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Overactive Bladder and Incontinence
suffering from a well-studied disease: the ‘status’ of the patient (the S2–S3) receive afferent signals and govern reflex pathways acting on the
values of his specific parameters) is evaluated from the urodynamic data. motoneurones of the LUT. A number of excitatory and inhibiting reflexes
have been described, but without understanding the physiological
Using a Model importance of most of them in normal or disturbed situations. In fact, crucial
In theory, if the clinical status of a patient was known, solving the equations mechanisms are still largely unknown. Cybernetics and the search for the
would provide a solution that would be the computed flow rate and simplest assumptions allowed the building of the first unified model.
11
It
detrusor pressure versus time. However, in practice, the physician knows the assumes a mutual inhibition (directly or through the peri-aqueductal grey
solution (the recorded voiding curves) and searches for the clinical status of area) between the L-storage and the M-voiding regions of the pons. The
the patient. A trial and error correcting method leads to the result. Figures system has a bistable (a flip-flop) behaviour. During storage, bladder
1–4 show the gradual analysis of the flow rate and detrusor pressure afferent signals increase the sphincter excitation; during voiding, they
recordings of a patient suspected of BPE. Step 1 is to assume normal voiding increase the detrusor excitation. One has to add the effect of urethral
(see Figure 1): the computed curves do not fit the recorded ones. In step 2, afferent, a urethra–detrusor excitatory reflex during voiding and a urethral–
the hypothesis of a prostatic urethral compression is introduced (see Figure urethra excitatory reflex during storage. Very simple connecting equations
2): the flow curve is roughly fitted but the computed detrusor pressure is were tried that produced excellent qualitative results; however, this model
greater than expected; this phenomenon can be due to impaired detrusor did not include the spinal reflexes. Several variants including the spinal cord
contractility. That hypothesis is tested in step 3 (see Figure 3): both curves have been published.
12–14
However, these attempts were not associated
are well fitted at the onset of the flow, not at the end. One could not see with an accurate description of the mechanical part; they do not allow
this discrepancy without using a model. The best fitting is obtained in step comparisons of computed and recorded voiding curves. An accurate unified
4 (see Figure 4), introducing a fading of detrusor excitation. Solving the model is needed.
equations leads to only one solution. However, the inverse evaluation
(starting from the recorded curves to evaluate the parameters) can lead to Usefulness of Today’s Knowledge Models
several outcomes. For instance, to distinguish urethral obstruction due to Looking at the whole shape of a curve (and not only at the critical point of
BPE from incomplete sphincter relaxation is not easy. The best method is the Q
max
), which takes into account the actual bladder volume at each time,
simultaneous analysis of successive voidings (free flows and/or intubated increases the accuracy of the analysis and thus the evaluation of SIs. Now,
flows). Circumstantial parameters (filling volume, stress) can vary during a high accuracy is needed for follow-up, watchful waiting of BPE patients
urodynamic session, but not the mechanical ones. This strong constraint and evaluation of chemical treatment (an increase of 2ml/second of Q
max
).
allows the elimination of most of the ambiguities. Such accuracy is reached by knowledge models but not by empirical ones.
Models Including Nervous Control Only one knowledge model of micturition, the VBN model, has been
In such a model, the input of the computation would be gender, filling applied to the analysis of voidings of both males and females. Some
volume and order to void, and an empirical complement to a knowledge interesting results have been obtained. First is the analysis of phenomena
model of the mechanical part of the lower urinary tract (LUT), i.e. the that cannot be directly measured during urodynamics (prostate
accuracy of the VBN model
5
allows the detrusor excitation for each relaxation, coupling of detrusor and bladder neck contraction),
15
voiding to be deduced from the recorded flow rate and detrusor pressure. behaviours that may vary from one voiding to the other (fading of
Some general laws have been identified from the analysis of more than detrusor excitation, incomplete sphincter relaxation and effect of a
1,000 voidings (male and female patients). For example, the curve of urethral catheter)
16
and effect of chemical treatment (α-blockers,
17
detrusor excitation increased slowly from the onset of voiding till the end, Tadenan
®18
). Second is the evaluation from FFs of an index of voiding
except in the case of detrusor fading (break of excitation), whoever the dysfunction in men with BPE,
19
of the cuff method
9
and surgery outcome
patient is. In case of a break, the curve remains smooth and simply related (transurethral resection of the prostate [TURP] in men;
19
surgery for
to the previous one.
10
Unfortunately, while the occurrence and time of incontinence and/or prolapse in women
20
).
abnormalities of the nervous control and abdominal straining can be
observed, they cannot be predicted. This imperfect model would have to Conclusion
be included in a wider knowledge model. Mathematical knowledge models in urodynamics are powerful tools
to increase our knowledge of the course of the micturition process, to
Unified Knowledge Models help to analyse urodynamic recordings and to choose the most
It is known that the cerebral cortex takes the decision (voluntary control) to convenient treatment for LUT dysfunction. They will be still more
void. The brainstem (mainly the pons) and the spinal cord (mainly at levels useful with the expected progress in nervous control modelling. ■
1. Enhörning G, Acta Chir Scand, 1961;(Suppl 276):1–68. 8. Nelson P, Valentini F, C R Acad Sc Paris série III no. 9, 2003;22:45–53.
2. Griffiths DJ, Höfner K, Van Mastrigt, et al., Neurourol Urodyn, 1989;298:545–8. 16. Valentini FA, Marti BG, Robain G, et al., Neurourol Urodyn,
1997;16:1–8. 9. Valentini F, Besson G, Nelson P, Neurourol Urodyn, 2008;27:297–300.
3. Schäfer W, Sterling AM, ICS 25th Annual Meeting, Sydney, 2004;23:469–70. 17. Valentini FA, Besson G, Malavaud B, et al., Eur Urol,
1995;388–9. 10. Valentini FA, Nelson PP, Besson GR, Ann Réadap Med Phys, 1996;30(Suppl. 2):97.
4. Valentini FA, Griffiths DJ, Zimmern PE, et al., Ann Readapt Méd 2003;46:594–600. 18. Valentini FA, Besson G, Nelson PP, Modelized analysis of the
Phys, 2005;48:11–19. 11. Hosein RA, Griffiths DJ, Neurourol Urodyn, 1990;9: 601–18. effect of Tadenan (Pygeum africanum extract, PA) on the bladder
5. Valentini FA, Besson GR, Nelson PP, et al., Neurourol Urodyn, 12. Hübener U, Van Mastrigt R, Urodinamica, 1994;4:81–90. of patients with benign prostatic hyperplasia (BPH): Blind vs
2000;19:153–76. 13. Bastiaanssen EHC, Van Leeuwen JL, Vanderschoot J, et al., open study of uroflows, 20th Annual Meeting SUFU, Dallas,
6. Schäfer W, Abrams P, Liao L et al., Neurourol Urodyn, J Theor Biol, 1996;178:113–33. USA, 1 May 1999.
2002;21:261–74. 14. Van Duin F, Rosier PFWM, Rijkhoff NJM, et al., Neurourol 19. Valentini FA, Nelson PP, Besson GR, et al., BJU Int,
7. Griffiths DJ, Medical Physics Handbook, Vol 4, Bristol: Adam Urodyn, 2000;17: 175–96. 2008;101:995–9.
Hilger Ltd, 1980. 15. Valentini FA, Zimmern PE, Besson GR, et al., Neurourol Urodyn, 20. Pigne A, Valentini FA, Nelson PP, Pelv Perineol, 2007;2:110–16.
68 EUROPEAN UROLOGICAL REVIEW
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