Noninvasive Assessment of Impotence

Noninvasive Diagnosis of Vascular Diseases

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Noninvasive Assessment of Impotence

Ralph G. DePalma, MD, * Fn;derick]. Schwab, MD, t Helene A. Emsellem, MD,:j: Elizabeth Massarin, BS,§ and Deane Bergsrud, PA-GII

Penile erection depends on adequate arterial inflow combined with closure of cavernosal veins. Both are mediated by an intact neural mechanism and relaxation of the smooth muscle of the corpora cavernosa. 7 It is now postulated that increased arterial inflow conditions cavernosal closure of venous outflow. During erection, intracavernous pryssure increases to levels approximating 80 to 90 mm Hg, with higher pressures generated by perineal muscular contraction. Vascular surgeons have long used noninvasive methods to assess extremity circulation. The problems encountered in assessing penile hemodynamics are similar in some ways but, as can be seen from considerations of the erectile process, unique in others. This article discusses noninvasive methods of assessing vascular and neural function associated with the erectile process. Because some of the methods involve measurements of intracavernous pressure and responses to artificial erection, we also describe certain invasive methods, including pharmacologically induced artificial erection, cavernosometry, and cavernosal artery closing pressure. Generally, testing of penile hemodynamics is applied as a sequence of diagnostic steps that were previously outlined by our group5 as well as by Dr. Vaclav Michal. 15

NONINVASIVE VASCULAR TESTS

Penile BrachiatBlood-Pressure Index The penile brachial blood pressure index (PBPI) is the ratio between systolic pressure detected by a Doppler probe that is placed distal to a penile cuff and systemic or brachial arterial pressure. The principle involved is From The George Washington University Medical Center, Washington, D.C.

*Professor and Chairman, Department of Surgery

t Assistant Professor of Radiology, Department of Radiology :j:Associate Professor of Neurology, Department of Neurology §ChiefTechnologist, Noninvasive Vascular Laboratory, and Department of Surgery tlChief Technologist, Neurophysiology, and Department of Neurology

Surgical Clinics of North America-Vol. 70, No.1, February 1990

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analagous but not precisely like the ankle-to-arm pressure indices used in lower extremities. In an average-sized penis, a cuff of at least 2.5 cm in size is used and inflated, then deflated. The reappearance of Doppler signals in dorsal artery branches just proximal to the corona of the glans is detected, and this pressure is noted. Penile brachial pressure index is expressed as a ratio between pressure in the distal branches of the dorsal arteries over systemic pressure. A ratio ofPBPI above 0.75 suggests that no major obstacle exists between the aorta and the distal measurement point. Generally, low 'PBPI, less than 0.6, is related quantitatively to major vascular obstructions in the aortoiliac bed and is associated with erectile failure. IS The PBPI is always calculated on measurements in the flaccid state and does not convey the pressure available for erection. A PBPI below 0.75 but above 0.6 does not exclude lesions involving the distal vessels, such as the proper internal pudendal and penile arteries. Just as in the lower extremities, the application of exercise while measuring PBPI before and after can be useful in demonstrating pudendal-flow restriction, which is detected when demand is placed on the lower extremities. 16 Pressure gradients across stenoses or occlusions occur only when flow through the stenosis occurs at a high enough rate to cause a drop in pressure. Thus, pressure gradients occur when the resistance offered by the stenosis is higher than peripheral resistance. Generally, the aortoiliac vessels provide blood flow to extensive pelvic collaterals as well as to the lower extremities. There are large areas of the arterial circulation with a low peripheral resistance; therefore, flow phenomena related to large vessel disease usually produce decreased distal pressure. On the other hand, the penile arteries exclusively, and the internal pudendals almost exclusively, supply the corpora cavernosa, which, in the flaccid state, offer high peripheral resistance. Many lesions of these arteries cannot be detected by PBPI because they become hemodynamically significant only at the time that demand is placed on these small vessels by the erectile process. Recording of Penile Pulse Volume Penile plethysmographic pulse volume recording is performed using an air-cuff plethysmograph with a contained transducer. 6 ,14 Penile pulsatile expansion in response to arterial flow is recorded in the flaccid state. Variables characterizing pulse waves are crest time, waveform, and presence or absence of dicrotic notches. The waveform reflects the pulsatility (that is, the contribution of all the arterial elements) of penile expansion. Pneumoplethysmographic recording offers several advantages. The cuff measures the pulsation in all the arteries as it compresses the spongy penile tissue, which tends to absorb ultrasound. In contrast to pulse volume recordings obtained in the lower extremities, however, as the cuff is progressively inflated, waveforms tend to be well maintained because the arteries are not compressed against bone. Also, reactive hyperemia may accompany cuff occlusion. The test is simple to perform but should be standardized for each cuff and laboratory using plethysmography; details of performing penile pulse volume recording have been previouslydescribed6 ,14 and will be summarized here. Pulse volume recording more sensitively separates impotent

