Mechanism of penile erection in the dog. Pressure-flow study combined with morphological observation of vascular casts

A pressure-flow study of the corpus cavernosum penis in the dog was performed during the flaccid, tumescent, erect and rigid stages. Perfusion was selectively made into the penile deep artery. The erect stage was induced with the local administration of papaverine hydrochloride, and the rigid stage by electrostimulation of the ischiocavernous muscle during the erect stage. Concurrently, vascular casts of the penis at each stage of erection were observed under a scanning electron microscope for the anatomical analysis of the mechanisms controlling cavernous pressure. In the pressure-flow study, it was demonstrated that a combination of decreased arterial resistance and restricted venous outflow was essential to both cause and maintain the erect state. The rigid stage was generated by contraction of the ischiocavernous muscle tightly compressing the crus penis. In the rigid stage, the cavernous pressure was elevated as high as five times the perfusion pressure; nevertheless, no backflow from the cavernous sinus to the deep artery was recognized. By use of the casts, it was confirmed that venous outflow restriction in the erect and rigid stages was due to compression of the postcavernous venules and penetrating veins in the tunica albuginea. The deep artery was occluded in the tunica albuginea in the casts made during the rigid stage, suggesting that the backflow from the corpus cavernosum penis to the deep artery was prevented by this occlusion. Therefore, in the rigid stage, the arterial and venous occlusion isolated the cavernous sinus from the systemic circulation; this mechanism seems to account for the maintenance of the extremely high cavernous pressure.     

Two circulatory routes within the human corpus cavernosum penis: a scanning electron microscopic study of corrosion casts

The microvascular architecture of the human corpus cavernosum penis was studied by scanning electron microscopy of vascular corrosion casts. The corpus cavernosum was supplied by the penile deep artery. It gave off branches to become either arteries distributed within the corpus cavernosum or those directly supplying the corpus spongiosum urethrae. The former arteries further divided into small arteries which fell into two categories: 1) arteries breaking up into capillaries, and 2) arteries draining directly into the cavernous sinuses. The capillaries were collected into venular networks just beneath the tunica albuginea (the subalbugineal venular plexus), while the cavernous sinuses were collected into venules at the periphery of the corpus cavernosum. These postcavernous venules also received venules from the subalbugineal venular plexus, and left the corpus cavernosum. Thus, two circulatory routes are evident within the corpus cavernosum. These findings suggested that the penile erectile cycle is controlled by hemodynamic changes between these two routes within the corpus cavernosum.     

Basic and clinical research of impotence--its present situation and problems involved

From detailed investigation of the vascular structure of the penis, it has been proposed that there exists a valvular structure, consisting of smooth muscle, located at a point immediately before the helicine artery, bifurcated from the deep artery, opens to the cavernous sinuses, an area where autonomic nerves are densely distributed, participating in opening and closing the valve. On the other hand, there is said to be no valvular structure in the vein outflowing from the cavernous sinuses, and blood flows into the dorsal penile vein by penetrating the albuginea obliquely or vertically after running parallel in the region immediately below the albuginea. It is considered that, when the valve of the helicine artery opens, blood flows into the cavernous sinuses, expanding them, and as a result the outflowing vein is compressed between the sinuses and the albuginea, or the albuginea itself, acting like a valve and therefore assuming an important function in maintaining erection by disturbing the reflux of blood flow. It is also presumed that the contracting of ishiocavernous muscle plays a part in developing the rigidity of the penis. It is considered, moreover, that the trabecula of the cavernous body consisting of smooth muscle also plays a part in the promotion and disappearance of erection. It is very important to run functional tests of erection when diagnosing impotence, and today many tests are available for differential diagnosis; including papaverine test, dynamic cavernosometry and cavernosography. As for therapy, treatments involving vasoactive agent infusion, such as papaverine or prostaglandin E1 into the cavernous body, have become common. For cases with venous impotence, ligation of the penile deep vein and crus of the penile cavernous body have come to be attempted. Furthermore, revascularization of penile artery can be performed to treat arterial impotence. For cases in whom these methods are not effective, implantation of various penile prostheses into the penis has been shown to be successful.     

