Comparison of 30-day, 90-day and in-hospital postoperative mortality for eight different cancer types.

BACKGROUND: Various definitions are used to calculate postoperative mortality. As variation hampers comparability between reports, a study was performed to evaluate the impact of using different definitions for several types of cancer surgery. METHODS: Population-based data for the period 1997-2008 were retrieved from the Rotterdam Cancer Registry for resectional surgery of oesophageal, gastric, colonic, rectal, breast, lung, renal and bladder cancer. Postoperative deaths were tabulated as 30-day, in-hospital or 90-day mortality. Postdischarge deaths were defined as those occurring after discharge from hospital but within 30 days. RESULTS: This study included 40,474 patients. Thirty-day mortality rates were highest after gastric (8·8 per cent) and colonic (6·0 per cent) surgery, and lowest after breast (0·2 per cent) and renal (2·0 per cent) procedures. For most tumour types, the difference between 30-day and in-hospital rates was less than 1 per cent. For bladder and oesophageal cancer, however, the in-hospital mortality rate was considerably higher at 5·1 per cent (+1·3 per cent) and 7·3 per cent (+2·8 per cent) respectively. For gastric, colonic and lung cancer, 1·0 per cent of patients died after discharge. For gastric, lung and bladder cancer, more than 3 per cent of patients died between discharge and 90 days. CONCLUSION: The 30-day definition is recommended as an international standard because it includes the great majority of surgery-related deaths and is not subject to discharge procedures. The 90-day definition, however, captures mortality from multiple causes; although this may be of less interest to surgeons, the data may be valuable when providing information to patients before surgery.

Trends in incidence, treatment and survival of patients with stage IV colorectal cancer: a population-based series.

AIM: The incidence, patterns of care and survival were determined in patients with stage IV colorectal cancer (CRC) in a population-based series. METHOD: Computer records for patients diagnosed with stage IV CRC diagnosed from 1 January 1995 to 31 December 2007 were retrieved from the Rotterdam Cancer Registry. Surgical resection of the primary tumour, chemotherapy use, hepatic surgery and survival were evaluated according to year of diagnosis, age, gender and primary tumour site. RESULTS: In the southwestern part of the Netherlands, 19 014 new patients with CRC were diagnosed and synchronous metastatic disease was found in 3482 (18%). This proportion increased during the study period, from 16% to 21%. Surgical resection of the primary tumour was performed in approximately 50% of the patients and did not change over time. Postoperative 30-day mortality was 8%. Chemotherapy use increased from 18% in the first period to 56% in the latest period. Liver surgery increased from 4% in the first period to 10% in the latest period. Median survival increased from 7 months to 12 months and 2-year survival increased from 14% to 28%. Two-year survival declined with increasing age and was significantly worse for right-sided tumours (14%). CONCLUSION: Survival of patients with stage IV CRC has improved over time and this is probably a result of the increased use of chemotherapy and the increased numbers of patients who underwent hepatic surgery.

Evaluation of the digital rectal examination as a screening test for prostate cancer. Rotterdam section of the European Randomized Study of Screening for Prostate Cancer.

BACKGROUND: The utility of digital rectal examination (DRE) as a screening test for early detection of prostate cancer has not been established. Therefore, we evaluated the usefulness of DRE as a stand-alone screening test and in conjunction with measured serum prostate-specific antigen (PSA) levels of 0-3.9 ng/mL and transrectal ultrasonography (TRUS). METHODS: Our study population consisted of 10,523 men aged 54-76 years who were randomly assigned to the screening arm of the Rotterdam, The Netherlands, section of the European Randomized Study of Screening for Prostate Cancer. The underlying prevalence of detectable prostate cancer was estimated by logistic regression analysis and used for calculating the sensitivity of DRE as a test. Pathologic characteristics of 105 radical prostatectomy specimens were used to determine the aggressiveness of the tumors diagnosed (and missed) by DRE. RESULTS: The overall detection rate for prostate cancer in this population when serum PSA measurement, DRE, and TRUS were used was 4.5%, and the detection rate with DRE alone was 2.5%. The positive predictive value of DRE ranged from 4% to 11% in men with PSA levels of 0-2.9 ng/mL and from 33% to 83% in men with PSA levels of 3.0-9.9 ng/mL or more. Most tumors detected by DRE in men with PSA levels of less than 4.0 ng/mL were small (mean volumes = 0.24-0.83 mL), and most were well differentiated (Gleason scores of 6 or less). Minimal, moderate, and advanced cancers were seen in 42%, 42%, and 16% of men, respectively, with a PSA level of 4.0 ng/mL or less. DRE alone allowed detection of 264 (55.8%) of 473 cancers; 82 (17.3%) of the 473 cancers would have remained undetected by PSA-based screening alone (i.e., no follow-up procedures for PSA values of 0-3.9 ng/mL). CONCLUSIONS: For PSA values of 0-3.9 ng/mL, the positive predictive value and sensitivity of DRE, tumor volume, and tumor grade were strongly dependent on PSA level. DRE has a poor performance in low PSA ranges.

