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Hessel Wijkstra

Publications and source records attributed to Hessel Wijkstra.

16 recordsLinked to original sources
PubMed2006

Diagnostic accuracy of noninvasive tests to evaluate bladder outlet obstruction in men: detrusor wall thickness, uroflowmetry, postvoid residual urine, and prostate volume.

OBJECTIVES: The aim of this prospective study was to compare the diagnostic accuracy of detrusor wall thickness (DWT), free uroflowmetry, postvoid residual urine, and prostate volume (index tests) with pressure-flow studies (reference standard) to detect bladder outlet obstruction (BOO) in men. METHODS: During a 2-yr period, men older than 40 yr with lower urinary tract symptoms and/or prostatic enlargement had the following tests: ultrasound measurements of DWT, free uroflowmetry (Q(max), Q(ave)), postvoid residual urine, and prostate volume. Pressure-flow studies were used to divide obstructed from nonobstructed bladders. RESULTS: One hundred sixty men between 40-89 yr of age (median: 62 yr) were included in the study; 75 patients (46.9%) had BOO according to pressure-flow studies. The results of all investigated index tests differed significantly between obstructed and nonobstructed men. DWT was the most accurate test to determine BOO: the positive predictive value was 94%, specificity 95%, and the area under the curve of ROC analysis 0.93. There was an agreement of 89% between the results of DWT measurement and pressure-flow studies. CONCLUSIONS: Measurements of DWT can detect BOO better than free uroflowmetry, postvoid residual urine, or prostate volume. In clinical routine, DWT measurements can be used to judge BOO noninvasively.

Adult↗
PubMed2006

A reproducibility study of corpus cavernosum electromyography in young healthy volunteers under controlled conditions.

INTRODUCTION: Although the corpus cavernosum electromyography (CC-EMG) has been studied already for 16 years, doubts regarding its reproducibility have remained. AIM: To assess the reproducibility of CC-EMG under controlled conditions and the influence of confounding factors. METHODS: Three CC-EMG recording sessions were performed in 13 healthy young men under the same conditions. Furthermore, the effects of potentially confounding factors, such as intake of caffeine, alcohol and smoking, and sexual activity, were investigated in the same population. Using auto- and cross-correlation techniques, CC-potentials were characterized with parameters amplitude (A), duration (D), dominant frequency (DF), maximum cross-correlation coefficient of longitudinal and bilateral CC-potential pairs (Rmax-lon. and Rmax-bi.), and propagation velocity (PV ). MAIN OUTCOME MEASURES: Comparison of CC-EMG parameters A, D, DF, Rmax-lon., and Rmax-bi. between three recording sessions and assessment of the impact of confounding factors on these parameters. RESULTS: DF, D, A, and Rmax-lon. showed significant correlations among three sessions; PV showed significant correlations between two sessions performed within the same day but not between those performed on different days; Rmax-bi. did not show significant correlations between any two sessions. Intake of caffeine, alcohol, and smoking did not affect CC-potentials, while the recordings shortly after ejaculation showed more irregular oscillations and less CC-potentials with smaller A. CONCLUSIONS: CC-potential parameters DF, D, A, and Rmax-lon. have been demonstrated to be reproducible. The results provide a basis for the clinical and scientific application of CC-EMG. CC-potentials are not sensitive to confounding factors such as intake of caffeine, alcohol, and smoking, while measurements shortly after ejaculation should be avoided.

Adult↗
PubMed2006

Ultrasound measurement of detrusor wall thickness in healthy adults.

