Comparison of Duplex Ultrasonography and Nocturnal Penile Tumescence in Evaluation of Impotence

0022-5347 /94/1516-1525$0'.JJJO/O THE JOURNAL OF UROLOGY Copyright 1994 by AMERICAN UROLO(;JCAL ASSOClATlON, INC.

Vol. 151,

June 1994 in USA.

COMPARISON OF DUPLEX ULTRASONOGRAPHY AND NOCTURNAL PENILE TUMESCENCE IN EVALUATION OF IMPOTENCE RICHARD P. ALLEN, RAINER M. E. ENGEL, JAMES K. SMOLEV AND CHARLES B. BRENDLER From the James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institution, Baltimore, Maryland

ABSTRACT

Duplex ultrasound is used commonly to evaluate vascular function in impotent men. There is evidence, however, that some men with normal vascular function may have falsely abnormal duplex ultrasound results because of suppression of response to pharmacological stimulation due to anxiety. We performed a prospective blinded study of 40 impotent men comparing duplex ultrasound to a formal nocturnal penile tumescence evaluation. Duplex ultrasound was done with a standard 10 MHz. color Doppler unit after intracorporeal pharmacological stimulation. Nocturnal penile tumescence was performed at a sleep laboratory, and included measurements of penile circumference, axial rigidity, arterial pulsations, and direct patient and observer evaluation of erections. Of 40 men 20 had an abnormal duplex ultrasound result (maximum arterial velocity less than 30 cm. per second), including 9 who had normal nocturnal penile tumescence with at least 1 rigid erection (greater than 550 gm. axial rigidity) lasting at least 5 minutes. All 9 men had evidence of psychogenic dysfunction on history and personality inventory, and only 1 had evidence of vascular disease. Of the other 11 patients with abnormal duplex ultrasound and nocturnal penile tumescence findings, only 2 had evidence of psychogenic impotence and 9 had evidence of vascular disease. In these 11 men there were significant correlations between maximum arterial velocity on duplex ultrasound, and maximum rigidity and arterial pulsations on nocturnal penile tumescence. Of 40 patients 20 had a normal duplex ultrasound finding (maximum velocity greater than 30 cm. per second). Nine of these patients had a normal nocturnal penile tumescence test, of whom 5 had evidence of psychogenic impotence and only 1 had evidence of vascular disease. Eleven men with normal duplex ultrasound had an abnormal nocturnal penile tumescence test, including only 2 with any evidence of psychogenic impotence, while 9 had vascular disease and 1 had a history of neurological disease. Based on this study 9 of 14 men (64 %) with a normal nocturnal penile tumescence test and other evidence of psychogenic impotence had abnormal duplex ultrasound. Therefore, an abnormal duplex ultrasound study should be interpreted cautiously if there is evidence of psychogenic impotence. In men with vasculogenic impotence there is an excellent correlation and cross-validation between maximum velocity on duplex ultrasound, and axial rigidity and arterial pulsations on nocturnal penile tumescence. KEY WORDS:

ultrasonography, penile erection, impotence

Duplex ultrasonography is being used widely to evaluate penile arterial blood flow in impotent men. 1•2 Validation of duplex ultrasound has been done mainly by convergent agreement with results obtained by clinical history. 3 Limited studies comparing duplex ultrasound with penile angiography have yielded conflicting results.4· 5 To our knowledge there has been only 1 study comparing duplex ultrasound with nocturnal penile tumescence testing in the evaluation of impotence. 6 In that study 3 of 29 patients with abnormal duplex ultrasound had a normal nocturnal penile tumescence test. Although 2 of these 3 patients were believed to have the pelvic steal syndrome, another possible explanation is that patient anxiety interfered with pharmacological stimulation of the penis, resulting in a falsely abnormal duplex ultrasound study. Indeed, anxiety-related inhibition of pharmacological stimulation has been recognized previously but not formally evaluated by comparing the results of a thorough clinical history, physical examination, duplex ultrasound and nocturnal penile tumescence. We performed a prospective, blinded study of 40 unselected patients presenting to our male sexual dysfunction clinic with a chief complaint of impotence. We tested 2 hypotheses: 1) in men with psychogenic impotence, anxiety and resultant symAccepted for publication November 12, 1993.