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from potent patients in whom borderline PBPIs range from 0.6 to 0.75. 19 We also believe that it may detect small vessel disease when PBPI is normal as measured in the flaccid state. Our vascular laboratory uses the following procedures. The examination is carried out with the patient covered and resting quietly in a supine position in a warm room. For sanitary purposes, the penis is first wrapped with polyethylene material and the plethysmographic cuff (Buffington) is applied. The apparatus is atta~hed to a pressure transducer contained within the cuff itself, including an attached anaeroid manometer and 'a lO-ml syringe for cuff inflation. The cuff is positioned snugly at the base of the penis and inflated to approximate mean arterial pressure. We now believe that we are detecting flow in distal branches of the dorsal arteries and not in the deep caverilOsal arteries. The systolic pressure in the branches of the dorsal artery can be determined with a 5- to lO-MHz ultrasonic Doppler probe to locate the loudest signal just proximal to the corona of the glans. The same cuff is inflated and deflated, and the manometer is observed for the pressure at which Doppler signals disappear and reappear. Penile systolic pressures obtained from Doppler signal!! just proximal to the glans ate used to calculate pressure ratios between penile arterial systolic blood pressure and brachial systolic blood pressure, or PBPL Then, using the cuff inflated to the arm .diastolic pressure plus oIl.e third of systemic pulse pressure, plethysmographic recording is made of penile pulse volume. Waveforms are recorded on a polygraph with a chart speed of 25 mm per second and a sensitivity setting of 1. The duration of systolic upstroke, including time to reach peak crests, along with characteristics in amplitude of the pulse waveforms are measured. In the abse.nce of significant arterial disease, penile waveforms are quite similar to those of normal lower extremities. A characteristic pattern exhibits a rapid upstroke with a waveform resembling the normal pulse-pressure wave, often with a dicrotic notch. The l~tter feature may be absent in some normals. The upstroke is usually completed by 0.2 seconds (5 mm), and normal waveforIIi amplitude will vary from 5 mm to 30 mrri in height. Plethysmographic recording reflects volume changes in the member and does not detect flow in individual vessels. Waveforms are affected by ventricular stroke vohime, blood pressure, vasomotor tone, muscularity or tissue turgor, and finally cuff position. It is important that the cuffbe applied consistently at the base of the penis. ·The slope of the first portion of the curve appears to be the most important waveform characteristic. Waveform changes suggesting inflow restrictions are increased time to maximum amplitude, with rounding and delay of the crest of the curve and abnormal amplitudes or marked flattening. At times, unusual pulse-wave recordings and pressure indices are noted. With deep respiration, superimposed waveforms due to venous transmission occur. Some patients with heart failure or cardiac arrhythmias exhibit beatto-beat variations in waveform. Borderline or flattened waveform patterns occur in heavy smokers and in patients using adrenergic nasal inhalers. These often disappear when these practices are stopped. The precise clinical relevance of plethysmographic findings and pressure findings requires further study. We have noted that some impotent men show elevated PBPI by

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Table 1.

DEPALMA ET AL.

George Washington University Impotence Screening Experience (September 1983-January 1989) Total number of patients Age range Mean age Normal penile perfusion Abnormal penile perfusion

658 17-78 54.6 356 (.')4.1%) 302 (45.9%)

Doppler examination while at the same time exhibiting attenuated plethysmographic waveforms. Between September 1983 and January 1989, we examined 658 men complaining of impotence using pulse volume recording and PBPI. Table 1 shows the age range and findings of these patients. There is no difference in mean age (approximately 54.5 years) between men with normal arterial perfusion and men with abnormal arterial perfusion. Table 2 shows the distribution of abnormalities detected with PBPI and pulse volume recording among 302 patients with abnormal arterial perfusion. Impotent men with abnormal penile perfusion exhibit risk factors for arterial disease 73.5 per cent of the time as compared with 68.0 per cent of those having normal perfusion (Tables 3 and 4). The most common risk factor found in mel). with Table 2.

