British Journal of Urology (1975). 41, 559-566 0

Role of Uroflowmetry in the Assessment of Lower Urinary Tract Obstruction in Adult Males’ ISMAIL SHOUKRY, JACQUES G . SUSSET, MOSTAFA M. ELHILALI and DANIEL DUTARTRE

Department of Urology, Sherbrooke University, School of Medicine, Sherbrooke, Quebec, Canada

The indications for surgical relief of prostatic obstruction are usually based on the case history, clinical, endoscopic and radiological examinations. In many instances there is no clear indication for surgery. Symptoms may be minimised by the patient, who may not be aware of them because of the insidious onset of obstruction. The size of the prostate bears no relation to the degree of obstruction. Cysto-urethroscopy provides only a static assessment of an essentially dynamic process. Radiological examination may be helpful in advanced degrees of obstruction, but is of little help in early cases. It is the purpose of this paper to demonstrate the value of uroflowmetry as a useful clinical tool in the diagnosis and follow-up of prostatic obstruction.

Materials and Methods

173 patients presenting with symptoms of lower urinary tract obstruction were submitted to a prospective study over a period of 18 months following a protocol designed for computer analysis. Results were analysed on an IBM 360-40. The evaluation included: history and clinical examina- tion, urine analysis and culture, and intravenous urography with post-voiding film. Pre- and postoperative urine flow studies were done using a flowmeter based on the principle of air displacement’ (Picker et a/. , 1972; Susset et al., 1973). The range of normality was obtained by analysis of 300 recordings obtained from normal males using this flowmeter. A minimum of 3 preoperative flow records were obtained in each patient. Most of the curves correlated well. All traces showing an irregular pattern suggesting psychological inhibition or vesical atony were discarded from the study. Postoperative flow measurements were studied at 3 months, from 3 to 12 months and over I year. Again, several measurements were made which confirmed that they were comparable.

The normal range of flow rate was determined (Fig. l), which shows maximum, minimum and mean values. These are also expressed graphically. This normal flow curve was superimposed on the patient’s records to allow immediate comparison. The percentage deviation from the lower limit of normal was also calculated.

Four observations are believed to be of particular significance: maximum flow, mean flow, flow at 2 seconds and time to maximum flow (Susset er al., 1973). The technique used to compare these 4 observations is presented in Figure 5. These figures were also compared with the clinical, radiological and endoscopic information.

Patients were divided into 4 groups according to the aetiology of obstruction: group I, benign prostatic hypertrophy, 122 cases; group 11, prostatic cancer, 27 cases; group 111, chronic pros- tatitis, 21 cases; group IV, urethral strictures, 3 cases.

The average age for each group was respectively 63.8, 70, 59.2 and 60 years. The average duration of obstructive symptoms was respectively for each group 38.5, 23.5, 39 and 36 months. Only cases of benign prostatic hypertrophy subjected to surgery were included in the second and

1 Read at the annual convention of the Canadian Urological Association, Vancouver, 9th to 14th June 1973. 2 UF-1. Physico-Medical Systems Corp., 9250 Park Avenue, Suite M-101, Montreal, Quebec, Canada, H2N 1Z9.

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Fig. 1. Graphic recording of a normal Row curve. The maximum and minimum flow rates for this volume are shown in dotted lines. The table represents the report sent to the patient's chart for this study. The columns marked minimum and maximum are obtained from normal subiects for that volume.

560

Time (sec)

Fig.2.Graphic recording and report oia patient with a markedly obstructive curve.

Time (sec)

Fig. 3. Graphic recording and report in ;L patient wllh a questionable obstruction. Psychological inhibition or bladder atony could produce a similar curve.

Time (sec)

the third period of follow-up because of the unpredictability of cancer cases and the fact that most cases of chronic prostatitis were not subjected to operation.

Transurethral prostatectomy was done in 80 patients, a retropubic prostatectomy in 18. In cases of prostatic cancer, combined treatment of transurethral prostatic resection and oestrogen or radiotherapy were carried out in 1 1 patients. 20 patients were treated by other methods: antibiotics, urethral dilatation, etc. Finally, no treatment was decided upon in 44 patients of these series, including 34 patients with benign prostatic hypertrophy.

Results

Figure 2 represents an example of a markedly impaired micturition. Curves of the type shown in Figure 3 were rejected from the study since it is impossible to be certain if their irregularity is due to the patient's psychological inhibition or to bladder incompetence. Atonia of the bladder is demonstrated in Figure 4, where the cystometrogram confirms the abnormally large bladder capacity. This condition is more easily revealed if the intravesical pressure is recorded at the same time as the urinary flow since it demonstrates when rises in pressure are just due to straining.

