Congenital diaphragmatic hernia

Congenital diaphragmatic hernia
Other names	CDH
Chest radiograph of a newborn with CDH, showing bowel loops in the chest.
Specialty	Neonatology, pediatrics
Symptoms	Respiratory distress at birth
Usual onset	Congenital
Types	Bochdalek hernia, Morgagni hernia
Causes	Abnormal development of the diaphragm
Diagnostic method	Prenatal ultrasound, chest radiography
Treatment	Respiratory support, surgical repair
Prognosis	Variable; depends on severity and associated anomalies
Frequency	2–3 per 10,000 live births

Congenital diaphragmatic hernia (CDH) is a rare birth defect that occurs when incomplete formation of the diaphragm allows abdominal organs to protrude into the chest. This herniation of abdominal organs compresses developing lung tissue and impairs lung development, typically causing respiratory distress shortly after birth. The cause of the defect is generally unknown. Diaphragmatic defects may occur in the posterolateral or anterior portion of the diaphragm, known as Bochdalek and Morgagni hernias, respectively. Bochdalek hernias are the most common type (95% of cases) and are generally more severe. The severity of CDH ranges from mild to life-threatening and is closely related to the degree of pulmonary hypoplasia and pulmonary hypertension. Treatment of CDH first involves cardiorespiratory stabilization, and definitive treatment is surgical repair of the diaphragmatic defect. CDH occurs at a frequency of 2-3 cases per 10,000 live births, and outcomes are variable.

Classification

Congenital diaphragmatic hernia is generally classified by the location of the defect.

Bochdalek hernia

Main article: Bochdalek hernia

The Bochdalek hernia, also known as a posterolateral diaphragmatic hernia, is the most common manifestation of CDH, accounting for more than 95% of cases. In this instance the diaphragm abnormality is characterized by a hole in the posterolateral corner of the diaphragm which allows passage of the abdominal viscera into the chest cavity. The majority of Bochdalek hernias (80–85%) occur on the left side of the diaphragm; right-sided and bilateral defects are less common. The defect may range from a small opening to near-complete absence of one side of the diaphragm.

Morgagni hernia

This rare anterior defect of the diaphragm is variably referred to as a Morgagni, retrosternal, or parasternal hernia. Accounting for approximately 2% of all CDH cases, it is characterized by herniation through the foramina of Morgagni which are located adjacent and posterior to the xiphoid process of the sternum. Morgagni hernias are less often associated with severe symptoms at birth and may be found later in life or incidentally.

Other diaphragm anomalies

Congenital diaphragmatic anomalies also include hiatal hernia and diaphragmatic eventration, though in these conditions the diaphragm remains intact.

Presentation

Most infants with CDH develop respiratory distress soon after birth. They may also have poor oxygenation with bluish discoloration of the skin, known as cyanosis. Physical findings can include reduced breath sounds on the affected side, displacement of heart sounds away from the hernia, and a sunken or concave abdomen, known as a scaphoid abdomen. In a minority of cases (5-10%), CDH presents after the newborn period. An estimated 1% of cases are asymptomatic.

Mechanism

Congenital diaphragmatic hernia results from incomplete formation of the diaphragm during gestation. The diaphragm develops from multiple embryologic components that normally fuse to separate the thoracic and abdominal cavities. Failure of this fusion, most commonly involving the pleuroperitoneal membranes, leaves a persistent defect. Through this defect, abdominal organs such as the stomach, intestines, spleen, and sometimes the liver can enter the chest. The herniated organs occupy space needed for normal lung growth. As a result, the lungs remain underdeveloped, a condition known as pulmonary hypoplasia. This underdevelopment includes reduced branching of the airways, fewer alveoli, and diminished surface area for gas exchange. In affected lungs, the pulmonary vasculature is also abnormal, with fewer vessels and thickened arterial walls. These vascular changes contribute to pulmonary hypertension after birth.

The underlying cause of congenital diaphragmatic hernia is unknown. The majority of cases occur sporadically, with no identifiable familial link.

Diagnosis

Congenital diaphragmatic hernia: coronal obstetric ultrasound (head to right of image, thorax centre, abdomen left) shows the stomach and heart both within the thorax.

CDH is most commonly identified on prenatal ultrasound, typically during the routine mid-pregnancy anatomical scan at 18-20 weeks' gestation. However, prenatal detection rates vary, and screening ultrasound fails to identify CDH in approximately one-third of cases. Prenatal assessment may include measurement of the observed-to-expected lung-to-head ratio, evaluation for liver herniation, and fetal echocardiography. These tests help assess the severity of pulmonary hypoplasia and identify associated abnormalities.

After birth, diagnosis is usually confirmed by chest radiography, which may show bowel loops in the chest, the heart shifted toward the opposite side of the chest, and reduced gas in the abdomen. Genetic evaluation is often recommended because CDH may occur with chromosomal abnormalities or genetic syndromes.

Treatment

Left-sided congenital diaphragmatic hernia before (left) and after (right) surgical repair.

The first step in management is orogastric tube placement and securing the airway (intubation). Ideally, the baby will never take a breath, to avoid air going into the intestines and compressing the lungs and heart. The baby will then be immediately placed on a ventilator. Extracorporeal membrane oxygenation (ECMO) has been used as part of the treatment strategy at some hospitals. ECMO acts as a heart-lung bypass.

Surgical repair is usually performed after cardiopulmonary stabilization, and is generally essential for survival. The operation involves moving the abdominal organs out of the chest and closing the diaphragmatic defect. Small defects may be closed with sutures, while larger defects or absent diaphragmatic tissue may require a patch or muscle flap. Open surgical repair is the standard approach, especially for large defects; minimally invasive repair is used in selected cases but has been associated with higher rates of recurrence.

Prognosis

In the modern era, congenital diaphragmatic hernia has a survival rate of approximately 60-70%, with some tertiary care centers reporting a survival rate of up to 92%. Individual rates vary greatly dependent upon multiple factors: size of hernia, organs involved, additional birth defects and/or genetic problems, amount of lung growth, age and size at birth, type of treatments, timing of treatments, complications (such as infections) and lack of lung function.

See also

• Diaphragmatic rupture

External links

• Congenital Diaphragmatic Hernia Study Group under University of Texas Health Science Center at Houston
• DHREAMS (Diaphragmatic Hernia Research & Exploration; Advancing Molecular Science) Project coordinated at Columbia University Medical Center
• CDH International – A global initiative to stop Congenital Diaphragmatic Hernia