Stanford School of Medicine
- What is TB?
- TB epidemiology
- TB pathogenesis
- Primary and Secondary TB
- Pulmonary TB
- Extrapulmonary TB (part 1)
- Extrapulmonary TB (Part 2)
- Mantoux test (aka. PPD or TST)
- Interpreting the PPD
- Diagnosing active TB
- Preventing TB transmission
- Preventing TB using the "4 I's"
- Treatment of Active TB
- Drug-resistant TB
- TB and HIV
Learn about how TB can spread beyond your lungs. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Stanford School of Medicine.
Want to join the conversation?
- I can't hear anything after8:48.(3 votes)
- I guess they did that on purpose to cut off their voices once they were done or to cut it off so there would be two parts.(9 votes)
- What makes the TB patient urinate blood as mentioned at5:43(3 votes)
- Peeing blood is called 'haematuria' and is a nonspecific sign of infection of or damage to the urinary tract including the ureter, bladder or urethra.
The presence of an invader (such as Mycobacterium tuberculosis) triggers the immune system's inflammatory response which can be damaging to the sensitive lining of the urinary tract. Tissue destruction disrupts the barrier causing red (and sometimes white) blood cells to leak into the urine.
Sometimes the effect is so small that it can only be detected with microscopy and other tests. If there is a fair amount of damage there might be a noticeable colour change to the urine.(2 votes)
- what does inflammation mean(1 vote)
Voiceover: This is Charles Prober. Voiceover: And I'm Morgan Theis and today we're going to talk about the extrapulmonary disease associated with tuberculosis, which I find kind of interesting, because I always think of tuberculosis as a lung disease. Voiceover: In fact, you're correct, Morgan that the most prominent infection associated with tuberculosis is pulmonary disease, is lung disease, but extrapulmonary disease is also very important. In fact, it's so important that we're going to make two videos about extrapulmonary disease. The first one we're going to focus on disease involving the lymph nodes and the genitourinary tract and then the second one, we're going to talk about involvement of the bones, the central nervous system, the gastrointestinal tract, and the heart. The reason that it's so important to give this much time to extrapulmonary disease is that we call tuberculosis, the bug infects one-third of the world's population. After that initial infection, some go on and immediately develop disease and others, as we talked about before, develop secondary disease and it comes out later and the infection may present in a myriad number of ways. In fact, that's one of the reasons that tuberculosis is referred to as one of the great imitators. It can imitate so many other kinds of disease. Two videos. Voiceover: Okay, so TB, the great imitator. Voiceover: Exactly and some of the other great imitators people talk about these days are lupus, which is, of course, not an infectious disease, HIV infection, which is an infectious disease, Epstein-Barr virus infection, which is a viral infection. Those are other great imitators, but today we're talking about tuberculosis. Voiceover: Okay and these are good things to remember because since they can present in so many ways, we always have to have them on our differential diagnosis, so we don't forget about them. Voiceover: Exactly. The first site that I'm going to talk about, Morgan, is the lymph nodes and I'm talking about that first because it actually is the most common place that TB goes, after the lungs. Voiceover: Okay and which lymph nodes are we talking about? Because they're everywhere in the body, right? Voiceover: That is true, they're everywhere in the body and the infection of the lymph nodes can occur anywhere in the body, but the most common sites are posterior cervical, so the lymph nodes at the back of the neck, and then another common site is the supra clavicular area, so that space above the clavicle. Oftentimes, when you feel a lymph node above the clavicle, you appropriately think of some sort of malignancy in the abdominal area, because that's a sentinel node, the supra clavicular lymph node, but something to remember that can also cause that is tuberculosis. One of the features of a lymph node infection with tuberculosis is that the lymph nodes tend to be painless, so they don't hurt the person, and also they tend to be not particular tender, so when you push on them, they also don't hurt the person. They often have a lack of overlying redness or heat, because there really isn't much of an acute inflammatory response, it's more of a chronic, slow process, so these lymph nodes tend to sneak up on you, gradually enlarging. As they gradually enlarge, some of them, however, can, because it's a long-term process, can actually cause fistulas tracks, that is a connection that goes from the lymph node all the way up to the skin with drainage. Voiceover: Oh gosh. Voiceover: So if you see a fistulas track associated with an enlarged lymph node, tuberculosis should be on your list. The way these are diagnosed is that a sample of the lymph node may be obtained and when looked at under the microscope, you may actually see the tuberculous bacilli, those little red snappers, as they're sometimes called, or you may culture them if you don't actually see them. Taking a chest x-ray of patients with suspected TB in the lymph nodes is a good idea. Voiceover: Right. Voiceover: However, half the time or more than half the time, the chest x-ray is negative, so don't be discouraged from the diagnosis if the chest x-ray is negative, because it oftentimes is negative. Voiceover: Got it. Voiceover: The next site that I'd like to talk about is the genitourinary site and I'm talking about this site next because after lymph node involvement comes the so-called GU, or genitourinary involvement. Thought to represent maybe 10 or 15% of cases of extrapulmonary TB, as opposed to lymph nodes, that's more like 35%. This is about half as common. As is true of any infection that can involve the genitourinary site, the kidneys and the genital area, the patients may have very nonspecific complaints, such as blood in their urine or pain when they urinate or needing to get up at night to urinate. If you examine their urine under the microscope, you may actually see white blood cells, so pyuria, but you don't see any bacteria, typically, so that can be a finding. Voiceover: I'm confused about that, because why wouldn't the bacteria actually be in the urine? Voiceover: The main reason is that the amount of tuberculous bacilli that are often present at one of these extrapulmonary sites is quite small and unless you either centrifuge the urine or otherwise concentrate it and stain it with tuberculous specific stains, you will not see bacteria. That's in contrast to regular bacterial infections of the urinary tract, where there is typically hundreds of thousands to even millions of bacteria that show up in the typical stains that are used. The term that's used here is when you see the white cells in urine and you don't see any bacteria, and then you culture them for regular bacteria, and they don't show up, because TB doesn't show up on regular cultures, it's culture negative pyuria. Culture negative pyuria should make you think of tuberculosis. Now, if you actually send those urine samples to the lab and say, "I'm looking for tuberculosis," and they're set up on tuberculosis specific media, then you often will grow the TB, but if you don't think about it, you won't do the test, and if you don't do the test, you won't make the diagnosis. Voiceover: So you're asking for a TB culture? Voiceover: Exactly. I mentioned the chest x-ray in the context of lymph node involvement and it's often negative. With genitourinary involvement, the chest x-ray is often positive. If you see culture negative pyuria and you're thinking of tuberculosis, the chest x-ray may have value. The other part of the genitourinary infection that I'll mention here is specific to women and it's that tuberculosis may actually involve the internal genitalia of women, that is the fallopian tubes and the endometrium and the importance of recognizing that is that this is one of the causes of infertility, especially in the developing world, where tuberculosis is more common. Men can also get infection of their internal genital organs, including epididymis and the testicles. They can also have prostate involvement. Again, tuberculosis can cause an -itis, an inflammation in multiple organs. In this case, in the genitourinary area. Voiceover: And you say endometritis is one of them, as well? Voiceover: Endometritis in women can occur and I mentioned the fallopian tubes and when you have inflammation in those areas, that can result in infertility.