Quantitative analysis of the decay of immunoreactivity in stored prostate needle biopsy sections.

Application of immunohistochemistry to assess the presence of prognostic tissue markers is used widely. The quantitation of these markers may be hampered by a time-related loss of antigenicity in formalin-fixed paraffin-embedded tissue stored on glass slides. Potential loss of immunohistochemical staining intensity was studied on prostatic needle biopsy sections stored for a maximum of 4 years with antibodies against p27kip1, CD-44s, MIB-1, and androgen receptor (AR). In benign tissue, the positive/total ratio for p27kip1 was determined, while CD-44s staining intensity was assessed semiquantitatively. For MIB-1 and AR, nuclear staining intensity was assessed using computed image analysis. An exponential and significant decay of immunoreactivity was seen for p27kip1, CD-44s, MIB-1, and AR, with half-lives of 587 days, 214 days, and 290 days for p27kip1, MIB-1, and AR, respectively. Immunohistochemical assessment of prognostic tissue markers on stored slides must be considered with care in research and clinical settings.

Complications of transrectal ultrasound-guided systematic sextant biopsies of the prostate: evaluation of complication rates and risk factors within a population-based screening program.

OBJECTIVES: Screening for prostate cancer to reduce the mortality and morbidity from this disease has become an important issue in recent years. Of all procedures used to diagnose prostate cancer, biopsy of the prostate is the cause of most complications. To evaluate the safety of the screening procedure, we have studied the complications and risk factors for complications within the screened population of the European Randomized Study of Screening for Prostate Cancer (ERSPC), Rotterdam section. METHODS: Between June 1994 and July 1996, 1687 transrectal ultrasound-guided systematic sextant biopsies were performed after screening 6198 men through prostate-specific antigen level, digital rectal examination, and transrectal ultrasonography. RESULTS: From these 1687 biopsies, 302 cases of prostate cancer were diagnosed. Mild complications such as hematuria and hematospermia were reported frequently with rates of 23.6% and 45.3%, respectively. More severe complications were far less frequently seen. Fever, usually of low grade, was seen after 4.2% of biopsies. Seven men (0.4%) were admitted to a hospital after biopsy. Risk factors for complications could not be identified. CONCLUSIONS: Review of the literature concerning transrectal biopsies of the prostate shows that the complication rates within this screened population are comparable to those reported within referred patients. The admittance rate is slightly lower. Transrectal ultrasound-guided systematic sextant biopsy of the prostate is a safe procedure for the diagnosis of prostate cancer within the general population; however, identification of risk factors for complications might further improve the safety of the screening procedure.

The value of screening tests in the detection of prostate cancer. Part I: Results of a retrospective evaluation of 1726 men.

OBJECTIVES: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the differentiation between prostate carcinoma and benign conditions in selected series of patients. In this study the F/T ratio was analyzed for its ability to improve the specificity of total serum PSA, digital rectal examination (DRE), and transrectal ultrasonography (TRUS) for the detection of prostate cancer in an unselected screening population of men identified in the Rotterdam population. METHODS: In 1726 men between 55 and 76 years old, 67 prostate carcinomas were detected by DRE, TRUS, and total serum PSA (Abbott IMx, Hybritech Tandem E). The DELFIA ProStatus PSA EQM and ProStatus PSA Free/Total assays (Wallac) were applied in retrospect to determine total and free serum PSA. Age, total prostate and inner zone volumes were taken into consideration. RESULTS: Sixty-seven carcinomas were detected, two by TRUS and three by DRE alone. Total serum PSA was the most important single predictor of prostate cancer, followed by DRE. The F/T ratio increased the specificity of total serum PSA in the PSA range between 4.0 and 10.0 ng/mL. However, this improved specificity was not significant, nor for gland volumes restricted to 50 mL or less. CONCLUSIONS: The combination of total serum PSA and DRE remains the standard for detection of prostate carcinoma in a screening population. Their specificity may be improved minimally by the F/T ratio, but not significantly in a sample of 1726 screened men. The threshold of the F/T ratio, and the optimal PSA range for its application, remains to be assessed prospectively.