Treatment of erectile dysfunction in cases of venous and corporovenous insufficiency of phallus

A total of 230 patients of different age with impaired venous drainage of penis cavernous bodies were examined. Test with intracavernous injection of papaverin, dopplerography of the vessels and cavernosometry were employed. To treat venous and corporovenous insufficiency, it is suggested to make a resection of the deep dorsal vein, ligation of the superficial and circular veins with suturing tunica albuginea. In negative result of the surgery viagra in a done 50 (100) mg is recommended or penile implants.     

The mechanism of blood outflow from the cavernous tissue of human penis by computer graphics

There are two theories concerning the mechanisms of human penile erection and its maintenance. One theory goes that the artery responsible for blood inflow into the cavernous space relaxes, while the vein responsible for blood outflow actively contracts. The other theory asserts that no active closing mechanism in present in the penile venous system, but rather the erection is totally controlled by the amount of blood inflow. In order to corroborate the vascular construction of the penis, we prepared serial sections of the penis specimens obtained at autopsy and observed these sections by light microscopy, and we investigated the construction of veins which let blood flow out from the corpus cavernosum penis by computer graphics. As a result, we were unable to find any valves in the blood outflow system. Moreover, efferent vessels were seen to let blood flow from the cavernous spaces, after running immediately below the tunica albuginea for a small distance, to the tunica albuginea, running obliquely through inner veins toward the outside of the tunica albuginea in the direction of the long axis of the penis; then these veins are continuous to the veins on the tunica albuginea. From the above-mentioned structures we can infer the following mechanism of penile erection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Study of human penile venous system and hypothesis on its behavior during erection

To determine the role of the venous outflow restriction during human erection, we compared intracavernous pressure with deep dorsal vein pressure in 6 normal subjects during papaverine-induced erection and penile saline infusion. In addition, flows necessary to produce and maintain erection were measured in 10 cadavers before and after resection of the deep dorsal vein alone or together with ligation of the cavernous veins. Elongation of tunica albuginea was measured at the crural and mid portions of the penis. At rigidity there was complete blockage of the venous return through the emissary veins. The venous outflow through the cavernous veins was reduced but still persisted. The distention of the tunica albuginea was less important at the crural portion than at the distal portion and could explain why the cavernous veins were not blocked completely.     

Mechanisms of venous occlusion during canine penile erection: an anatomic demonstration

Hemodynamic studies have clearly demonstrated that intracorporeal injection of papaverine causes an increase of venous outflow resistance, and we therefore undertook a study of the venous drainage of the canine penis to delineate the anatomic changes in the venular structure during papaverine-induced erection. In 11 dogs, the corpora cavernosa were examined by corrosion casting in six and serial trichrome staining and histologic sectioning in five. Low-power scanning electron microscopy of the corrosion casts demonstrated the existence of a venular plexus interposed between the tunica albuginea and the sinusoidal spaces. After papaverine injection, this subalbugineal venular plexus is compressed between the dilated sinusoids from below and the tunica albuginea from above, such that venous drainage is effectively impeded. Examination of two cadaveric human penile corrosion casts by low-power scanning electron microscopy revealed evidence of a similar subalbugineal venular plexus draining into the emissary veins along the shaft of the penis. Based on the above, a model for the anatomic basis of venous occlusion during penile erection is outlined. Along with arteriolar and sinusoidal smooth-muscle relaxation, this can account for the three basic hemodynamic changes necessary for erection: increased arterial inflow, increased intracorporeal pressure, and increased venous outflow resistance.     

Systemic complication of intracavernous papaverine injection in patients with venous leakage

Intracavernous papaverine injection is often used in the diagnosis and treatment of male impotence. Prolonged erection and/or priapism are well known local complications. Systemic side-effects characterized by discomfort and dizziness due to rapid escape of the drug into the vascular circulation also can occur in patients with venous leakage. Thus, venous leakage should be ruled out prior to intracavernous injection of papaverine in the treatment of impotence. Ligation of the deep dorsal vein and the small veins around the tunica albuginea will lessen the problem.     

