal HY and to assess the ability of prenatal US to predict an unfavourable outcome.

      Study Design

      Six years (2002-2007) cohort retrospective study including fetuses with HY with 100% infant follow-up. US was performed in the II and III trimester. At the last scan HY was classified as: I degree (5-7mm), II degree (8-15 mm) or III degree (> 15 mm). Postnatal US was performed at 1, 3, 6 months.

      Results

      HY was diagnosed in 109/22, 137 fetuses (0.7%), with 143 kidneys involved. Postnatal outcome was favourable in 82% of the affected kidneys, with HY regression in 3.3 ± 3.1 months. In 18% postnatal outcome was unfavourable, with a diagnosis of significant uropathy. The risk of uropathy was 11%, 18% and 46% for HY of I, II and III degree, respectively (P=0.03). There was a significant difference between the value of the average antero-posterior diameter of renal pelvis in favourable outcome group (9.6 ± 3.7 mm) and unfavourable outcome group (15.9 ± 9.3 mm) (p<0.001). The most optimal threshold of antero-posterior (AP) pelvic diameter to predict significant uropathy was 7 mm (sens.100%, spec.23%).

      Conclusion

      The risk of uropathy increases significantly according to the degree of antenatal HY. Postnatal follow-up studies are warranted if the AP pelvic diameter is ≥7 mm in the III trimester of pregnancy.
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