AIMS: Measurements of detrusor wall thickness (DWT) are used to diagnose bladder outlet obstruction (BOO). No values of DWT exist in healthy adults so far. These values, however, are necessary to judge DWT in patients with suspected BOO correctly. The aim of this study was to determine DWT in healthy adults and to investigate if bladder filling, gender, age, or body-mass index (BMI) influences DWT. MATERIALS AND METHODS: In 55 healthy adult volunteers between 15 and 40 years of age, DWT was measured at the anterior bladder wall with a 7.5 MHz ultrasound probe and with a full bladder. In nine of those volunteers, an urodynamic investigation was performed additionally during which DWT was measured in steps of 50 ml until 300 ml and in steps of 100 ml until the maximum bladder volume. RESULTS: DWT decreases rapidly during the first 250 ml of bladder filling but, thereafter, remains almost stable until maximal bladder capacity. No statistical difference was found between DWT at 250 ml and DWT at a higher bladder filling. Men had a greater DWT compared to women (1.4 vs. 1.2 mm, P < 0.001). The age and BMI did not have a significant impact on DWT. CONCLUSIONS: DWT remains stable at a bladder filling of 250 ml. At this state of bladder filling, DWT between different groups are comparable. Men have to be evaluated separately from women.

Adolescent↗
PubMed2006

Clinical utility of "blind placement" prostatic stent in patients with benign prostatic obstruction: a prospective study.

OBJECTIVES: To assess the efficacy and safety of two versions of a blind placement temporary prostatic stent in the treatment of patients with benign prostatic obstruction. METHODS: Two versions of a prostatic stent (blind placement stent 1 [BPS-1] and BPS-2) were blindly inserted in an outpatient setting under local anesthesia. An assessment of voiding function, symptom scores, and complications was performed at baseline, directly after stent insertion, and at 14 and 28 days after stent placement. RESULTS: A total of 55 men were enrolled in the trial. Most stents of both types were successfully placed. Spontaneous voiding was achieved in all patients immediately after stent insertion, with improvements in voiding parameters and symptom scores. In patients with the BPS-1, migration occurred in 85%. In patients with the BPS-2, migration occurred in 5%. The median indwelling time of the stent was 16 and 38 days for the BPS-1 and BPS-2, respectively. Removal was successful in all but 1 case (BPS-2). CONCLUSIONS: The BPS-1 is not suitable for clinical practice because of the significantly high migration rate. The bulbar segment of the BPS-2 can prevent stent migration. However, patients experienced significant discomfort after insertion of the BPS-2. The voiding parameters and symptom scores of the BPS-2 were not significantly improved. Therefore, the BPS-2 is also not useful for clinical practice. Additional adjustment in the design of the BPS is needed to overcome these problems.

Aged↗
PubMed2006

Ultrasound imaging and contrast agents: a safe alternative to MRI?

Microbubble contrast media are used to enhance ultrasound images. Because ultrasound is a real-time investigation, contrast-enhanced ultrasound offers possibilities for perfusion imaging. This review is conducted to evaluate the safety of contrast-enhanced ultrasound and its possible role in medical imaging. The safety of diagnostic ultrasound is still an important field of research. The wanted and unwanted effects of ultrasound and microbubble contrast media as well as the effects of ultrasound on these microbubbles are described. Furthermore, some of the possible applications and indications of contrast-enhanced ultrasound will be discussed. The shared advantages of MRI and ultrasound are the use of non-ionizing radiation and non-nephrotoxic contrast media. From this review it can be concluded that, for certain indications, contrast enhanced ultrasound could be a safe alternative to MRI and a valuable addition to medical imaging.

Contrast Media↗
PubMed2006

Training in laparoscopic urology.

PURPOSE OF REVIEW: Training in laparoscopy has become an important issue in the current surgical scenario. In this overview we aim to update the current knowledge in the field of laparoscopic urological training and to highlight the potential dangers of using simulation for accreditation and selection purposes at this stage. RECENT FINDINGS: Physical simulators are widely available and seem to be equally efficient as virtual reality simulators. Transfer of training has been proven to be beneficial in randomized controlled trials for virtual reality and cholecystectomy. A model for the vesico-urethral suture has been described and integrated in a skills laboratory program. The program has construct validity and can discriminate at least between beginners and advanced laparoscopists. Efforts have still to be made in defining appropriate tools to assess competence and evidence for reliability, and validity must be obtained before including simulators in accreditation programs. SUMMARY: In spite of the abundant literature there is still little evidence about the learning mechanism involved in acquiring laparoscopic skills. Physical and virtual reality simulators have been proven to be efficient in improving dexterity and some evidence exists of a positive transfer from virtual reality to the operating room in cholecystectomy. Very few models, however, have been described for reconstructive urology, and effective transfer to the operating room has not yet been proven, although validation work is in progress in the field of urology.