Among the 173 patients, nocturia was present in 80%, weakness of stream in 82.5% and urgency in 44.5 % (Table 1).

UROFLOWMETRY IN LOWER URINARY TRACT OBSTRUCTION IN MALES

Table I Average Preoperative Uroflowmetry

56 1

Group I Group 11 Group 111 Group 1V

Volume (cc) 192 126 310 250 N N N N

Maximum flow (cc/sec) 9.9 14.7 7.7 11.0 16.0 18.8 16.0 17.0 Mean flow (cclsec) 7.0 9.5 5.0 6.5 11.0 13.1 10.0 11.5 Flow at 2 seconds (cclsec) 4.8 4.4 4.6 2.6 10.0 6.4 10.0 5.5 Time to maximum flow (sec) 9.8 9.6* 8.4 85* 8.9 lo%* 6.7 10.3*

N = Minimum of normal for same volume. * = Maximum of normal for same volume.

Table I1

Impairment of Flow Parameters in relation to Symptoms

2 seconds Time at Maximum Average flow maximum flow flow flow

% Freouencv 40

% 38

% % 82 67 . -

Urgency 35 29 80 65 Difficulty 42 34 82 74

The average value of flow parameters before operation was compared with the lower limit of normal for a given volume.

Symptoms of prostatic obstruction were commonly associated with a reduction in the maximum flow rate, and most of these patients were finally recognised as having significant obstruction (Table V). 138 patients complained of nocturia, moderate in 44 and marked in 94. The maximum flow rate was normal in 35 of these patients. It was reduced in the remainder and reduced by more than 50 % in the majority of these. This compares with the normal average flow rate in 44 patients complaining of nocturia. There is no obvious correlation between the degree of obstruc- tion and time to maximum flow or the flow rate at 2 seconds. When compared with other clinical evidence, it was found that the maximum flow rate reflects obstruction accurately, average flow is less relevant and the other values are immaterial.

The impairment of flow parameters in relation to symptoms is presented in Table 11. The 18 % to 20 % of patients in which the maximum flow was normal corresponds to the group of patients in whom obstruction could not further be demonstrated. It is therefore reasonable to assume that in the analysis of a urinary flow curve, the most important indicator of obstruction is the maximum flow.

The next group of results (Table 111) points out the possible errors of diagnosing obstruction from the symptoms. Of 35 patients who had no nocturia, 27 (77%) presented an obstructive curve. 17 out of 30 patients who had no difficulty in micturition had objective evidence of obstruction by uroflowmetry.

It is well known that the size of the prostate by rectal examination is a poor indication of the degree of obstruction. Only 69 % of 80 patients presenting moderate prostatic enlargement had reduced maximum flow and 11 % of 93 patients with a grade I1 to I11 enlargement had a normal maximum flow rate.

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Uroflometry : Vol. I 10 ml

BRITISH JOURNAL OF UROLOGY

Time (sec) C ystomeirogram

80 c

I 1 I I I I I

o 100 200 300 400 so0 mo 700

Combined uroflometry and rectal pressure recording Rectal pressure

Bladder capacity (ml)

Uroflometry : Vol. 85 ml I

Time (sec)

Fig. 4. Micturition study of a patient with severe prostatic symptoms showing a flow curve that is interrupted with a large bladdercapacity. Simultaneous measurement of rectal pressure demonstrates the use of abdominal muscles during micturition.

The relation between the degree of bladder trabeculation as shown by cystoscopic examination and the degree of maximum flow impairment is presented in Table IV. It was found that in 509” of 60 cases where no trabeculation was noted at cystoscopy, there was a reduction of 50% or more of the maximum flow indicating significant obstruction. On the other hand, 12% of the 40 patients where the degree of trabeculation was recorded as marked presented a normal maximum flow rate. Vesical diverticula were present in 21 patients, in all of whom the maximum flow rate was reduced.

The assessment of residual urine by a post-voiding cystogram is recognised to be of value only when it is absent. If residual urine is present on the post-voiding film and the maximum urinary flow is normal, either the patient had not voided properly before the film was taken, or too long an interval was allowed before the last exposure was taken. 22% of 44 patients showing a large residual urine on the post-voiding film were shown to have normal maximum flow and absence of significant prostatic obstruction.

UROFLOWMETRY IN LOWER URINARY TRACT OBSTRUCTION IN MALES

Table 111 Table IV

Obstructive Curves and lack of Obstructive Symptoms Flow

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Relation between Trabeculation and Maximum

Obstructive curve present - 0 1 70

No nocturia (35) (27) 77.0 Trabeculations No urgency (96) (75) 78.0 No difficulty (30) (17) 57.5

Absent (60) Mild (73) Marked (40)

Maximum flow

Normal maximum reduction flow rate 2 5 0 %

% % 25 50 21 62 12 60

The endoscopic evaluation of bladder outlet obstruction may be misleading. Among patients with no obvious prostatic intrusion 20 % presented with obstructive curves.

