Risk factors for early mortality in infants with congenital anomalies of the kidney and urinary tract: a nested cohort study

Background To investigate predictive factors associated with neonatal mortality in infants with congenital anomalies of the kidney and urinary tract (CAKUT). Methods This study included a cohort of neonates with CAKUT born at a tertiary hospital between 1996 and 2021. Controls were matched with CAKUT cases by sex, time, and place of birth at a ratio of approximately 2:1. The covariates included in the analysis were sex, gestational age, birth weight, neonatal classification, and birth order. CAKUT was categorized into four phenotypes: urinary tract dilatation, lower urinary tract obstruction (LUTO), cystic diseases, and agenesis/hypodysplasia. The primary outcome was neonatal mortality. Survival analysis was performed using the Cox proportional hazards model. Results 857 cases and 1,755 controls were included in the analysis. The overall early mortality rate was 7.2%. After controlling for confounding factors, CAKUT cases exhibited a higher risk of early mortality than controls (hazard ratio [HR], 25.1; 95%CI, 14.0–45.2). The following covariates were independently associated with early mortality: prematurity (HR, 1.7; 95%CI, 1.2–2.5), LBW (HR, 2.4; 95%CI, 1.6–2.5), VLBW (HR, 2.9; 95%CI, 1.7–1.1), oligohydramnios (HR, 3.2; 95%CI, 2.2–4.8), cystic diseases (HR, 3.8; 95%CI, 2.3–6.4), LUTO (HR, 5.1; 95%CI, 3.0–8.5), kidney agenesis/hypodysplasia (HR, 5.1; 95%CI, 2.9–8.7), and extra-renal malformations (HR, 2.6; 95% CI, 1.7–3.9). Conclusions Our findings indicate that CAKUT was associated with an elevated early mortality rate compared with controls. Factors including prematurity, LBW, oligohydramnios, extra-renal malformations, and specific CAKUT phenotypes with kidney involvement were associated with increased mortality risk.