The only confident method available for correctly diagnosing BOO is by a pressure flow study.61 It should be considered if an invasive treatment is considered i.e surgery or if surgical treatment has failed. Pressure-flow studies differentiate between patients with a low Qmax secondary to obstruction and those whose low Qmax is caused by a decompensated or neurogenic bladder.18Patients with a history of neurologic disease that are known to affect bladder or sphincteric function, as well as patients with normal flow rates(Qmax greater than 15ml} but bothersome symptom, may also benefit from urodynamic evaluation, especially if surgical therapy is considered.18 The test involves the simultaneous measurement of the voiding pressure (driving pressure) and resulting flow rate. This study was first performed by Rehfish,62 followed much later by Von Garrelts63 and Millers.64This method is invasive, expensive, time consuming and most times uncomfortable for the patients.53 This limits the application of this method both for clinical diagnosis and for research. Also, trans-urethral catheter influences voiding thus limiting the accuracy of the method, depending on the size of the catheter used. To increase accuracy, a
suprapubic catheter can be used, but this increases the pain and risk of injury to the patient.53
Different approaches to the interpretation of the result of pressure flow studies exist. In 1997, the International Continence Society published a provisional nomogram extracted on the basis of previous knowledge.65 (Appendix 1). This nomogram divides patients into clearly obstructed, unobstructed, and equivocally obstructed.
Urodynamic pressure flow studies are obtained by inserting a catheter into the bladder and rectum, filling the patients bladder and asking him/her to void into a flow meter while the pressure is measured. The catheters are connected to a pressure transducer. The rectal catheter measures intra- abdominal pressure. Detrusor pressure equals intra-vesical pressure minus intra-abdominal pressure.55 Because the test is largely invasive, various non invasive measurements of bladder pressure have been proposed. One method involves a combination of isovolumetric detrusor pressure and free flow rates. Bladder pressures can also be measured by using a small inflatable cuff around the penis analogous to blood pressure measurements.55 Another method involves the use of a pressure transducer attached to an incontinence condom applied to the penis.55 The pressure can be measured non-invasively. Sound produced by the flow of urine through the prostatic urethra can also be used to detect bladder obstruction.55 This method seems
promising but has not yet been tested sufficiently to provide a definite conclusion. Finally, the value of pressure-flow measurement in predicting treatment is uncertain.18In a study by Abrams et al32, the inclusion of pressure-flow data in the preoperative evaluation and indication for surgery reduced the subjective failure rate to 12% (down from 28%) when patients were certified as candidates for surgery without urodynamic data. Pressure-flow studies permit more accurate categorization of patients.
CHAPTER FOUR AIMS AND OBJECTIVES
1. To determine if simple uroflowmetry and symptom score results correlate with severity of LUTS.
CHAPTER FIVE
PATIENTS AND METHODS
The study is a hospital based cross-sectional prospective study of males presenting with LUTS due to BPH, in the urology clinics of NAUTH Nnewi. Approval was obtained from the hospital ethical committee, before commencement of the study. Informed consent was obtained from the patients through a properly filled consent form.
The inclusion criteria were all men above 40 years presenting to the urology clinic with LUTS due to BPH. All patients were examined and urine flow rate carried out by the researcher under supervision. Criteria for diagnosis included a history, physical examination including a DRE, plus serum PSA levels to rule out cancer of the prostate. Controls were selected from male subjects who present with other symptoms unrelated to the urinary tract, like infertility and from normal adult male volunteers. DRE and physical examination was also done in all the control subjects to exclude the presence of an enlarged prostate.
Mode of assessment of the symptom score was by the self- or physician- administered IPSS questionnaire, which was modified to include some relevant biodata of the patient and the duration of his symptoms.
(Appendix II).
Urine flow rates was measured using the electrically powered Urodyn 1000 (Dantec) machine (serial no. 5534). Here the urine is directed onto a spinning disk whose rotational velocity is kept constant by a tachometer and feedback circuit. As fluid hits the disk, more electrical energy is required to maintain the constant angular velocity and measurement of the extra current can be plotted graphically. The machine automatically prints the flow rates.
Three flow rate recordings were obtained from both patients and controls.
This was to ensure that the values were consistent.. Patients were instructed not to waggle the stream when voiding as this can produce artifacts. Only urine volumes equal to or greater than 150mls was used for the study and patients were advised to void only when they have the strong desire to pass urine, so that they can pass enough urine volume.
