Congenital diaphragmatic hernia: prenatal evaluation with MR lung volumetry--preliminary experience.

PURPOSE: To determine the interobserver variability of prenatal magnetic resonance (MR) lung volumetry and to assess the value of MR lung volumetric findings as predictors of outcome in fetuses with congenital diaphragmatic hernia. MATERIALS AND METHODS: Prenatal MR imaging was performed in 26 fetuses with unilateral congenital diaphragmatic hernia. Two independent observers performed planimetric measurement of lung volume. Relative lung volume was calculated as the observed total lung volume expressed as a percentage of the total lung volume predicted from fetal size. Relative lung volume was correlated with the ultrasonographic lung-head ratio in left-sided congenital diaphragmatic hernias evaluated before 27 weeks gestation (n = 21) and with pregnancy outcome in all cases of isolated left-sided congenital diaphragmatic hernia without prenatal intervention (n = 11). RESULTS: Observers demonstrated excellent agreement in total lung volume measurements at MR imaging, with an intraclass correlation coefficient of 0.95. Relative lung volume was positively correlated with lung-head ratio (r = 0.78, P <.001). By using rank order analysis in the pregnancy outcome group, relative lung volume was predictive of prognosis (P <.05) when adjusted for gestational age at delivery and birth weight. Three of four fetuses with a relative lung volume of less than 40% died. CONCLUSION: Interobserver agreement is high at MR lung volumetry, and its findings are predictive of outcome in fetuses with isolated left-sided congenital diaphragmatic hernia.