Diarrhea: Pathology, Types & Causes – Pediatric Gastroenterology | Lecturio
17
October

By Adem Lewis / in , , , , , , , , , , , , , , , , , , , , , , , , , , /


So what about a patient with diarrhea? The definition of diarrhea
is more than 10 ccs per kilo per day of fluid
loss through stools. That might be on a test. I find it fairly useless
in terms of a definition. Mostly because it’s almost
impossible to measure how many ccs per kilogram per day
of stool is coming out of a child. The leading cause
of death worldwide in terms of morbidity and mortality
in children is infectious diarrhea. Rotavirus is a killer in
the developing world. In the United States, much less common because we have a
medical system where children can come and get help
if they’re feeling dehydrated. Generally, we will define
diarrhea as acute or chronic. The vast majority of
diarrhea is acute and it is less than two weeks
prior to presentation. If a patient has more than two
weeks of duration of diarrhea, we will call that chronic, and we’ll go through in a bit
what the differences are in terms of etiologies of these
various types of problems. So let’s go through types of diarrhea because this is important to understand and
can sometimes show up on exams as well. Secretory diarrhea is when
intestinal epithelial cells are actively secreting water into
the intra-intestinal compartment. And electrolytes are going along with it and through osmotic forces are causing
water loss out into the stools. The classic example here is cholera toxin. It is extremely rare
to encounter secretory diarrhea in children in
developing countries. Osmotic diarrhea is much more common. This is generally because
of ingested solutes, which are poorly absorbed
causing water to get extruded into the intestinal
compartment and then stooled out. An example of this is a child
who drinks too much juice. Unfortunately, we see this a lot. We sometimes even see children
who are failing to thrive because of excessive
juice consumption. So, children who eat large amounts of
osmotic material will start to stool out. Motility disorders can occur occasionally
happen which can decrease transit time. Generally, this is through
bacterial overgrowth. This is not too common. Lastly, and especially in children
with things like short gut syndrome, patients may have
decreased surface area, and thus, an inability to
actually absorb material creating what is effectively
an osmotic diarrhea. Short gut syndrome is really common
in some of our NICU graduates, especially those who
have made it through an experience of surgical
necrotizing enterocolitis. So let’s drill down into the
causes of acute diarrhea. By far and away, the most
common cause is infectious. And among infectious causes, by far and
away, the most common is viral etiologies. Viral illness used to be more in the
spring with rotavirus outbreaks. That’s less common now because
of the vaccination that we do. So, it now tends to be a
little bit more in the summer, and perhaps, into
the fall as well. And of course, in the winter, we see
some viral gastroenteritis as well. Bacterial etiologies are not uncommon. We see Campylobacter, E. coli,
Salmonella, Shigella, even Yersinia. And all of these can
cause bloody stools. In patients who have been exposed to
antibiotics, you may see C. difficile. There may be systemic infections that are
causing children to have acute diarrhea, especially younger
children who may just have that as a response to
their general infection. And parasites are possible although
more common in developing countries. In older children, you may see
that with food poisoning. Although with food poisoning, which
is ingestion of a preformed toxin rather than the actual
bacteria causing the problem, more commonly, patients
have vomiting as well. There are, of course, noninfectious
causes of acute diarrhea. Antibiotic associated diarrhea
is common with some antibiotics such as amoxicillin/clavulanic acid, which may cause diarrhea in up to 40% of
the patients who are taking the drug. Hirschsprung toxic colitis is an unusual
but important condition to know about. I say noninfectious because
the patient has an underlying problem with
Hirschsprung disease, as you recall, and there is
another lecture on Hirschsprung. Patients will have a lack of ganglions
in their rectal muscular tissue which causes them to be tonically
constricted and get constipation. However, if these patients get diarrhea, an acute viral gastroenteritis
or bacterial gastroenteritis, they can get very, very sick because the
diarrhea has a hard time getting out, and bacteria can invade
the intestinal wall, and these patients can go into shock. Neonates, and we’re seeing
more of this than ever before, are exposed to opium
or opiates in utero. And as they come out, diarrhea is a common
result of withdrawal from opiate exposure. Patients with congenital adrenal hyperplasia
will often have diarrhea at birth. In older children, we again see the
antibiotic-associated diarrhea. Appendicitis may cause diarrhea but it’s more common there to
have vomiting and abdominal pain. Chronic diarrhea can also
cause problems in children although it’s much less
rare than acute diarrhea. Examples in both infants and older children include parasites and abscesses
around the appendix, as in an old perforated appendix that’s healed up and they have
some residual diarrhea leftover. Patients may have malabsorption problems. And again, this will cause
more of that osmotic diarrhea. So examples would be post-infectious. After their diarrhea, children can rub
off the lactase in their intestinal wall and be translated
lactose intolerant. Patients can have food protein
intolerance or allergy. Children can get cystic fibrosis,
Celiac disease, toddler’s diarrhea. In older children, we do see
true lactose intolerance even though that’s much rarer in
the younger children and infants. Adolescents who are trying to lose weight
inappropriately may use laxatives. Celiac disease and very, very
rarely secretory neoplasms can cause a secretory diarrhea. Of course, autoinflammatory
processes occur. In younger children, we see
eosinophilic gastroenteritis. And in older children, we would add in the potential diagnosis
of inflammatory bowel disease. All of these diseases are where children
would have prolonged areas of diarrhea going on for a long
period of time, and you’d start to drill down into some
of these diagnoses in such a patient. Additionally, you may see
children with immunodeficiency. These children will usually
get other infections as well, things like severe combined
immune deficiency or HIV. Again, adrenaline sufficiently can cause
this, as can hyper or hypoparathyroidism. So, endocrinopathies can
also cause chronic diarrhea. Other problems can cause
chronic diarrhea as well. Rare things like lymphangiectasias
in children, toxin exposure, and rarely congenital
bowel disorders. In older children, you may see constipation
causing what appears to be diarrhea, when in fact, it’s not,
it’s just encopresis; liquid stools squirting
around the hard ball of stool that the child can
no longer get out. Irritable bowel syndrome starts
to happen in older children, and of course, toxins can
rarely cause this as well.


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