DATA ANALYSIS
Sample size was estimated using the formula:66 Ns = (Z/E)2(p)(1-P).
Where Ns = the required sample size
Z = the standard score corresponding to a given confidence level, E = the proportion of sampling error in a given situation, and
P = the estimated proportion or incidence of cases in the population.1
Since the estimated disease incidence is about 10%1, then p=0.10 of the whole population. Using a confidence level of 95%, with a tolerable amount of error of not greater than 0.10. The estimated sample size was:
Ns= (1.96/0.10)2(0.10)(1-0.10) (19.6)2(0.10)(0.9)
384.160.100.9 Ns= 35.5.
Therefore, the estimated sample size is approximately 36.This number was expanded to about 50 patients, to take care of patients whose results may be inconclusive, or patients who for one reason or the other may not be able to complete the test.
The student t-test was used for statistical analysis and Pearson correlation coefficient for test of correlation. All analysis was performed using SPSS for windows™ statistical software.
CHAPTER SIX RESULTS.
A total of 51 patients with LUTS due to BPE met the criteria for inclusion into the study. Equal number of controls, matched for age was selected from normal male volunteers.
Figure 1.
The age distribution of the patients is shown in Fig. 1. The highest incidence of BPH was seen in the eighth decade of life, accounting for 44.2% (23) of all patients. This was followed by the seventh decade,
accounting for 29.4% (15) of patients. The mean age of the patients was 67.2
0 5 10 15 20 25
No. of patients
20-29
30-39
40-49
50-59
60-69
70-79
80-89 Age(yrs)
Age distribution of patients
Series1
± SD 9.7years, with a range of 40 – 89years, a median of 68.0 years. No patient was seen below the age of 40years.
Most of the patients 84.6% (44), presented with symptoms, which had lasted for more than one month. No patient was seen with symptoms less than a week. Majority of the subjects 58.8% (30), had primary education, 19.6% (10) had secondary education while 21.6% (11) had tertiary
education.
Table 1. Distribution of patients according to IPSS grading..
IPSS No. Percentage (%)
Mild (0 – 8) 12 23.5
Moderate (9 – 19) 30 58.9
Severe (20 – 35) 9 17.6
Total 51 100
Table 1 shows the distribution of patients according to the level of symptom severity. Scores 0 – 8 represent mild symptoms, 9 – 19 represent moderate symptoms, and 20 – 35 represent severe symptoms. Thirty patients
(58.9%), had moderate symptoms, 23.5% (12) had mild symptoms, and 17.6% (9) had severe symptoms.
Table 2. Distribution of patients IPSS symptoms.
Symptoms No. Percentage (%)
Nocturia 51 100
Frequency 50 98.0
Straining 47 92.2
Weak Stream 43 84.3
Urgency 21 41.2
Incomplete voiding 20 39.2
Intermittency 18 35.3
The patients symptoms analysed in the International Prostate
Symptom Score are shown in table 2. The commonest symptom seen in all patients was nocturia (100%), closely followed by frequency (98.0%) and straining (92.2%). The least occurring symptoms were incomplete voiding (39.2%) and intermittency (35.3%).
Table 3. Quality of life assessment of the patients.
Assessment No Percentage (%)
Delighted (0) 0 0
Pleased (1) 0 0
Mostly satisfied (2) 2 3.9
Mixed (3) 15 29.4
Mostly unsatisfied (4) 7 13.7
Unhappy (5) 21 41.2
Terrible (6) 6 11.8
Total 51 100
Table 3 shows the degree of bothersomeness of the symptoms to patients(QOL).No patient was delighted or pleased with his symptoms, implying that some form of distress was experienced by all patients. Six patients (11.8%), felt terrible with their symptoms. Most were unhappy representing 41.2% (21) of the patients.
Table 4. Distribution of patients mean scores of IPSS.
IPSS Number(n) Mean SD
Mild 12 6.8 1.8
Moderate 30 13.5 3.0
Severe 9 23.8 4.6
Table 4 shows the mean scores of IPSS for the various levels of symptom severity for the patients. Of the patients who had mild symptoms the mean score was 6.8 SD 1.8. Those with moderate symptoms had a mean score of 13.5 3.0. While those with severe symptoms had a mean of 23.8 4.6.
Table 5.Distribution of patients mean IPSS with age.