Deep dorsal vein arterialisation in vascular impotence

A series of 12 patients with vasculogenic impotence (4 arterial lesions; 8 arterial and venous lesions) underwent deep dorsal vein arterialisation after pre-operative assessment by a multidisciplinary approach. Cumulative graft patency was 58% (7 of 12 patients) up to 21 months but only 4 patients developed almost normal erections. Digital angiography, with and without the intracavernous injection of papaverine, was performed during follow-up to determine the vascular physiological status. At flaccidity, the corpora cavernosa were never opacified in the absence of a venocorporeal shunt. The penile glans was always visualised. Opacification of the deep dorsal vein and the circumflex system decreased with penile rigidity, resulting from their compression between Buck's fascia and the tunica albuginea. Intracavernous pressure recorded before and after the surgical procedure showed a marked increase when a caverno-venous shunt was performed. Hypervascularisation of the glans occurred in 2 cases. The relevance of this new surgical technique and its functional mechanism are discussed.     

Electron microscopic findings of penile tissues in veno-occlusive dysfunction: Is penile biopsy necessary?

In this study, we examined the biopsy patterns of penile tissues taken during operation from patients subjected to surgical treatment for veno-occlusive dysfunction, and evaluated the importance of penile biopsy. We evaluated the findings from 17 patients with venous impotence. Fourteen of them underwent total vein ligation and the rest penile prosthesis implantation. Tissue speciments taken from superficial and deep dorsal veins, tunica albuginea and corpus cavernosum during operation were examined under electron microscope. Tissue specimens taken from 3 cadavers were used as the control group. Although the deep and superficial vein specimens of all patients did not show significant differences, oedema and increase of fibroblasts in collagen fibres of the corpus cavernosum and tunica albuginea were demonstrated. We concluded that penile biopsy as an invasive method does not give enough information about the choice of treatment for erectile dysfunction.     

Increase in venous outflow from the corpora cavernosa during mild erection in dogs.

The venous outlet of the corpus cavernosum is generally believed to be obstructed during erection. Some researchers, however, have demonstrated an increased venous outflow during erection. To elucidate this discrepancy, we carried out a pressure-flow study using a perfusion model of the penile deep artery in dogs. Various states of the corpus cavernosum, which were different in cavernous pressure, were induced by a delicate control of electrostimulation to the cavernous nerve. Inflow rate into the corpus cavernosum, inflow resistance and outflow resistance were simultaneously evaluated. The inflow rate in mild erection was higher than in the flaccid state, and the outflow rate was estimated to be also higher than in the flaccid state. A probable reason for the increased outflow rate was that the arterial resistance decreased remarkably, while the venous resistance only slightly increased. In full erection, both the inflow and outflow rates were lower than in the flaccid state because of a great venous resistance. Histological observation of the canine penis indicated that compression of draining veins passing through the tunica albuginea was weak in mild erection, while intense in full erection. It was proposed that in mild erection, the effect of venous occlusion was slight though that of arterial dilation was noticeable, resulting in an increase in the venous outflow.     

Functional evaluation of penile arteries with duplex ultrasound in vasodilator-induced erection

In 657 impotent patients in whom erection was induced by intracavernous injection of papaverine, we evaluated changes in the pulsation, diameter, and blood flow velocity of the penile arteries by duplex sonography and pulsed Doppler spectrum analysis. An additional 18 patients who were proved to have good erection by nocturnal tumescence testing were used as controls. All patients were studied before achieving full erection after papaverine injection. In the flaccid state, the inner diameter of the deep penile arteries averaged 0.51 mm, and blood flow velocity was rarely measurable. The normal arterial reaction to papaverine was an initial increase in the inner diameter of the scanned segment of the cavernous artery with good concentric pulsations and a mean peak blood flow velocity of 34.8 cm per second and a mean diameter of 0.89 mm. With this technique, we assessed the functional capability of each deep and dorsal artery. Arterial and erectile response allowed indirect evaluation of the venous system. Of the 657 patients, 48 had neurogenic or psychogenic impotence or both. In 97, impotence could be ascribed to venogenic causes, in 210 to arteriogenic causes, and to mixed arteriogenic and venogenic causes in 282 patients. The exact cause of impotence in the remaining 20 patients could not be determined. Statistically, patients who were older or had diabetes mellitus or coronary artery disease tended to have smaller penile arteries and lower peak blood flow velocity after papaverine injection.     

