Proposal for a strategy on the follow-up in Japanese neonates with mild congenital hydronephrosis

Abstract

Congenital hydronephrosis (CH) have the highest incidence among congenital malformations that are found in the fetal or neonatal period. As the prognosis of the CH is not always benign, neonates with CH need to be followed up. Although repeated renal ultrasonographic examination is recommended for the follow-up of CH, no standardized strategy is currently available for mild CH due to lack of large cohort surveys on their natural course. Therefore, this study was conducted to determine a follow-up plan for mild CH in Japanese individuals. Among 1009 neonates, CH was detected in 118 affected renal units of 100 (9.9%) patients. According to the definition of the Society for Fetal Urology, 118 affected renal units were graded as grade 1 in 87 (74%), grade 2 in 30 (25%), grade 3 in one (1%) and grade 4 in 0 units. The grade 1 CH was improved 90% and 99%, by 13 and 25 months of age. The grade 2 CH was improved 32% and 60%, by 13 and 25 months of age. In conclusion, Grade 1 CH does not need to be followed up, because it mostly shows spontaneous resolution by 2 years of follow up without any complications. However, ultrasonographic examinations at 1-year intervals for grade 2 CHs are recommended to determine the subsequent follow-up plan of patients.