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MLA Full: "Is Urine Really Sterile?" YouTube, uploaded by SciShow, 1 July 2014,
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APA Full: SciShow. (2014, July 1). Is Urine Really Sterile? [Video]. YouTube.
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For some reason, the TV seems to be full of guidance about what you can do with your pee.  Like maybe you're watching one of those wilderness survival shows and the guy falls down into the ravine and gets a gash on his leg and he's like, "Oh!  No worries!  I'll just pee on it!  A little urine'll spruce that right up."

Maybe you're watching Lost and Hurley steps on a sea urchin or a jellyfish or whatever and he's like, "Pee on it!  Somebody pee on my foot!"

I got news for ya:  Despite television's teachings, and in fact what many doctors and nurses were taught, there's increasing evidence that your urine is NOT sterile.

The idea that urine, and by extension your bladder, is free of bacteria stems from the fact that, under normal circumstances, it won't produce results in a laboratory culture.  But that means, if a sample of urine is added to a growth medium and incubated in the right conditions, it won't produce big, flourishing colonies of bacteria if you're healthy.

Doctors have been using these urine cultures for generations because they're really good at detecting large amounts of certain kinds of bacteria, like E. coli and Klebsiella, that can cause infections in your bladder or urethra.

However, if your culture comes back negative, it does not mean that there's nothing there.

For one thing, the threshold that labs use to diagnose bacterial infection in your urine is kinda high.  And to get your results, lab technicians count colonies of bacteria, and each colony is basically a little speck growing on the growth medium.

And if there are fewer than 100,000 colonies growing in a single mL of your urine, that's about 1/5 of a teaspoon, they will give that a negative result.  They just assume that those germs were picked up on the way out of your body, or simply aren't statistically significant and they want to avoid reporting false positives.

But even then, the bacteria that show up in these cultures are only the ones that we can test for.  Fact is, only a small percentage of bacteria can actually be cultured in labs.  There are entire genera of bacteria thriving out there in nature, eating and being eaten and recycling elements and basically makin' the world work, that we don't know how to grow in petri dishes.

And it's also worth considering, that you're literally teeming with bacteria right now.  I'm talkin' on the order of trillions of microorganisms, inside and out, forming what scientists call your "human microbiome," basically the habitat your body provides for lots and lots of tiny livestock.

And recent research has shown that your bladder is part of it.

Several studies in the past few years have found lots of unculturable bacteria swimming around in the urine of otherwise healthy people.  And they found them, not by using the old petri dish technique, but by scanning the pee for tiny sequences of DNA, specifically tell-tale genetic markers that we use to identify and classify bacteria.

In one study, urine was sampled from two groups of women.  One who had some symptoms of urinary infections and another healthy control group.  All of the women had already tested negative for bacteria by conventional means, but 91% of them turned out to have bacteria living in their pee, including some kinds that cause infections.

In a separate experiment, similar techniques were used to compare the urine of healthy women with that of women who had overactive bladder syndrome, a condition that makes patients feel like they have to pee frequently, even when their bladders aren't full.

Results showed that both groups had ample bacteria growing in their urine, but the populations in women with overactive bladders were different than those in the control group, suggesting that the syndrome might be microbially caused.

In the end, the researchers say your urine may well have some bacteria in it that are causing problems, they're just hard to detect.  But it's even more likely it contains bacteria that pose no danger and who knows, some of them might even be beneficial.

So next time you pass your pee test at the doctor's office, keep in mind that that doesn't mean your pee is sterile, so don't do anything crazy with it.

And if you happen to skin your knee while you're out in the woods, wash it with soap and water, not with pee.  Eeeh.

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