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H Wijkstra

Publications and source records attributed to H Wijkstra.

At least 55 records · Page 3Linked to original sources
PubMed1996

Standardized assessment to enhance the diagnostic value of prostate volume; Part I: Morphometry in patients with lower urinary tract symptoms.

BACKGROUND: The diagnostic value of prostate volume results has been evaluated in patients with prostate problems of benign cause. METHODS: For 247 patients, automated volume results were compared to manual results of planimetric reference volume and of the classical ellipsoid formula. Also, transition zone volume was estimated and growth curves of the prostate and prostate dimensions over age were investigated. RESULTS: Application of automated volume determination gives accurate results compared to the reference volume (Pearson correlation, R = 0.938). The ellipsoid volume results were slightly less correlated (R = 0.921). Average growth of the entire prostate was 1.7% per year, for the transition zone the growth was 4.3%. Compared to growth rates for a community-based population, comparable growth rates were found for our group that had higher mean prostate volume. CONCLUSIONS: The results indicate that the age of onset of volume growth is the determining factor in developing benign prostate enlargement not a change in growth rate.

Adult↗
PubMed1996

Standardized assessment to enhance the diagnostic value of prostate volume; Part II: Correlation with prostate-specific antigen levels.

BACKGROUND: Standardized estimations of prostate volumes are used for interpretation of prostate specific antigen (PSA) levels. METHODS: In 243 patients with clinically benign diagnosis, automated and reference prostate volumes and transition zone volumes are correlated to PSA levels. Besides, growth curves of PSA level when aging are determined. RESULTS: The strongest correlation was found with multiple regression analysis between PSA and transition zone volume and rest volume (R = 0.854). Mean PSA density was 0.092 ng/mL2, its labelling quality for benign disease was 91% (threshold = 0.15 ng/mL2). An average growth factor for PSA levels of 2.9% per year was obtained. CONCLUSIONS: The contribution per unit tissue to PSA level was for the transition zone 1.9 times higher than for the rest volume. Average growth of PSA per year is in consonance with the increase in normal levels of age specific PSA ranges, although only weak correlations were found between PSA and age and PSA density and age.

Adult↗
PubMed1996

Comparison of passive urethral resistance relation and urethral resistance factor in analysis of bladder outlet obstruction in patients with benign prostatic enlargement.

Analysis of the pressure/flow relation renders objective and detailed information on bladder outlet obstruction. The benefit of pressure/flow analysis for clinical and fundamental research questions, however, cannot be acknowledged without comparison of the different methods that exist. We compared one parameter analysis (URA) with two parameter (PURR) analysis in 99 consecutive patients with benign prostatic enlargement. The normal (instantaneous intrapatient) variability of both the PURR parameter Pvoidmin (minimal pressure during voiding) and the URA is approximately 10-15 cm H2O. Within these limits agreement between the two methods of analysis in the quantification of (minimal) outlet obstruction was observed in about 50% of the cases. However, when Qmax is less than 6 ml/s (in 49.5% of the patients) the URA number exceeds the value Pvoidmin in 96% of the cases. Predominantly this is caused by the fact that in the majority of these cases the type of bladder outlet obstruction is more constrictive than the URA curve, based on Pdet at Qmax indicated. In patients with a low flow rate and/or a constrictive type of obstruction, the Pvoidmin resulting from PURR analysis indicates a lower minimal pressure during voiding compared to URA.

Aged↗
PubMed1996

Morphometric data of canine sacral nerve roots with reference to electrical sacral root stimulation.

Experiments to investigate restoration of lower urinary tract control by electrical stimulation of the sacral nerve roots are mostly performed on dogs, yet little morphometric data (such as canine root and fiber diameter distributions) are available. The aim of this study was to acquire morphometric data of the intradural canine sacral dorsal and ventral roots (S1-S3). Cross-sections of sacral roots of two beagle dogs were analyzed using a light microscope and image processing software. The cross-sectional area of each root was measured. The diameters of the fibers and the axons in the cross-sections of the S2 and S3 roots were measured and used to construct nerve fiber diameter frequency distribution histograms. The results show a unimodal diameter distribution for the dorsal roots and a bimodal distribution for the ventral roots. In addition the average ratio g of the axon diameter to fiber diameter was calculated for each root.