Noninvasive Laboratory Results

Normal penile perfusion Abnormal penile perfusion Abnormal PBPI and PVR Abnormal PBPI and normal PVR Normal PBPI and abnormal PVR

Table 3.

(54.1%) (45.9%) (42.7%) (15.6%) (41.7%)

Impotent Men with Normal Vascular Lab Studies

No vascular risk factors One or more risk factors Hypertension Diabetes Smoking One of above risk factors Two of above risk factors Three of above risk factors

Table 4.

356 302 129 49 126

114 242 131 77 129 136 87 18

(32.0%) (68.0%) (36.8%) (21.6%) (36.2%) (38.2%) (24.4%) (5.0%)

Impotent Men with Abnormal Vascular Lab Studies

No vascular risk factors One or more risk factors Hypertension Diabetes Smoking One of above risk factors Two of above risk factors Three of above risk factors

80 222 116 69 148 122 74 23

(26.5%) (73.5%) (38.4%) (22.8%) (49.0%) (40.3%) (24.5%) (7.6%)

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Table 5.

Large Vessel Disease and Penile Perfusion

Occlusive aortoiliac disease Abnormal perfusion Normal perfusion Aortoiliac aneurysmal disease Abnormal perfusion Normal perfusion

22 15 7

9 4

5

normal vascular lab studies is the combination of hypertension and diabetes; cigarette smoking is more commonly present in those with abnormal vascular lab studies. Large vessel disease and abnormal penile perfusion are also closely associated. Normal versus abnormal arterial perfusion in the presence of large vessel disease, either aneurysmal or occlusive, is summarized in Table 5. It can be seen with occlusive large vessel disease that normal perfusion can be noted in about a third of the cases. In aneurysmal disease, about half the men were found to have abnormal penile perfusion. Table 6 shows the sensitivity and specificity of noninvasive arterial screening as correlated with a "gold standard" of pudendal arteriography. The sensitivity of the combination of PBPI and pulse-volume recording in predicting an abnormal arteriogram was 85 per cent. The specificity or the per cent of true negatives was 70 per cent. These sample numbers are still small, and sensitivity and specificity depend on operator-receiver characteristics in selecting candidates for arteriography. We feel the sensitivity-that is, the per cent of true positives in predicting an abnormal arteriogram-is a fair indication of the actual sensitivity of the noninvasive arterial screening tests in our laboratory. Prior to any operative procedure to treat impotence, however, we believe it necessary to perform arteriography, cavernQso~aphy, and cavernosometry. Table 6.

Ncminvasive Arterial Screening Versus Pudendal Arteriographv ARTERIOGRAPHY

P E N I L E P E R F U

S I

o

N

ABNORMAL

/'

NORMAL

ABNORMAL (No. of Case,)

(No. of pase,)

29

3

5

7

NORMAL

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Table 7.

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Range and Time Intervals (msec) for Normal Men PUDENDAL EVOKED POTENTIALS CONTROLS (NUMBER: 41; AGE: RANGE = 21 to 55; MEAN = 32)

Lumbar point Cz/ CCT

Range

Mean

SD

Mean +3SD

10.8-15.8 35.8-43.8 23.7-31. 7

12.98 40.3 27.3

1.04 1.90 1.60

16.1 46.0 32.1

BULBOCAVERNOSAL REFLEX CONTROLS (NUMBER: 22)

BCR

28.3-37.5

30.4

1.89

36.0

Abbreviations: Cz/ = electrode position 2 cm posterior to vertex, CCT = central conduction time, BCR = bulbocavernosal reflex controls.