pathetic stimulation might suppress penile response to pharmacological stimulation, and 2) in men with vasculogenic impotence there would be a significant correlation between duplex ultrasound and nocturnal penile tumescence. MATERIALS AND METHODS

A total of 40 men who presented to our male sexual dysfunction clinic with a history of persistent impotence at least 6 months in duration underwent a complete evaluation, including a psychosexual history interview, Minnesota Multiphasic Personality Inventory, physical examination, serum testosterone, duplex ultrasound and nocturnal penile tumescence. There· were no other selection criteria. Mean patient age was 60 years (range 25 to 75 years). The clinical history and examination results were recorded without knowledge of the duplex ultrasound or nocturnal penile tumescence results. Duplex ultrasound and nocturnal penile tumescence testing were performed independently by separate clinicians at different facilities on different dates and without knowledge of either duplex ultrasound or nocturnal penile tumescence results. Nocturnal penile tumescence testing. A single nocturnal penile tumescence study was conducted at a sleep disorders center. Although our practice previously was to perform these studies on 2 nights, we have found 1-night studies to be equally reliable provided that the patient achieves adequate rapid eye move-

1525

1526

COMPARISON OF DUPLEX ULTRASONOGRAPHY AND NOCTURNAL PENILE TUMESCENCE

ment sleep. We were able to achieve this condition by having patients sleep only 4 hours the night before the nocturnal penile tumescence study. If patients still have difficulty sleeping, we administer 0.125 to 0.375 mg. triazolam at the sleep laboratory. Triazolam does not alter sleep patterns and, specifically, it does not affect the duration or quality of rapid eye movement sleep. With these modifications, most patients achieve adequate duration and quality of rapid eye movement sleep during a 1-night study, making multiple night evaluations unnecessary. Obviously, this has also decreased the cost of nocturnal penile tumescence, making it affordable to more patients with a greater likelihood of reimbursement by third party carriers. All nocturnal penile tumescence recordings were interpreted by a board certified sleep disorders specialist (R. P. A.), who was unaware of the results of the previous duplex ultrasound evaluation. Nocturnal penile tumescence measurements included sleep electroencephalography, penile base and glans circumference measurements, rigidity measurements, photographs and visual ratings by trained technicians of maximum rigidity obtained at the time of rigidity measurements, and measurement of bulbocavernosus and ischiocavernosus muscle activity. The sleep electroencephalography was recorded and classified into rapid eye movement and nonrapid eye movement sleep following previously established criteria. 7 Penile circumference measurements were made using mercury-filled strain gauges placed at the penile base and glans penis. Rigidity measurements were obtained using a tonometer applied to the end of the penis at the time of maximal erection to measure axial rigidity, defined by grams of force necessary to induce penile buckling. We showed previously that axial rigidity measurements correlate closely with trained observer ratings of erections and are more accurate than measurements of radial rigidity. 8 Rigidity measurements were obtained at discrete intervals when the glans circumference showed an increase of at least 80% of the maximum increase observed. Rigidity was measured in grams of axial force at the buckling point. 9 Minimal normal rigidity was defined as 550 gm., which is marginally greater than the minimum rigidity (500 gm.) found to be adequate for vaginal penetration. 10 A photograph of the erection and subjective rating of rigidity by a trained technician were obtained at the time of the rigidity challenge to verify accuracy of the placement of the strain gauges and validity of the rigidity measurements. In this study all of the photographs showed correct gauge placement and visual ratings of rigidity correlated closely with axial rigidity measurements. Bulbocavernosus/ischiocavernosus muscle activity was measured from electromyographic electrodes placed on the perineum. Bursts of this activity were measured during all periods of rapid eye movement sleep that were associated with at least partial erections. The number of arterial pulsations observed on the strain gauges during erections were also measured and recorded as the ratio of pulsations-to-bulbocavernosus/ischiocavernosus muscle bursts ( the normal ratio or arterial pulsation density in potent men varies from 0.7 to 1.0). 11 Therefore, nocturnal penile tumescence measurements for this study were the duration of rapid eye movement sleep, maximum duration of full nocturnal penile tumescence events, maximum axial rigidity and arterial pulsation density. A nocturnal penile tumescence study was defined as normal if there was at least 1 full nocturnal penile tumescence event sustained for at least 5 minutes. A study was considered invalid if it was abnormal and either the duration of rapid eye movement sleep was less than 30 minutes or phasic activity in rapid eye movement sleep was abnormally decreased. Invalid nocturnal penile tumescence studies were repeated and a valid test was obtained on all patients entered into this study. Nocturnal penile tumescence was considered abnormal if it was a valid

