Abstract
Lung thorax transverse area ratio (LT ratio) was proposed for ultrasonograpnic evaluation of lung hpoplasia in fetal diaphragmatic hernia. LT ratio was defined as a square area of bilateral lungs divided by that of thorax measured at the chest transverse section containing 4 chambers of the heart. The coefficient of variation of the measurements were 8.3% in inter-examination reproducibility and 6.4% in inter-examiner reproducibility. The LT ratio of 156 normal fetuses from 17 to 38 gestational weeks ranged from 0.43 to 0.64 (0.52 ± 0.04). There was no significant difference among 5 groups of 17-20, 21-25, 26-30. 31-35 and 36-38 gestational weeks. The LT ratios of 17 cases with diaphragmatic hernia ranged from 0.08 to 0.42 (the mean ± SD; 0.20±0.09), which was significantly lower than that of the normal controls. In the 13 cases without major cardiac anomalies, the LT ratio was significantly correlated with postnatal preductal arterial blood PO_2, PCO_2, PH and A-aDO_2. There was a significant difference in a requirement of HFO (high frequency oscillation) and ECMO (extracorporeal membrane oxygenation) and survival rate between two groups with the LT ratio greater than 0.20 and less than 0.20. From these data, measurement of the LT ratio using a fetal ultrasonography may be a reliable method for evaluating the degree of lung hypoplasia in diaphragmatic hernia.