NEUROLOGIC TESTING It is difficult to separate neural from vascular elements that contribute to erectile failure. Subtle changes in both require measurement beyond the capability of ordinary physical examination. Bulbocavernosus reflex latency time (BCR) was originally quantified by electrical stimulation of the dorsal penile nerve with electromyographic recording using needle electrodes inserted in the bulbocavernosus muscles'! More recently, however, experience has been acquired using surface perineal electrodes, which make this measurement more comfortable and feasible. Our laboratory at George Washington University measures BCR after dorsal penile nerve stimulation using the method of Haldeman and colleagues lO and measures pudendal evoked responses over the lumbar spinal cord and somatosensory cortex. This testing offers promise in evaluating spinal or sacral nerve root disorders contributing to impotence. We have previously described the use of pudendal evoked potentials in the evaluation of impotence. 5 We and others have shown that reproducible responses can be obtained to determine normal reference latencies for pudendal, lumbar, and cortical somatosensory evoked potentials. 8 Because a proportion of impotent patients are diabetic, responses are also compared with spinal and cortical evoked responses from the posterior tibial nerves in our testing sequence. 5 Normative data from our laboratory are summarized in Table 7 in 41 normal patients for pudendal evoked potential controls and 21 patients for BCR norms. Among 290 patients evaluated with evoked potentials and BCR, 84 (28 per cent) exhibited at least one abnormality or more; 15.2 per cent of the study population had abnormalities in the tibial evoked potentials, 10.7 per cent in the pudendal evoked potentials, and 9.3 per cent in the bulbocavernosus reflex time.

ARTIFICIAL ERECTION In our clinic, both arterial and neural testing are completed prior to the first office examination. The next test in assessment of penil~ circulation

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is invasive-intracavernous injection of a vasoactive agent to cause pharmacologic erection. Artificial erection can then actually be observed in the clinical setting. The discovery of the pharmacologic agents that cause erection has added an important dimension to the investigation of erectile physiology.3.20 Papaverine and alpha blockers are the commonly used agents for intracavernous injections. The procedure has now become standardized such that we use dosages ranging initially from 15 to 60 mg of papaverine intracavernosally; alternatively, 10 f.Lg of prostaglandin EI is now used by some clinicians. Intracavernous injection of pharmacologic agents and the noninvasive studies can be used to classify vasculogenic impotence and help separate arteriogenic from venogenic impotence. A normal response after intracavernous papaverine injection is an erection that occurs within 20 minutes and lasts for approximately 2 to 3 hours. With venous incomp((tence, a transient erection or tumescence may occur but is rapidly lost. With arterial insuffi'ciency, there may be only minimal delayed tumescence. Warnings have now been established about the risk of prolonged painful erection after injection of papaverine. We believe it important to begin with smaller doses of papaverine, 15 to 30 mg, and to observe the patient in the clinic until the erection subsides. Initial dosage selection for artificial erection can be based on the results of noninvasive testing and clinical findings. With flat plethysmographic recordings and low PBPI with frank aortoiliac occlusion, for example, an initially higher dose of papaverine (60 mg) can be used. If prolonged erections develop after papaverine injection, aspiration of blood from the cavernosal bodies and intracavernous injection of dilute metaraminol successfully reverses the episode of prolonged erection. Failure to achieve erection after an adequate intracavernous dose of papaverine in the presence of normal arterial flow suggests the possibility of venous leakage. Men with normal neural-arterial noninvasive testing who do not achieve erection after papaverine injection then become candidates for cavernosometry and cavernosography. At this time, it is also possible to further gauge arterial inflow by measurement of cavernosal artery occlusion pressure. CAVERNOSOMETRY AND CAVERNOSAL ARTERY OCCLUSION ,PRESSURE

These tests measure intracavernosal pressure by insertion offine needles into the cavernous bodies. Various techniques of cavernosometry to assess venous competence have been described. 2,17,22 Loss of cavernosal artery Doppler signals during artificial erection stimulated by roller-pump infusion can also be detected by a Doppler probe that is placed at the base of the penis and 'directed respectively toward each crura. The values obtained indicate the pressure available through each of the deep cavernosal arteries for erection. Cavernosal artery occlusion pressure (CAOP) is the intracavernous pressure measured at the moment during erection that the deep cavernosal artery flow disappears. Determination of penile arterial insufficiency can be obtained relatively noninvasively during the performance of cavernosometry using CAOP meas-

