Urodynamics

Bladder contractility and urethral resistance relation: what does a pressure flow study tell us?

Hydrodynamic analysis of a pressure flow study is the only reliable method to determine the presence or absence of a bladder outlet obstruction, especially benign prostatic obstruction. To interpret the results of pressure flow study in benign prostatic obstruction, understanding the outlines of the basic theory about evaluation of the relationship between bladder contractility and urethral resistance relation is of paramount importance. In contrast, hydrodynamic analysis of pressure flow study in conditions other than benign prostatic obstruction is complicated by the limits of theories about the hydrodynamics of the lower urinary tract. In this review, the proposed hydrodynamic theories about the relationship between bladder contractility and urethral resistance relation are outlined. Then, problems encountered in the application of hydrodynamic analysis of pressure flow study to diseases other than benign prostatic obstruction are discussed.

The comparative pressure-flow plot properties of radiological bladder neck and prostatic obstruction

OBJECTIVES

To test the hypotheses that: (i) significant differences should exist in pressure/flow data between radiologically determined bladder neck and prostatic obstruction; (ii) these differences should inform understanding of the pathophysiology of male outflow obstruction. The biomechanics of the voiding/pressure/flow plot imply that a urodynamic assessment trace should identify outflow obstruction and characterise the urethral viscoelastic properties. Micturating cystourethrograms (MCUG) images might provide a useful diagnostic dichotomy for testing these assumptions.

MATERIALS AND METHODS

The pressure/flow data from 71 men who also provided video-urodynamic imaging data that a radiologist could classify unequivocally as showing bladder neck obstruction (42) or prostatic obstruction (29) were analysed. The following variables were recorded: the detrusor pressure at initiation of voiding (P(det.open)); the detrusor pressure at the end of voiding (P(det.close)); the detrusor pressure at maximum flow rate (Q(max)), (P(det.)Q(max)), and Q(max). The urethral resistance relation (URR) was drawn onto the pressure-flow plot and the gradient of the URR, DeltaP(det)/DeltaQ, was calculated.

RESULTS

There were significant between group differences in P(det.open) (95% confidence interval of the difference 5.2-28.6, U = 352, P = 0.003); P(det.close) (0.2-15.0, U = 428, P = 0.034); P(det).Q(max) (0.0-18.9, U = 439, P = 0.05); Q(max) and DeltaP(det)/DeltaQ did not distinguish between the MCUG groups (95% confidence interval of the difference 2.3-18, U = 111; P = 0.004). The best-fit model from linear combinations of the data achieved an area under the receiver operator curve of 0.72 for discriminating between the MCUG groups.

CONCLUSIONS

The urodynamic assessment identified interesting and coherent biomechanical differences, and could distinguish between the obstructions with a moderate degree of accuracy.

Physiology of female micturition

Micturition is a dynamic physiologic process consisting of alternating storage and expulsion phases and is accomplished by complex interactions among innervation, smooth muscle, connective tissue, urothelium and supportive structures. Although our current understanding of the anatomy and physiology of the lower urinary tract is far from complete, intensive research over the last decade has dramatically improved our appreciation of the neural, biomechanical, biochemical, and morphologic properties of the bladder and urethra, as well as the hormonal influences and unique pelvic and perineal anatomy of women. Continued research related to the physiology of female micturition promises to offer new insights into the complex bladder-urethral interactions and to provide a basis for developing better management strategies for a variety of voiding dysfunctions in women.

Similarities and differences in female and male rat voiding

We measured in adult rats, under anaesthesia, bladder pressure by transvesical cystometry and flow rate by an ultrasound transducer in the distal urethra. The urinary flow was discontinuous in both sexes. No difference between the sexes in bladder pressure oscillations or in non-oscillatory voiding was found but during the oscillatory activity there was a difference in the relationship between bladder pressure and urinary flow. In the female, the bladder pressure decreased when the flow started and increased when the flow decreased resembling species whose urinary flow is continuous. Basically the flow was stable but it was divided into periods of variable duration by full or partial closure of urethral sphincter. In the male rat, the oscillatory flow consisted of short, fast spikes occurring just before the bladder pressure reached the maximum, after which the flow spike decreased slowly. Overall, no differences were seen in bladder pressure data between the genders. However, the maximal flow rate was lower and micturition time was shorter in female rats. When we recorded occasionally occurring micturitions without high-frequency oscillations of intraluminal pressure (IPHFOs) (non-oscillatory voiding), no differences between the genders were seen. The difference during oscillatory voiding between male and female rat can be understood against anatomical and hormonal backgrounds, and by the relative role of rhabdosphincter, which did not activate during non-oscillatory voidings when no differences were detected.

