MP70-02: The Utility of Renal Medullary Pyramidal Thickness Measurements on the First and Second Postnatal Ultrasound in Infants with Congenital Hydronephrosis
Introduction: Prior studies demonstrating a medullary pyramid thickness (PT) < 3mm as a marker of obstruction and risk of pyeloplasty used the postnatal ultrasound (u/s) demonstrating the largest degree of hydronephrosis (hydro). Since early identification of children at risk of obstruction is clinically useful, we reviewed the PT on the 1st and 2nd postnatal u/s in infants with congenital hydro. Objectives were to determine the prognostic value of: 1) the PT on the 1st and 2nd u/s, 2) a change in PT between the 1st and 2nd u/s, and 3) the ratio of the PT in the hydronephrotic kidney to the contralateral PT in the normal kidney in those with unilateral hydro. We hypothesized that a smaller PT on either the 1st or 2nd ultrasound, as well as a decreasing PT between the 1st and 2nd u/s, and a decreased PT ratio with unilateral hydro, would each be early predictors of pyeloplasty. This study also analyzed the impact on predictive ability of the PT obtained on an u/s obtained <3 days of life compared to those in which the 1st u/s was obtained >3 days of life. Methods: A chart and u/s review of children with isolated SFU grade 3 or 4 hydro was performed. 91 infants (77 boys and 14 girls) met eligibility criteria (105 kidneys). The median age (IQR) at 1st u/s was 1.5 (1.0-15.0) days and 54.0 (27.5-123.0) days at the 2nd u/s. Results: For the group overall, a smaller PT on both the 1st and 2nd u/s was associated with an increased risk of pyeloplasty (p=0.02 and <0.001, respectively), however, a PT obtained on an u/s < 3 days of life was not predictive. A PT of <3mm on an u/s obtained >3 days of life was associated with higher risk of pyeloplasty (AUC=0.8). In addition, a decreasing PT between the 1st and 2nd u/s was a risk factor for pyeloplasty (p=0.002). The PT ratio of hydronephrotic to normal contralateral kidney of the children who had their 1st u/s > 3 days of life was also significant in predicting pyeloplasty(p=0.018;). A ratio < 6mm, 6-9 mm, and > 9mm conveyed a very high risk, intermediate risk, and low risk of pyeloplasty, respectively (AUC =0.83). Conclusions: PT measured on the 1st and 2nd postnatal u/s is useful in determining the risk of pyeloplasty. The PT obtained on the 1st u/s was less predictive when obtained < 3 days of life compared to > 3 days of life. A decreasing PT between 1st and 2nd u/s was a risk factor for pyeloplasty. With unilateral hydronephrosis, a smaller PT ratio of the hydronephrotic kidney to the normal contralateral kidney was a significant predictor of pyeloplasty. SOURCE OF Funding: Tyrone D. Artz Chair in Urology