Age(years) Mean IPSS SD
40 – 49 n=3
11.7 2.5
50 – 59 n=8
10.6 5.3
60 – 69 n=15
16.5 8.7
70 – 79 n=23
14.0 5.0
80 – 89 n=2
10.0 2.8
Table 5 shows the distribution of mean IPSS with age. The age group 60 – 69 years had the highest mean score of 16.5 SD8.7. Those in the age range of 50 – 59years had the least mean score of 10.6 5.3.
Table 6. Analyses of serum PSA results of patients.
PSA (ng/ml) No Percentage (%)
0 – 4 28.0 54.9
4 – 10 17.0 33.3
10 – 20 6 11.8
Greater than 20 - -
Total 51 100
Table 6 shows the distribution of serum PSA results of the patients studied. Fifty four percent had PSA values less than 4ng/ml. Forty - five percent had PSA values greater than 4ng/ml. Patient with PSA above 10ng/ml had trans-rectal trucut needle biopsy to exclude cancer of the prostate.
Table 7. Comparison of mean voided volume of patients and controls.
Patients Controls
Age (yrs)
Mean (ml)
Median Mode Mean
(ml)
Median Mode ‘t’
Value
Significance level P< 0.05 40-49
n=3
250.7+
171.8
152.0 152.0 280.3+ 36.1 268.0 268.0 -0.293 0.7843
50-59 n=8
282.0+125.1 257.0 257.0 197.8+ 38.5 186.0 186.0 1.820 0.0901
60-69 n=15
163.6±11.3 162.0 162.0 174.6±19.8 164.0 158.0 -1.867 0.0724
70-79 n=23
175.7±46.8 163.0 152.0 178.7±30.9 170.0 164.0 -0.257 0.7986
80-89 n=2
163.8+ 17.6 169.0 169.0 155.3+ 2.3 154.0 154.0 0.812 0.4621
n=51 193.0 ±79.2 163.0 152.0 186.9±38.7 172.0 164.0 0.617 0.5399
Table 7 shows a comparison of mean volume of urine passed by patients with LUTS due to BPE and that of the control subjects. In patients with LUTS, there was a decrease in the volume of voided urine, with a maximum of 282.0ml for patients between 50-59years. After that age there was a decline to 163.6ml in those between 60-69years. Another elevation to 175.7ml was seen in those aged 70-79years, with another decline to 163.7ml
in those aged 80-89years. This result did not show any regular pattern in the voided volume for the various age groups. A similar result was noted for the control group. Maximum mean volume of 280.3ml was noted for those between 40-49years. After which there was a decline to 174.6ml in those aged 60-69years, and another decline to 155.3ml in those aged 80-89years.
The overall difference between the mean voided volumes for the patients and control was not statistically significant (p>0.05). The
differences in the mean voided volumes were also not statistically significant within the various age groups (p>0.05).
Table 8. Comparison of mean maximum flow rate of patients and controls.
Patients Controls
Age (yrs)
Mean (ml/s)
Median Mode Mean
(ml/s)
Median Mode ‘t’
Value
Significance level P<0.05 40-49
n=3
19.9+ 4.5 22.3 22.3 23.5+2.9 24.3 24.3 -1.205 0.2946
50-59 n=8
15.8+ 4.7 16.1 16.1 21.9+ 1.7 22.4 22.0 -3.407 0.0043
60-69 n=15
10.1±4.8 8.4 6.6 19.4±2.3 20.1 20.1 -6.863 <0.0001
70-79 n=23
13.1±5.9 11.7 8.4 17.6±3.7 18.1 18.4 -3.155 0.0029
80-89 n=2
10.1+ 2.1 10.0 10.0 16.6+5.2 19.4 19.4 -0.154 0.8848
n=51 15.6±18.7 14.0 16.1 19.3±3.4 19.8 -6.725 <0.0001
Table 8 shows the comparison of mean maximum flow rates of patients with LUTS and control subjects. There was a gradual decrease in the maximum flow rate of patients with LUTS with age, from a mean value of about 19.9ml/s in patients aged between 40 – 49 years to a value of 10.1ml/s in those aged 60 – 69 years. An increase to 13.1ml/s was noted for those between 70-79years. Age for age maximum flow rates was higher in
the control group. A decrease in mean maximum flow rate was also noted for the control group, with a maximum of 23.5ml/s in those aged 40-49years and lowest value of 16.6ml/s in those aged 80-89years.