Clinical Competence↗
PubMed2005

Hourglass-shaped nitinol prostatic stent in treatment of patients with lower urinary tract symptoms due to bladder outlet obstruction.

OBJECTIVES: To assess the efficacy and safety of the thermoexpandable hourglass-shaped nitinol prostatic stent in the treatment of patients with lower urinary tract symptoms due to bladder outlet obstruction. METHODS: The stents were inserted in an outpatient setting under local anesthesia and direct vision. Five different stent lengths (2.0 to 4.0 cm) were used, depending on the length of the prostatic urethra. Assessment of voiding function and symptom scores was performed at baseline, directly after stent insertion, at 14 days, and 1, 3, 6, and 12 months after stent placement. RESULTS: We enrolled 35 men in the trial. In 5 patients, insertion of the stent failed, mainly because of anatomical limitations. After all placement procedures, minimal temporary hematuria was observed. Spontaneous voiding was achieved in all patients, with immediate significant improvements in voiding parameters and symptom scores. The median indwelling time of the stent was 70 days. Kaplan-Meier survival analysis showed that at 14 days and at 3, 6, and 12 months, the stent was still in situ in 73%, 40%, 33%, and 23% of the patients, respectively. The main reason for removal of the stent was migration (93%), in most cases toward the bladder. Removal was uneventful in all but 1 case. CONCLUSIONS: The placement of the thermoexpandable hourglass-shaped nitinol stent results in relief of outflow obstruction and improvement of symptom scores. Because of the high migration rate, however, this stent design needs further improvement to be suitable for clinical practice.

Aged↗
PubMed2005

Corpus cavernosum electromyography during morning naps in healthy volunteers: further evidence that corpus cavernosum potentials reflect sympathetically mediated activity.

PURPOSE: We assessed the practicability of corpus cavernosum (CC) electromyography (EMG) in volunteers during morning naps in the laboratory and further validated this method. MATERIALS AND METHODS: A total of 11 healthy volunteers with a mean age of 23.8 years (range 19 to 31) were included. CC-EMG was started between 6:30 a.m. and 7 a.m. Two surface electrodes were placed at the base of the penis bilaterally and a reference electrode was placed on 1 kneecap. A strain gauge or Barlow gauge (Behavioral Technology, Salt Lake City, Utah) was used to monitor changes in penile circumference. Subjects were asked to sleep. Recording duration was 2 to 3 hours. Two recordings were performed per subject. RESULTS: Full erection was observed on 17 of the 22 recordings (77%), partial erection was noted on 3 (14%) and no tumescence was observed on the other 2 (9%). CC potentials consistently disappeared during tumescence and erection, while continuous CC potential oscillations reappeared during detumescence. During flaccidity bursts of CC potentials and electrical silence were recorded. Penile shrinkage was observed to accompany CC potentials but not to accompany electrical silence. CONCLUSIONS: CC-EMG during morning naps is a practical and valid method for investigating CC electrophysiology. CC-EMG signal patterns during tumescence, detumescence and flaccidity fit the existing theory that CC potentials reflect cavernous smooth muscle sympathetically mediated activity.

Adult↗
PubMed2004

Contrast specific imaging in the detection and localization of prostate cancer.