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urements. Both tests can be performed with minimal patient discomfort either in an office setting or in a radiology suite, but we perform this testing in a radiology suite, which permits simultaneous cavernosography. Although impotence due to inadequate arterial supply is common, closure of the venous outflow system is needed to achieve and maintain erection. The mechanisms of erection are complex and have been considered in detail elsewhere. 4 In brief, the two functions, arterial and venous, are related. Erection is initiated by smooth muscle relaxation of the sinusoidal tissue, which decreases peripheral vascular resistance within the penis to increase arterial flow. The dilatation of the sinusoidal spaces occludes emissary veins that pass through the tunica albuginea, dramatically reducing venous outflow. During maximal erection, sinusoidal pressure at some point equilibrates with arterial inflow pressure. This defines CAOP. If arterial perfusion pressure is reduced by vascular disease or traumatic proximal occlusion, satisfactory penile rigidity cannot occur. Cavernosal pressure also cannot rise if venous leakage is excessive. Such leakage can be due to either congenital spongious leaks or, more commonly, to acquired leaks through the tunica albuginea. Quantitative determination of cavernosal venous sinusoidal leakage is a sensitive procedure. Cavernosometry was originally performed using a roller pump without pharmacologic enhancement. Most centers, however, including ours, now also use intracavernous injection of papaverine or phentolamine. Papaverine induces sinusoidal dilatation and occlusion of competent emissary veins. Erection is produced in the absence of any erotic influences. Cavernosometric data obtained following papaverine injection are now felt to be more physiologic than those obtained using other methods. 13 The technique at George Washington University has been modified from those used by Bookstein2 and Goldstein. 9 Constant cavernosal pressure monitoring and an infusion pump are used. We initially used a modified cardiac bypass pump but now use a standard Medrad angiographic injector. Life Tech, Inc. (Houston, TX) also manufactures a pump specifically designed for cavernosometry. For cavernosography, radiographic imaging with rapid l00-mm filming or cine capability is best performed at the time of cavernosometry. To perform cavernosometry, after preparation of the penile skin, 21-gauge butterfly needles are placed into each corpora cavernosa for infusion of pharmacologic agents, saline, and pressure monitoring. Sixty milligrams of papaverine and 1 mg of phentolamine are diluted to a total volume of 5 cc and injected into the corpora cavernosa. A Penrose drain is looped about the base of the penis for 2 to 3 minutes to limit systemic circulation of the vasodilators. After 15 minutes, heparinized saline is infused at a rate of 20 ml per minute and gradually increased until the patient achieves a rigid erection; cavernosal pressure usually then exceeds 100 mm Hg. The infusion rate is then lowered to achieve a steady-state cavernosal pressure of 100 mm Hg. The flow rate to induce erection (FIE) and the flow rate to maintain erection (FME) are recorded. The infusion rate is then increased to produce a suprasystolic cavernosal pressure of 150 mm Hg and the infusion is stopped. The rate of fall of cavernosal pressure over the succeeding 30 seconds is recorded. For cavernosography, diluted nonionic contrast medium is injected and

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spot filming in various obliquities performed to identifY specific abnormally opacified veins. Following these procedures to investigate the venous system, CAOP is measured. The Doppler probe is placed at the base of the penis and each cavernosal artery pulse signal is identified. Saline is injected until full erection occurs and the cavernosal artery signal is lost. The infusion is stopped and, as the penis detumesces, CAOP is recorded at the pressure at which the Doppler signal returns. Simultaneous brachial pressure is measured and a ratio obtained. These studies yield two sets of data: the rate of saline infusion necessary to maintain a steady-state cavernosal pressure of 100 mm Hg (FME) and the rate of cavernous pressure fall from a suprasystolic erection. An FME of less than 12 ml per minute has been proposed as normal by Bookstein. 2 A flow rate greater than 45 ml per minute exceeds the ability of normal arterial system to compensate for increased venous leakage. Intermediate results are of uncertain clinical significance. Goldstein 9 demonstrated that a rate of pressure fall of greater than 1 mm Hg per second strongly suggests cavernosal leakage. We have examined 52 patients undergoing cavernosometry; 36 patients exhibited flow rates exceeding normal criteria with multiple draining penile veins identified during cavernosography. Normal cavernosal artery occlusion pressures should be equal to or greater than 80 to 90 mm Hg, the cavernosal pressure necessary to produce erection sufficient for intromission. Although a CAOPlbrachial-pressure gradient greater than 20 mm Hg also strongly suggests arterial insufficiency, it is not clear whether certain patients have arteriogenic impotence even if the CAOP is greater than 90 mm Hg. The CAOP represents a physiologic index of penile arterial supply. As noted previously, penile blood pressure obtained in the flaccid state may not correlate with the functional potential needed for erection. The Doppler signal is usually obtained from the dorsal penile arteries, which usually do not contribute to erectile function. As mentioned previously, decreased PBPI is more of an indicator of gross aortoiliac occlusion. We have compared the CAOP and PBPI. We identified five patients with normal PBPIs but with abnormal CAOPs. One patient had a CAOP of 110 but exhibited a cavernosal brachial gradient of 30 mm (Fig. 1). All five patients underwent selective pudendalarteriography, and all demonstrated significant atherosclerotic disease of the penile inflow vessels. Figures 1 through 3 illustrate these cases. In each case, the cavernosal artery occlusion pressure and brachial pressure are indicated along with the angiographic abnormality. ULTRASONOGRAPHY

