Diagnosis 101: Congenital Diaphragmatic Hernia

*Disclaimer - Again, just a medical student here writing about what I learned from my own cases* 

A diagnosis of a congenital diaphragmatic hernia is another one of those incredibly scary diagnosis that you never want to hear. Very often, babies with a CDH are severely, severely ill and it's not uncommon for there to be a poor prognosis associated with the diagnosis.

So what exactly is a congenital diaphragmatic hernia? It's an inborn developmental malformation of the diaphragm when the fetus is forming. Because the diaphragm does not close correctly between weeks 4-10 of development, it's unable to properly separate the chest cavity from the abdominal cavity and as such, the abdominal contents such as your intestines, liver, stomach, or spleen can theoretically herniate through the diaphragm defect and into the chest. Most often, the diaphragm defect occurs on the left side because the liver on the right side is somewhat protective.

Photo cred: The Lucina Foundation. Notice how the intestines herniate through on the left side of the baby into the chest cavity and thus pushes the heart towards the right side and prevents the lungs from expanding.

Nowadays, most of the diagnosis of CDH is made while the fetus is still in the mom's uterus by ultrasound. You may also be able to see polyhydramnios on the ultrasound which means that there is too much amniotic fluid surrounding the baby. Now it's interesting to think about why there would be polyhydramnios in this case. Babies, while still in the stomach, actually swallow the amniotic fluid and then later pee it out; in essence, they recycle the fluid. However, if there's excess structures in the chest, such as a lump of intestines, then it can compress on the esophagus, thus preventing the baby from swallowing the fluid. So that's how you get polyhydramnios. This brings me to the next point, what usually resides in the chest cavity? Pretty easy - your lungs and your heart. So if you have extra organs up in the chest, it can also take up space and prevent the lungs from developing normally in the way that it should. In fact, much of the difficulty and sequelae of a congenital diaphragmatic hernia arises not in that the abdominal contents are misplaced, but rather that there is pulmonary hypoplasia - poor development of the lungs which causes respiratory distress, hypoxia, acidosis, and eventually pulmonary hypertension - which is also one of those things you never want to hear, especially in a young baby. If you're able to detect CDH while the baby is still in utero, one of the major things you want to do now is to make sure that the mom delivers her baby at a hospital that's capable of handling the case. It's so important that as soon as the baby is delivered there is a NICU that can stabilize the baby and then determine the proper course of treatment.

What if you don't diagnose CDH on ultrasound? What if it's a late-onset CDH that doesn't appear until after the baby is born? What are some signs that can make you think of CDH? Some things I think about make a lot of sense when you think about the process of CDH - you might be able to hear bowel sounds in the chest cavity, you may also see a scaphoid or concave abdomen because of the decreased abdominal contents. The baby could also present with a number of respiratory or GI symptoms - signs such as grunting, flaring, retractions while breathing, or vomiting after eating. Most likely if there are any of these symptoms, you'll get a chest x-ray and you might notice a shift of the mediastinal structures (including your heart and your trachea) to the right side of the baby. Hopefully, you'll also see what could be intestines or other organs abnormally located in the left side of the chest. If it's still unclear by x-ray, you could always do a upper GI bowel study which allows contrast to run through the intestines and show up much more clearly.

Case courtesy of Dr Ahmad Thuaimer via radiopaedia.org. Arrows and circles drawn by me! The red circle around the entire left chest shows an intestinal gas pattern (red arrow) which indicates intestines that have herniated into the chest cavity. The yellow arrow points to the endotracheal tube after the baby was intubated. Although hard to see, the purple arrow points to the NG tube going down the esophagus and into the stomach.

After you diagnose CDH in a baby, the next step of course, is to stabilize the baby (of course your ABCs - airway, breathing, and circulation) and then hopefully correct the underlying problem. Some things you want to avoid is to use any bag or mask ventilation because you would be blowing more air into the GI tract and intestines which could further increase compression of the lungs. Most likely, the baby will have to be intubated and mechanically ventilated for proper oxygenation. You would also want to drop a NG tube into the stomach to decompress the GI organs too. Another management point to consider is getting an echocardiogram to detect any cardiac abnormalities and see if there is any pulmonary hypertension. Lastly, hopefully the baby can be stabilized enough to undergo surgery to reduce the hernia and close the defect in the diaphragm.

The prognosis of a baby diagnosed with CDH will vary depending on how severe the pulmonary hypoplasia is. The mortality rate can be over 50% if CDH is diagnosed prior to 25 weeks gestational age and it is very possible for babies to have to be on ECMO (Extracorporeal membrane oxygenation) for a long time. ECMO is a machine and technique that acts as the heart and lungs for the baby until the baby's own heart and lungs begin to work correctly to adequately exchange gasses. I have seen one patient on ECMO so far, and let me tell you, it is by far one of the most complex machines I have ever seen. It's really a miraculous piece of equipment and requires several intensivist Attendings to be watching over it and the patient.

Grabbed from google images - an ECMO set-up. Pretty intense right? 

I spent this post discussing Congenital Diaphragmatic Hernias because I had a patient who was diagnosed with it too. Luckily, hers was never detected on routine prenatal ultrasound and was a minor case of CDH. She was a trooper in the NICU and only had to be intubated for less than 48 hours after her surgery. I hope she's flourishing well now!!