# Why don't we pass air when we pee? **URL:** \ **Category:** Factual Questions\ **Created:** [May 17, 2005, 3:17pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248 "2005-05-17T15:17:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [May 17, 2005, 3:17pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/1 "2005-05-17T15:17:30Z")
Why isn’t any air expelled when we urinate (through the urethra, not the anus, I realise it’s common to fart when you pee). You would think that _some_ air would get trapped in the bladder and need to be either absorbed or passed. What does happen to any air in the bladder since, as far as I can tell, I have never released any externally. Remember, this is the Straight Dope, so no making jokes about farting penises. ---
**Author:** ![Captain\_Amazing](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Captain\_Amazing](https://boards.straightdope.com/u/Captain_Amazing)\ **Post date:** [May 17, 2005, 3:29pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/2 "2005-05-17T15:29:22Z")
How would air get in the bladder? ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [May 17, 2005, 3:48pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/3 "2005-05-17T15:48:40Z")
There is (usually) no connection between the urinary tract and anywhere that air or gas is produced. So, it’s not too surprising that we don’t fart through our urethrae (pee tubes). Now, if you were talking about those unfortunate souls with fistulae (abnormal connections) between their bowels and urinary tracts, I could blow you away with information. ---
**Author:** ![Little\_Bird](https://avatars.discourse-cdn.com/v4/letter/l/3ec8ea/32.png) [@Little\_Bird](https://boards.straightdope.com/u/Little_Bird)\ **Post date:** [May 17, 2005, 3:52pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/4 "2005-05-17T15:52:03Z")
There is no way for air to get in there. The urine is extracted from your blood, and if you have air in your blood you will have more things to worry about than farting when you pee! ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [May 17, 2005, 4:04pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/5 "2005-05-17T16:04:59Z")
Farts are created by bacteria in the intestines digesting fecal material and producing methane gas. There is no such potential nutrient source for bacteria in the bladder. Since no gasses are produced in the bladder, and there is no other anatomical mechanism for air to be introduced into the bladder, there are no gasses in the bladder to be expelled during urination. ---
**Author:** ![Bearflag70](https://avatars.discourse-cdn.com/v4/letter/b/8e7dd6/32.png) [@Bearflag70](https://boards.straightdope.com/u/Bearflag70)\ **Post date:** [May 17, 2005, 4:10pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/6 "2005-05-17T16:10:26Z")
What is left in the bladder after a pee then? Nothing? Wouldn’t that make it a vacuum? If air cannot get into the bladder, how do we pee at all? ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [May 17, 2005, 4:21pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/7 "2005-05-17T16:21:50Z")
> [@Bearflag70](#): > > What is left in the bladder after a pee then? Nothing? Nothing. The bladder is an elastic bag, not a solid, rigid tank. It collapses (flattens) and shrinks as it’s emptied, just like a tube of toothpaste or a rubber balloon. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 17, 2005, 4:23pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/8 "2005-05-17T16:23:36Z")
It’s a bladder, not a beaker. It’s very good at stretching. Bladder tension coupled with certain muscle contractions causes the urine to be expelled. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [May 17, 2005, 4:29pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/9 "2005-05-17T16:29:22Z")
> [@Captain Amazing](#): > > How would air get in the bladder? See, that’s what I was wondering. According to the replys so far there is no function that would produce air (or any gas) in the bladder. What about certain folks with a bladder infection? Do the bacteria in this case produce a noticeable amount of gas? Also, is there any (im)balance of chemicals/nutrients/waste that collect in the bladder that could cause gas to develope? ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [May 17, 2005, 5:06pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/10 "2005-05-17T17:06:03Z")
As I said above - people with connections (fistulae) between their urinary tracts and their intestines _will_ have pneumaturia (farts in their urine). Another, rarer, possibility is so-called emphysematous pyelonephritis (almost always occurring in diabetics) where there is a huge amount of infection in the kidney, and, due to the presence of high sugar levels, the infecting bacteria produces a **lot** of gas due to its fermentation of the sugar. ---
