Determination of intrapenial blood volume using 99mTc-labeled autologous red blood cells

Courses of Arginine-Vasopressin in the Systemic and Cavernous Blood through Different Stages of Sexual Arousal in Healthy Males and Patients with Erectile Dysfunction

To investigate the role of the peptide arginine-vasopressin (AVP) in controlling the function of penile erectile tissue, we determined the course of AVP through different stages of sexual arousal in both the systemic and cavernous blood of healthy males and patients presenting with ED. Twenty-five healthy males and 45 patients with ED were exposed to erotic stimulation to induce sexual arousal. Blood was withdrawn from the corpus cavernosum and a cubital vein during penile flaccidity, tumescence, rigid erection (attained only by the healthy individuals), and detumescence. AVP (ng/l plasma) was determined by means of a radioimmunoassay. Effects of AVP (0.1 to 100 nM) on isolated human CC were examined using a tissue bath system. AVP elicited contraction of isolated CC. In the healthy subjects, a decline in AVP levels (5.4 to 3 ng/l) was seen in the systemic blood when the flaccid penis became rigid. In the cavernous blood, no alterations were registered. In the group of ED patients, AVP in the systemic circulation did not display a transient decline. The drop in systemic AVP in healthy males during sexual stimulation might be a prerequisite to enable penile erection.

Course of transforming growth factor ß1 in the systemic and cavernous blood of healthy males through different penile conditions

Studies on erectile dysfunction (ED) have revealed a relationship between smooth muscle atrophy and the accumulation of collagen in the corpus cavernosum (CC). Transforming growth factor ß1 (TGF ß1) is a cytokine which has been proposed to be involved in the fibrotic process in the CC. We aimed to evaluate the course of TGF ß1 in the systemic and cavernous blood of 17 healthy males through different phases of the sexual arousal response (exemplified by the penile conditions flaccidity, tumescence, rigidity and detumescence). An enzyme-linked immunoassay was used to measure the concentration of TGF ß1 (ng/ml) in both the systemic and cavernous blood at the stages of flaccidity, tumescence and detumescence. TGF levels were significantly higher in the cavernous compartment than in the systemic blood. A linear decrease was evident in the cavernous blood when the flaccid penis became tumescent (24.3 ± 14.5 to 13.9 ± 6.5) and rigid (to 8.7 ± 3.1). At detumescence, TGF increased to 18.3 ± 10.4. In contrast, the levels in the systemic circulation remained unchanged. The results are in support of the hypothesis that the concentration of TGF ß1 in the CC is regulated by adequate blood flow and oxygenation.

Penile Length: Measurement Technique and Applications

INTRODUCTION

Penile size has long been an important fixation in men's lives. On the one hand, a smaller penis has been associated with anxiety and apprehension; on the other hand, a larger penis has generally been related to virility and strength. These perceptions predominate during an erection, when penile size is representative of a man's masculinity.

AIM

To assess adult penile length and summarize average penile length assessments from the literature; analyze how various urologic diseases and therapies affect penile length and volume; and review how surgical treatments for Peyronie's disease, penile prosthesis implantation, and radical prostatectomy can affect penile size to appropriately counsel patients seeking such therapies and set realistic goals for patients.

METHODS

To achieve the aim of this review, we analyzed the literature on penile size and volume and how these can be affected by various urologic diagnoses and therapies. We summarize common diagnoses and therapies that can affect penile size.

MAIN OUTCOME MEASURE

We thoroughly discuss how the aforementioned diagnoses and therapies can negatively affect penile size. In doing so, we allow readers to understand the intricacies of penile size when faced with such diagnoses and therapies in their patients.

RESULTS

Surgical treatments for Peyronie's disease, penile prosthesis implantation for refractory erectile dysfunction, and radical prostatectomy for prostate cancer can lead to a decrease in penile size.