Animals↗
PubMed1996

Construction and application of hierarchical decision tree for classification of ultrasonographic prostate images.

A non-parametric algorithm is described for the construction of a binary decision tree classifier. This tree is used to correlate textural features, computed from ultrasonographic prostate images, with the histopathology of the imaged tissue. The algorithm consists of two parts; growing and pruning. In the growing phase an optimal tree is grown, based on the concept of mutual information. After growing, the tree is pruned by an alternating interaction of two data sets. Moreover, the structure and performance of the constructed tree are compared to the results using a slightly modified corresponding growing and pruning algorithm. The modified algorithm provides better retrospective and prospective classification results than the original algorithm. The use of the tree for automated cancer detection in ultrasonographic prostate images results in retrospective and prospective accuracy of 77.9% and 72.3%, respectively. Using this tissue characterisation, a supporting tool is provided for the interpretation of transrectal ultrasonographic images.

Algorithms↗
PubMed1996

Improved reliability of uroflowmetry investigations: results of a portable home-based uroflowmetry study.

OBJECTIVES: To compare the results obtained using a portable home-based uroflowmeter with the results of traditional flowmetry performed in the out-patient department (OPD). PATIENTS AND METHODS: Sixty-seven patients (mean age 61 years, range 38-79) with lower urinary tract symptoms and/or benign prostatic enlargement used a home-based uroflowmeter comprising a datalogger and specially designed fluid sensors incorporated into disposable beakers. The results of these measurements were compared with those from uroflowmetry in the OPD and with other clinical variables. RESULTS: There was a good correlation between the uroflow results obtained when voiding at home and at the OPD. The highest measured maximum flow and voided volume were obtained with the home-based uroflowmeter system. However, the mean of all consecutive home-based maximum flow and voided volume measurements were lower than those obtained by single-void uroflowmetry in the OPD. CONCLUSIONS: Home-based uroflowmetry provides reliable voiding results which are comparable with those obtained in the OPD.

Adult↗
PubMed1996

Reproducibility of prostate volume measurements from transrectal ultrasonography by an automated and a manual technique.

OBJECTIVE: To assess the reproducibility of estimates of prostate volume determined by planimetry from transrectal ultrasonography (TRUS) images. MATERIALS AND METHODS: Two sequential sessions of images obtained by TRUS were obtained from 30 patients, with the ultrasound probe removed and inserted between the sessions. The stored images were outlined, both manually and by computer, and measurements of prostate volume obtained planimetrically. In addition, the ability of the urologist to accurately draw the contour was assessed by outlining predefined contours. RESULTS: The mean (SD) variability of manual outlining between sessions was 3.5 (3.4)%, within one session was 1.7 (1.3)% and of computer outlining between sessions was 4.3 (3.8%). Comparing the results of manual and computer outlining showed a mean (SD) variability of 7.5 (5.6)%, with larger values obtained from computer outlining. The mean (SD) variation in manually outlining predefined contours was 1.4 (1.4)%. CONCLUSIONS: The variability of computer outlining was slightly higher than expected theoretically. The within-session variability was higher than the variation caused by errors in outlining predefined contours, indicating that the interpretation of TRUS images differed with time. Automated determination of prostate volume can save time during clinical investigation and the variability is within the clinically acceptable range of 5%.

Aged↗
PubMed1996

The correlation between urodynamic and cystoscopic findings in elderly men with voiding complaints.

