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UTIs in pregnancy

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. 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 Nauroz Syed.

Video transcript

- [Voiceover] You know, it's not unheard of for a guy to have a UTI or urinary tract infection, but still, it's pretty reasonable to say that UTIs are way more common in women. And in fact, there's a statistic that I once read that said that one in five women will have a UTI at some point in their life. So, yeah, I guess you could say it is pretty common in women. And to understand why this infection is so common in women, you have to understand the female anatomy. And I know that's not an easy thing to do. Female urinary anatomy is a bit complicated. So let's simplify it. So, okay, if this is a woman's body, what we're going to do is kind of slice it down the middle and take a look down the midline. So if we do that, towards the back, towards the back of the body, we have the digestive system, so we have the rectum. And that's what I'm drawing here, the rectum. The rectum and with the anus, so this is the anus right here. And almost immediately in front of the anus is the vagina. Okay, so the vagina. And the vagina is this canal that leads up to the uterus. So this is the uterus, the uterus, and this canal is the vagina. Okay. And then immediately in front of the vagina is the urethra. Now, urethra, urethra is the end or the outlet for the bladder. So this is the bladder, the bladder, and this is the urethra. And the bladder stores urine, right? We know that. And that urine is made up in the kidney, which is then carried through the ureters and into the bladder. So this is the kidney, all right, the kidney. And these are the ureters or a ureter, leading up to the bladder. So it's really apparent from this diagram that there's a lot cramped into a pretty small space. Okay. So back to urinary tract infection. So the term urinary tract really implies anything from the kidney down to the urethra. But to be a little bit more specific, infection of the urethra or this part right here, this part, and I'm coloring it a different color, is called urethritis. So the infection of this part right here, the urethra, is called the urethritis. Infection of the bladder, right, so this portion right here, this portion, is called cystitis. So the infection of the bladder is called cystitis. And then finally, infection of the kidneys, right here, so infection of the kidney is called pyelonephritis. It's called pyelonephritis. And the fact is when most people talk about UTIs, they're actually talking about cystitis or infection of the bladder. And the word "infection" implies some sort of pathogen, some bacteria of sorts. The bacteria in this case is usually e-coli, which comes from contamination from feces from back here in the anus. And that actually explains why UTIs are so common in women. The anus and the urethra are so close together in women that it makes contamination a lot more likely. And the urethra in women is also a lot shorter than it is in men, so the bacteria have a much shorter climb on their way to the bladder, also contributing to the fact that UTIs are more common in women. And that brings me to kind of a random but important point. So like I said, most UTIs, something like 80% of them, are caused by e-coli. And one of the most important reasons for that is that e-coli have these things on them called pili that actually enable them to stick to the urinary tract and to climb up the urinary tract. So the pili are kind of like those suction cup things that ninjas and spies use in those movies to climb up the outside of buildings. That's how I like to think of them. And pili are important because when urine comes rushing down the urinary tract, the e-coli are washed away like other bacteria without pili would be. So then, why are we talking about UTIs in pregnancy? Well, it turns out that they're even more common in pregnant women. And a lot of that has to do with the uterus becoming larger throughout the course of the pregnancy, with the growing baby. So the large uterus does a couple of different things. Firstly, it makes it pretty difficult to maintain hygiene in the area, making contamination more likely. And secondly, the uterus pushes on the bladder, making it hard to empty the bladder completely. So that means that each time the woman urinates, some urine is left behind. And that urine sitting around for a long time serves as a good medium for bacteria to grow and to thrive in. And another thing that happens in pregnancy is that the GFR or the glomerular filtration rate, or the rate at which blood is filtered through the kidneys, increases, so the GFR increases in pregnancy. And so what that means is that things like glucose are filtered a lot more out of blood and into the urine. And more glucose in the urine means more food for bacteria to grow, right? And finally, pregnancy, especially the very end of pregnancy, is a sort of state of immune suppression, right? And so that predisposes the mom to all sorts of infections, infections including UTIs. So then, let's talk about some of the symptoms of cystitis, right, so some of the symptoms that you get when you have an infection of the bladder. Burning and discomfort with urination, right, that's called dysuria, occurs pretty commonly with cystitis. Also a symptom called urinary frequency or feeling like you have to urinate really frequently, occurs pretty commonly. And urinary urgency, or feeling like you have to urinate immediately, is another common symptom. And occasionally, you can also have something called hematuria. And hematuria refers to blood in the urine. And this consolidation of symptoms or this group of symptoms, they're really important to know because a person has to have these symptoms in order to be treated for the UTI. That is to say that they can't be treated if they have only evidence of bacteria in their urine, but they don't have any symptoms of the UTI. But one of the important exceptions to that rule is pregnancy. So a pregnant woman who has bacteria in her urine without any symptoms of UTI, which is called asymptomatic, it's called asymptomatic, so without symptoms, bacteriuria, so when you have bacteria in the urine but don't have any symptoms, right? In a pregnant woman, that needs to be treated. And the reason for that is something like 25% of pregnant women with asymptomatic bacteriuria end up with pyelonephritis. And that's dangerous, very dangerous. In fact, because pyelonephritis in a pregnant woman can lead to sepsis. It can lead to kidney dysfunction, premature labor, and even death of the fetus. So that's why we always, always collect the sample of urine in the very first trimester, even if a woman has absolutely no symptoms of UTI, to look for bacteria in the urine. And if there's evidence of bacteria in the urine, again, even if she has no symptoms, we go ahead and treat. And that brings me to what it takes to diagnose a UTI. So when we're trying to diagnose a UTI, we collect a sample of urine, and what we're looking for is a urine culture in which we have more than 100,000 colony-forming units, so more than 100,000 colonies of one type of bacteria that's known to cause a UTI. Now, I want to mention one other important difference in UTIs in non-pregnant versus pregnant women, and that is treatment. So in a non-pregnant woman, or even a man, for that matter, your choice of treatment is pretty diverse. It could be something like Trimethoprim, Trimethoprim, Sulfamethoxazole, right? I know it's a mouthful. And that's a very popular treatment. Another popular treatment is Nitrofurantoin, right? And a third popular choice is Ciprofloxacin. Ciprofloxacin, okay. And there are other less commonly used antibiotics also available for your choice. But your treatment choice in a pregnant woman is very different from that in a non-pregnant woman, because a lot of these choices are dangerous to the fetus. Trimethoprim, for example, is a folate antagonist, so it blocks the use of folate by the baby. And we know that folate is really important for neural tube development. So for that reason, it's usually avoided in the first trimester. And Sulfamethoxazole can increase bilirubin levels in the baby, which can be pretty dangerous. So for that reason, it's avoided. And Ciprofloxacin is also avoided in pregnancy due to problems with bone development. So it leads to problems with bone development. So if you can't have those options available to you, some of the options that are available in pregnant women for the treatment of cystitis include Amoxicillin, right? You may have heard of that one before. Amoxicillin is used for a bunch of different things. You can also use Nitrofurantoin. So Nitrofurantoin is one of those drugs that you can use safely in both pregnant and non-pregnant women. Another popular option is Cephalexin. Cephalexin. And also Fosfomycin. So those are some of the options that you have available to you for the use in pregnant women. So there you have it. That's quite a bit of information on a very common disorder, urinary tract infection.