静脉性勃起功能障碍中阴茎静脉漏的彩色多普勒超声观察

目的 探讨静脉性勃起功能障碍(ED)患者阴茎静脉的血液动力学变化. 方法 静脉性ED患者32例,年龄26～63岁,平均41岁.病程6个月～10年,平均2.5年.采用前列腺素E1试验后行常规阴茎彩色多普勒超声检查,观察阴茎背深静脉、海绵体静脉、球静脉的超声表现,分析其与海绵体动脉阻力指数(RI)的相关性. 结果 32例患者诱发勃起前静脉内径(0.06±0.15)mm,血流速度(4.30+1.36)cm/s,诱发勃起5 min后阴茎静脉管径(1.23±0.30)mm,血液回流增多,血流速度(11.50+4.02)cm/s.阴茎背深静脉、海绵体静脉、球静脉流量与海绵体动脉RI的相关系数r分别为-0.55,-0.53,-0.24(P＜0.05).考虑存在混合性静脉漏因素的前提下,阴茎静脉流量与海绵体动脉RI的r为-0.88(P＜0.001). 结论 高频超声能清楚显示阴茎静脉漏部位,可初步判断静脉性ED患者的静脉漏部位及其程度.     

Evaluation of a no-needle penile injector: a preliminary study evaluating tissue penetration and its hemodynamic consequences in the rat

Objectives

Intracavernous needle injection is an effective delivery method for pharmacotherapy of erectile dysfunction. Needle phobia, pain, and concern about local tissue injury have stimulated the search for new, less invasive means of inducing penile erection. In this preliminary communication, we evaluate a jet injector as an alternative to needle injection for intracavernous delivery of vasoactive drugs.

Methods

Jet injection was evaluated in three groups of rats receiving either India ink, saline, or papaverine into the penis. The ability of the jet injection to penetrate through the tunica albuginea and deliver liquid to the corpora cavernosa smooth muscle was assessed by the degree of staining within the corpus cavernosum (ink group), histologic change (saline group), and rise in intracavernous pressure (papaverine group). Erectile capacity following cavernous nerve electric stimulation was compared before and 1 hour after injection of saline or papaverine.

Results

Ink traversed the skin and tunica albuginea with extensive deposition noted within the cavernous spaces. Varying degrees of subcutaneous hemorrhage were seen with saline jet injection; however, the corpus cavernous smooth muscles showed no evidence of injury. Jet injection of papaverine 3250 gmg significantly increased cavernous pressure (39.4 ± 4.6 cm H₂O) compared with saline injection (2.8 ± 1.3 cm H₂O).

Conclusions

We conclude that acute jet injection is an effective method for intracavernous delivery of drugs. Long-term effects should be evaluated prior to clinical use.     

Functional evaluation of penile veins by cavernosography in papaverine-induced erection

Of 49 patients in whom cavernosography was performed after papaverine-induced erection 38 had abnormal venous leakage to various drainage systems (corpus spongiosum, cavernous vein or superficial and deep dorsal veins). Because the effect of papaverine on penile arteries, sinusoids and veins is similar to that caused by electrostimulation, we believe that this technique is better than other reported means of evaluating the functional status of the penile veins. However, we recommend that only patients with a normal arterial response but poor erection after papaverine injection be considered candidates for erection cavernosography, since they most likely will benefit.     

阴茎体白膜两侧睾丸鞘膜移植阴茎增粗术实验研究

目的:探讨犬阴茎体白膜两侧自体睾丸鞘膜移植阴茎增粗术的治疗效果及手术并发症。方法:取5只雄性杂种狗自体睾丸鞘膜移植于阴茎白膜两侧的纵形切口,以扩大阴茎白膜腔、增大阴茎海绵体容积、增粗阴茎;手术前后进行疲软及勃起状态下阴茎海绵体周径的测量及两侧阴茎海绵体动态灌注测压(DIC);术后3个月行组织学检查。结果:施行5只10侧,术后3个月勃起状态下阴茎海绵体周径平均增加21.1%,疲软状态下增粗不明显,DIC参数与术前相比无统计学差异;无其他严重并发症;组织学检查移植物内轻度炎性反应和纤维化,其上有白膜的重新形成。结论:该手术方法使勃起状态下阴茎增粗效果显著,是一种安全的、真正针对勃起组织的阴茎增粗方法。     