The overall difference between the mean maximum flow rates for the patient and control was statistically significant (p<0.05). The differences between the mean maximum flow rates for those between 40-49years and 80-89years was not statistically significant (p>0.05). The differences between the means for the other age groups was however statistically significant (p<0.05).
Table 9. Comparison of mean voiding time of patients and controls.
Patients Controls
Age (yrs)
Mean (sec)
Median Mode Mean
(sec)
Median Mode ‘t’
Value
Significance Level p<0.05 40-49
n=3
26.3+ 18.9 22.0 22.0 20.7+2.3 20.0 22.0 0.516 0.633
50-59 n=8
33.3+ 15.3 38.5 54.0 21.6+6.5 22.0 22.0 1.983 0.0674
60-69 n=15
46.2±18.4 52.0 52.0 25.1±5.4 28.0 30.0 4.250 0.0002
70-79 n=23
46.8±17.2 48.0 52.0 36.2±10.6 36.0 26.0 2.521 0.0154
80-89 n=2
47.3+6.4 51.0 51.0 43.7+14.0 38.0 38.0 0.412 0.7015
n=51 44.7±18.1 48.0 52.0 29.8±10.6 28.0 22.0 4.713 <0.0001
Table 9, shows the comparison between voiding time of patients with LUTS due to BPE and control subjects. The mean voiding time for patients with LUTS, showed a gradual increase from about 26.3 ±18.9secs in the 40 – 49 age group to 47.3secs in the 80 – 89 years age group. The control group also showed a gradual increase in the voiding time with age, with lowest value of 20.7±2.3secs in those aged 40-49years and maximum of
43.7±14.0secs in those aged 80-89years. Age for age,voiding time was longer in patients with BPE than in the control subjects.
The overall difference between the mean voiding time for patients and control was statistically significant (p<0.0001). The differences in the means for the various age groups was also statistically significant (p<0.05), except for those in the age groups 40-49years (p>0.05) and 80-89years (p>0.05).
Table 10. Comparison of mean flow time of patients and controls.
Patients Controls
Age (yrs)
Mean (sec)
Median Mode Mean
(sec)
Median Mode ‘t’
Value
Significance Level p<0.05 40-49
n=3
28.7+15.9 20.0 20.0 14.7+ 2.3 14.0 14.0 1.511 0.2054
50-59 n=8
34.8+12.3 37.0 44.0 17.3+ 4.4 18.0 22.0 3.795 0.002
60-69 n=15
39.1±15.1 33.0 50.0 19.3±4.1 22.0 16.0 4.921 <0.001
70-79 n=23
40.9±16.5 44.0 44.0 28.4±11.6 24.0 32.0 2.976 0.0047
80-89 n=2
40.0+ 2.0 41.0 41.0 22.0+
10.4
16.0 16.0 2.946 0.0421
n=51 38.0±14.2 40.0 22.0 22.7±9.8 19.0 16.0 6.16 <0.0001
Table 10, shows the comparison between the flow time of patients with LUTS due to BPE and controls. Mean values increased from about 28.7±15.9sec in those aged 40 – 49 years to about 40.9±16.5sec in those aged 70 – 79 years. There was a decline to 40.0sec in those aged 80-89years.
A similar increase was also noted in the control group, from about
14.7±2.3sec in those aged 40-49years to 28.4±11.6sec in those aged 70-79years. There was a decline to 22.0sec in those aged 80-89years.Age for age flow time was higher in patients with LUTS.
The overall difference between the mean flow time of patients and control was statistically significant (p<0.0001). The difference between the mean flow time in patients between 40-49years was however not statistically significant (p>0.05), but the differences in the mean flow time for the other age groups was statistically significant (p<0.05).
Table 11. Comparison of average flow rate of Patients and Controls.
