Pulmonary TB | Infectious diseases | NCLEX-RN | Khan Academy


Voiceover: I’m Charles Prober. Voiceover: And I’m Morgan Theis. Voiceover: And in this
video, we’re going to talk about pulmonary disease
caused by tuberculosis. The reason we’re dedicating a
full-on video to pulmonary disease is that pulmonary disease is the most
common form of clinical tuberculosis. It represents somewhere between
60 and 80% of all clinical disease attributable to tuberculosis
worldwide, so it’s way important. Voiceover: Okay. Voiceover: With pulmonary disease,
as with any form of tuberculosis, disease may result either
from a primary infection that is the first time the
host is seeing the infection, and that’s called primary,
or it may be secondary, which results from reactivation
of dormant infection or sometimes from infection
from a second source in a person who had a prior infection. It’s their second experience
with tuberculosis. The distinction between these two
is that with primary tuberculosis, pneumonia following primary tuberculosis, or pulmonary disease
following primary tuberculosis is more common amongst
children than adults. Children are more likely to
manifest pulmonary disease with their primary infection. Then the other contrasting element
is that with primary tuberculosis, the part of the lung which is involved is usually the lower
lobes or the middle lobes. That’s contrasted from
secondary tuberculosis, where the part of the lung that’s
involved is usually the upper lobes. it is said that this difference
results from the higher oxygen tension in the upper lobes, which I
think facilitates reactivation, but I’m not sure about the
mechanism, but nonethless, it is an association which
has stood the test of time. From a clinical standpoint, the
disease caused by tuberculosis can be the same whether it’s
resulting from a primary infection or from a secondary infection. The disease can be along
an entire spectrum. At one end of the spectrum is mild disease with a minimal amount of symptoms
attributable to the infection and at the other extreme
it can be very severe with progressive lung damage, severe
disability, even leading to death. Not only is there differences
along that clinical spectrum, but in parallel, there are radiographic
differences along the spectrum. In some occasions, pulmonary
disease is associated with a small infiltrate, a small
abnormality on the chest x-ray, whereas at other times the
disease may be widespread throughout both lungs and may
take on a cavitary appearance, which results from lung
parenchymal destruction, so really across a broad spectrum. Voiceover: Okay, so with either
primary or secondary pulmonary TB, you can be anywhere on this spectrum? Voiceover: Exactly. Voiceover: Okay. Voiceover: The other
thing that I would say about pulmonary tuberculosis
is if it is not recognized and not treated or back in the day where there was no
anti-tuberculous therapy, the clinical course of disease,
a so-called natural history, that is what happens
if you don’t treat it, was divided a third, a third, and a third. One-third of patients went on to die
of their untreated pulmonary disease, and that death could often be
quite rapid and it was called, back in the day, galloping consumption,
consuming the person’s life. That’s about a third. A second third, the patients would
actually spontaneously remit, they would get better. Their signs and symptoms would go
away and they would then be well. Then the final third would have
progressive lung involvement, not galloping, but more slow,
and this was often referred to as consumption without the
word galloping in front of it. That would be the natural
history of tuberculosis. Voiceover: It always seems
like they should just call it the natural course, instead of the
natural history, but there you go. Voiceover: I think that
that’s a good point. Now, when you see somebody who
may be infected with tuberculosis, they often have, in addition to
their pulmonary signs and symptoms, they have other nonspecific
signs and symptoms. So, this person who’s lying
in bed and you can see, first of all, the person
appears to be quite thin. In fact, weight loss is very
common as a nonspecific finding of any chronic illness, but
in this context, tuberculosis. Other common so-called systemic
symptoms associated with tuberculosis are fevers and the fevers may
go on for a long period of time, days to weeks to months. The fevers may be
associated with sweating, and that sweating often is most
prominent at nighttime, I’m not sure why, but that’s so called night sweats,
and this combination, of course, makes somebody just feel generally unwell, they have so-called malaise,
they don’t want to eat, so they’re anorexic and that
contributes to the weight loss. These are the systemic symptoms
that may accompany any kind of tuberculous infection,
including lung disease. Then there are some signs, in