Long-term results of autologous venous grafts for penile morphological reconstruction

In order to evaluate the long-term results of autologous venous grafts, we present an overview of patients who underwent a procedure utilizing a venous patch from the deep dorsal vein with or without combination of the cavernosal vein in treating penile deformity. From March 1995 to March 2005, a total of 85 consecutive patients with Peyronie disease or congenital penile deviation underwent venous grafting. Tunical corporotomy was covered using transplanted venous wall sutured microscopically to collagen bundles of the inner circular and outer longitudinal layer of the tunica albuginea. The vein was sutured with the serosal side outward, after it had been detubularized, properly constructed, and spliced together. In this cohort, 48 patients with Peyronie disease and 37 with congenital penile deviation were respectively categorized as belonging to the Peyronie and congenital groups. All patients were evaluated preoperatively and postoperatively with the International Index of Erectile Function (IIEF-5) scoring, angle measurement of erectile penis, satisfaction with the penile shape, and a cavernosogram which was further available for 15 patients. Histological confirmation in 5 cases was followed up for up to 10 years. The mean angle improvement was 44.8 +/- 3.6 degrees for the Peyronie group and 37.6 +/- 3.8 degrees for the congenital group. A satisfactory penile shape was achieved in 77 (90.6%) patients, although 8 men (9.4%) complained of mild deviation of the penis (<15 degrees). Erectile function was good in 81 patients, although 6 of them had to use oral sildenafil/tadalafil postoperatively. Overall, they had a mean preoperative IIEF-5 score of 19.7 +/- 2.8, which increased to a mean postoperative score of 21.6 +/- 2.2. The cavernosograms consistently disclosed a good penile shape. The histological confirmation showed that the donor vein retained its histological character despite the fact that perfect coalescence and lining up with the tunica albuginea were noted. The autologous vein appears to be an acceptable graft material, and the transplanted vein may have a modeling action rather than a scaffolding role in venous patch surgery on the penile tunica albuginea. Careful microsurgical manipulation is required to achieve a satisfactory, sustainable outcome.     

Cavernous vein arterialization for vasculogenic impotence: An animal model

We designed acute and chronic animal models to evaluate a new procedure of arterialization of the cavernous vein. In the acute study, arteriogenic impotence was induced in 6 dogs by bilateral ligation of the penile arteries just proximal to the crus of the penis. The cavernous vein and penile artery were anastomosed proximal to the site of ligation, and the pudendal vein was ligated proximally to prevent the diversion of arterial blood away from the penis. Erection was induced either by electrostimulation of the cavernous nerves or by intracavernous injection of papaverine, and the erectile response was studied before and after cavernous vein arterialization. Four dogs were followed up for two months to evaluate the long-term effects of the procedure. Shortly after arterialization of the cavernous vein, the basal flow rate in the internal pudendal artery increased dramatically to almost six times the control rate, and the erectile response to neurostimulation was approximately 85 percent of control. Selective pudendal arteriography at two months confirmed the patency of all arteriovenous anastomoses. However, scanning electron microscopy and histologic examination revealed sinusoidal damage most probably consequent to the chronically elevated arterial flow.     

Implantable penile venous compression device: initial experience in the acute canine model.

We have designed a venous compression device implantable at the base of the penis outside the tunica albuginea. Because it does not require exposure of individual veins for ligation, the risk to the cavernous nerve is practically nil. It occludes the venous return only temporarily, and thus collaterals are less likely to occur. In this preliminary acute study in dogs (N = 13), the penile venous compression device was shown to be effective and safe in controlling penile venous drainage and maintaining rigid erection.     

Dorsal vein rupture after practice of taqaandan, necrotising cavernositis, penile reconstruction, urethroplasty and penile prosthesis implantation

Penile fracture is an uncommon and emergent urologic condition defined as traumatic rupture of the corpus cavernosum secondary to a blunt trauma of the erect penis. Tunica albuginea is thinned and stretched in the erect state, and a transverse tear in the corpus cavernosums may occur by a buckling force. However, penile dorsal vein tears may mimic penile fracture. Also, corporeal infection and purulent cavernositis are associated with trauma, cavernosography, priapism, intracavernosal injection therapy and penile prosthesis.