In the present study, the overall survival rate of isolated RCDH was 70.6%. The survival rate of RCDH in our study is similar to the range (29% − 78%) reported in previous large studies.(18–25) Moreover, the survival rate in our present study is comparable to that in our previous study of 27-year single-center data of patients with CDH, of which 85% patients had LCDH.(26) Controversy continues on whether the laterality of CDH affects mortality.(21–25, 27–29) The uncertainty regarding the effect of laterality might be because of the small sample size, relative difficulty in prenatal diagnosis of RCDH, and postnatal management policies such as the timing of surgical repair. However, two recent large-scale studies in the United States found no difference in the overall mortality rates of RCDH and LCDH.(27, 30) Although the closure of the right pleuroperitoneal canal occurs before that of the left pleuroperitoneal canal, the mechanism of abdominal viscera herniation into the thoracic cavity resulting in the compression of the fetal lungs and leading to pulmonary hypoplasia is less likely to differ by the side.(31) Although a lower survival rate of RCDH (67%) versus LCDH (72%) was reported in a large international registry, the difference disappeared after controlling the diaphragmatic defect size.(28) The defect size, which could be observed only in patients who underwent surgical repair, did not differ between the survivors and non-survivors in our study. Overall, our results suggest that the defect laterality per se is not associated with mortality in isolated CDH.
In our study, the O/E LHR was a significant risk factor for isolated RCDH. The prognostic predictability of the O/E LHR was quite favorable, and the best O/E LHR cut-off value for mortality and mortality or requirement for ECMO support was 47%. This is consistent with the range of the predictive O/E LHR cut-off value (45–50%) in LCDH proposed by CDH EURO Consortium Consensus and antenatal CDH registry.(32, 33) The degree of pulmonary hypoplasia, as estimated by the LHR or O/E LHR, is known to be the most important determinant in predicting the outcome in infants with CDH. A recent meta-analysis indicated that the LHR and O/E LHR were significantly related to ECMO support requirement in isolated LCDH.(34) However, whether the O/E LHR can predict survival in RCDH is debatable because the number of RCDH cases is less, as it is relatively rare. Jani et al. demonstrated that the O/E LHR is useful for predicting subsequent survival in both LCDH and RCDH, in which no survival has been reported for an O/E LHR of < 25%.(7) DeKoninck et al. reported that after expectant in utero management, the survival rates in patients with RCDH and an O/E LHR of < 45% and < 30% were 17% and 0%, respectively.(21) In contrast, Victoria et al. raised questions regarding the reliability of the O/E LHR as a predictor of RCDH.(20) In this single-center study, the survival rate of RCDH was relatively high (up to 60%) even in patients with an O/E LHR of < 45%, probably because the results were derived from only five cases. In the registry of isolated LCDH, the survival rate was reported based on the O/E LHR interval (15%, 25%, 35%, and 45%) along with the presence of liver herniation.(32) A recent ECMO guideline for CDH proposed a prenatal risk stratification system, which includes an O/E LHR cut-off value of < 25%, liver herniation, and the O/E total lung volume.(35) However, it remains unclear whether such a graded classification can be used for RCDH. To the best of our knowledge, no study has investigated whether a dose–response relationship exists between the O/E LHR value and mortality or ECMO support requirement in RCDH with an O/E LHR of < 45%.
A well-known predictor of outcome in LCDH is the intrathoracic position of the liver.(15, 33, 36) However, the anatomical difference between left and right CDH makes the application of the liver status irrelevant because the liver is almost always up in every case of RCDH. Similar to previous reports, liver herniation was observed in almost all patients with RCDH.(15, 20) The degree of liver herniation, manifested by the percentage of the herniated liver and measured by fetal magnetic resonance imaging (MRI), was suggested as a prenatal indicator of LCDH(37); however, the volume of the herniated liver was not found to be predictive of survival in a recent study on RCDH.(20) We had no data on the herniated liver volume because fetal MRI data were unavailable. Other fetal ultrasound findings, such as mediastinal shifting and polyhydramnios, were not associated with neonatal outcome in RCDH.(38)
This study has some limitations. First, because of the rarity of RCDH, the sample size was relatively small albeit it included all patients examined during a 15-year time period. Second, although prenatal ultrasound data of all patients were available, the O/E LHR was available for relatively recently diagnosed cases alone. However, our single-center study is strengthened by the uniformity of antenatal diagnosis and postnatal management. We expect to report more data in the near future and intend to provide a graded O/E LHR cut-off criteria.