Prostate cancer (PCa) is the most common cancer in elderly men and is one of the most important causes of death from cancer in men. The diagnosis of PCa is based on a combination of digital rectal examination, PSA and transrectal ultrasound (TRUS). However, this combination does not reach the accuracy of detection and localization necessary for proper decisions on treatment methods. Therefore, biopsies are performed in all cases for which the suspicion of PCa is raised. Even with biopsies, staging and grading of PCa is far from optimal. More accurate imaging is necessary to improve the biopsy sampling, the goals being to replace systematic biopsies by a targeted approach and to improve staging and grading of PCa. Ultrasound imaging of the prostate remains the first choice of imaging to visualize the prostate, however, gray-scale ultrasound imaging has an accuracy of about 50-60% for the detection of PCa and TRUS used for local staging has an even lower accuracy. The development of PCa is associated with changes in the metabolism of tumor cells, and therefore with changes in the blood perfusion of the involved tissue. This paper focuses on contrast specific imaging techniques to visualize these changes in blood perfusion. Techniques such as color and power Doppler imaging, and contrast enhanced imaging techniques using color and power Doppler, harmonic imaging and intermittent imaging are discussed.

Contrast Media↗
PubMed2003

Quantification of prostate shrinkage after microwave thermotherapy: a comparison of calculated cell-kill versus 3D transrectal ultrasound planimetry.

PURPOSE: To compare prostate shrinkage after transurethral microwave thermotherapy (TUMT) with calculated cell-kill. MATERIALS AND METHODS: The calculated cell-kill from 33 males with benign prostatic hyperplasia (BPH) treated with TUMT according to the ProstaLund Feedback Treatment (PLFT) method was compared to the post-treatment prostate volume change. The prostate volume was estimated with three-dimensional transrectal ultrasound (3D-TRUS) planimetry at baseline, 3, 6, and 12 months follow-up. A paired t-test was used to test the statistical significance of differences between the cell-kill volume and the prostate volume change. Linear regression was used to infer a relationship between the cell-kill and the 3D-TRUS data. The reproducibility of the 3D-TRUS method was assessed in repeated measurements. RESULTS: The mean prostate volume at baseline (N=33) was 56.1cm(3). After 3 (N=25), 6 (N=29) and 12 months (N=23), it was 45.5 cm(3), 39.7 cm(3), and 45.1cm(3), respectively. The corresponding average cell-kill volume was 16.4 cm(3), 17.1cm(3), and 17.2 cm(3), respectively. Predicted cell-kill volume was significantly larger than prostate shrinkage at 3 (p<0.0001), 6 (p=0.0002), and 12 months (p<0.0001), and showed a strong correlation at 3 and 6 months (r=0.74, p<0.0001). Correlation at 12 months was moderate (r=0.57, p=0.0041). Examination and investigation variability both averaged 2.5%. CONCLUSIONS: Cell-kill calculations of the PLFT method are proportional to the 3D-TRUS prostate shrinkage by a factor of 0.5 and have a precision of approximately +/-10 cm(3) for 90% of the patients during the first year after treatment.

Aged↗
PubMed2003

The value of dynamic contrast enhanced power Doppler ultrasound imaging in the localization of prostate cancer.

OBJECTIVES: The objective of this study is to define enhancement characteristics that correlate to the presence of prostate cancer (PCa) and to evaluate the value of these characteristics in the localization of prostate cancer. METHODS: 29 patients with proven prostate malignancy, scheduled for radical prostatectomy, underwent an ultrasound examination prior to surgery. A bolus injection of contrast agent was administered intravenously. The distribution of the contrast enhanced blood to the prostate was monitored using Transrectal Contrast Enhanced Power Doppler Ultrasound. Fixed protocols and settings were used for all patients. The percentage of a selected area that showed enhancement was observed in time. The resulting enhancement curves were described using the parameters time to start, time to the maximum of the enhancement, the maximum value of the enhancement, and the rise time of the enhancement. Three evaluation-protocols divided the prostate into a number of areas of interest: into two areas using the Left-Right (LR) and Dorsal-Ventral (DV) protocols and into four areas using the Quadrant-protocol (Q). The enhancement parameters of the areas of interest were compared to identify the most affected area. The results were compared to the histopathological findings. RESULTS: For the LR-protocol, the minimal time to peak proved to be the most predictive parameter for selecting the major malignant area. 78% of the patients were diagnosed correctly (N=23). Accurate localization of the major malignancy in either the ventral or dorsal side of the prostate was not feasible using the current protocol. CONCLUSIONS: Malignancies can be accurately localized in either the left or the right side of the prostate based on the time to the maximum of the enhancement. An accurate discrimination between malignancies in either the dorsal or ventral side of the prostate cannot be performed. This is most likely due to anatomical differences between the dorsal and ventral area.