The value of screening tests in the detection of prostate cancer. Part II: Retrospective analysis of free/total prostate-specific analysis ratio, age-specific reference ranges, and PSA density.

OBJECTIVES: The ratio between free and total prostate-specific antigen (PSA) in serum (F/T ratio) was shown to improve the specificity of total serum PSA for the detection of prostate carcinoma in selected populations. In this study, the value of the F/T ratio for screening of prostate cancer was compared with that of age-specific reference ranges for PSA and PSA density (PSAD) by a simulation experiment. METHODS: In 1726 men between 55 and 76 years old, 67 prostate carcinomas were detected by application of digital rectal examination (DRE), transrectal ultrasonography (TRUS), and total serum PSA. A serum PSA of 4.0 ng/mL or more, an abnormal DRE, or an abnormal TRUS were the indications to perform 308 biopsies. A simulation was performed in which an F/T ratio of 0.20 (ProStatus PSA Free/Total), age-specific PSA reference ranges, and a PSAD of 0.12 ng/mL/cc were used to study their capability to increase the specificity of total serum PSA in predicting prostate biopsy results. RESULTS: Using age-specific PSA reference ranges and DRE as indicators for biopsy, a reduction of 37% (113) of biopsies would have been obtained with a loss of detected cancers of 12% (11). For the use of PSAD and DRE, these numbers were 28% (96) and 11% (7), respectively. Application of a serum PSA of 4.0 ng/mL or more and an F/T ratio of 0.20 or less and an abnormal DRE as indicators for biopsy would reduce the number of biopsies by 37% (112) and the number of detected cancers by 11% (7). The biopsy to prostate cancer ratio of these simulations varied between 3.3 and 3.6. Minimal loss of cancer detection of 3% (2) with a reduction in the number of biopsies of 17% (53) is obtained when TRUS is omitted from the screening protocol. Selecting men by a total serum PSA value of 2.0 ng/mL for further diagnostic workup by TRUS and DRE would have reduced the number of biopsies by 30% (102), and the number of cancers detected by 6% (4). CONCLUSIONS: The most cost-effective protocol for screening prostate carcinoma appears to be prescreening by total serum PSA. The F/T ratio might be used to detect carcinomas in the PSA range below 4.0 ng/mL, but the best threshold remains to be assessed.

Comparison of prostate-specific antigen corrected for total prostate volume and transition zone volume in a population-based screening study.

OBJECTIVES: To compare the discriminatory potential between prostate cancer and benign conditions of the prostate in a population-based screening study, of serum prostate-specific antigen levels (PSA) and PSA corrected for both the total prostate volume (PSA-D) and the transition zone volume (PSA-T). METHODS: In a randomized population-based screening study (Rotterdam section of the European Randomized Study of Screening for Prostate Cancer), in which 10,865 men have been screened, the biopsy results of 1202 men with PSA levels of 4 ng/mL or more were evaluated. Planimetric and prolate ellipsoid volumes of the total prostate as well as of the transition zone were measured. The measured volumes were compared with the volumes of 57 radical prostatectomy specimens through Spearman's rank correlation coefficient and agreement tests. A receiver operating characteristic (ROC) curve analysis was done of sensitivity and specificity of biopsy indications through PSA and PSA corrected for the volumes measured with transrectal ultrasound. RESULTS: In the 1202 men studied, 361 cases of prostate cancer were diagnosed. Both PSA-D and PSA-T showed a significantly higher area under the ROC curve (0.77 and 0.79, respectively) than PSA alone (area 0.65). There was no significant difference between PSA-D and PSA-T. The use of a PSA-D threshold value of 0. 10 ng/mL/cc would have avoided 28% of biopsies at the cost of 10% of detectable cancers. A PSA-D threshold of 0.15 ng/mL/cc would have avoided 73.8% of biopsies at the cost of not diagnosing 43.8% of detectable cancers. CONCLUSIONS: The planimetrically obtained prostate volume showed a more favorable agreement with the radical prostatectomy volume than the prolate ellipsoid volume. The discriminatory potential of the corrected PSA value is better at predicting the results of needle biopsy of the prostate when compared with PSA alone. The use of the transition zone volume for this correction results in a higher discriminatory potential when compared to the use of the total prostate volume; however, the observed difference was not statistically significant.

