Comparative analysis of the reproducibility and applicability of the condom catheter method for noninvasive urodynamics in two Dutch centers.

OBJECTIVES: We compared the applicability and reproducibility of the condom catheter method for noninvasive urodynamics in two Dutch studies. MATERIALS AND METHODS: A longitudinal study of changes in bladder contractility secondary to benign prostatic enlargement is taking place at the Erasmus MC in Rotterdam. Volunteers aged 38-77 years will be studied three times in 5 years. The first series of measurements has been completed in 1,020 men. A randomized controlled trial to test the effect of additional water intake on bladder function has been completed at the University of Maastricht. 184 subjects aged 55-77 years with International Prostate Symptom Scores of 8-19 were investigated twice in 6 months. Bladder contractility was measured noninvasively with the condom method. Two consecutive measurements were attempted in each subject. Reproducibility was tested according to Bland and Altman and compared by calculating the normalized standard deviation of the differences by dividing by the difference. RESULTS: The success rate for single measurements was 95% in both studies. The success rates for double measurements varied from 87 to 90%. The normalized standard deviation of the differences between the double measurements was 0.15 for the longitudinal noninvasive study and randomized controlled trial at baseline, and 0.13 for the randomized controlled trial at 6 months. CONCLUSION: Both studies showed good reproducibility of the noninvasive method comparable to invasive urodynamics.

Bladder volume sensitivity of isovolumetric intravesical pressure.

AIMS: Recently, methods have been introduced for non-invasively measuring the isovolumetric bladder pressure. This pressure can also be measured invasively using a stop test. In itself, the isovolumetric pressure is a measure of urinary bladder contractility, by combining it with maximum urinary flow rate it can be used to diagnose infravesical obstruction. We have studied the (possible) volume dependence of this pressure in order to enhance the accuracy of this type of measurements and to explore its physiological background and possible diagnostic relevance. MATERIALS AND METHODS: In 1,020 healthy subjects, recruited for an ongoing longitudinal study of changes in bladder contractility secondary to prostatic enlargement, we measured the isovolumetric bladder pressure using the condom catheter method. In each subject, voiding was repeatedly interrupted. The resulting pressure-volume relations were normalized and averaged. RESULTS AND CONCLUSIONS: There is an optimum bladder volume for isovolumetric pressure measurements, averaging 264 +/- 122 ml (mean +/- SD). Measurements should be taken at or above the optimum volume. At volumes below the optimum volume, the pressure decreases by approximately 5% for each 10% of volume decrease. At bladder volumes smaller than 247 ml pressure readings in 50% of subjects are suboptimal. The optimum volume for isovolumetric pressure generation is only marginally related to voiding diary parameters. Probably it represents mechanical properties of the bladder, whereas voiding diary parameters more likely represent neurophysiological properties. However, the optimum volume does not reflect the optimum (smooth) muscle length for force generation of the bladder wall: during normal voiding bladder smooth muscle always operates at a suboptimal length for force generation.

Epidemiological aspects of recruitment of male volunteers for non-invasive urodynamics.

INTRODUCTION: We studied epidemiological aspects of recruitment of volunteers for a non-invasive urodynamic study. MATERIALS AND METHODS: 9,236 volunteers were invited by 20 general practitioners (GPs), using two different recruitment methods, i.e. by mail only, or during a subsequent visit to the GP's office. Factors influencing the response rates were analyzed. We also tested how much the recruited population of volunteers differed from the general population, by comparing it to another, proven representative study carried out earlier in 1,662 subjects. RESULTS: In the recruited population the prostate volumes were not significantly different from the proven representative study, but the symptom score was statistically significantly higher, although the difference was so small it may be called clinically irrelevant. Recruitment of volunteers in two steps, i.e. asking them first to visit the GP's office, and inviting them there to visit the outpatient clinic, rather than directly inviting them (in writing) to the clinic seemed to lead to a higher response, although this effect could not be statistically discriminated from the difference in response rates between GPs. CONCLUSION: The population recruited was not urologically different from the general population. The response depended on age, being highest around the age of 60, and increased with social economic status. It also depended on the GP who recruited the subjects, and/or on the recruitment method.

Correlation of non-invasive urodynamics with International Prostate Symptom Score (IPSS) and prostate volume.

AIM: To study the correlation between non-invasive urodynamic data, the International Prostate Symptom Score (IPSS) and the prostate volume. MATERIALS AND METHODS: Data of 667 healthy volunteers participating in a longitudinal study of changes in urinary bladder contractility secondary to BPE were analyzed. The prostate volume was assessed by transabdominal ultrasonography. Uroflowmetry followed to verify if a minimum free flow rate of 4.5 ml/sec could be achieved. While (re)filling the bladder by drinking, the subjects completed the Dutch version of the IPSS. Next, the bladder pressure was non-invasively measured using the condom catheter method. The urethral resistance (URR) was calculated from the maximum condom pressure and the maximum free flow rate. RESULTS: The IPSS ranged from 0 to 29, (6.1 +/- 4.8) (mean +/- SD), whereas the prostate volumes ranged from 8 to 140 cm3, (34 +/- 18). Twenty eight percent (185/667) of the subjects had a non-invasively quantified high URR and a significantly higher IPSS (7.3 +/- 5.2) than those with a low URR (IPSS (5.7 +/- 4.6)), Mann-Whitney U-test: P < 0.001. The IPSS and the URR were significantly correlated, Spearman's rho (rho) = 0.20, P < 0.001. A significant difference between the prostate volumes, 36 +/- 21 cm3 in the high URR versus 33 +/- 17 cm3 in the low URR group, was not found, P = 0.18. CONCLUSIONS: A weak though statistically significant correlation was found between the non-invasively quantified URR and the IPSS. This suggests that an elevated resistance is a necessary, but not a sufficient condition for lower urinary tract symptoms (LUTS). No correlation was found between the URR and the prostate volume.

