الفهرس 
EMBERIOLOGY OF THE DIAPHRAGMOnly 14 pages are availabe for public view
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Abstract
The incidence of congenital diaphragmatic hernia has been reported as 1 in 3000–5000 live births, however,in population studies – including cases resulting in premature terminations, still births and neonatal deaths prior to transfer to tertiary centres – the incidence approaches 1 in 2000.
Over the past two decades, antenatal diagnosis rates have increased, the pathophysiology has become better understood, and advances in clinical care have occurred. The significant long-term morbidity has become apparent, and the need for long-term follow-up established.
Herniation of abdominal contents occurs most often, in
over 95% of cases, through the posterior foramen of Bochdalek, posterior and lateral to the spine, with 80%occurring on the left side. Less commonly, retrosternal
herniation occurs, through the foramen of Morgagni.
The exact mechanism of lung hypoplasia in CDH is a matter of debate. The traditional view involved a diaphragmatic defect resulting from failed closure of the pleuroperitoneal canals by the end of the embryonic period (weeks 8–10 of gestation). Herniation of abdominal viscera into the thorax resulted in compression of the developing ipsilateral lung, and to a lesser extent the contralateral lung.
The newborn with congenital diaphragmatic hernia usually has a measure of respiratory distress and a scaphoid abdomen. Clinical suspicion is usually easily confirmed on a plain radiograph. occasionally two films taken at different times are required to confirm that the suspected gas pattern has changed, so distinguishing congenital diaphragmatic hernia from a cystic lesion. Contrast is rarely required.
Fetal surgery is controversial and involves in utero repair or plugging the trachea to encourage lung growth. In utero repair is an experimental procedure that involves opening the uterus and the fetal chest or abdomen to allow repair so that lung development improves. The PLUG procedure (plug the trachea until the lung grows)is another antenatal attempt to encourage lung growth for which the selection criteria and benefits have not been assessed. After birth, persistent pulmonary hypertension of the neonate and the persistent fetal circulation are managed, sometimes for many days, until they have subsided before surgery.
The pathophysiology involves a self perpetuating hypoxia with hypercarbia and acidosis that leads to pulmonary artery vasoconstriction and pulmonary hypertension. This leads to persistent fetal circulation, right to left shunting (through the patent ductus arteriosus and foramen ovale) and intrapulmonary shunting, which exacerbates the hypoxia and hypercarbia. The pulmonary hypertension leads to right ventricular dilation, which compresses the left ventricle and reduces cardiac output. Some centres finetune management with cardiac echocardiography to follow the right ventricar dilation and adjust therapy accordingly. In addition to the bilateral pulmonary hypoplasia, the vasculature is more muscular and more reactive.
The key to stabilization of neonates with congential diaphragmatic hernia and in severe respiratory distress is added oxygen, endotracheal intubation, paralysis and gentle ventilation, and options include conventional mechanical ventilation, high frequency ventilation, inhaled nitric oxide and extracorporeal membrane oxygenation.
Repair is typically carried out through the abdomen, with reduction of herniated contents and excision of sacs before repair. The defect may be closed primarily or a muscle patch/inert graft may be needed. A pneumothorax is present postoperatively because of the small ipsilateral lung . Suction would be required and mediastinal shift would result if air was removed. Some surgeons leave a chest tube to drain effusions that later develop in the thoracic cavity. Occasionally there is malrotation of the small intestine with an unstable mesentry, requiring a Ladd’s procedure to place the intestine in the nonrotated position.
Survival data vary markedly depending on the population considered. Figures are high for late diagnoses and live births; low for series incorporating antenatal diagnoses and multiple associated anomalies. Long term follow up shows that those who required extracorporeal membrane oxygenation, patches or oxygen at discharge often have problems later.
A few babies escape early detection and present with respiratory or gastrointestinal symptoms in infancy (and even childhood). Survival rates depend on age of diagnosis and associated Anomalies.