Antenatal hydronephrosis: a five-year retrospective study

Introduction: Antenatal hydronephrosis (ANH) is common in fetal ultrasounds. Though mostly transient, it can be associated with congenital abnormalities and kidney injury. The authors went to assess the evolution of children with ANH and identify risk groups. Methods: Retrospective cohort study of children with ANH from 2013‑2017. Renal pelvis anteroposterior diameter (APD) of 4 and 7mm or more in the second and third trimester, respectively, defined diagnosis of ANH. APD also defined severity stratification. The primary out‑ comes included occurrence of urinary tract infection (UTI) and congenital anomalies of the kidney and urinary tract (CAKUT). Results: We identified 198 cases, with male predominance (76.8%) and a 2.1% incidence. It resolved antenatally in 12.1%, with a lower mean value of APD in these cases (p=0.017), and persisted in 43.4%. CAKUT were found in 8.6% of the patients. At least 1 episode of UTI occurred in 9.1% of patients during follow‑up. The degree of ANH in the 3rd trimester was related to postnatal persistence and degree (p<0.001) and the postnatal degree was related to the occurrence of UTI (p=0.008). The 3rd trimester and postnatal degree were also associated to the presence of CAKUT (p=0.036; p=0.001), although not with vesicoureteral reflux (VUR). The persistence of ANH through the 2nd and 3rd trimester was related to postnatal persistence (p=0.002) and degree (p=0.007), and the presence of CAKUT excluding VUR (p=0.034). The optimal cut‑off for the APD in the 3rd trimester to predict the occurrence of negative outcomes (CAKUT and/or UTI), through a receiver operating characteristic (ROC) curve, was 8.225mm with 76% sensitivity and 59% specificity. Discussion: ANH is frequent and reflects a wide range of conditions, requiring follow‑up. Most cases resolve spontaneously and require no further intervention other than ultrasounds. 3rd trimester and postnatal degree are related to prognosis, allowing the definition of risk groups and the improvement of patient management.