study and maximum duration of full nocturnal penile tumescence events was less than 5 minutes. Duplex ultrasound evaluation. Duplex ultrasound was performed using a standard 10 MHz. pulsed Doppler unit to assess arterial flow through the penile cavernous arteries before and after injection of 1.0 ml. of a solution containing 30 mg. papaverine. Arterial diameter and blood flow velocity were measured before and after pharmacological stimulation. The post-injection measurements were obtained 5 minutes after injection before development of a maximal erection. Peak systolic arterial velocity and maximal diameter were measured in the left and right cavernous arteries. A duplex ultrasound study was considered normal if the maximal arterial velocity in either cavernous artery was greater than 30 cm. per second, which represents an intermediate value between previously reported minimum normal values of 25 1• 4 and 40 cm. per second. 2 Our acceptance of a maximal arterial velocity of greater than 30 cm. per second in either cavernous artery was arbitrary but, on reviewing the literature, most investigators do not specify whether velocities were measured in 1 or both cavernous arteries and simply report 1 value. Statistical analysis. Patients were divided into 4 groups based upon the nocturnal penile tumescence and duplex ultrasound diagnoses: group 1-both studies normal, group 2-nocturnal penile tumescence normal and duplex ultrasound abnormal, group 3-nocturnal penile tumescence abnormal and duplex ultrasound normal, and group 4-both studies abnormal. Linear regression was used to compare the nocturnal penile tumescence and duplex ultrasound results for each of these groups separately. RESULTS

All men in this study had a normal serum total testosterone level (greater than 275 ng./dl.). The results of the psychosocial history, medical evaluation, duplex ultrasound evaluation and nocturnal penile tumescence study in the 40 patients are shown in table 1. A total of 20 men had an abnormal duplex ultrasound study with a maximum penile arterial velocity of less than 30 cm. per second (groups 2 and 4). Of these 20 men 9 (group 2) had normal nocturnal penile tumescence with at least 1 rigid erection (greater than 550 gm. axial rigidity) at least 5 minutes in duration. The mean axial rigidity in these 9 men was 950 gm. and 5 had an axial rigidity of greater than 1,000 gm. In addition, all 9 men had normal penile arterial pulsation densities (greater than 0.70), and all 9 had evidence of psychogenic dysfunction on history and personality inventory (only 1 had a medical history of vascular disease). The remaining 11 men with abnormal duplex ultrasound had an abnormal nocturnal penile tumescence test (group 4). In these 11 men the mean arterial velocity was 20.9 cm. per second, which is not significantly different from that in the 9 men in group 2 (17.7 cm. per second). However, in group 4 the mean axial rigidity on nocturnal penile tumescence was 308 gm. and 4 men had an axial rigidity of less than 250 gm., which is severely abnormal. Of the 11 men 6 also had an abnormal arterial pulsation density of less than 0.7. Only 2 of these men had any history to suggest psychogenic impotence, and 10 had a history of significant medical disease (9 had a history of vascular disease and 1 had the Guillian-Barre syndrome). Interestingly, the latter patient with presumed neurogenic impotence had a borderline abnormal maximum arterial velocity on duplex ultrasound of 28.1 cm. per second, and a normal arterial pulsation density on nocturnal penile tumescence of 0.74 but an abnormal axial rigidity on nocturnal penile tumescence of only 360 gm. In the 11 men in group 4 there were highly significant correlations between maximum arterial velocity on duplex ultrasound, and maximum axial rigidity (fig. 1) and arterial pulsation density (fig. 2) on nocturnal penile tumescence. Interestingly, there was no correlation in this group or in any of the other groups of patients between the per cent

1527

COMPARISOi\T OF DUPLEX ULTRASOI'-IOC~RAPI-IY Al'-JD NOCTLRf'JAL PEi\TlLE TUIVIESCENCE TABLE

L Duplex ultrasound and nocturnal penile tumescence findings for each patient with significant medical and psychological factors from the history -------------------------------Maximum Post-Injection Arterial Velocity

Medical Factors

Psychological Factors

Maximum% Increase in Penile Diameter

Maximum Axial Rigidity (gm.)