CONCLUSION

Urologists must recognize that the different therapies they offer can affect a man's penile size, often negatively. This in turn can lead to poorer satisfaction outcomes in patients. Davoudzadeh EP, Davoudzadeh NP, Margolin E, et al. Penile Length: Measurement Technique and Applications. Sex Med Rev 2018;6:261-271.

Is there a significance of histamine in the control of the human male sexual response?

Although histamine has been suggested to be involved in the control of male sexual function, including the induction of penile erection, its role in the human corpus cavernosum penis is still poorly understood. The aim of our study was to evaluate the course of histamine plasma levels through different stages of sexual arousal in the systemic and cavernous blood of healthy male subjects. Thirty four (34) healthy men were exposed to erotic stimuli to elicit penile erection. Blood was aspirated from the corpus cavernosum and a cubital vein during the penile conditions flaccidity, tumescence, rigidity and detumescence. Blood was also collected in the post-ejaculatory period. Plasma levels of histamine (ng ml(-1)) were determined by means of a radioimmunoassay. Histamine slightly decreased in the cavernous blood when the penis became tumescent. During rigidity, histamine decreased further but remained unaltered in the phase of detumescence and after ejaculation. In the systemic circulation, no alterations were observed with the initiation or termination of penile erection, whereas a significant drop was registered following ejaculation. Results are not in favour of the hypothesis of an excitatory role of histamine in the control of penile erection. Nevertheless, the amine might mediate biological events during the post-ejaculatory period.

Systemic and cavernous plasma levels of neuropeptide Y during sexual arousal in healthy males

Neuropeptide Y (NPY) has been shown to induce contraction of isolated human penile erectile tissue and potentiate the response to noradrenaline. The purpose of our study was to measure in the cavernous and systemic blood of healthy male volunteers the course of NPY through different stages of sexual arousal. Whole blood was drawn simultaneously from the corpus cavernosum and the cubital vein of 16 healthy male volunteers during penile flaccidity, tumescence, rigidity and detumescence. Tumescence and erection were induced by applying audiovisual and tactile stimulation. Plasma levels of NPY (given in pmol l(-1)) were determined by means of an enzyme-linked immunoassay. NPY significantly decreased in the cavernous blood on sexual arousal, when the flaccid penis became tumescent and, finally, rigid (F: 88.8 ± 35.8, T: 62.4 ± 22.7, R: 62.3 ± 19.7), and only slightly rose in the phase of detumescence (64.8 ± 23). In the systemic circulation, no pronounced alterations in the concentration of NPY were registered (F: 64.4 ± 27, T: 65.8 ± 19, R: 59.6 ± 25, D: 67.6 ± 29.3). Our findings are in favour of the hypothesis that NPY could contribute to the maintenance of the resting state of cavernous smooth muscle.

Is serotonin significant for the control of penile flaccidity and detumescence in the human male?

For more then 15 years, there has been speculation on the significance of serotonergic pathways in the control of male sexual function, especially in the maintenance of penile flaccidity and the initiation of detumescence. However, only a few in vivo studies on peripheral serotonergic transmission have been carried out. The aim of the present study was to evaluate further the effects of serotonin (5-HT) on isolated human erectile tissue and to detect serum levels of 5-HT in the systemic and cavernous blood taken during different penile conditions from healthy males. The effects of 5-HT on isolated human corpus cavernosum (HCC) were investigated using the organ bath technique. A total of 41 healthy, adult male subjects were exposed to erotic stimuli in order to elicit penile tumescence and rigidity. Whole blood was simultaneously aspirated from the corpus cavernosum and the cubital vein during different penile conditions. Serum levels of 5-HT (ng/ml) were determined by means of an enzyme-linked immunosorbent assay. The cumulative addition of 5-HT (0.001-10 microM) induced contraction in the isolated HCC strips. The contractile response was abolished in the presence of 5-HT(1alpha)-receptor antagonist NAN-190. No attenuating effect of 5-HT was observed on electrically induced relaxation of the tissue. Moreover, amplitudes of relaxation remained unaltered in the presence of NAN-190. In the healthy volunteers, a significant increase in 5-HT levels was detected in the cavernous serum from flaccidity (113+/-62) to tumescence and rigidity (140+/-69 and 141+/-54, respectively), followed by a decrease in the detumescence phase (123+/-79). Changes in 5-HT levels in the systemic serum were less pronounced. Under all penile conditions, systemic 5-HT levels were higher than those registered in the cavernous serum. Although 5-HT does not appear to be involved in postsynaptic transmission in the HCC, our results may provide evidence for a physiological significance of 5-HT in the control of penile flaccidity and detumescence. Thus, our findings may give a rationale for the use of 5-HT antagonists in the pharmacotherapy of erectile dysfunction.

