Biology of Holding Pee ~ By Doc Calloway

Hi Marianne!

Thank you for the wonderful site on women pee records!
I am a very large bladder -ed male and I posted my stats on the male section of the site -- you can see them there.
I have a Ph. D in biochemistry so I've studied bladders, urethrae and pee -- in both sexes for some time now (I'm 35 years old). And I've learned much about female peeing from my wife (we pee together and on each other a lot).
At the bottom of this note I have attached my paper called the "Biology of Holding Pee" I hope you find it interesting and I'd like your opinion on it. I have added links to urology sites for folks to look up stuff themselves instead of just taking my word. I would love to get your feedback.

I was so excited to see your data. The max volumes looked believable. About what I thought would be the case for a females with a large bladders. But as I went on, I think some of these women are inflating their numbers as they start to look "flakey".
The best is the first woman Svetlanna Superpeeer (or whatever);
She claims 1.66 L capacity -- OK I buy that.
But then she gives a pee flow rate of 89 mL/sec (humm - I wonder about that my wife has a terrific flow rate and she can make about 40 mL/sec.).
Finally she has a record pee time of 159 seconds. OK what's going on here?
89 mL/sec X 159 sec - 14.15 mL or 14.2 L What???!!!!!! No, I don't think so!!

But later this week I will enter the data from your site in to a statistical program that I've used to analyze pee data from urology paper and I'll let you know what I find.
Meanwhile here is the Biology of Holding Pee --and thanks again for you neat site!!


Biology of Holding Pee ~ By Doc Calloway

The question of who can hold their pee the longest, (men or women) has often been discussed on various pee forums. Many people give anecdotal examples from their own lives about this topic each often believing that their observations reflect the general condition. But these stories may or may not reflect the typical real world situation at all. For this objective facts are needed.

Since I am a biological scientist (biochemist/ecologist) I spent some time reviewing the urology literature and so here are some medical facts about the “biology of holding urine”. Because I know urine holding is a fantasy and is erotic for many people (myself included) – I would warn that if you think cold scientific facts will “ruin it for you” then please do not read this.

First there are two factors that determine how MUCH urine you can hold:
1) Your bladder capacity (size), and
2) The power of your voluntary tensors (urine holding) muscles – or your urethral sphincter.

If you are dealing with how LONG a person can hold their urine there is another factor to consider:
3) That is how fast your kidneys make urine (which can also be affected by the amount of liquid you have consumed).

First, on bladder size:
We have heard arguments on which sex -- male or female is the most endowed in this regard. But this question cannot meaningfully be answered by looking at the comments of individuals who happen to know someone with a large bladder. This question can only be answered in a scientific study.  Fortunately, there is a lot of medical data on bladder size. Each year tens of thousands of medical autopsies are performed on thousands of human bodies of both sexes and are dissected in medical school anatomy classes. In each case, organs are removed and weighed and from this huge data base the medical field knows a LOT about bladder sizes. The “pee community” might not be aware of the information but it is out there.
It is clear from this huge database that typically, bladder size, like most other internal organs e.g., liver, spleen, kidneys, heart, blood volume etc., can be predicted by ALLOMETRY. This means that, on average, there is a constant relationship between an individual’s body weight/size and their bladder size.
The take-home-lesson is that on average – considering the entire human population -- big people will tend to have bigger bladders and small people will tend to have smaller bladders. OF COURSE there will be exceptions! (also this would be referenced to your “normal” body weight – an overweight person is not a “large” person in this context). So it means nothing really if you happen to know some small woman with a large bladder or a large woman with a small bladder – these are the exceptions to the rule – keep in mind there are 6 billion people on the planet – of course there will be a few million exceptions to the general rule.
But a big person with a big bladder does not necessarily have any clear “advantage” over a small person with a small bladder. Why? Because a big person will also tend to have larger kidneys and a larger volume of blood to purify --- so the big person will make urine faster than the small person. So all other things equal their bladders will fill at similar rates.
Now statistically, on average, men are larger than women so, on average they will also have larger bladders so they can probably hold MORE urine. Again, this is the typical situation and obviously there are some women who can hold a lot or urine and some men with small bladders in this world as noted above.
Second, on urethral sphincter strength (holding power)?:
As a famous urologist once joked, the only thing that stands between you and “wet pants” is your urethral sphincter. This is the voluntary striated muscle that squeezes off your urethra and holds the urine in your bladder. When this muscle is relaxed or when it is overwhelmed, the urine escapes the bladder – so there can be voluntary releases or an involuntary ones.
On this point of closing power, males have a clear biological advantage over females. It all boils down to three factors and these are plumbing, plumbing and plumbing!
The female urethra is about 3 – 4 cm long (1 – 1.5 inches) and the female urethral muscle is about 3 cm in length.
In contrast, the male urethra is about 20 – 25 cm (8 – 10 inches) long and the male urethral muscle mass controlling his sphincter is over 6 cm long. It is a much larger and more powerful muscle system in males than in females. But the male advantage does not end only with the size of the muscle mass.
The urethral sphincter muscles in females are located only along the sides or the urethra.
In contrast, in males the sphincter muscle totally surrounds the urethra with a series of bundled muscle bands in sheaths. The typical male can totally clamp off the urethral tube when he “squeezes” (that's why men do not "jiggle" as much for most of their urine holding is done with their relatively more powerful urethral sphincter).
This bigger and stronger sphincter muscle gives males an advantage that can actually be measured with scientific equipment.
Small electrical pressure transducers called micropiezometers can be inserted into the urethra to measure pressure generated when the patient “clamps down” – the transducer sends a signal back to a computer which records the strength and length of the squeeze. This is a standard instrument for urologists who treat incontinence.
On average females can exert a pressure equal to about 50 - 60 cm-water with their urethral sphincter – while the average for a male urethra is at least 80 - 100 cm-water.
This means when the pressure from the urine volume in a bladder reaches 60 cm-water (or more) the typical women’s urethral sphincter will be overwhelmed and she will be unable to hold the urine – and varying amounts will escape past her sphincter and she will start to lose urine involuntarily.
In contrast, a typical man should still be able to hold his urine in until the pressure exceeds 80 – 100 cm-water.
Of course there is biological variability and while some females are able to generate pressures as high as 100 cm-water -- likewise some males can clamp down with a pressure of 185 cm-water or greater.
In a question & answer session at an international conference on treatment of incontinence, a noted European urologist made the comment that a male should be able to contain a full bladder about twice as long as a female due to the differences in the urethral sphincter strength (this is obviously a generalization – and would vary among individuals).
However, a similar comment can be found in a web-based encyclopaedia on the general topic of the urethral sphincter and its strength in males and females:
Because the treatment of urinary incontinence (mostly in females) is a big medical business, many tools and instruments have been developed in response. A whole new field to study normal and abnormal urine flow called urodynamics has come about as a sub-specialty of urology.