PURPOSE: We evaluated the urethrocystoscopic findings and results of urodynamic studies in elderly men with voiding complaints. MATERIALS AND METHODS: A total of 492 consecutive patients with voiding complaints underwent a standardized screening program, including transrectal ultrasonography of the prostate, urodynamic investigations with pressure-flow study analysis and flexible urethrocystoscopy. RESULTS: A significant correlation was found between bladder trabeculation and grade of bladder outlet obstruction. Detrusor instability correlated significantly with grade of trabeculation. Grade of obstruction showed a clear correlation with prostatic occlusion of the urethra and the presence of a middle lobe at cystoscopy. CONCLUSIONS: The findings at urethrocystoscopy correlate well with those of urodynamic investigations.

Adult↗
PubMed1996

Results of the treatment of neurogenic bladder dysfunction in spinal cord injury by sacral posterior root rhizotomy and anterior sacral root stimulation.

PURPOSE: We evaluated the results of treatment of neurogenic bladder dysfunction in spinal cord injury by sacral posterior root rhizotomy and anterior sacral root stimulation using the Finetech-Brindley stimulator. MATERIALS AND METHODS: In 52 patients with spinal cord lesions and urological problems due to hyperreflexia of the bladder complete posterior sacral root rhizotomy was performed and a Finetech-Brindley sacral anterior root stimulator was implanted. All patients were evaluated and followed with a strict protocol. A minimal 6-month followup is available in 47 cases. RESULTS: Complete continence was achieved in 43 of the 47 patients with 6 months of followup. A significant increase in bladder capacity was attained in all patients. Residual urine significantly decreased, resulting in a decreased incidence of urinary tract infections. In 2 patients upper tract dilatation resolved. In 3 patients rhizotomy was incomplete and higher sectioning of the roots was necessary. One implant had to be removed because of infection. CONCLUSIONS: The treatment of neurogenic bladder dysfunction in spinal cord injury by anterior sacral root stimulation with the Finetech-Brindley stimulator in combination with sacral posterior root rhizotomy provides excellent results with limited morbidity.

Adolescent↗
PubMed1996

Formula-derived prostate volume determination.

OBJECTIVES: Despite disadvantages such as time-consuming and tedious to the user, planimetric volumetry is considered to be the most accurate method for prostate volume determination. This study investigates the possibilities of formula-derived volume determination and reveals the best alternative to planimetric volumetry. METHODS: The prostate volume is calculated using prostatic dimensions (length, height and width) in four mathematical descriptions for prostate volume calculations. As reference, the planimetric results obtained with 4 mm step size were used. RESULTS: Compared to the results of planimetric volumetry obtained with 4-mm intersection distance, the best results for volume determination with mathematical calculation were obtained with a formula describing a spheroid volume using half the mean of width, height and length as radius. CONCLUSION: Although planimetric volumetry remains the most accurate method for prostate volume determination, the spheroid formula is the best alternative method for quick volume assessment with reasonable accuracy.

Humans↗
PubMed1996

Clinical diagnosis of bladder outlet obstruction in patients with benign prostatic enlargement and lower urinary tract symptoms: development and urodynamic validation of a clinical prostate score for the objective diagnosis of bladder outlet obstruction.

PURPOSE: We attempted to improve the method of objective clinical evaluation of patients with benign prostatic enlargement and lower urinary tract symptoms. MATERIALS AND METHODS: We compared the results of free uroflowmetry and transrectal ultrasound prostate size determination with those of pressure-flow analysis of bladder outlet obstruction in 871 consecutive elderly men. RESULTS: Maximal flow, prostate size, and post-void residual and voided volumes were correlated with bladder outlet obstruction to derive a clinical prostate score. CONCLUSIONS: Clinical prostate score shows a superior correlation with bladder outlet obstruction than isolated objective parameters or symptom scores.

Adult↗
PubMed1996

Evaluation of detrusor activity during micturition in patients with benign prostatic enlargement with a clinical nomogram.