Detection of low-molecular-mass plasma peptides in the cavernous and systemic blood of healthy men during penile flaccidity and rigidity--an experimental approach using the novel differential peptide display technology

OBJECTIVES

To use Differential Peptide Display (DPD) technology to evaluate the patterns of low-molecular-mass peptides and small proteins in the systemic and cavernous blood taken from healthy adult male volunteers during the penile stages of flaccidity and rigidity. Results from basic research implicate a role of various peptides in the control of mammalian penile erectile tissue. Nevertheless, it is not yet known which particular peptides are essential in the regulation of penile flaccidity, tumescence, rigidity, and detumescence.

METHODS

Five healthy male subjects were exposed to visual and tactile erotic stimuli to elicit penile erection. Whole blood was simultaneously aspirated from the corpus cavernosum and cubital vein during penile flaccidity and rigidity. Plasma aliquots were subjected to DPD analysis by means of matrix-assisted-laser-desorption-ionization mass mapping and electrospray-ionization quadrupole--time-of-flight mass spectrometry.

RESULTS

High-resolution two-dimensional peptide mass mapping revealed differences in the systemic and cavernous plasma samples related to penile flaccidity and rigidity. Distinct signals were recognized in the cavernous but not in the systemic plasma obtained during flaccidity. These signals were not registered in the plasma samples obtained from the corpus cavernosum during rigid erection. Although one signal was identified as the blood coagulation-activating peptide XIIIa, the remaining two signals could not be related to any known peptide. These signals may represent unknown local peptidergic factors that might be involved in the regulation of penile flaccidity.

CONCLUSIONS

Our study demonstrates that DPD is a feasible method for detecting differences in the cavernous and systemic blood in relation to the different functional conditions of the penile erectile tissue. Additional studies using DPD should include the analysis of blood samples taken from the cavernous meshwork of healthy subjects during penile tumescence and detumescence to establish DPD as a valuable tool in contemporary corpus cavernosum basic research.

Serum levels of human growth hormone during different penile conditions in the cavernous and systemic blood of healthy men and patients with erectile dysfunction

OBJECTIVES

To detect changes in growth hormone (GH) serum levels during different penile conditions in the cavernous and systemic blood of patients with erectile dysfunction and compare them with the course of GH registered in healthy men. It has been suggested that human GH is involved in sexual maturation and plays a regulatory role in male reproductive function. Deficiency may result in fatigability, loss of sexual desire and erection, or oligospermia or azoospermia. It is assumed that the biologic effects of GH include insulin-like growth factor 1-mediated stimulation of endothelial nitric oxide formation. It has recently been demonstrated that GH serum levels in the systemic and cavernous blood of healthy men increases during developing penile erection.

METHODS

Thirty-five healthy adult men and 45 patients with erectile dysfunction of either organogenic or psychogenic etiology were exposed to visual and tactile erotic stimuli to elicit penile tumescence and, in the group of healthy subjects, rigidity. Whole blood was simultaneously aspirated from the corpus cavernosum and the cubital vein during the different functional conditions of the penis. Serum levels of GH were determined by means of an immunoradiometric assay.