Patients Controls
Age (yrs)
Mean (ml/s)
Median Mode Mean
(ml/s)
Median Mode ‘t’
Value
Significance Level p<0.05 40-49
n=3
8.4+1.0 8.0 8.0 19.8+6.1 15.3 15.3 -3.212 0.0325
50-59 n=8
8.7+4.2 8.6 8.6 12.3+4.3 12.6 12.6 -1.682 0.1148
60-69 n=15
5.1±2.7 4.1 8.1 9.6±2.3 8.3 8.3 -4.897 <0.0001
70-79 n=23
5.4±3.1 4.3 3.4 7.3±2.9 7.5 9.3 -2.118 0.0398
80-89 n=2
4.1+0.3 4.2 4.2 7.9+2.9 9.6 9.6 -2.290 0.0838
n=51 5.9±3.3 4.9 3.0 9.6±4.4 9.2 8.6 -5.26 <0.0001
Table 11 shows the comparison between the average flow rate of patients with LUTS due to BPE and controls. The average flow rate is a derivative of the voided volume and the flow time, in ml/sec. In patients with LUTS, mean values decreased from about 8.4±1.0ml/sec in those aged 40 – 49years to 4.1±0.3 ml/sec in those aged 80 – 89 years. Higher values
were noted for the controls. A decline was also noted from a value of 19.8±6.1ml/sec in those aged 40-49years to 7.3ml/sec in those aged 70-79years. There was an increase to 7.9ml/sec in those aged 80-89years.
The overall difference between the average flow rates of the patients and control was statistically significant (p<0.0001). The differences between the average flow rates for the various age groups was also statistically
significant (p<0.05).
Table 12. Comparison of time to maximum flow of patients and controls.
Patients Controls
Age (yrs)
Mean (sec)
Median Mode Mean
(sec)
Median Mode ‘t’
Value
Significance Level p<0.05 40-49
n=3
13.0+ 8.5 14.0 14.0 14.7+2.3 9.0 9.0 -0.326 0.7607
50-50 n=8
5.4+3.1 6.5 4.0 14.8+6.9 10.0 11.0 -3.493 0.0036
60-69 n=15
10.3±4. 9 10.0 10.0 19.3±4.1 12.0 14.0 -5.435 <0.0001
70-79 n=23
9.7±3.7 11.0 11.0 15.1±9.9 12.0 12.0 -2.474 0.0173
80-89 n=2
11.7+2.9 12.5 12.5 16.3+5.1 18.5 18.5 -1.373 0.2417
n=51 9.5±4.6 10.0 4.0 12.0±4.7 11.0 12.0 -2.505 0.0155
Table 12 shows the comparison between the time to maximum flow of urine in patients with LUTS due to BPE and controls. Mean values are
variable. Maximum mean value of 13.0± 8.5sec was observed in patients aged 40 – 49 years. Lowest value was noted for patients between 50 – 59 years, with a value of 5.4 ± 3.1sec. The control group showed a similar
pattern in the time to maximum flow with a maximum of 19.3secs in those aged 60-69years and the lowest value of 14.7sec in those aged 40-49years.
The overall difference between the mean time to maximum flow between patients and controls was statistically significant (p<0.05). Within the various age groups the differences in the mean times to maximum flow was also statistically significant (p<0.05) except for those in the age groups 40-49years and 80-89years, which showed no significant difference in the mean time to maximum flow (p>0.05).
Table 13. Correlation coefficient between IPSS of patients and their
maximum flow rate, voided volume, flow time, voiding time, average flow rate and time to maximum flow.
Hypothesized correlation = 0
Count Correlation Z-value P-value
IPSS vs T100 51 0.220 1.552 0.1207 N.S
IPSS vs TQ 51 0.128 0.889 0.3741 N.S
IPSS vs Qmax 51 -0.368 -2.675 0.0075 S
IPSS vs Qave 51 -0.203 -1.430 0.1528 N.S
IPSS vs Vcomp 51 -0.164 -1.147 0.2513 N.S
IPSS vs Tqmax 51 -0.246 1.742 0.0815 N.S
S = Significant N.S = Not significant
Table 13, shows the correlation between IPSS and maximum flow rate, voided volume, voiding time, flow time, average flow rate, and time to maximum flow of the patients, using the Pearson’s correlation coefficient.
IPSS showed a weak correlation with voiding time (r =0.220 p>0.05) and
flow time (r = 0.128 p>0.05). This correlation was statistically not
significant. IPSS showed no correlation with maximum flow rate ( r = -0.368 p<0.05), average flow rate (-0.203 p> 0.05), voided volume (r = -0.164 p>0.05) and time to maximum flow (r = 0.246 p>0.05).