Pulsation Density

Group I-Duplex ultrasound and nocturnal penile tumescence normal (9 pts.) None

None

Agoraphobia, depression Depression

Coronary artery disease, hypertension, cerebra! vascular disease None None

Cyclothymia

None

Anxiety

None

Adjustment reaction

None

Alcoholism

None Coronary artery disease None

30.8 31.8 42.8 32.2

1.14 0.71 0.64 1.67

700 550 750 620

1.00 1.00 0.73 1.00

32.9 31. 7 35.9 46.3 38.8

1.60 1.50 0.67 1.14 13.00

940 1,400 1,000 550 650

0.94 0.70 0.75 0.80 1.00

950 550 1,200 1,040 560 1,120 960 1,040 1,130

1.00 1.00 1.00 0.88 1.00 1.00 0.83 0.77 0.88

Group 2-Duplex ultrasound abnormal, nocturnal penile tumescence normal (9 pts.)

Depression

7.5 19.6 11.3 12.3 18.0 21.2 22.6 22.3 24.4

11.00 1.50 4.0 0.75 1.50 1.00 1.00 0.88 0.71

Group 3-Duplex ultrasound normal, nocturnal penile tumescence abnormal (I I pts.) None

Depression Anxiety Adjustment reaction

Adult onset diabetes mellitus, sleep apnea Hypertension Hypertension, sleep apnea Adult onset diabetes mellitus, hypothyroidism Peripheral vascular disease, hypothyroidism Hypertension, adult onset diabetes mellitus None Pelvic fracture Hypertension Coronary artery disease

30.4 30.7 31.8 34.9 35.4

1.00 1.14 0.17 0.60 3.33

240 540 310 110 510

0.65 1.00 0.74 0.50 0.33

36.9 37.0 54.4 32.9 42.1 52.0

1.13 0.86 1.67 0.50 1.00

200 480 560* 100 510 540

0.44 0.60 1.00 1.00 0.54 0.92

100 400 170 520 340 300 160 240 360 320 480

0.00 0.56 1.00 1.00 0.69 0.28 0.43 0.44 0.74 0.86 0.96

1.14

Group 4-Duplex ultrasound and nocturnal penile tumescence abnormal (I I pts.) None

Hypertension

Alcoholism Depression

Peripheral vascular disease Coronary artery disease, hypertension Adult onset diabetes mellitus Hypertension, adult onset diabetes mellitus Guillain-Barre disease None Cerebral vascular disease

13.5 21.0 23.1 26.9 15.4 16.4 19.0 20.5 28.1 21.0 25.7

3.00 1.00 3.33 10.00 4.50 12.00 0.71 1.50 0.88 1.29 0.71

Patients are grouped by duplex ultrasound and nocturnal penile tumescence results.

* Normal rigidity but duration of full nocturnal penile tumescence was abnormally short (less than 5 minutes).

increase in arterial penile diameter on duplex ultrasound and either maximum arterial velocity, axial rigidity or arterial pulsation density. A total of 20 patients (groups 1 and 3) had a normal duplex ultrasound study (maximum velocity greater than 30 cm. per second). Nine men (group 1) had a normal nocturnal penile tumescence test with a mean axial rigidity of 795 gm., which is not significantly different from that in group 2 (abnormal duplex ultrasound and normal nocturnal penile tumescence). Of the 9 men in group 1, 5 had a significant history of psychogenic illness, while only 1 had any history of vascular disease. The remaining 11 men with a normal duplex ultrasound had an abnormal nocturnal penile tumescence test (group 3). Of these men 10 had a history of either vascular or neurological disease, including 3 who also had coexisting psychogenic factors. One patient in this group had no history of either organic or psychological disease and he had the highest arterial velocity (54.4 cm. per second) of any patient studied, as well as a normal arterial pulsation density of 1.00. The axial rigidity in this patient was 560 gm. but he was classified as having an abnormal

nocturnal penile tumescence test because the duration of full nocturnal penile tumescence was less than 5 minutes. We suspect that this patient might have had improved nocturnal penile tumescence at evaluation on another night but he was classified as having an abnormal result with the aforementioned criteria. DISCUSSION