If you are really interested, here is a complete set of medical papers on how to properly evaluate bladder function, urine holding and urine flow in a urology office – but these are very technical and some might find them boring. I personally do not find them that way – I loved reading them – but then I’m a bit weird myself -- being a scientist by training.
In fact, some interesting things have come to light that reflect this difference in urethral sphincter efficiency. In the 1980’s when the United States military started letting women into combat positions, a strange thing happened. About 15 – 20 % of the female recruits who entered the airborne training experienced involuntary urine loss when they landed from a parachute jump. Keep in mind that these were young women (18 – 23 years old), who had never been pregnant and were in excellent physical condition. This problem of “forced urine loss” had never been seen in male recruits.
In fact, the weakness of the urethra is one of the major factors behind a large level of female incontinence.

So there you have it! Perhaps this will stimulate some interesting discussion. If anyone is sceptical I can direct you to additional places where you can read it for yourself.

By the way, there is a biological reason for the more powerful male urethral sphincter. During sex the male urethra must do double duty – keeping urine out of the semen and keeping semen from back washing into the bladder. Ejaculations of semen are under tremendous pressure, so the male urethra needs to be very powerful because urine is toxic to spermatazoa and reduces the viability of these cells. In the female the urethra only has one function – holding urine.

Other points that are often stated but that are not relevant to the subject:

The lower abdominal cavity: It has been stated that women can hold more urine because they have a wider pelvis so they have more space down there for the bladder to expand into. Actually this aspect (width) of the pelvic space probably has very little to with this matter. Yes, women have a wider pelvis but the bladder never expands laterally to the edge of the lower abdominal cavity in either sex. So that is a non-issue. Furthermore, when one considers the vertical expansion of the bladder, males have more room actually because the in the female, vertical expansion of the bladder is limited by the fact that the fist-sized uterus lies directly on top of the urinary bladder.

Gray’s Anatomy. Many, especially those in the UK will often state or write that Gray’s Anatomy, (probably the one of the oldest and best known books on human anatomy) states that female bladders are larger. Actually Gray’s Anatomy says nothing of the kind.  Here the actual complete (and only) quote from Gray’s Anatomy on the female bladder size:

“It has been said by some that the female bladder is more capacious than that of the male, but probably the opposite is true”.

Thus, when the entire statement is read it is clear that anatomists even in the days of Dr. Gray also believed from their observations that male bladders were generally larger – because they are larger individuals. Today we know that that this is merely a reflection of the generally large male body size.

So all things considered for a male and female with equal bladder size the man should be able to hold for a larger volume because he can control a higher pressure. However, some of this advantage could be lost if the male produces urine at a faster rate because he would "fill up" faster.
Summary, a male should be able (on average) to hold more urine, but how long the urine could be held might be closer between them and could also depend on the rate the two individuals make urine and how much fluid they have consumed.

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