What is CDH?
CDH is the abbreviated name for Congenital Diaphragmatic Hernia. ‘Congenital’ means born with , ‘Diaphragmatic’ means of or affecting the diaphragm; which is a thin sheet of muscle that helps us to breath and keeps our chest and stomach contents separate. ‘Hernia’ is a general term used to describe a ‘bulge’ or ‘protrusion’ of an organ, for example the stomach, through the structure or muscle that usually contains it. CDH occurs in approximately 1 in 2500 births and accounts for around 8% of all major congenital abnormalities.
There is no firm evidence that it occurs more in one particular sex. However, some studies have suggested that males are more commonly affected than females with a ratio of 3:2. Familial clusters (running in families) have been observed in less than 2% of cases and the risk in future pregnancies is said to be 2%. There is currently no known cause or risk factor, but studies have suggested that it is probably multifactorial, meaning there maybe a number of factors involved including environmental and genetic.
The diaphragm normally develops in the unborn baby by around the 7-10 week gestation period of the baby’s development and CDH occurs when the diaphragm fails to form correctly or fails to develop in the unborn baby, allowing the abdominal contents to herniate into the chest cavity, which in turn prevents the lungs from developing properly. Depending upon at what stage the abdominal contents (also referred to as ‘Viscera’) herniated, how much, and the size of the hole in the Diaphragm will determine how much the unborn baby’s lungs and other internal organs, such as the heart, have been affected.
There are different types of CDH; the most common type is Bochdalek which accounts for over 90% of diaphragmatic hernias and is usually on the left side. Morgagni hernias are less common and are found behind the sternum (breastbone) with most being slightly to the right side. Diaphragmatic eventration occurs when the diaphragm is still intact but is weak and abnormally high in the chest (can be either unilateral or bi-lateral). They may simply be refered to as left-sided, right-sided or bi-lateral.
In a left-sided hernia, varying amounts of abdominal contents can herniate, including small and large bowel, stomach, spleen and sometimes the liver. In right-sided hernias, it is usually only the large bowel and or liver A correctly formed abdomen that herniates. Bilateral hernias are uncommon and as the term suggests; affects both sides.
In most cases and particularly in left-sided hernias, the condition is isolated, which means that there are no other associated anomalies. Rarely, CDH is part of a chromosomal syndrome such as Edward’s Syndrome (Trisomy 18), Patau’s syndrome (Trisomy 13), Down’s Syndrome (Trisomy 21) and Turner Syndrome (Monosomy X). However, a Karyotype test is usually offered to confirm that the hernia is isolated. Uncommonly, other syndromes such as Cornelia De Lange and Fryn’s syndrome have also been associated with CDH.
Other features of CDH can include variable degrees of Lung Hypoplasia (incomplete development of the lungs), Pulmonary Hypertension (increased pressure in the pulmonary arteries) and heart defects. These are often difficult to diagnose and confirm to what extent they are present until after baby is born. Other malformations can occur and are principally the cardiovascular (heart, lungs etc) genitourinary (kidneys, bladder etc) and gastrointestinal systems (stomach, bowel etc).
Currently the prognosis (outlook) for babies diagnosed with CDH remains statistically at 50%. A measurement called LHR (lung:head ratio) is often used by Doctors as an indicator to help them to assess the severity of the hernia and to assist them with planning the best management for your baby. This is taken during an ultrasound scan and your Doctor can explain this further to you. As each case is different, each case warrants its own outlook; some babies with extremely good prospects before birth fail to do well and some babies with very little lung and a poor outlook will do extremely well.