Possible action of the proximal rhabdosphincter muscle in micturition of the adult male rat

Micturition requires high bladder pressure and simultaneous opening of the urethra. In adult male rat, a rhabdosphincter (RB) is known to be electrically active when the bladder pressure is high. This indicates a closure rather than an opening of the urethra, which is inconsistent with the requirements of optimal urodynamics. In order to solve this problem, we simultaneously recorded electromyogram (EMG) of the proximal RB, bladder pressure, and flow rate. Micturition was evoked by an increased volume of saline in the bladder. A computer-based recording device was used with minimal filtering. The EMG was recorded with a monopolar flexible suction electrode. The suction electrode records action potentials resembling those obtained with a microelectrode technique. During the early high-frequency intraluminal pressure oscillation period (IPHFO), the increase of pressure initially associated with a decrease of potential of the RB. When the first flow peak appeared, the relationship of the bladder pressure and RB single EMG activities changed. The increasing pressure coincided with the positive potential wave (depolarisation). It was interrupted by a transient negative polarity period called transient repolarisation (TRP) coinciding with a flow rate peak, thus indicating an opening of the RB lumen. After the TRP, the depolarisation continued. Additional experiments employing different methods are needed for positive identification of the TRP mechanism.

Diaphragm use and urinary tract infections: analysis of urodynamic and microbiological factors

To investigate how diaphragm use predisposes to urinary tract infection we studied 22 women who experienced 1 or more urinary tract infections while using a diaphragm and 21 who used a diaphragm and did not have a urinary tract infection. For women with and without a prior urinary tract infection the mean peak urine flow rate was significantly less with than without a diaphragm. However, the mean decrease in peak urine flow rate with a diaphragm was not significantly greater for women with a prior urinary tract infection. There also was no significant increase in time to peak flow with the diaphragm in place. Women who reported a sensation of obstruction to voiding with a diaphragm demonstrated a significant decrease in peak urine flow rate and this finding was particularly apparent in those with a history of urinary tract infection in whom the peak urine flow rate decreased by an average of 10.0 ml. per second. Current users of a diaphragm with a history of urinary tract infection had heavier growth of coliform organisms from cultures of the vagina and urethra, and significantly more episodes of infection than women without such a history (p equals 0.03 and 0.05, respectively). We conclude that use of a diaphragm can cause urinary obstruction in some women but that the obstruction is of relatively small magnitude and does not correlate with the acquisition of a urinary tract infection. Changes in vaginal flora associated with diaphragm use may be of greater importance.

Study of micturition parameters in healthy young adults using a uroflowmetric method

Using the 21 F 01 DISA Mictiograph, the instant urine flow curves of fifty normal males and thirty-three females (aged from 18 to 35 years) were analysed. A total of 363 micturitions was obtained (146 in the female group, 217 in the male group). Ten parameters were derived from each of the urine flow curves. These parameters were: the voided volume, the micturition time, the average-flow rate, the flow at 2 s, the maximum flow rate, the percentage of difference between the maximum flow rate and the average-flow rate, the duration until the maximum flow rate, the initial slope of the curve, the slope at the time from micturition initiation of voiding to maximum flow, and the difference between the two slopes. This study demonstrated that the urine flowmeter allowed, even at very low voided volume, a complete interpretation of micturition flow curves, a finding which might be useful in paediatric patients. It was also shown that the flow parameters were significantly more favourable in females than in males, and consequently that better hydrodynamics conditions for micturition exist in women compared to men.

