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Diarrhea: Lab Work & Imaging – Pediatric Gastroenterology | Lecturio

September 17, 2019


So what lab work would you get? Again, serum electrolytes. You might get stool
bacterial cultures. The question is if this is cost effective, because the reality is the vast
majority of bacterial enteritis, we do not treat
with antibiotics. They get better on their own. In fact, there was some
evidence that the varieties of E. coli that cause
hemolytic uremic syndrome may be more likely to cause hemolytic
uremic syndrome if treated. We really reserve treatment of
bacterial enteritis for Shigella, Salmonella that’s severely bad or in
children under three months of age, or a child who simply isn’t getting
better from the bacterial enteritis. There is now emerging stool PCR panels that are very effective at picking
up a variety of illnesses that can cause gastroenteritis. These panels are available
through rectal swab or through stool collected
and sent to the lab. Right now, the cost for
these panels is very high. At our hospital, it
costs upwards of $800. So it’s important to have a very good
reason why you’re getting this test. If it’s preventing a child from going
to the operating room for endoscopy, it’s probably worth it. But if it’s just to see what
it is, it might not be. Waiting for the child to get
better may be your best option. Stool microscopy for ova and parasites may be effective in a child who you
suspect has an ova and parasite, however, remember
this is also costly. It’s labor-intensive in the lab. And so don’t send it on every patient. Really limit it to patients where
you strongly suspected a parasite. For example, someone who’s
recently been abroad. If you’re suspecting
hemolytic uremic syndrome and we will talk about that
more in another lecture, it’s critically important to assess renal
function to test for E. coli O15:H7. And of course, to get a CBC to look
for thrombocytopenia and anemia. If you suspect failure
to thrive in a child, the child is not gaining weight and this
is associated with prolonged diarrhea. It’s important to consider cystic fibrosis. Tests we can get include
stool elastase, but the cheapest test and the easiest
test is simply is a sweat test. For inflammatory bowel
disease patients, we might check for elevated
inflammatory markers such as the ESR, the
sed rate, or the CRP. But remember that those
tests maybe normal even during an inflammatory
bowel disease flare. Probably the best test we can
get is the fecal calprotectin. For patients where we
suspect malabsorption, a child with for example edema, who might have a low protein level
causing them to be edematous, it can be done that we can check for
things like stool-reducing substances, which would check for sugar, fecal fat,
or alpha-1 anti trypsin in the stool. If we suspect immunodeficiency, of course, getting an HIV test
should be every one’s priority as well as checking
for lymphocyte counts and looking at their
immunoglobulin profile. So if we have a patient has
prolonged diarrhea and emesis and we, despite all those labs,
cannot figure out what’s going on, we will usually proceed to
endoscopy or colonoscopy, depending on which side has the problem. So examples of this would be a child where
we suspect inflammatory bowel disease. These children, really endoscopy is
the best way to make that diagnosis. If there’s an unclear
cause of malabsorption, we’ll do endoscopy to try and
figure out what’s going on. Sometimes, the
biopsies can show us a problem with the brush border
in the colon for example, which may give us a clue
as to what’s going on and why that child is not
able to absorb nutrients. In patients with celiac disease, we think about getting the tTG and
the IgA levels from the blood. And that is how we can make a
presumptive diagnosis. But most physicians will
want an actual biopsy of the intestinal wall to
verify that that’s diagnosis because the diagnosis of celiac disease
is a tough one to give to a patient. Remember, they have to change their
diet for the rest of their lives. Obviously, in any patient
with a severe GI bleed, we want to go do endoscopy
to try and stop the bleed. Remember GI bleeds can happen very quickly
and can be very severe and life-threatening. Lastly, certainly if we suspect
suspicion for enteric disease such eosinophilic esophagitis
or eosinophilic gastritis, a biopsy is necessary to
truly make that diagnosis. Also, visualization of the enteric wall
may give us clues as to what’s going on. So that’s my summary of
everything that has to do with children who are vomiting
or have diarrhea. And it’s a good overview for
you to keep in mind as we delve into more of these
diseases in further lectures. Thanks for your time.

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