female ejaculation, and the problem with 'average'

A fascinating study (Nature and Origin of “Squirting” in Female Sexuality) was just published on female ejaculation. It was the first such study I’ve seen that concluded that “squirting is essentially the involuntary emission of urine during sexual activity” – indeed, the research I’ve seen before has said just the reverse.

So of course I read it with interest!

It turns out the headline is way more interesting, but also way more complicated, than “it’s urine.”


First, a brief summary of the research:

The participants were seven women who had experienced ejaculation. They emptied their bladders – this was verified with by ultrasound and a urine sample was collected – then masturbated or had partner sex in the lab. Two more pelvic ultrasounds were conducted – first when they were highly aroused but had not ejaculated and then after they ejaculated – and the ejaculate was collected. The women then emptied their bladders again, and again a urine sample was taken.

Chemical analysis of urine before sex (BSU), urine after sex (ASU), and the ejaculate itself (S for “squirt”) were compared.

So. Result?


Way more interesting than “involuntary emission of urine”: 

The authors conclude that their results support the idea of two different physiological events being involved in female ejaculation – a hypothesis I mentioned in that other blog post, but which I’ve never seen further support for. This all by itself is fascinating! The idea here is that “squirting” is a combination of a small amount of fluid – not even a quarter of an ounce – directly from the paraurethral gland (you may know it as the “g-spot”) and the rest of the volume – maybe an ounce or two? – from… somewhere else?

That somewhere else is bladder, it looks like, because all seven women experienced “a remarkable bladder filling during sexual arousal followed by the complete bladder emptiness after squirting.”

What interests me here is this

Let me confess here that I genuinely did not know that a “gradual filling of the bladder” is a thing that happens during sexual arousal – or at least, in this case, during sexual intercourse… except… wait… except when it (PDF) isn’t (PDF).

Huh? Does the bladder fill during arousal?

As usual, the answer seems to be… women vary.

Except these women don’t. All of them experienced bladder filling. And all of them had experienced ejaculation.

Is this a difference between women who ejaculate and women who don’t?

Or is the research that doesn’t report bladder filling simply missing it, and it happens to all women?


Way more complicated than “involuntary emission of urine”:

Please. I’m really asking: Can you find a pattern of chemical changes that is consistent across even 5 out of 7 participants?


Per‐participant (P1–P7) concentrations of urea, creatinine, uric acid, and PSA in the three samples
BSU = before sexual stimulation urine;
S = squirting fluid;
ASU = after squirting urine.


The results are reported as medians – that is, the central tendency, as measured by literally “the one in the middle,” which seems to be Participant 4 for urea and creatinine, Participant 3 for uric acid and prostatic-specific antigen (PSA). But look at the variability across subjects, and, moreover, the variability of the relationships each measure has from subject to subject. In P1, urea went down from before sex to after sex, but for P4, it went way up!

So… is it important that these numbers are different, participant to participant? Is it important that they change differently, from participant to participant? What can we actually conclude from all of that?


Here’s just a few things I want to know now:


So yeah. That’s frickin’ INTERESTING… but I think “it’s urine” is maybe not the conclusion I draw from it.