RESULTS

In the healthy subjects, systemic GH serum levels significantly increased during penile tumescence, followed by a transient decline from tumescence to rigidity and detumescence. In the unselected patients, the mean GH levels during penile flaccidity were determined to be about sevenfold lower than those registered in the blood of the healthy men. During penile tumescence, the mean increase in the GH levels in the systemic and cavernous blood of psychogenic patients was comparable to that seen in healthy men, but, in the group of organogenic patients, this increase was found to be negligible.

CONCLUSIONS

We believe our data provide strong evidence that GH may be of major importance in the maintenance of male erectile capability-probably through a stimulating effect on cyclic guanosine monophosphate generation in human cavernous smooth muscle-and that a decline in GH release may contribute to the manifestation of erectile dysfunction.

Cavernous and systemic plasma levels of norepinephrine and epinephrine during different penile conditions in healthy men and patients with erectile dysfunction

OBJECTIVES

To examine and compare the courses of norepinephrine (NE) and epinephrine (E) plasma levels in the systemic and cavernous blood taken during different penile conditions from healthy men and a group of patients with erectile dysfunction (ED). Knowledge concerning the neurophysiology of penile erection has improved tremendously during the past two decades. However, only few in vivo studies on human peripheral neurotransmission have been carried out to date.

METHODS

Fifty-three healthy adult male subjects and 47 patients with ED of different etiologies were exposed to erotic stimuli to elicit penile tumescence and, in the group of healthy subjects, rigidity. Whole blood was simultaneously aspirated from the corpus cavernosum and the cubital vein during different penile conditions. Plasma levels of NE and E were determined by means of a radioimmunoassay.

RESULTS

In the healthy subjects, a significant reduction of NE in cavernous plasma was detected from flaccidity (362 +/- 173 pg/mL) to rigidity (248 +/- 122 pg/mL), followed by an increase in the detumescence phase (336 +/- 199 pg/mL). Changes in NE levels in the peripheral plasma were less pronounced. Cavernous E levels significantly increased from flaccidity (47 +/- 41 pg/mL) to tumescence (130 +/- 106 pg/mL) and dropped from rigidity (113 +/- 67 pg/mL) to detumescence (76 +/- 57 pg/mL). The course of systemic E plasma levels was similar to that in the cavernous blood. In contrast, median NE levels in the systemic and cavernous blood of the ED group slightly increased from flaccidity to tumescence (from 199 +/- 88 pg/mL to 210 +/- 99 pg/mL and from 273 +/- 140 pg/mL to 278 +/- 118 pg/mL, respectively).

CONCLUSIONS

In healthy men, penile erection is accompanied by a reduction of NE in the cavernous blood and a rise in E levels in the peripheral and cavernous blood. That NE levels in the cavernous and systemic blood increase during sexual arousal in patients with ED might be an indication of a somatic dysregulation in sympathetic transmission or alterations of NE reuptake mechanisms as a cause of impaired erectile function.

Cavernous and systemic testosterone plasma levels during different penile conditions in healthy males and patients with erectile dysfunction

OBJECTIVES

To determine the testosterone plasma levels in the cavernous and peripheral blood taken during different penile conditions from patients with erectile dysfunction (ED) and to evaluate whether these courses are different from those detected in the blood of healthy males. Although the determination of the systemic testosterone concentration (TC) has been fairly well established in the diagnostic workup of ED, the exact role of testosterone in adult male sexual function remains unclear.

METHODS

Blood samples were drawn simultaneously from the corpus cavernosum and cubital vein of 54 healthy males with normal erectile function and 46 patients with ED during the penile stages of flaccidity, tumescence, rigidity (reached by the healthy males only), and detumescence. Tumescence and rigidity were induced by audiovisual and tactile stimulation. The TC was determined by means of a radioimmunoassay.