Postoperative results were both examined qualitatively and quantitatively. Figure 6 represents a case of prostatic obstruction treated by transurethral prostatectomy. The flow curve is within normal limits at 1 month and at 5 months after operation.

The average pre- and postoperative maximum and mean flows in benign prostatic hypertrophy are shown in Table V. The maximum flow improved after prostatectomy from 32% below the lower limit of normal to 9 % above this limit 3 months after the operation. It represents an average increase of 41 % for the maximum flow. In the same period of time, the average flow increased by 40 %.

No treatment was advised in 34 patients presenting benign prostatic hypertrophy. In 26 of them (76 %) the maximum flow was normal or only within 25 % of reduction in relation to the lower limit of normal. In 8 patients operation was contra-indicated by their poor general condition.

Z second How Maximum flow Time to maximum How Average flow

Nocturia n None 35 Moderate 44 - Marked 94

Fig. 5. An example of the statistical analysis done of the flow curve parameters in association with, nocturia. The columns represent the number of patients presenting with a normal (N), more than normal ( +) or less than normal ( - ) in each parameter.

564 BRlTlSH JOURNAL OF UROLOGY

20 ,/ -- 30bJ:.w 10 , , ~ , - ,

0 0 5 10 IS 20 25 30 35 40 45 50 55 M)

Time (sec)

Time (sec) Time (sec)

Fig. 6. Graphic recording of flowmetry pre- and postoperatively.

Discussion

Drake in 1948 described a uroflowmeter based on recording the weight of urine per time interval. He found that patients with lower urinary tract obstruction have reduced urine flow rates com- pared to normal subjects, and that flow rates improved markedly after operations aiming at the relief of obstruction. Von Garrelts ( 1958) submitted that patients with prostatic hyperplasia have flow curves which are different from normal.

Stewart in 1960, using Kauffman's uroflowmeter, was of the opinion that urinary flow measure- ment is of limited value in the diagnosis of lower urinary tract lesions. The inaccuracy of the latter apparatus for volumes below 200 cc may explain this attitude. Scott et al. (l967), using an electromagnetic uroflowmeter, studied flow rate before and after prostatectomy. They concluded that uroflowmetry is the most objective means for the diagnosis of lower urinary tract obstruction. 8Castro ( 1973) reported the parallel improvement of symptoms and flow rate following prostatec- tomy. The uroflowmeter based on air displacement used in this study offers the advantage of accuracy for volumes as low as 40 cc. Normal flow rates as reported by different authors vary greatly. This is to be expected since flow rate should always be related to volume.

Most urologists agree that the patient's history is not always reliable as a means of evaluating prostatic obstruction. This statistical study confirms this impression. Urethroscopy is valuable in the assessment of the size of the prostate, but its evidence is unreliable in determining treatment. Large prostatic intrusion may cause relatively few symptoms and no residual urine. On the other hand, one is frequently faced with the presence of a questionable prostatic obstruction on urethro- scopy in patients presenting marked obstructive symptoms. In such instances it is often reluctantly that a transurethral prostatectomy is decided upon. The presence of an obstructive curve should allow the urologist to be more confident in reaching this decision. Chronic inflammation may simulate obstruction. The decision for surgical intervention in these cases is not straightforward, and flow measurements may be of value.

Detrusor trabeculation may be absent in prostatic obstruction (Table V), and its degree should not be the only factor used to determine treatment. On the other hand, 12% of 40 patients pre- senting with marked trabeculation were found to have a normal maximum flow rate. It is postu- lated that the detrusor reacts to prostatic obstruction in 1 of 2 ways. The majority of patients

UROFLOWMETRY IN LOWER URINARY TRACT OBSTRUCTION IN MALES 565

Table V

Average Pre- and Postoperative Maximum and Mean Flow in Benign Prostatic Hypertrophy

Preoperative (10) 3 months (50) 3-12 months (21) > 1 year (7)

Volume (cc) 192 180 172 230 Maximum flow (cc/sec) 9.9 15.6 13.9 17.3

Mean flow (cclsec) 7.0 10.3 8.5 10.6 (N = 14.7) (N = 14.2) (N = 13.7) (N = 16.3)

(N = 9.5) (N = 9.1) (N = 8.6) (N = 10.9)

N = Lower limit of normal for same volume between parenthesis.

develop bladder hypertrophy and trabeculation. The majority will not. Hypertrophy is a com- pensatory mechanism and a normal flow rate may be maintained for many years. Frequency may become intolerable or the detrusor may decompensate resulting in urinary retention making surgery mandatory. Finally, diverticula may appear. Our 21 patients with diverticula showed obstructive flow rates which is a sign of failure of the compensatory mechanism.