Our results confirm both of our hypotheses. It appears clear that in men with a history of psychogenic illness duplex ultrasound is unreliable. Of 14 men with a history of psychogenic illness and a normal nocturnal penile tumescence test 9 (64 %) had abnormal duplex ultrasound findings (mean maximum arterial velocity 17.4 cm. per second and none had an arterial velocity greater than 24.4 cm. per second). However, the mean axial rigidity in this group was 950 gm., including 5 patients with an axial rigidity of greater than 1,000 gm. In addition, all 11 men had a normal arterial pulsation density. It is presumed that anxiety and increased sympathetic stimulation result in a

1528

COMPARISON OF DUPLEX ULTRASONOGRAPHY AND NOCTURNAL PENILE TUMESCENCE

30

•

28 26

•

24 22 20 18 16 14

•

10+-~...-~...-~..---.---.-~..-~...-~..-~..-..--, 50 100 150 200 250 300 350 400 450 500 550 Maximum penile axial rigidity (grams) FIG. 1. Correlation between maximum arterial velocity and maximum penile axial rigidity in men with abnormal duplex ultrasound and nocturnal penile tumescence.

30 CJ

28 0Q)

26

~

24

~

.?:·o 0

22

Qi

20

"iii -~

18

>

<(

E ~ E

·xco

:!?

16 14 12 10 - .2

0

.2

.6 .8 .4 Penile Pulsation Density

1 .2

FIG. 2. Relationship between maximum arterial velocity and penile arterial pulsation density in men with abnormal duplex ultrasound and nocturnal penile tumescence.

falsely abnormal response to pharmacological stimulation and subsequent duplex ultrasound measurements. This observation that men with psychogenic impotence have a falsely abnormal response to pharmacological stimulation has been suggested previously. Mellinger and Vaughan reported that penile arterial velocity and acceleration following pharmacological stimulation were significantly higher in 8 potent men than in 5 other men with psychogenic impotence. 12 They concluded that this difference raises doubt about the appropriateness of using psychogenically impotent men as controls. Montague et al reported a study of 50 impotent men comparing infusion pharmaco-cavernosometry and nocturnal penile tumescence. 13 When traditional normal values were used for infusion pharmaco-cavernosometry parameters poor correlation with nocturnal penile tumescence status was observed. They concluded that when vasoactive drugs are injected intracavernously for diagnostic purposes, anxiety and/ or the absence of sexual stimulation following the injection may prevent complete cavernous smooth muscle relaxation and result in falsely abnormal values. Lowe et al reported similar findings in 20 potent and 38 impotent men studied with infusion cavernosometry. 14 There was considerable overlap in resistance values and infusion rates