Contrast Media↗
PubMed2003

Transrectal ultrasound imaging and prostate cancer.

Prostate cancer is one of the most important causes of death from cancer in men. Ultrasound imaging is frequently used in the diagnosis of prostate cancer. This paper presents an overview of currently available ultrasound imaging techniques. The underlying principles and methods are discussed briefly and examples of the clinical application are presented. Techniques such as gray-scale imaging, Doppler imaging and contrast enhanced imaging techniques using power Doppler, color Doppler, harmonic imaging and intermittent imaging are discussed.

Adenocarcinoma↗
PubMed2002

Quantitative microbubble enhanced transrectal ultrasound as a tool for monitoring hormonal treatment of prostate carcinoma.

BACKGROUND: We quantified changes in prostate carcinoma vascularity treated with anti-androgens using color Doppler and power transrectal ultrasound in combination with microbubble contrast agent Levovist. METHODS: Thirty-six men with prostate carcinoma were studied at baseline and at intervals during treatment. At each attendance, Levovist((R)) (10 ml, 300 mg/ml) was given as an iv bolus. Using quantitative analysis, we calculated the pre-enhancement scores, arrival time, time to peak, peak value, and area under the time-enhancement curve (AUC). These were compared to pre-treatment values and serial PSA measurements. RESULTS: The pre-enhancement, peak value, and AUC each showed a marked response with reductions within one week. The average AUC declined to 68% +/- 9% (mean +/- standard error) by week 1, 56% +/- 9% by week 3, and 20% +/- 4% by week 6. A strong correlation with changes in the mean PSA (r = 0.95, P < 0.001) was also measured. In four patients, Doppler indices did not fall with PSA: two patients with the most marked discrepancy relapsed at 6 months. CONCLUSION: The vascular enhancement declined with therapy, similar to PSA. Microbubble enhanced ultrasound can show early response to treatment.

Androgen Antagonists↗
PubMed2002

Computerised assessment of maximum urinary flow: an efficient, consistent and valid approach.

OBJECTIVES: To evaluate the relative accuracy of a computerised method to quantitatively assess maximum urinary flow. METHODS: A total of 1147 uroflows were evaluated by the computerised method and by three experts from different European countries. The sample consisted of uroflows from the respective visits by a 20% sample of randomly chosen patients (n = 223) with lower urinary tract symptoms with participation in two clinical trials in which the efficacy and safety of Permixon was evaluated. The proportions of automated maximum flow values included in the 10% extended range of experts (and their 95% confidence intervals) were assessed, as well as the concordance coefficients between experts and the computerised method and the paired Student's t-test for the average differences between experts and computer. RESULTS: The rate of agreement between experts and computer varied between about 95 and 100% over factor levels for visit, type of machine and country. Concordance coefficients indicated good agreement between experts and the automated method. When looking at average differences between experts and the computer, the smallest differences were observed between experts 2, 3 and the computer (differences not statistically significant). Statistically significant average differences were observed between expert 1 and the other experts as well as between expert 1 and the computer. CONCLUSIONS: The computerised assessment decreases the fraction of variability of maximum urinary flow caused by artifacts as well as intra- and inter-expert variation. The computerised assessment of maximum urinary flow is an efficient, consistent and valid approach to quantitatively assess maximum urinary flow in clinical trials.

Decision Making, Computer-Assisted↗