Welcome. We're going to talk about a particularly troublesome
and potentially lethal disorder called necrotizing enterocolitis.
Necrotizing enterocolitis or NEC is inflammation
with ulceration and necrosis,
hence, the name necrotizing that occurs in neonates
and primarily affects the terminal ileum and the colon.
The epidemiology of this. So, it's the most common
cause of GI emergencies and intestinal perforation
in premature infants and the key
phrase there is premature infants.
So, prematurity is going to be a major
risk factor for this entity.
Overall, necrotizing enterocolitis occurs
in approximately one in 1000 live births.
The incidence however goes up quite a bit if you
have prematurity and up to 5% of preterm infants
admitted to the neonatal intensive care unit
will develop necrotizing enterocolitis.
There is no single identified cause.
There are a number of risk factors.
Then, again, number one for you to remember and tuck
away forever is being born less than 32 weeks of age.
This is going to be a combination of an immature gut, perhaps
abnormal GI colonization of the gut with certain microbiota.
This may be immature vasculature. But no single
identified cause is going to be able to be pointed to.
A low birth weight, totally independently
of prematurity can also give risk to this entity.
And then, there is a lot of epidemiologic
evidence that formula feeding,
especially, cow-based, bovine-based milk
formulas can give rise to NEC
and that may be due to the microbiota that
particularly thrive on casing derived formulas.
Perinatal stress and it's not just,
oh, the mom is stressed out.
But the fact that there may be shock and or sepsis
due to infection is also a risk for NEC in the newborn.
Interestingly, there seems to be an association
with congenital GI or cardiovascular defects.
Some of this may be because those defects
are also associated with prematurity
but there may be a completely
independent and genetic association.
In terms of the pathophysiology, it's attributed
to a poorly regulated innate immune systems.
So, again, in the premature infant, the immune
system is not exactly ready to rock and roll
and if there are microbiota that the immune
system somehow is prime to respond to,
that can lead to adverse accumulation of
inflammatory mediators and ultimately, severe injury.
We've already kind of hinted at many of these
associated findings that may predispose to NEC
but certain genetic conditions, premature
delivery leading to intestinal immaturity,
an imbalance in intestinal microvascular tone,
so, an immature vasculature,
abnormal microbial colonization,
and increased immunoreactivity.
So, all of these and maybe all of these are required
in some measure to give rise to NEC.
This is a schematic to try to give you a sense of how the various
factors may coalesce to give rise to necrotizing enterocolitis.
Here we have our immature immune
system, our immature epithelium,
and we have colonization by some bacteria
indicated in the lumen.
There may be damage not otherwise
specified and this may be due to ischemia,
this may be due to inflammatory mediators,
but the lightning bolts represent injury.
As we get injury, we're going to have
increased inflammatory cell recruitment
which will increase permeability to all of the
organisms that are present within the GI tract.
Those GI microbes, again, dependent on the specific microbiota
may have increased production of hydrogen gas
and methane gas and other fermentation
products which may dilate the bowel.
As you have increased bowel dilation, you will have increased pressure
and compromise of a vasculature that may be relatively immature.
A combination of all of those things, we go from healthy pink cells
to kind of unhealthy dead epithelial cells
of the bowel flora into the peritoneum.
The clinical presentation is as you might expect.
So, there is ongoing necrosis of the colon and distal ileum.
There is non-specific feeding intolerance with vomiting because
we are not passaging things through the entire GI tract.
With necrosis of the colon, we may get
hematochezia that is present on a diaper.
There will be abdominal distension and abdominal tenderness
and most worrisome is that there are completely absent bowel sounds.
A stethoscope placed on the abdomen
hears nothing. And that's kind of ominous.
It can rapidly progress within hours
to irreversible hypotensive septic shock.
So, how are we going to make an expeditious diagnosis?
This is a bad, lethal disease.
We need to find out sooner rather
than later that it's happening in your patient.
An x-ray will commonly show dilated loops of bowel
with air fluid levels as shown on the left-hand side.
And what's being shown on the right-hand
side is a particularly ominous finding.
If you have bowel with air within the walls
of the bowel, that's called pneumatosis intestinalis.
It means that you have bacteria within the walls
of the bowel which means that they're translocating
and the patient is at extreme risk
of developing septic shock very shortly.
Ultrasound may be a method of analysis
but a plain x-ray works just find.
The laboratories, if there is extensive bleeding,
there will be anemia.
We will expect to see leukocytosis with the left shift.
However, in very severe disease,
you may have relative myelosuppression
and there may even be leukopenia.
And as we are getting necrosis, we are actually activating,
recruiting, and thrombosing vessels with -
and losing platelets so there'll be
a relative thrombocytopenia.
Stool will show an occult blood but frequently,
it's bright red blood.
How are we going to manage this once we made the diagnosis?
We want to get antibiotics on board as soon as possible to stave off a septic
shock picture and unfortunately, the bowel is dead.
There's nothing to be done other than
to resect it and we need to resect it.
As a result, the neonate will survive hopefully
but will have a short bowel syndrome for the rest of their life.
Not a happy ending for a
very important and serious disease.
But at least, now, you have some fundamental
understanding of necrotizing enterocolitis.