RESULTS

In the flaccid phase, the TC in the cavernous blood taken from the healthy volunteers was 2.9 +/- 1.2 ng/mL. The TC significantly increased during tumescence (4.3 +/- 1.3 ng/mL) and rigidity (4.4 +/- 1.4 ng/mL), P <0.001. In the detumescence phase, the TC decreased appreciably to 3.5 +/- 1.4 ng/mL. In the systemic blood, the increase from flaccidity (4.1 +/- 1.1 ng/mL) to tumescence (4.4 +/- 1.4 ng/mL) was found to be less pronounced but, nevertheless, significant (P = 0.001). No further increase was detected during rigidity. From rigidity to detumescence, the systemic TC dropped to 4.1 +/- 1.2 ng/mL. In the patients with ED, the mean increase in systemic and cavernous testosterone levels from flaccidity (cubital vein 3.0 +/- 1.0 ng/mL, corpus cavernosum 2.6 +/- 1.0 ng/mL) to tumescence (cubital vein 3.2 +/- 1.1 ng/mL, corpus cavernosum 3.0 +/- 1.0 ng/mL) was less pronounced. Nevertheless, the course of testosterone detected in the systemic and cavernous plasma of the patients during flaccidity, tumescence, and detumescence resembled that registered in the healthy controls. In the flaccid phase, the mean cavernous TC in the healthy subjects was found to be 30% lower than the level in the peripheral blood; in the patients with ED, this difference was only 13%.

CONCLUSIONS

In the healthy males, the penile erection was accompanied by an increase in the cavernous and peripheral TC. The difference between the peripheral and cavernous TC in the healthy subjects and patients with ED in the flaccid phase, when the blood flow through the cavernous body is minimized, might be a diagnostic tool to evaluate the amount of bioavailable testosterone, as well as the density of testosterone receptors, in the cavernous smooth musculature.

Cavernous and systemic testosterone levels in different phases of human penile erection

OBJECTIVES

To examine changes in testosterone levels in the cavernous and peripheral blood during different phases of erection because, although the determination of systemic testosterone levels has been well established in the diagnostic workup of erectile dysfunction, the exact role of testosterone in adult male sexual function remains unclear.

METHODS

Blood samples were drawn simultaneously from the corpus cavernosum and the cubital vein of 54 healthy and normally potent volunteers during four different stages of the cavernous erectile tissue (flaccidity, tumescence, rigidity, and detumescence). Penile erections were induced by audiovisual and tactile stimulation, and testosterone levels were determined by radioimmunoassay.

RESULTS

The mean testosterone level in the corpus cavernosum plasma during the flaccid state was 2.9 +/- 1.2 ng/mL. During tumescence and rigidity, the testosterone levels in the cavernous blood significantly increased, to 4.3 +/- 1.3 ng/mL and 4. 4 +/- 1.4 ng/mL, respectively. During detumescence, the cavernous testosterone levels dropped to 3.5 +/- 1.4 ng/mL. The changes in the testosterone levels in the peripheral plasma were less pronounced. A significant increase was also found in the peripheral testosterone levels from flaccidity (4.1 +/- 1.1 ng/mL) to tumescence (4.4 +/- 1. 4 ng/mL). No further increase in testosterone occurred during the phase of rigidity. From rigidity to detumescence, the peripheral testosterone levels dropped to 4.1 +/- 1.2 ng/mL.

CONCLUSIONS

Penile erection was found to be accompanied by a significant increase in cavernous and systemic testosterone plasma levels. The estimated difference between the systemic and cavernous testosterone levels during penile flaccidity, when blood flow through the cavernous body is minimized, might be a diagnostic tool to evaluate the amount of bioavailable testosterone and the activity of testosterone receptors in the corpus cavernosum smooth musculature.

Application of nocturnal electrobioimpedance volumetric assessment: a feasibility study in men without erectile dysfunction

PURPOSE

Electrobioimpedance volumetric assessment is based on the principle of delivering a constant, nondetectable alternating current to a tissue segment. A potential difference measured between the electrodes is converted to impedance. Since impedance changes with variations in blood flow, penile volumetric change is measured noninvasively. We applied this procedure to the development of a new device to evaluate erectile activity nocturnally, and we report our findings in men with no history of erectile dysfunction.