Computer-controlled wheelchair ergometer.

A new wheelchair ergometer has been designed in which a combination of realistic simulation of wheelchair propulsion--with adjustable parameters for rolling resistance, air drag, wind speed and slope--and force measurement has been realised. The static solution enables the measurement of physiological and kinesiological parameters. All data from force transducers in seat and backrest, torque transducers in the wheels and force transducers in the wheelframes as well as the acquired speed are sampled in a data-acquisition system. An offline curve processor allows the acquired data to be processed with standard or custom-programmed routines. Preliminary results have been added and are discussed.

Fertility potential in men with a history of congenital undescended testes: a long-term follow-up study.

Men with a history of congenital undescended testes (UDT) have an increased risk of fertility problems. Despite no definitive proof, current guidelines recommend early surgical intervention because this may have a positive effect on future fertility potential by preventing degenerative changes of the testes in early life. Also surgical intervention facilitates observability of the testes in view of possible malignancy. We evaluated testicular function in adult men with previous UDT treated at different ages before puberty. A long-term follow-up study of men with previous UDT was performed. Andrological evaluation included medical history taking, physical examination, scrotal ultrasound, determination of reproductive hormones, and semen analysis. Findings were compared with those of a control group of men with normal testicular descent. The influence of age at orchiopexy on future fertility parameters was evaluated in a multivariate regression analysis. 62 men were included of whom seven had had bilateral UDT. Twenty-four patients had had their orchiopexy before the age of 24 months of whom eight men had it before 12 months of age. Forty-eight men had had unsuccessful luteinizing-hormone-releasing-hormone (LHRH) nasal spray treatment during childhood, whereas 14 of 24 men operated before 24 months of age had not received LHRH treatment before orchiopexy. Fertility potential in men with a history of UDT is compromised in comparison with controls. We could not detect any influence of age at orchiopexy on fertility parameters. However, the number of patients operated before the age of 12 months is limited. This study does not support the assumption that early orchiopexy results in better fertility potential.

The interobserver variability of digital rectal examination in a large randomized trial for the screening of prostate cancer.

BACKGROUND: To analyze to what extent the percentage of suspicious digital rectal examination (DRE) findings vary between examiners and to what extent the percentage of prostate cancers (PCs) detected in men with these suspicious findings varies between examiners. METHODS: In the first screening round of the European Randomized study of Screening for PC (ERSPC) Rotterdam, 7,280 men underwent a PSA-determination and DRE of whom 2,102 underwent prostate biopsy (biopsy indication PSA > or = 4.0 ng/ml and/or suspicious DRE and/or TRUS). Descriptive statistics of DRE-outcome per PSA-range were used to determine the observer variability of six examiners. Because this analysis did not correct properly for other predictors of a suspicious DRE (PSA-level, biopsy indication, TRUS-outcome, prostate volume and age), a logistic regression analysis controlling for these explanatory variables was performed as well. RESULTS: In 2,102 men biopsied, 443 PCs were detected (PPV = 21%). For all PSA levels the percentage suspicious DRE varied between examiners from 4% to 28% and percentage PC detected in men with a suspicious DRE varied from 18% to 36%. Logistic regression analysis showed that three of six examiners considered DRE significantly more often abnormal than others (ORs 3.48, 2.80, 2.47, P < 0.001). For all examiners the odds to have PC was statistically significantly higher in case of a suspicious DRE (ORs 2.21-5.96, P < 0.05). This increased chance to find PC was not significantly observer-dependent. CONCLUSIONS: Three of six examiners considered DRE significantly more often suspicious than the others. However, under equal circumstances a suspicious DRE executed by each examiner increased the chance of the presence of PC similarly.

A critical comparison of methods proposed for quantification of bladder outlet obstruction.

Performance studies of parameters for bladder outlet obstruction in BPH patients before and after a TURP in terms of sensitivity and specificity can easily be criticized because in roughly 25% of the patients it is not clear if the clinical symptoms are related to increased outlet obstruction or impaired bladder contractility. This abstract presents objective alternatives.