in the potent and impotent groups, and they concluded that this overlap might be due to psychologically caused vasospasm leading to less complete sinusoidal relaxation and activation of the veno-occlusive mechanism. In the only other study comparing duplex ultrasound and nocturnal penile tumescence reported to date, Shabsigh et al studied 50 men with both tests performed in a sleep laboratory setting. 6 In this study there was fairly good agreement between duplex ultrasound and nocturnal penile tumescence. Of 32 men with abnormal duplex ultrasound findings 29 had an abnormal nocturnal penile tumescence test. Of the 3 patients with divergent results on both tests 2 were believed to have the pelvic steal syndrome. Unfortunately, it is difficult to compare the results of that study with our own, since the results of duplex ultrasound and nocturnal penile tumescence were reported simply as normal or abnormal without stating the criteria upon which the diagnoses were established. These investigators did not state whether the criteria for a normal duplex ultrasound were based on maximal arterial velocity and/or increase in penile arterial diameter, and they did not state whether the criteria for an abnormal nocturnal penile tumescence were based on penile circumference and/or rigidity measurements. Our study might be criticized because we used papaverine alone at a dose of 30 mg. for pharmacological stimulation before duplex ultrasound. It might be argued, and we would agree, that improved vascular dilatation and sinusoidal relaxation would have been achieved either with higher doses of papaverine or with a different agent, such as prostaglandin El. When we began this study, however, we adopted the protocol described by Lue et al for pharmacological stimulation, in which papaverine was used alone at a dose of 60 mg. 1 We decreased the dose to 30 mg. because we believed that this would provide adequate stimulation in most men and lessen the risk of priapism. Since we initiated our study, there has been a trend towards using prostaglandin El either alone or in combination with other agents for pharmacological vascular testing but uncertainties still exist over the optimal combination of drugs and doses to be used. 15 Although a better response might have been obtained in some patients with a different pharmacological regimen, this would not have altered our conclusion that anxiety and resultant sympathetic stimulation may interfere with pharmacological stimulation and, therefore, that functional evaluation of the penile arteries with duplex ultrasound cannot be used to distinguish psychogenic from organic impotence. Thus, an abnormal duplex ultrasound study should be interpreted cautiously if the possibility of psychogenic impotence exists and has not been ruled out by nocturnal penile tumescence testing. Our second hypothesis also appears to have been substantiated by our data. In men with abnormal duplex ultrasound and nocturnal penile tumescence tests there is a strong statistical correlation between maximal arterial velocity on duplex ultrasound, and axial rigidity and arterial pulsation density on nocturnal penile tumescence. Of the 11 men in whom both studies were abnormal only 2 had any evidence of psychogenic illness and 1 of these also had a history of vascular disease. Overall, 9 of the 11 men in this group had a significant history of vascular disease and 1 had a history of neurological disease, with resultant minimally decreased arterial velocity on duplex ultrasound (28.1 cm. per second) but a markedly decreased axial rigidity (360 gm.) on nocturnal penile tumescence. To our knowledge, this correlation between duplex ultrasound and nocturnal penile tumescence in men with organic impotence has not been reported previously and represents an encouraging cross validation of the 2 diagnostic tests. Therefore, the combination of an abnormal duplex ultrasound and nocturnal penile tumescence test is conclusive evidence of organic impotence. Two other observations can be made from this study. 1) The change in cavernous arterial diameter on duplex ultrasound did not correlate with maximum arterial velocity, axial rigidity or

CO!'v1PARISON OF DUPLEX ULTRASONOGRAPHY AND NOCTURNAL PENILE TUMESCENCE

Diagnoses based on the combined outcome of duplex ultrasound and nocturnal penile tumescence

TABLE 2.

Nocturnal Penile Tumescence

Duplex Ultrasound

Abnormal

Normal Normal

Psychogenic

Abnormal

Psychogenic

Mild~moderate vasculogenic or neurogenic Severe vasculogenic

1529

rigidity and arterial pulsation density on nocturnal penile tumescence. The combination of duplex ultrasound and nocturnal penile tumescence provides useful diagnostic information with conclusions as outlined in table 2. A nocturnal penile tumescence study should be obtained whenever treatment recommendations are to be based on etiology and before any invasive vascular testing. REFERENCES 1. Lue, T. F., Mueller, S. C., Jow, Y. R. and Hwang, T. I.: Functional

arterial pulsation density in any of the patients studied. Although Lue et al reported that an increase in arterial diameter of greater than 75% signifies normal arterial capacity,1 others have found that the change in arterial diameter is not a reliable indicator of arterial function. 2 We would agree with the latter view and conclude from our data that change in arterial diameter may not be worth measuring. 2) In our study there was no correlation between maximum arterial velocity on duplex ultrasound and either axial rigidity or pulsation density on nocturnal penile tumescence testing in men with a normal duplex ultrasound and an abnormal nocturnal penile tumescence test. All but 1 of these men had a history of organic disease but presumably had sufficient arterial capacity to respond to pharmacological stimulation despite having inadequate axial rigidity on nocturnal penile tumescence testing. We did not measure axial rigidity during the duplex ultrasound evaluations, and it is possible that some men with normal arterial velocity on duplex ultrasound might have decreased rigidity, which would correlate with the abnormal rigidity observed on nocturnal penile tumescence. Further evaluation is in progress to test this hypothesis. In summary, we believe that nocturnal penile tumescence remains the only validated diagnostic method capable of distinguishing psychological and organic impotence. Therefore, we believe that a nocturnal penile tumescence study should be obtained in all patients in whom treatment recommendations will be based on diagnosis. This does not mean that a nocturnal penile tumescence study must be obtained in all impotent patients, since many men obviously can be treated without an accurate diagnosis, particularly with the variety of noninvasive therapies available to date. However, since anxiety and resultant sympathetic stimulation may interfere with response to intracorporeal injection of vasoactive agents and invalidate a subsequent vascular diagnostic procedure, we believe that a nocturnal penile tumescence study should be obtained before any invasive vascular testing.

