The views expressed in editorials and editorial comments are not necessarily representative of the views of the International Continence Society.
Letter to the Editor
Re: Petros, P. An anatomical explanation for “urodynamic features and artifacts”. Neurourol Urodyn 2014; 33:153–4
Article first published online: 1 MAY 2013
© 2013 Wiley Periodicals, Inc.
Neurourology and Urodynamics
Volume 33, Issue 1, page 155, January 2014
How to Cite
Griffiths, D. (2014), Re: Petros, P. An anatomical explanation for “urodynamic features and artifacts”. Neurourol Urodyn 2014; 33:153–4. Neurourol. Urodyn., 33: 155. doi: 10.1002/nau.22418
Conflict of interest: none.
Christopher Chapple led the peer-review process as the Associate Editor responsible for the paper.
- Issue published online: 11 DEC 2013
- Article first published online: 1 MAY 2013
Peter Petros is to be commended for trying to invent alternative interpretations for the changes in pressure during bladder filling and voiding identified by Hogan et al., and I agree with him that, in the pelvis, complicated anatomical changes occur, with mechanical effects that are difficult to foresee. However, someone challenging convention requires compelling evidence that something is wrong with the older view, and in this particular case the difficulty is that anatomical imaging, however carefully done, gives information only about changes in geometry and not about the forces causing them. So any inference based on forces is purely speculative: it requires further experimental evidence to make it at least plausible.
For example, a displacement of the vagina during voiding can be seen in Figure 2 of Petros's letter, but its cause is not clear. Petros seems to ascribe it to the action of “posterior vectors,” but they merely represent movement, not forces. Of course the movement might be caused by a force acting along the line of the displacement vector, but (1) there are other possibilities and (2) there is no obvious structure (such as a ligament) running along this line that could carry the force. That makes it implausible and so fails to support the new, unconventional interpretation championed by Petros.
In fact the figure caption makes it clear that Petros is using an interpretation based on forces, as it reads:
“The posterior urethral wall is opened out by the posterior vectors (arrows) *stretching* the vagina backwards/downwards. These *pull* against the uterosacral ligament”. (I have emphasized the “force” terminology with *.)
As another example, Petros seems to believe that, because the urethra opens during voiding, something must *pull* it open, and he makes a suggestion about what it should be. However, it might alternatively be *pushed* open by an increased fluid pressure in the bladder. Anatomical images cannot distinguish between these explanations; carefully designed “pressure” (force) measurements in multiple organs might indeed help, but they require to be done before we can decide whether the unconventional interpretation is a better starting point than the conventional one.
The remaining interpretations put forward by Petros are similarly speculative. This is not say that they are necessarily incorrect, but that they need to be supported by measurements of a different sort, that can distinguish between the Petros suggestions and the conventional view and so convince us—the establishment—to change our minds.
March 27, 2013