Lue and associates 12 described the usefulness of high-resolution ultrasonography in the evaluation ofvasculogenic impotence. Using duplex scans, it is possible to visualize both dorsal and deep cavernosal arteries at various times before and after intracavernous injection of agents producing artificial erection. A knowledge of the diameter and flow velocity detected by the

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Figure 1. Arteriogram of a 72-year-old man with arteriogenic impotence. Note highgrade stenosis of internal iliac origin at arrow. Left cavernosal artery occlusion pressure is 110 mm Hg; systemic pressure is 140 mm Hg. Note gradient of 30 mm Hg.

Doppler ultrasound signal provides an estimate of total flow and is a useful indicator of arterial insufficiency. The failure to dilate in response to intracavernous injection of a pharmacologic agent may indicate lack of smoothmuscle responsiveness and either small or large vessel occlusion. Application of this test in the vascular laboratory requires the physician's presence for injection of the pharmacologic agent. More quantitative data are needed in the application of ultrasound to relate the findings to the timing of the changes occurring during the erectile process and to anatomic variations in the penile and cavernous arteries. We have had only limited experience with duplex scanning but have found it quite useful in visualizing arterial flow in the presence ofPeyronie's plaques. Interestingly, using our noninvasive methods, the prevalence of abnormal arterial perfusion is quite similar to that cited by Lue and associates l 2..-that is, about 50 per cent with ultrasonography versus 46 per cent in our series (see Table 2).

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Figure 2. Arteriogram of a 61-year-old man. Note stenosis of penile arteries at arrow. Left cavernosal artery occlusion pressure Ijs 75 mm Hg; systemic pressure is 145 mm Hg.

NOCTURNf\L PENILE

TUMESCE~CE

TESTING

Our sequence has not used nocturnal penile tumescence (NPT) testing routinely. The reader is referred to an excellent recent summary of NPT testing. 21 When this test is performed, testing is done in a formal sleeplaboratory setting. Measurement of penile rigidity is carried out by a trained observer during maximum increase in penile circumference. In a normal, fully rigid penis, resistance to a "rigidometer" device used in our laboratory exceeds the value suggested by Karacan and coworkers,11 which is 500 gm as a cutoff between a functional and nonfunctional erection. This cutoff value relates to minimum rigidity needed for vaginal penetration. Nocturnal penile tumescence is a useful test in that if an adequate erection is observed and measured during sleep, an organic pattern of impotence can be ruled out. Recent data suggest, however, that during depression, grossly abnormal erection patterns occur during sleep. In the pres-

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Figure 3. Arteriogram of a 47-year-old man. Note internal pudendal artery occlusion at arrow. Left cavernosal artery occlusion pressure is 75 mm Hg; systemic pressure is 143 mm Hg.

ence of clinical depression we feel that NPT can be misleading, for normal nocturnal erections can be absent. Ideally, nocturnal monitoring should be conducted for two to three nights in a subject who has received no alcohol or drugs. Variations of this test that measure nocturnal changes in penile circumference (for example, postage-stamp test, in which the patient awakens in the morning to find a broken roll of postage stamps or the use of snap gauges) are crude equivalents. Changes in penile circumference without erection or even motion at night can yield misleading results. Portable home NPT systems have limitations in interpretation and depend on patient compliance. We believe that NPT conducted under controlled circumstances in a sleep laboratory is a valuable tool but does not substitute for other investigations, such as measurement of blood flow or neurologic testing. When a definite positive result is obtained, it is an excellent test; documentation of penile rigidity sufficient for vaginal penetration virtually rules out organic impotence. Because NPT requires monitoring by experienced personnel, two to three nights of observation are therefore expensive.