MATERIALS AND METHODS

Our study group comprised 10 men with a mean age of 44 years who had no history of erectile dysfunction. The NEVA device consists of a small recording device attached to the upper thigh, and 3 small adhesive electrode pads placed over the hip and on the penile base and glans, respectively. Each subject used the NEVA device for 2 nights.

RESULTS

Overall 20 nights of electrobioimpedance volumetric assessment were recorded. Tumescence monitoring revealed 3 to 6 erections per night per subject (mean 3.45) lasting 10 to 50 minutes (mean 17). As determined from the impedance measurements, mean volume change was 14.4 ml. with a 213% mean volume change over baseline.

CONCLUSIONS

The new NEVA device is small, comfortable to wear and easy to use. It determines the number and duration of erectile events and percentage increase of blood volume changes during these events in normal men in a noninvasive manner. Future directions of study include a comparison to men with erectile dysfunction and analysis of the dynamic information of the NEVA data.

The role of nuclear medicine in the evaluation of the male genital tract

Scintigraphic techniques for evaluation of impotence are still evolving. Blood pool studies are most useful in assessing the integrity of arterial inflow, but may also be used to generate indices of venous leak. A non-imaging version of this test may represent a simple and cost-effective alternative. Washout of intracavernosal xenon during erection seems the most useful method of testing venous integrity. Washout using Tc-RBC may emerge as a convenient alternative to the more technically difficult xenon examinations. Development of more effective pharmacologic stimuli may further improve the utility of this quantitative and physiologic examination.

Radionuclide genital imaging

Despite the emergence of newer cross-sectional imaging approaches, radionuclide techniques have maintained a significant role in genital imaging. While ultrasound is clearly superior for evaluation of scrotal anatomy, radionuclide scrotal imaging remains the most effective method for differentiating between testicular torsion and epididymitis. Labeled red blood cells have been used for varicocele detection in infertile men. Since radionuclide techniques can demonstrate the physiologic status of organs, they play a useful role in evaluating men with impotence (penile scan) and infertile women whose tubal patency is in question (radionuclide hysterosalpingogram).

Volume-dependent intracavernous hemodilution during pharmacologically induced penile erections

The change in the cavernous hematocrit following induction of pharmacological erection by an intracavernous injection of papaverine hydrochloride was documented in normal controls and patients with impotence. Blood samples taken from the penile cavernosa showed a significantly lower hematocrit compared to the systemic venous blood in all normal subjects. The decrease in the cavernous hematocrit was attributable to dilution of the cavernous blood pool by the injected volume of the drug, since this was not observed in erections produced by visual sexual stimulation. It appears that a restriction of the cavernous venous outflow in response to papaverine injection causes sequestration of the diluted blood in the cavernous compartment. The degree of cavernous hemodilution was found to aid in the differential diagnosis and was especially valuable in differentiating patients with arteriogenic impotence from those with venous leakage.

Nuclear medicine in problems of fertility and impotence

Nuclear medicine techniques may be used to test fallopian tube patency and penile vascular inflow and outflow. Radionuclide hysterosalpingography (HSP) is a readily performed method of evaluating fallopian tube patency, and is believed to be more physiologic and functionally informative than the accepted radiologic method of contrast HSP. The test is simple to perform and interpret and offers an accurate alternative to the contrast examination. For scintigraphic evaluation of impotence, blood pool studies are most useful in assessing the integrity of arterial inflow, but may also be used to generate indices of venous leak. Washout of xenon after subcutaneous injection, in the flaccid state, has been used as a measure of baseline penile perfusion, as has intracavernosal injections in the flaccid penis. Intracavernosal xenon washout during erection seems the most useful method of testing venous integrity. Washout using technetium-99m (99mTc)-labeled red blood cells (99mTc-RBC) may emerge as a convenient alternative to the more technically difficult xenon examinations.

