[Quantification of bladder-outlet obstruction in males: standard method vc VBN method]

Are nomograms based on free uroflows helpful to evaluate urethral obstruction in men?

AIMS

It was demonstrated earlier that reduced maximum flow-rate (Q_max ) during intubated flow (IF) in women may be the consequence of a urethral reflex. Over-estimation of outflow obstruction is the consequence. Our hypothesis, that a similar phenomenon could occur in men, is tested using results of a free uroflow (FF) preceding an IF to eventually correct the Abrams-Griffiths (AG) number.

METHODS

Retrospectively, analysis of 441 urodynamic studies of men suspected of bladder outflow obstruction (BOO) was performed. The Valentini-Besson-Nelson model links outflow obstruction (parameter pucp) and the detrusor contractility (parameter k) to Q_max and detrusor pressure at Q_max (p_det.Qmax ). AG and pucp are strongly correlated. Contractility is described by a graphical representation (a nomogram) which numerical fitting is an algebraic equation f(Q_max ,p_det.Qmax ). Nomograms based on IF allowed computing a calculated AG (corr-AG) on the basis of free flow.

RESULTS

Included files (N = 362) had filling volume during FF > 90 mL; corr-AG was compared to AG. When Q_max.FF  > 1.5*Q_max.IF (N = 114), 61 patients (53.5%) were found less obstructed with corr-AG, no one more obstructed. Increased BOO could be the result of a urethral reflex during IF and AG gave an overestimation. When Q_max.FF  < 1.5*Q_max.IF (N = 248), only 39 patients (12.1%) were found less obstructed with corr-AG and 28 (11.3%) more obstructed.

CONCLUSION

To obtain a reliable evaluation of BOO in men, it is suitable to perform a FF before IF. A corrected AG (corr-AG) obtained from IF analysis and nomograms based on FF may be helpful for evaluation of BOO in men.

Clinically relevant modeling of urodynamics function: the VBN model

BACKGROUND

For the past two decades, a mathematical model of micturition was built step by step. Fundamental studies, presentations of the model and several applications to various male and female lower urinary tract dysfunctions have been published. We expect now that other teams will be interested in using it. In order to do so, a VBN pack (software in Linux and tutorial) is freely available.

AIMS

The purpose of this review is to describe the model and to show its practical usefulness.

MATERIALS AND METHODS

After a short description of the basis of the model and of how to use it, some published applications were summed up. The main application of the VBN model is to obtain a coherent modelling for a given patient from a set of several recordings (free uroflows and pressure-flow study) obtained either during the same session or in follow up.

RESULTS

This experience gradually led us to study what information could be extracted from a free uroflow. In addition, the model is valuable to quickly compute the effect of some additional condition; thus, it can predict the effect of an experimental artefact (urethral catheter, penile cuff).

CONCLUSION

Because the process of fitting model computations and real recordings is a powerful way to detect unexpected phenomena, the use of the VBN model provides a method to improve the knowledge of misunderstood dysfunctions of the lower urinary tract.

Non-invasive evaluation of bladder outlet obstruction in men suspected of benign prostatic hyperplasia: usefulness of the d index

OBJECTIVE

To compare a new index of voiding dysfunction (D) based purely on free uroflow vs. Abrams-Griffiths (A-G) number obtained from intubated flow, for classification of bladder outlet obstruction in men.

PATIENTS AND METHODS

Urodynamic tracings of 60 non-neurological patients (30 before transurethral resection of the prostate and of 30 men suspected of benign prostatic hyperplasia included in a medical therapy trial) were retrospectively analyzed. The Valentini-Besson-Nelson model was used to evaluate the value of the D index. A-G was obtained from intubated flows. Obstruction was defined as D > 32.5 cm H2O (translation of A-G criterion).

RESULTS

D showed 82.05% sensitivity with 66.66% specificity; the positive predictive value was 82.05% and the negative predictive value 66.66% for the whole population, 83.3 vs. 80.9% sensitivity with 58.3 vs. 77.7% specificity for pre- transurethral resection of the prostate vs. medical therapy group.

CONCLUSION

D index which can be obtained from a free uroflow appears as a valuable alternative to invasive urodynamic investigations when the diagnosis of bladder outlet obstruction needs to be more solidly established before a treatment decision or in men suspected of benign prostatic hyperplasia who elect for watchful waiting.