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SUMMARY The examinations described provide quantitative data on hemodynamics of the erectile process. Comprehensive study cannot be totally noninvasive because it does require measurements of intracavemous pressure. Patients selected for invasive study should exhibit normal neurologic function. These tests generally do not display anatomy underlying the physiologic disorder, although ultrasound has great promise in this regard. Angiography is needed for rational planning of operative procedures. Angiographic examination that includes arteriography of large and small arteries and delineation of cavernosal venous drainage or cavemosography defines both the location and the nature of defects causing erectile failure. It is our belief that both noninvasive and invasive tests (physiologic meflsurements to assess penile blood flow and cavemosal competence and comprehensive angiography using artificial erection) must be obtained prior to operation.

REFERENCES 1. Blaivas JG, O'Donnell Jr, TR, Gottleib P, et al: Measurement of bulbocavernosus reflex latency time as part of a comprehensive evaluation of impotence. In Zorgniotti AW, Rossi AG (eds): Vasculogenic Impotence. Springfield, IL, Charles C Thomas, 1980, p 49 2. Bookstein Fellmeth B, Moreland S, et al: Pharmacoangiographic assessment of the corpora cavernosa. Cardiovasc Intervent Radiol 11:218, 1988 3. Brindley GS: Cavernosal alpha-blockade: A new technique for investigating and treating erectile impotence. Br J Psychiatry 143:332, 1983 4. DePalma RG: Anatomy and physiology of male sexual function. In Giordano JM, Trout HH III, DePalma RG (eds): The Basic Science of Vascular Surgery. Mt Kisco, NY, Futura Publishing, 1988, p 669 5. DePalma RG, Emsellem HA, Edwards CM, et al: A screening sequence for vasculogenic impotence.-J Vasc Surg 5:228, 1987 6. DePalma RG, Kedia K, Persky L: Surgical options in the correction of vasculogenic impotence. J Vasc Surg 14:92, 1980 7. DeTejada IS, Goldstein I, Azadzoi K, et al: Impaired neurogenic and endothelium-mediated relaxation of penile smooth muscle from diabetic men with impotence. N Engl J Med 320:1025, 1989 8. Emsellem HA, Bergsrud DW, DePalma RG, et al: Pudendal evoked potentials in the evaluation of impotence [abstract]. J Clin Neurophysiol 359:5, 1988 9. Goldstein I: Overview of types of results uf vascular surgical procedures for impotence. Cardiovasc Intervent Radiol 11:240, 1988 10. Haldeman S, Barkley WE, Bhatia NN, et al: Pudendal evoked responses. Arch Neurol 39:280, 1982 11. Karacan F, Moore C, Sabramay S: Measurement of pressure necessary for vaginal penetration. Sleep Res 14:209, 1985 12. Lue TF, Hricak H, Marick KW: Evaluation of vasculogenic impotence with high resolution ultrasonography. Radiology 155:777, 1985 13. Lue TF, Hricak 11, Schmidt R, et al: Functional evaluation of penile veins by cavernosography in papaverine-induced erection. J Urol 135:476, 1986 14. Merchant RF Jr, DePalma RG: The effects of femoro-femoral grafts on postoperative sexual functions: Correlation with penile pulse volume recordings. Surgery 90:962, 1981 15. Michal V: Arteriogenic impotence. Angio Archiv 8:4, 1985 16. Puech-Leao P, Albers MTA, Puech-Leao L: Post-exercise penile blood pressure in the diagnosis of vasculogenic impotence. J Vasc Surg 17:276, 1983 17. Puyau FA, Lewis RW: Corpus cavernosography: Pressure flow and radiography. Invest RadioI18:517, 1983

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18. Queral LA, Whitehouse WM, Flinn WR, et al: Pelvic hemodynamics after aortoiliac reconstruction. Surgery 26:799, 1979 19. Stauffer D, DePalma RG: A comparison of penile-brachial index (PBI) and penile pulse volume recordings (PVR) for diagnosis of vasculogenic impotence. Bruit 7:29, 1983 20. Virag R, Virag H: L'epreuve a la papaverine intracaverneuse dans l'etude de !'impuissance. J Mal Vasc 8:293, 1983 21. Ware JC: Monitoring erections during sleep. In Kryger MH, Roth T, Dement WC (eds): Principles and Practice of Sleep Medicine. Philadelphia, W. B. Saunders, 1989, pp 689-695 22. Wespes C, Delcour C, Struyven J, et al: Pharmacocavernometry-cavernography in impotence. Br J Urol 58:429, 1986 Address reprint requests to: Ralph G. De Palma, MD Department of Surgery George Washington University Medical Center 2150 Pennsylvania Avenue, N. W. Washington, D.C. 20037