Dual radioisotopic study: a technique for the evaluation of vasculogenic impotence

Arterial and venous systems are the main points for the evaluation of vasculogenic impotence. To evaluate both of these systems in the same study we propose a dual radioisotopic study in which 99mtechnetium (99mTc) and 133xenon (133Xe) were used. The changes in 99mTc and 133Xe radioactivities administered intravenously and intracavernously, respectively, were monitored before and after intracavernous papaverine injection. These changes were determined as time activity curves, which were generated from the region of interest over the penis. A 99mTc penogram index derived from the 99mTc time activity curve was significantly different in the control and arteriogenic impotence groups (131.67 +/- 74.6 versus 62.94 +/- 51.6, p less than 0.01). A meaningful correlation between 99mTc penogram index results and duplex ultrasonographic findings were observed (r = 0.905). 133Xe penogram index, derived from the 133Xe washout curve was significantly different in the control and venogenic impotence groups (-25.65 +/- 24.9 versus -56.09 +/- 13.4, p less than 0.01). Also, a meaningful correlation was obtained between pharmacocavernosometry and 133Xe penogram index results of venogenic impotent patients (r = 0.86). These findings suggest that the dual radioisotopic study will be a useful technique in the evaluation of the entire vascular system of the penis, since it is a noninvasive method.

Radionuclide studies in impotence

Impotence may be of physiological origin with causes including vascular or neurological pathology. Alternatively, it may be of psychogenic origin. Clinicians can distinguish between psychological and organic impotence by observing nocturnal penile tumescence. Non-radionuclide investigations for organic impotence include penile plethysmography or pulse Doppler analysis for arterial supply, cavernosometry for venous drainage, and biothesiometry or evoked potentials for neurological pathology. Radionuclide studies are primarily based on the use of technetium 99m-pertechnetate, 99mTc-red blood cells, or xenon 133 to study the blood flow, with or without pharmacological intervention, commonly papaverine.

Erotic erection versus nocturnal erection

To clarify the correlation between erotic and nocturnal erections, and to evaluate the diagnostic efficacy of the audiovisual stimulation penogram as an initial screening test for impotent patients, a comparative study of 137 impotent patients was designed. The audiovisual stimulation penogram shows dynamic penile blood flow change during audiovisual stimulation using a radioisotope (99mtechnetium) and is classified as type 1--similar findings to normal volunteers, type 2A--impossible erection due to insufficient blood flow, type 2B--unstable erection due to severe fluctuation in blood flow and type 2C--delayed erection. The compatibility ratios of the audiovisual stimulation penogram types 1, 2A and 2C with some tests for nocturnal erection were relatively high (63 to 80%) and when compared to the final diagnosis all but 1 of the compatible cases with nocturnal erection studies were able to be diagnosed correctly. However, the compatibility ratio of the audiovisual stimulation penogram type 2B was markedly low (35%) and this group had complicated etiologies, including many more psychogenic than organic causes. Although the mechanisms of the erotic and nocturnal erections have not been fully elucidated to date, our results suggest that the audiovisual stimulation penogram seems to be an appropriate initial screening step if we refine the criteria for type 2B, and a comprehensive interpretation of the tests for erotic and nocturnal erections will result in a more accurate diagnosis.

Cavernosometry: corroboratory method to surgical treatment of impotence due to venous leakage

There are still controversies about the mechanism of penile erection. Arterial aspects of impotence have received considerable attention, but just recently the venous component became widely recognized. Twenty patients with abnormal cavernosometry (flow rate over 280 mL/min) and no rigid erections (intracavernosal pressure lower than 80 mm Hg) were analyzed. Surgical ligation of the dorsal veins was performed in 12 cases, 9 of which also required ligation of the crus of each corpus cavernosum. After these ligations, erection improved sufficiently to allow satisfactory intercourse in 9 of 12 patients. Two patients became impotent after eight months of normal sexual performance. The 3 failures showed persistently high flow rates and one leakage by the crural edge which had not been ligated at surgery. In selected patients with organic impotence the venous abnormalities should be assessed routinely and dorsal veins and the crural edge of the corpus cavernosum should be ligated in an attempt to restore erectile function.