Other patients, who are the minority, will not demonstrate detrusor compensatory hypertrophy. In 30 of our patients, no evidence of bladder trabeculation was shown in spite of a marked reduction in flow rate. If the obstruction is not treated it is likely that this group of patients will accumulate an increasing amount of residual urine. In the light of this hypothesis it becomes clear that some of our classical concepts of prostatic obstruction may have to be revised. Chronic retention with a smooth bladder wall apparently does not represent a later stage of prostatic obstruction with detrusor hypertrophy and trabeculation ; it is infrequent for a patient with chronic retention to have a past history of marked nocturia and urgency. Furthermore, even 10 years after a prostatectomy, trabeculation is still present and has no tendency to disappear. Initial factors which determine detrusor reaction-to early hypertrophy or to early decom- pensation-are still unknown. The rate of the development of obstruction and the volume of fluid intake may be interesting factors to analyse.

Of the 4 parameters analysed, the best correlation with the degree of prostatic obstruction is the maximum flow rate. The average flow is less reliable although it has some value. It is interesting that maximum urinary flow appears also to be the most reliable parameter in the diagnosis of female urethral stenosis (Susset et al., 1974).

It is too early to state which percentage of maximum flow rate reduction should be considered as a definite indication for prostatectomy. It was, however, found that all patients operated upon for benign hypertrophy showed a reduction of over 25 % of the maximum flow rate in relation to the lower limit of normal for a given volume.

It was noted in this series that impairment of flow occurs early. 65 % of patients presenting with only mild nocturia and 61 % with only a slight difficulty on voiding showed over 50% reduction in maximum flow rate. We found it useful to keep a file of flow curves taken on a routine basis for patients suffering a mild degree of prostatism to follow objectively their evolution. It is hoped that this test will become of prognostic value.

Conclusions

This statistical study seems to confirm that accurate uroflowmetry is a valuable tool in the assess- ment of lower urinary tract obstruction in males. In our institution, we find it helpful to use uroflowmetry on a routine basis. Maximum urinary flow rate reflects bladder outlet obstruction

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better than other parameters. Repeated flow curves provide an easy method of follow-up of lower urinary tract obstruction and an objective assessment of therapeutic procedures. Objective evidence of obstruction has facilitated decisions on the advisability of prostatectomy.

Summary

A group of 173 prostatic patients were submitted to a prospective study to determine the respective value of symptoms, uroflowmetry, endoscopic and radiological findings in the assessment of the degree of urinary obstruction.

Uroflowmetry proved to bring objective evidence of the degree of obstruction with a reasonable degree of accuracy.

Maximum urinary flow appears to be more accurate than other flow parameters in the deter- mination of lower urinary tract obstruction. Project supported by Grant No. MT-3074 of the M.R.C.

References

CASTRO, J. E. (1973). The effect of prostatectomy on the symptoms and signs of benign prostatic hypertrophy.

DRAKE, W. M. (1948). The uroflowmeter: an aid to the study of lower urinary tract. Journalof Urology, 59,650-658. PICKER, P., KRETZ, M., FORGE, J. C., JOREST, R. and SUSSET, J. G. (1972). Un debitmetre urinaire de precision.

SCOTT, F. B., CARDUS, D., QUESADA, E. M. and RILES, T. (1967). Uroflowmetry before and after prostatectomy.

STEWART, B. H. (1960). Clinical experience with the uroflometer. Journal of Urology, 84, 414-419. SUSSET, J. G., PICKER, P., KRETZ, M. and JOREST, R. (1973). Critical evaluation of uroflowmeters and analysis of

normal curves. Journal of Urology, 109, 874-878. SUSSET, J. G., SHOUKRY, I., SCHLAEDER, G . , CLOUTIER, D. and DUTARTRE, D. (1974). Stress incontinence and

urethral obstruction in women : value of uroflowmetry and voiding urethrography. Journal of Urology. Accepted for publication.

VON GARRELTS, B. (1958). Micturition in disorders of the prostate and posterior urethra. Acta Chirurgica Scandina- vica, 115, 227-241.

British Journal of Urology, 45, 428-431.

L’Union Medicale du Canada, 101, 1132-1137.

Southern Medical Journal, 60, 948-952.

The Authors

Ismail Shoukry. MD, Research Assistant. Jacques G. Susset, MD, MSc, Professor and Chairman. Mostafa M. Elhilali, MD, PhD, Associate Professor. Daniel Dutartre, MSc, Research Assistant.