addition to the signs you will get because you have pneumonia, so the clinical signs
associated with pneumonia, or the clinical signs associated with progressive pulmonary symptoms, things like cough, shortness of
breath, inability to breathe well, especially when laying down at nighttime. In addition to those findings, there
are some other nonspecific things that you should keep in mind
when you’re contemplating TB as a diagnosis and they’re
shown in the pictures. One picture, the bottom
picture is of the legs of a young individual who has tuberculosis and it shows these elevated, red nodules. Red, erythema, and nodular, nodosum, and this is referred
to as erythema nodosum. It is not specific to tuberculosis. It can occur in other diseases,
including some fungal infections, like that caused by coccidioidomycosis, and including streptococcal infections, but it also is associated
with tuberculosis and the upper picture,
of course, is an eye and this is showing a particular
form of conjunctivitis, so redness of the eye,
and that is referred to as phlyctenular conjunctivitis
and that is something which is associated with
tuberculosis as well and I wouldn’t worry too
much about spelling it because it’s kind of difficult to spell. Voiceover: All right, well – Voiceover: As Morgan is demonstrating. L-Y-C-T-E-N-U-L-A-R, phlyctenular. Voiceover: Phlyctenular. Voiceover: Conjunctivitis. These are some of the signs and symptoms that may be associated with
tuberculosis in general in pulmonary TB, which is the
predominant form of clinical disease. Voiceover: Okay. Voiceover: The final
thing we’d like to spend a few moments talking
about, because it’s at least in the chest cavity is
pleural tuberculosis. This is little bit distinct
from pulmonary tuberculosis, of course the pleural membrane
is that which surrounds the lung and pleural disease caused by tuberculosis
can result in one of two ways. One is that it may be associated with
the first infection, primary infection and it is said that it can
be due to hypersensitivity, so an immune reaction of
the body to the infection. Then the other way that it can
result, either from primary disease, or I think with secondary
disease, as well, is as a result of contiguous spread. Direct spread of the infection from
the lungs into the pleural space. One of the distinguishing
features of pleural tuberculosis, compared to other forms
of a pleural infection is that the effusions may
really be quite large. The one that you’ve drawn showing it
in the lower part of the left lung, is a modest-sized pleural effusion, but sometimes it can be
even larger than that and extend along the whole
side of the pleural space. A large pleural effusion,
when you see that, you should think of tuberculosis
as sort of one cause. Pleural effusions result in an
extension of the pulmonary symptoms. You can imagine because they’re
squeezing down the lungs that the person is short of breath. If you percuss their chest
on physical examination, it sounds dull, because there’s
not air that you’re percussing, but rather the solid pleural fluid
and when you listen to their chest, they may have decreased breath sounds, because you’re not hearing
the lung as clearly, because the pleural fluid is in
between the stethoscope and the lung. The best way to figure out what’s
causing a pleural effusion in general and for tuberculosis specifically,
is to sample the pleural fluid, to do a pleurocentesis, a pleural tap. When you do that, the typical findings are that the fluid appears straw in
color, so yellowish in color, it typically has a very
high protein concentration, a low to normal glucose concentration, and white cells that number
between 500 and a few thousand. Voiceover: Is that high or low? Voiceover: That’s high, there should
be no white cells in the pleural space. There should be no pleural
fluid, so 500 to a few thousand. With a bacterial effusion, it may be a much higher white count than that,
but with TB it’s in that range. You can try to visualize
the TB in the pleural fluid by doing a TB specific stain, such as
a Ziehl-Neelson stain, or a ZN stain. Voiceover: So it’s
Z-I-E-H-L-N-E-E-L-S-E-N stain and that’s actually looking
for the tuberculosis bacteria. Voiceover: Right. Voiceover: Okay. Voiceover: The Ziehl-Neelsen
stain is positive somewhere between 10 and 25% of the time when TB is actually there,
so it’s not very sensitive. Culturing the fluid is more sensitive. It takes a longer time, it can take
up to four to six weeks to culture and it has a sensitivity
in the range of 25 to 75%. Actually, the best sensitivity
and the test, therefore, that you should do, if you think
that this effusion represents tuberculosis is to
biopsy the pleura itself and a pleural biopsy has
a yield of about 80%. If you think somebody’s got
pleural TB with an effusion, pleural biopsy certainly should be done.

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