Estimation of prostate cancer probability by logistic regression: free and total prostate-specific antigen, digital rectal examination, and heredity are significant variables.

BACKGROUND: Despite low specificity, serum prostate-specific antigen (PSA) is widely used in screening for prostate cancer. Specificity can be improved by measuring free and total PSA and by combining these results with clinical findings. Methods such as neural networks and logistic regression are alternatives to multistep algorithms for clinical use of the combined findings. METHODS: We compared multilayer perceptron (MLP) and logistic regression (LR) analysis for predicting prostate cancer in a screening population of 974 men, ages 55-66 years. The study sample comprised men with PSA values >3 microg/L. Explanatory variables considered were age, free and total PSA and their ratio, digital rectal examination (DRE), transrectal ultrasonography, and a family history of prostate cancer. RESULTS: When at least 90% sensitivity in the training sets was required, the mean sensitivity and specificity obtained were 87% and 41% with LR and 85% and 26% with MLP, respectively. The cancer specificity of an LR model comprising the proportion of free to total PSA, DRE, and heredity as explanatory variables was significantly better than that of total PSA and the proportion of free to total PSA (P <0.01, McNemar test). The proportion of free to total PSA, DRE, and heredity were used to prepare cancer probability curves. CONCLUSION: The probability calculated by logistic regression provides better diagnostic accuracy for prostate cancer than the presently used multistep algorithms for estimation of the need to perform biopsy.

Estimation of the lag time between detrusor pressure- and flow rate-signals.

In a urodynamic measurement setup there is a considerable spatial separation between the uroflowmeter and the location where the detrusor pressure is measured. Therefore, a "time shift" (or lag time correction) has to be applied to one of these signals in order to align related samples in studies where pressure and flow rate are considered simultaneously (e.g., assessment of bladder contractility or bladder outlet resistance). Currently, a heuristic value for this time shift of 0.8 s is applied. In this article, we present a method to estimate the lag time directly from the measurements. Using this method we have found, amongst others, that the mean lag time in our clinic is 0.6 s for males, 0.4 s for females voiding in sitting position, and 1.1 s for females voiding in standing position using a special receptacle in video urodynamics. Furthermore, we found that sphincter/urethral activity during voiding (which causes a drop in flow rate and an accompanying increase in detrusor pressure) is associated (on average) with shorter lag times than straining (when a positive pressure rise accompanies an increase in flow rate). Additionally strong evidence is provided that lag time correction is not a major source of error in urodynamics.

Free and total prostate-specific antigen in a screened population.

OBJECTIVES: To determine whether the ratio of free to total (F/T) prostate-specific antigen (PSA) can differentiate between men with prostate carcinoma or benign conditions in a screened population. SUBJECTS AND METHODS: Total and free serum PSA (measured using Delfia PSA assays, Abbott IMx and Hybritech Tandem E methods) were determined retrospectively in 1726 men aged 55-77 years, in whom 67 prostate carcinomas were detected by screening with a digital rectal examination, transrectal ultrasonography, and total serum PSA level. Predictors for a positive biopsy result were estimated as a function of total PSA, free PSA and the combination of both. RESULTS: There was an excellent correlation between the Delfia ProStatus, the Abbott IMx and the Hybritech Tandem E assays. Compared with the total serum PSA level, the F/T ratio improved the specificity significantly only in those men with a total PSA of > or = 7 ng/mL. Using the information given by the total and free PSA values, a maximum sensitivity of 75% at a specificity of 74% was obtained for the whole PSA range from 4 to 10 ng/mL; the maximum sensitivity was 79% with a specificity of 71%. CONCLUSION: The optimal mathematical combination of free and total serum PSA improves the specificity of total serum PSA level in detecting prostate carcinoma more than the does the F/T PSA ratio.

Tumour control according to pathological variables in patients treated by radical prostatectomy for clinically localized carcinoma of the prostate.