Prostate volume ultrasonography: the influence of transabdominal versus transrectal approach, device type and operator.

OBJECTIVES: We conduct a longitudinal non-invasive study of changes in urinary bladder contractility secondary to benign prostatic enlargement. In that study, the prostate volume is estimated by transabdominal ultrasonography. The accuracy of those measurements was verified by comparison of transabdominal to transrectal stepwise planimetric ultrasonography as the gold standard. Also, two different transabdominal devices used were compared, and the influence of different operators was studied. MATERIALS & METHODS: Two series of measurements in 100 patients each were done. In the first series, transabdominal and transrectal sonography were pairwise compared in each patient. In the second series, transabdominal measurements were done with two devices (a hospital Aloka SSD-1700 and a portable Aloka SSD-900). Transrectal scannings were done by three investigators whilst all transabdominal scannings were done by one. Regression graphs, ratio plots and statistical analyses of the data quantified the reproducibility of different methods, observers and device types. RESULTS: In the transrectal-transabdominal series of prostate volume measurements (in cm3), the Pearson correlation coefficient was 0.84 (p < 0.001), the mean of the means was 51.8 +/- 23.0 (mean +/- S.D.), and the mean of the differences was 1.0 +/- 1.4. In the series with two devices, the Pearson correlation coefficient was 0.73 (p < 0.001), the mean of the means was 31.0 +/- 10.9, and the mean of the differences was 1.0 +/- 1.3. CONCLUSION: No statistically significant differences were found between the transabdominal- transrectal ultrasonography, two different transabdominal devices nor between different observers. However, for those using these measurements in everyday clinical practice, it is worth to point out that in our data a transabdominal scan and a transrectal scan in the same patient, on the same day, differed more than 30% in one fourth of the patients and that two transabdominal scans in the same patient (with two different devices, on two different days) differed more than 30% in every fifth patient.

Comparison of repeatability of non-invasive and invasive urodynamics.

AIMS: We have developed a method for the non-invasive measurement of urinary bladder pressure, and we apply this method in a longitudinal study of changes in bladder contractility in response to prostatic enlargement. In each volunteer in this study, we measure the bladder pressure twice. In the present study we have used this data to compare the repeatability of the non-invasive method to that of pressure-flow studies in a comparable population of patients. METHODS: Difference plots were made of non-invasive bladder pressure measurements in 457 volunteers and of pressure-flow studies in a comparable population of 397 male patients. To compare the repeatability of two different methods for clinical measurement, the standard deviation of differences between repeated measurements in one individual needs to be normalised. Often a normalisation by dividing by the mean is done. We show that that normalisation may lead to erroneous results. We have normalised the standard deviations by dividing by the difference between the 97.5th and 2.5th percentile of the mean of the two observations in each subject. RESULTS: Normalised repeatability of the non-invasive method was 0.15, that of the various parameters derived from the pressure-flow studies varied from 0.11 to 0.22. CONCLUSIONS: We conclude that the repeatability of the tested non-invasive urodynamic method is comparable to, or slightly better than, that of pressure-flow studies. We further conclude that normalising standard deviations of differences by dividing by the difference between the 97.5th and 2.5th percentile of the mean is a suitable method to compare the repeatability of different methods for clinical measurement.

Applicability and reproducibility of condom catheter method for measuring isovolumetric bladder pressure.

OBJECTIVES: To report on the applicability, reproducibility, and adverse events of the noninvasive condom catheter method in the first 730 subjects of a longitudinal survey of changes in urinary bladder contractility secondary to benign prostatic hyperplasia, in which 1300 men will be evaluated three times in 5 years using this method. METHODS: Subjects were recruited by general practitioners, general publicity, and e-mail. Only those meeting the study criteria were entered in the study. If the free flow rate exceeded 5.4 mL/s, at least two consecutive condom pressure measurements were attempted using the condom catheter method. The condom pressure measured reflected the isovolumetric bladder pressure, a measure of urinary bladder contractility. The reproducibility of the method was quantified by a difference plot of the two maximal condom pressures measured in each subject. RESULTS: In 618 (94%) of 659 eligible participants, one condom pressure measurement was completed; two measurements were done in 555 (84%). The maximal condom pressure ranged from 28 to 228 cm H2O (overall mean 101, SD 34). A difference between the two pressures of less than +/-21 cm H2O was found in 80%. The mean difference was -1 cm H2O (SD 18), significantly different from 0. Some adverse events such as terminal self-limiting hematuria were encountered. CONCLUSIONS: The condom catheter method is very suitable for large-scale use. It has a success rate of 94% and a reproducibility comparable to that of invasive pressure flow studies.