Diagnosis 101: Necrotizing Enterocolitis

I wanted to start a fun segment like this because the nerd in me loves to talk about cool diagnoses. I thought it would be really interesting to document some of the cool cases that I see this year because it'll help me remember how to diagnose, treat, and manage my patients better in the future and hopefully it'll be fun for other people to learn about.

Of course, as a disclaimer, I'm only a medical student so it's not meant to be anything professional and I'm writing this all from memory based on what I learned in the hospital.

Today, I chose to write about Necrotizing Enterocolitis, or NEC, because it's one of the most feared feeding complications in a neonate and from what I was told by my Attending, one of the most feared diagnosis for a neonatal intensivist. NEC is basically a bacterial infection of the intestinal wall, usually in the right colon but can really happen anywhere. The infection causes necrosis which is death of tissue in the intestinal wall which can lead to pretty bad consequences for the baby. Normally our gut wall serves as a barrier, it keeps the gut bacteria in its own compartment, the GI tract. When the gut wall becomes necrotic, gut bacteria, other life-threatening bacteria, your stool contents, and basically everything that shouldn't cross the gut wall can now do so. If untreated, NEC can cause perforation of the gut wall (never a good thing...terrible in fact), sepsis (an overwhelming inflammatory response of the body), and death. The mortality rate for NEC is probably greater than 25% or even higher for babies with more severe infections.

Why are some babies at higher risk for developing NEC? It's been shown that premature babies are increasingly more likely to develop NEC. The more premature a baby is, the higher the likelihood, and that's simply because the intestines are that much more immature and underdeveloped compared to a full term baby. On top of that, feeding a premature baby formula further increases the risk of NEC. The research in this area has been so solid that doctors now recommend feeding the baby donor breast milk if the mom's supply hasn't come in yet rather than risk formula feeds. Donor breast milk, like blood, is also screened multiple times for harmful substances and molecules so it's really safe!

So what are the signs that maybe a baby is developing NEC? From what I've been taught, NEC can show up in several different ways. One is abdominal distention. When a baby's stomach gets tense, firm, and large, you should worry. Another is bilious emesis - a fancy term for yellow/greenish vomit. It's okay for babies to regurge a bit of white-ish colored milk but once they start vomiting higher volumes of yellow/green digested looking milk, that's not a good sign. A third sign is bloody stools which is what I saw in my patient. Usually a small amount of blood that shows up as red streaks in the diaper is not that concerning - you might think about something like an anal fissure which can cause the blood vessels around the anus to tear as the baby tries to poop. However, if the baby passes more and more stools containing blood, it becomes more worrisome. In our case, I eventually saw frank, bright red bloody diapers.....uh oh. There are signs that are more generic too and these are just signs that lead you to think of infection somewhere in the body - a fever of greater than 100.4 degrees (I can't emphasize how important it is that parents keep a working thermometer somewhere in the house), a fast heart rate, increased work of breathing, and perfusion of the body. Some of these are harder to pick up as babies normally have fast heart rates and fast respiratory rates anyway - which is why as a parent you have to be very in tune with how your baby acts and reacts. 

Once you suspect a possible NEC infection, what's your next step? In other words, what do you do to diagnose the neonate? Answer: Get a KUB - a Kidney - Ureter - Bladder X-ray. The most important part of this is that you must get a KUB in two dimensions - usually one with the baby lying on his or her back and another one lying on the L side (called a left decubitus view). The importance of this lies in the fact that you can easily miss the diagnosis of NEC or miss the appearance of free air if you only get one view. Note: Free air is bad!!!! Free air equals a surgical emergency. It means that you've perforated the intestinal walls so that the air from inside the intestines is now leaking out. So on the KUB, besides for looking for free air, you also want to look for pneumatosis (air in the intestinal bowel walls) and portal venous air (air in the veins going into the liver). I found two awesome pictures courtesy of Dr. Frank Gaillard and Dr. Jeremy Jones on Radiopaedia.org - one of my favorite sites to look at x-ray images. 

Pneumatosis intestinalis: Red arrow points to the "tram-track" appearance of the bowel wall layers - very diagnostic for NEC

Portal venous air: Usually the liver should be a homogenous color. In this case, you can see the air (a different density compared to the liver) show up on top of the liver.

Now that you've made the diagnosis of NEC, how would you treat it? There are two ways to consider treatment. 1) The first is more conservatively: medically with antibiotics - ampicillin, gentamicin, metronidazole all by IV. These three antibiotics cover the three big groups of bacteria: gram-positives, gram-negatives, and anaerobes. The typical course is 10 days of antibiotics. While being on these medications, you also absolutely cannot eat anything by mouth so we put the patient on NPO "nil per os." This is super important because after you get NEC, any food or liquid that go into the intestines will aggravate the body and will make the infection even worse. Since the baby can't eat now, we also will give the baby TPN (Total Parenteral Nutrition) which is your basic calorie needs through a central IV line. The last is putting in a NG or OG tube. A NG or nasogastric tube is a small tube inserted through the nose until it rests in your stomach and similarly, an OG or orogastric tube is one that's inserted through the mouth into the stomach. Both tubes function to suction fluids out of the intestines because even though you're not eating or drinking anything, the body naturally continues to secrete fluids into your stomach and intestines so it's important to get all of that out. 2) The other way to treat is surgical. This is a big step as undergoing surgery is never an easy process and has a whole bunch of risks in and of itself which I won't discuss now. The surgery functions to resect or cut out all of the necrotic or dead intestine segment and a) try to join the remaining two pieces together or b) create an ostomy (bringing an end of the intestine straight out into the open skin layer) and then doing a takedown 6 to 8 weeks later after the intestines have healed. A takedown is essentially connecting the two pieces of healed intestines back together again. I found a short video which you can watch here that kind of show how sick these kids that undergo surgery for NEC usually are. It really can be a disastrous, life-threatening disease if not caught early!

Anyway, all of this is pretty crazy. Who would've thought that in my first rotation in the NICU, I'd be able to see a case of NEC? Now I won't forget!