OBJECTIVE: To evaluate the diagnosis, outcome and final pathology of radical prostatectomy for prostate cancer performed by urologists in a clinic where six urologists perform a total of 50 radical prostatectomies a year, using radical prostatectomy specimens processed routinely. PATIENTS AND METHODS: Radical prostatectomy was performed in 273 patients who were followed prospectively. The radical prostatectomy specimens were evaluated for pathological stage, histological grade, capsular perforation, positive and apical margins of resection, seminal vesicle invasion, perineural invasion and vascular invasion; the lymph node status was also determined. The relationship between these variables and clinical progression, local recurrence, distant metastases, biochemical progression, overall survival and cancer-specific survival was assessed. RESULTS: All evaluated variables were significantly predictive for clinical and biochemical progression in the univariate analyses, and all but perineural invasion and lymph node status for cancer-specific survival. Multivariate analysis showed vascular invasion to be the most important prognostic variable, followed by capsular perforation, positive margins of resection and poorly differentiated carcinoma. The overall results for the evaluated variables were comparable to the results from centres with greater experience. CONCLUSIONS: The outcome of treatment in this small clinic was similar to that from larger clinics with more experience. The routine evaluation of the radical prostatectomy specimens identified pathological variables which were important prognostic factors, with vascular invasion, capsular perforation, positive margins of resection and poorly differentiated carcinoma being the most significant. The extent of vascular invasion should be part of the routine evaluation of radical prostatectomy specimens.

Analytical evaluation of the new Prostatus PSA Free/Total assay for prostate-specific antigen as part of a screening study for prostate cancer.

In this communication a limited analytical study is described on the new Prostatus PSA Free/Total assay. The study is considered as a side study of the European Randomized Study of Screening for Prostate Cancer. The between-day imprecision with 8 control samples for free prostate-specific antigen ranged from 10.3% at 0.17 microg/l to 3.7% at a concentration of 35.5 microg/l, while for total prostate-specific antigen we found 7.3% at 0.69 microg/l and 4.3% at 70.7 microg/l. For total prostate-specific antigen we found excellent agreement between the new assay and well-established assays like Abbott IMx and Hybritech Tandem-E, both for prostate cancer and benign prostate hyperplasia specimens. The age-specific reference ranges proved to be well-comparable with the literature data both for free and total prostate-specific antigen.

The free-to-total serum prostate specific antigen ratio for staging prostate carcinoma.

PURPOSE: We analyzed the relationship between the free-to-total PSA ratio and prostate cancer tumor stage and grade compared to total serum PSA. MATERIALS AND METHODS: In 123 patients clinical and pathological grade and stage were related to total serum PSA and free-to-total PSA ratio. RESULTS: Total serum PSA paralleled clinical staging of prostate cancer. The distributions of total serum PSA and the free-to-total PSA ratio were significantly different between benign and malignant diseases (any stage), and between any T category and nodal disease. For serum PSA significant differences were noted between the distributions of men with locally confined (stages T1 and T2) and locally extended (stage T3) disease, and between all T categories and systemic metastatic disease. This finding was not noted for the free-to-total PSA ratio. CONCLUSIONS: The free-to-total PSA ratio has no additional value in clinical staging of prostate carcinoma compared to serum PSA. The free-to-total PSA ratio may be considered the result of cell differentiation and not an indicator of tumor load.

Reasons for the weak correlation between prostate volume and urethral resistance parameters in patients with prostatism.

In an attempt to increase our understanding of the clinical syndrome of benign prostatic hyperplasia (BPH) an analysis was made of the association between prostate volume as measured by transrectal ultrasound and several reported urodynamically determined urethral resistance parameters. Two types of obstruction can be recognized on the basis of urodynamic data: a compressive type characterized by a high urethral opening pressure and a prolonged isovolumetric contraction phase before urine flow can start, and a constrictive type characterized by a normal opening pressure and an increased slope of the urethral resistance relation. A combination of both types is often seen in BPH. In our study, parameters that selectively quantify compression correlate weakly to moderately with prostate volume, whereas parameters that mainly quantify constriction do not correlate at all with prostate volume. Parameters that combine a measure for compression and constriction correlate less well with prostate volume than parameters that mainly quantify compression. The variation in prostate volume was found to determine the variation in urethral resistance by 15% or less depending on the parameter used, which implies that the different pathophysiological mechanisms that can increase urethral resistance in the complex process of clinical BPH are mainly determined by factors other than the volume of the prostate. Thus, despite the lack of correlation between prostate volume and urethral resistance, pressure-flow studies and the determination of urethral resistance parameters provide a valuable contribution to the understanding of the pathophysiology of voiding dysfunction in men with symptoms of prostatism.