A canine model for hemodynamic study of isolated corpus cavernosum

We developed a canine model which permits hemodynamic study of the isolated corpus cavernosum. The arterial and venous flow to the corpus cavernosum was measured and pressure was measured in each corpus cavernosum separately. To provide controlled inflow to the corpora, each side was perfused separately with the aorta clamped. It was demonstrated that arterial and nerve supply to the corpus cavernosum is crossed. During unstimulated corporal perfusion, venous outflow from the corpora increased with increased perfusion rate up to a maximum of 40 ml./min. Following pelvic nerve stimulation, intracorporal pressure increased at much lower rates of perfusion. Moreover, it was noted that intracorporal pressure was not transmitted from one side to the other. Thus, in the canine model, each corpus cavernosum may act as a control for the contralateral one. The technique we used to measure venous outflow from the corpora cavernosa, previously undescribed, permits accurate depiction of the hemodynamics of penile erection.

Further evidence of venous outflow restriction during erection

To elucidate the effect of venous outflow restriction during erection, we studied eight dogs during artificial saline perfusion of the penis with and without neurostimulation to induce erection. With the infrarenal aorta clamped temporarily, saline infusion rates of 0.9 and 1.9 ml/min raised the mean intracorporeal pressure to 34 and 42 cm H2O, respectively, before stabilisation or return to baseline. When cavernous nerve stimulation was initiated, the mean intracorporeal pressure rose to 124 and 184 cm H2O (with infusion rates of 0.9 and 1.9 ml/min respectively) to induce full erection. Our results show that venous outflow restriction takes place during erection and that it is necessary not only to induce full erection but also to maintain it. Evaluation of venous competence is therefore essential during the investigation of impotence.

Isotope phallogram: preliminary communication

The isotope phallogram is an investigation which uses radioisotope-labelled red cells in the imaging of penile arterial blood flow. In a preliminary series of 12 impotent patients undergoing both internal iliac arteriography and isotope phallography, the penogram index described by Fannous et al. (1982) has been modified to derive an accurate indicator of vascular disease.

Hemodynamics of erection in man

Inquiry was made into the theory that closure of the efferent vein from the corpora cavernosa is essential for erection of the human penis. To determine whether the venous closure is indeed a prerequisite to human penile erection, two tests were carried out in men: (1) direct infusion in 133Xe into corpora cavernosa and (2) performance of carvernosography. In each case, penile erection was induced by providing the subject with sexual stimulation. The behavioral changes were studied through the 133Xe clearance curve and the contrast medium, respectively. When the penis remained flaccid, the 133Xe clearance curve followed a gentle path and the contrast medium could be noted within the penis for a relatively long period. However, on erection with sexual stimulation, the 133Xe clearance curve fell rapidly instead of following the gentle course expected in the case of venous closure. Also, the contrast medium quickly flowed out of the corpora cavernosa. The human penis therefore can well erect without closure of the efferent vein from the corpora cavernosa.

Microsurgical revascularization of the canine corpus cavernosum penis

The concept of vasculogenic impotence in humans is addressed by attempting to surgically create and correct vasculogenic impotence in healthy dogs. Initial experience reveals that only by extensive pelvic vascular interruption can such impotence be created and that, at best, it is only temporary because of collateralization. Microsurgical revascularization using both direct femoral artery implantation and femoral vein interposition into the corpus cavernosum penis yielded low patency rates. Further studies on this technique are needed before it can be recommended for widespread use in human beings.

The possible role of the catecholamines of the corpora in penile erection

The etiology of impotence, which effects 50 per cent of the men with diabetes, is unknown. The neurotransmitter (norepinephrine) released from adrenergic neurons is thought to be the most direct regulator of vascular smooth muscle. We have measured the norepinephrine content of the erectile tissue of diabetic men. Our results indicate the presence of a dual neural regulator mechanism of the corpora that controls penile erection.