Qualitative Assessment of Foetal Lung Size in Left Congenital Diaphragmatic Hernia Using Ultrasound and MRI: A Retrospective Cohort Study

ABSTRACT Objective To evaluate the reliability of qualitative foetal lung size assessments on ultrasound (US) and MRI in left congenital diaphragmatic hernia (CDH) and their correlation with quantitative metrics and neonatal mortality. Design Retrospective cohort study. Setting Single tertiary center, 2008–2020. Population A total of 103 cases of prenatally diagnosed isolated left CDH underwent postnatal active care. Methods Two independent reviewers performed qualitative foetal lung size assessments on US and MRI. Interrater agreement was assessed, and correlations were determined between qualitative assessments, quantitative metrics (observed‐to‐expected lung‐to‐head ratio [o/e LHR] and observed‐to‐expected total Foetal lung volume [o/e TFLV]), and neonatal mortality. Main Outcome Measures Interrater agreement and correlation between qualitative and quantitative assessments of lung size and neonatal mortality. Results A total of 74 cases with both US and MRI imaging were included. Interrater agreement for qualitative lung size assessment was strong for US (weighted kappa: 0.80, 95% CI 0.68–0.93) and moderate for MRI (Cohen's kappa: 0.48, 95% CI 0.30–0.66). Both modalities showed a strong correlation between qualitative and quantitative lung size assessments. On US, qualitative and quantitative assessments had similar associations with neonatal mortality (Spearman's correlation: 0.44 for each reviewer vs. 0.49). On MRI, quantitative metrics correlated more strongly with neonatal mortality than qualitative assessment (Cramér's V: 0.44 vs. 0.34–0.35). Conclusions Qualitative foetal lung size assessment, by US more so than MRI, is a reliable and reproducible tool that correlates with established quantitative metrics and neonatal mortality. These findings support its role as a complementary method for prenatal risk stratification in left CDH.