CHAPTER SEVEN DISCUSSION
Low urine flow rate can be due to mechanical obstruction to urine flow or due to bladder hypo-contractility. These patho-physiological elements are all common in the elderly and may be present alone or in all possible combinations.53BPH is an age related disorder, causing significant discomfort and morbidity, and increases in prevalence with advancing age as shown by autopsy data and symptom survey.67-70
This study shows a rise in the incidence of BPH with age, with the highest incidence occurring between 70-79 years. No case was seen below the age 40years. The mean age of the patients was 67.2years 9.7years. This compares well with findings from other studies.35,54,60 Shoukry et al60 in their review of 173 patients with LUTS found that 122 had BPH, with a average age of 63.8years. Tarcan et al54 in their own review of 76 men with LUTS also showed that the average age of the patients was 65.2years (range 41-89years). Anyanwu35 in a local study of 125 patients in Nigeria with LUTS also showed that the average age of his patients was 66.7 years (range 46-87years). He attributed the rising incidence with age to increasing awareness, increase in life expectancy or a combination of both factors.
In this study, patients with BPH presented late. Over 84.6% of patients had symptoms, which had lasted for more than one month. Reasons
for this late presentation may not be easily adduced, since most studies on BPH seem to have played down on this aspect. It may be a reflection of ignorance on the part of the patient or delay in referral by the family physicians.
Previously, the indications for surgical treatment of BPH had been the presence of complications of BOO in the form of urinary retention and/or deteriorating kidney functions. More recently, these indications have included the presence of bothersome LUTS which impact severely on life style.53 This may also explain why some patients wait for too long before presenting to the hospital, since they are able to cope with these symptoms for some time. The impairment of life style (QOL) by LUTS was also observed in this study. All patients noticed some form of distress with their LUTS as none of the patients were delighted or pleased with their symptoms. This pattern was reflected in the mean scores of IPSS. Patients with mild symptoms showed a mean IPSS in the upper limit of their score range, while those with severe symptoms showed a mean IPSS in the lower limit of their score range (Table 4). This implies that most patients at the time of presentation invariably have symptom scores that fall within the moderate range score for IPSS.
In this study forty five percent of patients showed a PSA value greater than 4ng/ml, while fifty four percent had values within the normal range.
This may be attributed to the apparent non-standardization of PSA measurements in this environment or to the relative size of the prostate.
Serum PSA levels have also been shown to correlate with disease progression in BPH.71-73 Its use has also been extended to assess prostatic volume and disease progression as well as symptom progression in patients with BPH.74 When the PSA is above 10ng/ml it is important to rule out CAP, although it has been noted that 25% of patients with CAP may have serum PSA that is less than 4ng/ml.75
In this study, the total mean score of IPSS for the 51 patients was 13.7 6.5, with 58.9% having moderate symptoms. Emberton et al76 in assessing the effect of prostatectomy on symptom severity and QOL in 3237 men with LUTS, noted that the total mean pre-operative score was 20.17.8.
After prostatectomy, mean symptom scores fell to 7.45.1. This difference between the pre-operative mean scores of IPSS between the patients in this study and those of Emberton amongst Caucasians may well be due to a higher ability to tolerate their symptoms among Nigerians. It has been noted that the average Nigerian is characteristically resilient and tolerant to pain and discomfort.77
Men below the age of 60years have lower symptom scores compared to those above 60years from this study. This has been attributed to some socio-demographic factors. Studies in Caucasians have shown mean
operative symptoms scores were slightly but significantly lower in men
≤70years, men having their operation in the private sector, men who had received tertiary education and in men of a higher social class as defined by their last full time employment.76Apart from age, these socio-demographic factors are not easily assessed in this environment and were not included in this study.
In this study, irritative symptoms of nocturia (100%), frequency (98.1%), were the most common of the IPSS. These symptoms can arise from other lower urinary tract pathologies such as UTI. Age induced changes in the bladder and nervous system are known to cause urinary frequency, urgency and nocturia.18 In such patients urine flow rates are normal.32This emphasizes the importance of history and physical examination in the patient presenting with LUTS.
Uroflowmetry (simple plotting of urine flow rates with time) is a simple, accurate, reliable and non-invasive method to assess the dynamics of micturition.32For these reasons it can be incorporated easily into the routine preoperative assessment of patients with LUTS. If the flow rate is normal, the possibility of non-obstructive bladder disease such as detrusor instability or hypersensitivity should be considered and investigated by more extensive albeit invasive pressure flow studies.