Urorectodynamic evaluation of healthy volunteers

Twelve female and 8 male healthy volunteers underwent urorectodynamic evaluation. Mean bladder capacity was 594 ml. and mean maximal vesical pressure 12.5 cm. water (H2O). Maximal bladder pressure correlated significantly with maximal mural tension (r = 0.96) but did not correlate well with bladder capacity (r = 0.20). Mean bladder volume at first desire to void was 32 per cent of mean bladder capacity. The bladder volume at the first desire did not correlate significantly with the capacity. Mean bladder pressure at 100 ml. volume was 2.9 +/- 0.4 cm. H2O (X +/- SEM). After bethanechol injection, the bladder pressure at 100 ml. volume increased by 8.8 +/- 1.2 cm. H2O (X +/- SEM) at twenty minutes. In only 1 subject did bladder pressure rise higher than 15 cm. H2O (5 per cent). Rectal pressure increased from 1.4 +/- 0.3 to 14.1 +/- 2 cm. H2O (X +/- SEM) at sixteen minutes. Electromyogram (EMG) of the external and sphincter did not follow regular pattern with vesical filling or attempt of voiding. The data obtained in these normal subjects may serve as a basis for comparison in the interpretation of data obtained in patients.

Hydrodynamics of micturition following Marshall-Marchetti-Krantz procedure for stress urinary incontinence

Nineteen stress-incontinent females have passed a urodynamic study before and six months after Marshall-Marchetti-Krantz (M-M-K) surgical procedure. It is concluded that postoperative changes in the urethral pressure profile are very limited. However, urethral closure pressure was elevated and functional length shortened, both probably statistically significantly. Synchronous pressure-flow studies pre- and post-operatively showed only slightly and not statistically significantly decreased peak-flow values for three different micturition volumes at detrusor micturitions. At straining micturitions peak-flow was significantly reduced. For small micturition volumes (200 ml) detrusor pressure at peak-flow and at maximum detrusor contraction was significantly elevated after surgery. Urethral resistance was significantly increased for 200 ml and 400 ml micturitions postoperatively, but at micturition with maximum bladder capacity no changes were found. If micturitions are made as detrusor micturitions without strain and with an adequate filling of the bladder, the changes found postoperatively hardly bear clinical significance. Micturitions with heavy straining postoperatively, however, give a reduced flow and increased residual urine to the extent that micturitions in this way should be avoided.

Voiding abnormalities in children: methods of evaluation and results of treatment

Recent advances in technology have fueled interest in the field of urodynamics and have made possible accurate diagnosis of voiding abnormalities in children. A thorough understanding of the underlying physiology and institution of the appropriate pharmacologic agents and/or teaching techniques results in correction of the underlying problems in 90% of the cases. Symptoms, techniques of diagnosis, therapeutic regimens, and results of therapy are presented.

Clinical experiences of direct transmural measurement of the detrusor pressure

The clinical value of a technique using suprapubic catheters prevesically and intravesically for detrusor pressure recordings is analysed. The method has been used in 143 investigations including both males and females. The complication rate is low, 2.8%, and the advantages of a well defined measuring level and identical measuring systems for all pressure recordings are stressed. It is also concluded that there seems to be no risk of infection. For repeated investigations, such as when, for instance a second postoperative urodynamic check is wanted, this technique does not involve any drawbacks due to surgical trauma. The technique with two suprapubic catheters is well accepted by the patients and is preferred to rectal catheters by volunteers who have tried both types.

Cystometry in upright position: accurate identification of decompensated bladder

Cystometrograms obtained in the physiologic erect position have been found to picture accurately the classic decompensated bladder in women with recurrent urinary tract infections. The standard supine cystometrogram, however, may be inaccurate or normal in females with a history of infrequent voiding and prolonged vesical overdistention.

Rapid and slow-fill gas cystometry. Influence on bladder capacity and diagnosis of hyperreflexic bladder

Rapid-fill gas cystometry has been criticized for giving a falsely low value of bladder volume and for inducing an "artefact", the hyperreflexic bladder. This study in 72 patients revealed that the average capacity with slow-fill air cystometry was less than with rapid fill. The diagnosis of hyperreflexic bladder was made more often with slow fill than with rapid fill in these 72 patients.

Occult neuropathic bladder

The occult neuropathic bladder is a condition of uncertain etiology about which confusion has arisen with regard to diagnosis and management. Incontinence and upper urinary tract deterioration are secondary to high intravesical pressure associated with urinary retention and functional outflow resistance. Diagnosis is a matter of exclusion, and the various methods of investigation are discussed. Development of continence and preservation of renal function may be achieved by improving bladder evacuation and preventing reflux. Diversion may be unavoidable but should be considered only when conservative methods have failed.