PURPOSE: We investigated the accuracy of analysis of detrusor contraction during micturition with a simple to use pressure-flow nomogram (linear passive urethral resistance relation). The computer derived maximum detrusor contraction parameter was used as a reference. The correlation with bladder emptying capability was used as a control. MATERIALS AND METHODS: Advanced pressure-flow analysis was performed in 224 elderly men with lower urinary tract symptoms. RESULTS: All patients with a contraction classified as normal on the nomogram had good maximum detrusor contractions. However, 50% of the patients with a weak classification on the nomogram showed good maximum detrusor contractions. CONCLUSIONS: The nomogram is useful in the selection of patients with a good detrusor contraction.

Aged↗
PubMed1995

Is detrusor instability in elderly males related to the grade of obstruction?

Analysis of 185 consecutive patients with BPH revealed concomitant detrusor instability in 20% of the patients. Of all patients 30.9% were not obstructed, 51.8% were moderately obstructed and 17.3% were severely obstructed. Patients with detrusor instability during filling cystometry revealed no differences in average age, prostate volume or symptoms. Mean filling cystometry parameters revealed earlier sense of urge correlating with higher pressures at lower volumes in patients with detrusor instability. Pressure-flow analysis showed no differences between the patients with and without detrusor instability in bladder outflow obstruction parameters. Further analysis, however, revealed that the prevalence of patients with detrusor instability reaches a "steady state" at a moderate level of obstruction. On clinical epidemiological grounds, the conclusion is made that detrusor instability is developing in the early phase of obstruction. Probably detrusor instability and bladder outflow obstruction are concomitant, due to the aging process in many of these patients.

Aged↗
PubMed1995

Modelling selective activation of small myelinated nerve fibres using a monopolar point electrode.

The aim of this study is to investigate theoretically the possibility for activation of small myelinated nerve fibres without activating larger ones when stimulating a nerve fibre bundle using a monopolar point electrode. Therefore, the sensitivity of excitation and blocking threshold currents of nerve fibres to fibre diameter, electrode-fibre distance and pulse duration has been simulated by a computer model. A simple infinite, homogeneous volume conductor and a cathodal point source were used in combination with a model representing the electrical properties of a myelinated nerve fibre. The results show that selective activation of small myelinated fibres may be possible in a region at some distance from the electrode.

Computer Simulation↗
PubMed1995

Planimetric volumetry of the prostate: how accurate is it?

Planimetric volumetry is used in clinical practice when accurate volume determination of the prostate is needed. The prostate volume is determined by discretization of the 3D prostate shape. The are of the prostate is calculated in consecutive ultrasonographic cross-sections. This area is multiplied by the distance between the cross-sections and the total volume is determined by summation of all contributions. Besides the quality of the automated outlining, the accuracy of this method depends on this intersection distance and on the angle of the scan plane with the probe. Also, the location of the first cross-section is of influence. This paper describes the influences of these parameters on the accuracy of the volume determination using a simple prostate model. This theoretical influence is compared to clinical volume determinations using automated planimetric volumetry with different step sizes. From our data, it is concluded that a step size of 4 mm for planimetric prostate volume determination is a good compromise between investigation time and accuracy in a clinical setting.

Humans↗
PubMed1995

Urodynamic results of laser treatment in patients with benign prostatic hyperplasia. Can outlet obstruction be relieved?

PURPOSE: A urodynamic study was done to judge the capability of laser treatment to relieve bladder outlet obstruction. MATERIALS AND METHODS: Advanced urodynamic studies with pressure-flow analysis were performed before and 6 months after laser treatment using 3 different laser devices. RESULTS: Forty patients showed significant improvement in all obstruction parameters (detrusor pressure at maximum flow rate, urethral resistance relation, theoretical cross-sectional urethral area, minimal detrusor pressure and linear passive urethral resistance relation) together with significant subjective improvement in international prostate symptom score. After treatment 82 to 92% of the patients could no longer be considered to have obstruction. No difference in outcome among the devices used was found. CONCLUSIONS: Laser prostatectomy is indeed capable of relieving bladder outlet obstruction.

Aged↗