**Author:** ![bouv](https://avatars.discourse-cdn.com/v4/letter/b/bc8723/32.png) [@bouv](https://boards.straightdope.com/u/bouv)\ **Post date:** [May 17, 2005, 5:58pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/11 "2005-05-17T17:58:55Z")
> [@Uncommon Sense](#): > > See, that’s what I was wondering. According to the replys so far there is no function that would produce air (or any gas) in the bladder. > > What about certain folks with a bladder infection? Do the bacteria in this case produce a noticeable amount of gas? > Also, is there any (im)balance of chemicals/nutrients/waste that collect in the bladder that could cause gas to develope? No, the bacteria from a UIT won’t make a noticible anoumt of gas. For one thing, there is a LOT of bacteria in the intestine and a LOT of food there for them to eat and make gas with. For most people, there isn’t much food in the urethra or urine, so there isn’t as much bacteria, even with a UTI. Plus, they are certainly different types of bacterai with different wastes. ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [May 17, 2005, 6:22pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/12 "2005-05-17T18:22:37Z")
Gas is sometimes used during radiographic studies as a contrast agent. When gas is introduced into a dog’s bladder for a pneumocystogram, one of the humorous aspects are the mini-farts when the dog passes air via its urethra. (It is funny hehe, not funny HAHA). ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [May 17, 2005, 6:25pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/13 "2005-05-17T18:25:27Z")
> [@KarlGauss](#): > > As I said above - people with connections (fistulae) between their urinary tracts and their intestines _will_ have pneumaturia (farts in their urine). > > Another, rarer, possibility is so-called emphysematous pyelonephritis (almost always occurring in diabetics) where there is a huge amount of infection in the kidney, and, due to the presence of high sugar levels, the infecting bacteria produces a **lot** of gas due to its fermentation of the sugar. Ah, now we’re on to something. Where does this gas go? In what fashion does it escape? ---
**Author:** ![Clothahump](https://avatars.discourse-cdn.com/v4/letter/c/51bf81/32.png) [@Clothahump](https://boards.straightdope.com/u/Clothahump)\ **Post date:** [May 17, 2005, 6:28pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/14 "2005-05-17T18:28:13Z")
Obviously, it makes a pssssssssss sound. Sorry. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 17, 2005, 8:15pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/15 "2005-05-17T20:15:14Z")
> [@](#): > > Farts are created by bacteria in the intestines digesting fecal material and producing methane gas. Nitpick: Aren’t farts mostly carbon dioxide? Methane is awfully high energy to be expelling as a waste product. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [May 17, 2005, 8:25pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/16 "2005-05-17T20:25:17Z")
> [@Chronos](#): > > Nitpick: Aren’t farts mostly carbon dioxide? Methane is awfully high energy to be expelling as a waste product. I’m pretty sure that cows produce LARGE quantities of Methane, so much that it has occured to people to try and reclaim some of it. How, I have no idea. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [May 17, 2005, 9:22pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/17 "2005-05-17T21:22:52Z")
Farts are mostly carbon dioxide, methane, and hydrogen along with a submixture of odoriferous compounds. They’re all gases produced by bacterial fermentation. Different species of bacteria working on different foods produce different mixtures of gases. Not everyone has methane-producing bacteria and only the breakdown of lactose produces hydrogen. It’s hard, therefore, to generalize about composition. ---
**Author:** ![Nunavut\_Boy](https://avatars.discourse-cdn.com/v4/letter/n/e95f7d/32.png) [@Nunavut\_Boy](https://boards.straightdope.com/u/Nunavut_Boy)\ **Post date:** [May 17, 2005, 9:31pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/18 "2005-05-17T21:31:52Z")
**KarlGauss** I, for one, am interested in these urinary fistulae. Please continue. Any sort of horrible personal anecdotes would be appreciated. ---
**Author:** ![WolfpackJeep](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpackjeep/32/2921_2.png) [@WolfpackJeep](https://boards.straightdope.com/u/WolfpackJeep)\ **Post date:** [May 17, 2005, 9:43pm UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/19 "2005-05-17T21:43:02Z")
> [@Uncommon Sense](#): > > I’m pretty sure that cows produce LARGE quantities of Methane, so much that it has occured to people to try and reclaim some of it. How, I have no idea. I don’t think they reclaim it directly from cow farts, but [here’s a site](http://www.ncgreenpower.com/types/biomass.html) on “biogas”. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [May 18, 2005, 1:55am UTC](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248/20 "2005-05-18T01:55:12Z")
> [@Chronos](#): > > Nitpick: Aren’t farts mostly carbon dioxide? Methane is awfully high energy to be expelling as a waste product. Physiology 101. Carbon dioxide is the product of oxidation or combustion. Also by photosynthesis. Bacterial decomposition produces methane. Hence nasty smelling gaseous products… [Next page](https://boards.straightdope.com/t/why-dont-we-pass-air-when-we-pee/304248.md?page=2)