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

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.