2. 3. 4.

5. 6.

7.

8.

9. 10.

11.

12. 13.

CONCLUSIONS

14.

Duplex ultrasound cannot be relied upon to distinguish psychogenic from organic impotence. In men with organic impotence there is a highly significant correlation and cross validation between maximum velocity on duplex ultrasound, and axial

15.

evaluation of penile arteries with duplex ultrasound in vasodilator-induced erection. Urol. Clin. N. Amer., 16: 799, 1989. Benson, C. B. and Vickers, M. A.: Sexual impotence caused by vascular disease: diagnosis with duplex sonography. AJR, 153: 1149, 1989. Mellinger, B. C., Fried, J. J. and Vaughan, E. D., Jr.: Papaverineinduced penile blood flow acceleration in impotent men measured by duplex scanning. J. Urol., 144: 897, 1990. Quam, J. P., King, B. F., James, E. M., Lewis, R. W., Brakke, D. M., Ilstrup, D. M., Parulkar, B. G. and Hattery, R. R.: Duplex and color Doppler sonographic evaluation of vasculogenic impotence. AJR, 153: 1141, 1989. Rajfer, J., Canan, V., Dorey, F. J. and Mehringer, C. M.: Correlation between penile angiography and duplex scanning of cavernous arteries in impotent men. J. Urol., 143: 1128, 1990. Shabsigh, R., Fishman, I. J., Shotland, Y., Karacan, I. and Dunn, J. K.: Comparison of penile duplex ultrasonography with nocturnal penile tumescence monitoring for the evaluation of erectile impotence. J. Urol., 143: 924, 1990. Rechtschaffen, A. and Kales, A.: A manual of standardized terminology, techniques and scoring system for sleep stages of human subjects. Los Angeles: UCLA Brain Information Service/Brain Research Institute, 1968. Allen, R. P., Smolev, J. K., Engel, R. M. and Brendler, C. B.: Comparison of Rigiscan and formal nocturnal penile tumescence testing in the evaluation of erectile rigidity. J. Urol., part 2, 149: 1265, 1993. Hahn, P. M. and Leder, R.: Quantification of penile 'buckling' force. Sleep, 3: 95, 1980. Karacan, I., Moore, C. and Sahamay, S.: Measurement of pressure necessary for vaginal penetration. Sleep Res., 14: 269, 1985. Allen, R. P. and Smolev, J. K.: Bulbo-ischio-cavernosa muscle activity in determining the etiology of impotence. In: Proceedings of the First World Meeting on Impotence. Edited by R. Virag and H. Virag-Lappas. Paris: Les Editiones du CERI, p. 95, 1984. Mellinger, B. C. and Vaughan, E. D., Jr.: Penile blood flow changes in the flaccid and erect state in potent young men measured by duplex scanning. J. Urol., 144: 894, 1990. Montague, D. K., Lakin, M. M., Medendorp, S. V. and Tesar, L. J.: Infusion pharmacocavernosometry and nocturnal penile tumescence findings in men with erectile dysfunction. J. Urol., 145: 768, 1991. Lowe, M.A., Schwartz, A. N. and Berger, R. E.: Controlled trial of infusion cavernosometry in impotent and potent men. J. Urol., 146: 783, 1991. Benson, G. S.: Vascular evaluation: is it useful in 1992? In: World Book of Impotence. Edited by T. F. Lue. London: Smith-Gordon and Co., pp. 85-90, 1992.