Right sided congenital diaphragmatic hernia: Diagnostic, prognostic and therapeutic implications

The incidence of congenital diaphragmatic hernia (CDH) is approximately 1 in 2000-5000 live births. In the majority of fetuses with CDH, the defect is located on the left (85%), whereas right-sided (15%) and bilateral (≤1%) defects are less frequent. The etiology of CDH is unknown, however, 2% of cases have been noted to be familial and another 15% of patients have associated chromosomal abnormalities. In CDH, the degree of lung hypoplasia is a major determinant of survival. Pulmonary hypoplasia results in respiratory insufficiency and pulmonary hypertension. Right sided CDH (R-CDH) is a highly variable defect with many similarities to Left sided CDH (L-CDH), but with potentially important distinctions. R-CDH occurs through the defect resulting from failure of the anterior pleuroperitoneal membrane to fuse with the sternum and costal cartilages during embryogenesis. Controversy exist in regards with worse prognosis of RCDH as compared to left side, as review of literature reveals conflicting data. There are several theoretical explanations suggest that impact of RCDH might be worse. First, right lung normally accounts for 57% of total fetal lung volume and any compromise on its development may have a larger clinical impact. Second liver herniation through diaphragm is more frequently seen in right sided defects, because of anatomic adjacency of the right lobe. The size of defect necessary to permit herniation of liver on the right side is likely to be substantially larger than left sided defects hence associated with poor outcome. However the underlying pathophysiology needs to be investigated further. Diagnosis of CDH can be made prenatally or postnatally after birth. Right sided defects appeared more difficult to detect prenatally compared with left sided defect partly due to the echogenicity of the liver. In recent years new ventilation strategies such as nitric oxide, gentle ventilation, high frequency oscillatory ventilation, and extracorporeal membrane oxygenation (ECMO) therapy were introduced and improved post natal prognosis. The concept has changed from performing emergency repair to delaying repair for at least 24-48 hrs to allow for clinical stabilization and a fall in pulmonary vascular resistance. Surgery can be delayed for up to 7-10 days. There is no evidence that timing of surgery influence survival. Repair of CDH can be performed effectively using different surgical approaches such as thoracic approach, abdominal approach or VATS or laparoscopic technique. Surgical repair may be more challenging in R-CDH because of near universal liver herniation as well as potential for anatomical anomalies uniquely associated with right sided defect. This results in increase in morbidity in right sided vs. left sided survivors. To date, recognized prognostic factors for post natal outcome in newborns with CDH include pulmonary hypoplasia, intra-thoracic liver herniation, associated anomalies, prenatal diagnosis, low birth weight and prematurity. Long term pulmonary morbidity in CDH consists of impaired obstructive and restrictive lung function from altered lung structure and underdeveloped pulmonary vessels.