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Penile Venous Anatomy: An Additional Description and Its Clinical Implication

From the Microsurgical Potency Reconstructive Center, Taipei Medical University Hospital, Taiwan Adventist Hospital and Po-Jen General Hospital, Taipei, Taiwan, Republic of China.

Correspondence to: Dr Geng-Long Hsu, Microsurgical Potency Reconstructive Center, Taipei Medical University Hospital, 252 Wu-Hsing St, Taipei 110, Taiwan, Republic of China.

Received for publication April 29, 2003; accepted for publication July 11, 2003.

	Abstract

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The human penile venous system has been well studied and described but the demonstration of extra venous channels in imaging films prompted us to seek refinement of our anatomical knowledge of this venous system. Cavernosography in 37 patients who had venous stripping surgery and now suffered recurrent erectile dysfunction consistently showed an independent vein, smaller than the deep dorsal vein, running almost in the same position of the deep dorsal vein even though the latter had been removed unequivocally in previous surgery. Cavernosography in 9 patients who underwent intraoperative films also demonstrated the presence of this cavernosal vein in addition to the deep dorsal vein. Meticulous dissection of the penis under the microscope was then performed in 21 male cadavers and we found a cavernosal vein coursing along each corpus cavernosum all the way distally to the glans and draining directly into the Santorini's plexus in 19 subjects. This is in contrast to the previous description that this cavernosal vein was a short vein in the penile hilum. Two sets of para-arterial veins, which have not been reported in the literature, were found to accompany each dorsal artery in all 21 subjects. This more extensive and extra venous drainage might have important implication for venous stripping surgery in the treatment of erectile dysfunction.

     Key words: Deep dorsal vein, cavernosal vein, para-arterial vein, corpus cavernosum, tunica albuginea

View larger version (112K): [in this window] [in a new window]   Figure 1. Evidence of additional vein. (A) The deep dorsal vein (DDV, black arrow) is clearly seen in a preoperative cavernosogram of a 57-year-old patient who underwent penile venous stripping surgery in November 1999. (B) A follow-up film discloses a smaller DDV-like vein (arrowhead) in spite of the fact that the DDV system had been totally removed. The vein was found to be the cavernosal vein during the second venous operation in July 2001. The opacification of the corpus spongiosum (white arrow) denotes that it became an important route for venous drainage after the DDV was removed.

	Materials and Methods

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From March 1999 to May 2001, 37 patients who had previous venous stripping surgery in which the deep dorsal vein (DDV) system had been removed totally (Vale et al, 1995; Hsu et al, 2003), but the cavernosal vein system was inadvertently left intact for erectile dysfunction with good immediate functional results were seen in our clinic for gradually diminishing erection ability over 6 months to 7 years. The abridged 5-item version of the International Index of Erectile Function (IIEF-5) scoring was used to assess the erectile function of these patients who showed a preoperative score of 9.3 ± 4.1 and a postoperative score of 11.1 ± 4.3, which is indicative of impotence. Cavernosography in which 60 mL of 30% (diluted from 68%) loversol (Optiray, Pointe-Clair, Quebec, Canada) solution was injected intracavernously via a 21-gauge scalp needle were performed on these patients. In addition, 9 new patients with veno-occlusive dysfunction who were undergoing venous stripping surgery received intraoperative cavernosography immediately after the DDV system was removed.

From November 2000 to January 2003, meticulous dissections freeing all the tissues superficial and deep into the Buck's fascia under the microscope were done on the penis of 21 male cadavers. These tissues, including the deep dorsal vein, cavernosal veins, para-arterial veins, circumflex veins, dorsal nerves, and dorsal arteries were then carefully freed from the coronal sulcus all the way to the infrapubic angle, which had been exposed with a saw to separate the pubic symphysis.

The length of the deep dorsal vein was measured from the coronal sulcus of the glans to the infrapubic angle immediately distal to the Santorini's plexus. To measure its circumference, the deep dorsal vein was detubularized at the level of the infrapubic angle. Similarly the deep-seated cavernosal vein was identified and traced as distally as possible and then measured.

Methylene blue solution was injected into the corpus cavernosum until the deep dorsal vein and the cavernosal veins were stained. Serial sections 1 cm apart were taken from the tip of the penis and continued proximally until a complete septum was encountered. Each cut surface was examined for the neurovascular distribution and the length of the tunica albuginea was measured from the 3 to 9 o'clock position (designated as distance A) and from the 6 to 12 o'clock position (designated as distance B). The diameter (D) of the penis is calculated as (A + B)/2 and the circumference is derived from D. To assess the flow of the venous drainage, the circumference ratio is calculated by adding the circumferences of the deep dorsal and cavernosal veins and then dividing this sum by the circumference of the corpus carvernosum. All tissue blocks were stained with hematoxylin and eosin, alcian blue, periodic acid Schiff, Masson trichrome, Victoria blue, and orcein stain and examined under light microscopy.

	Results

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Cavernosographies (Figure 1A and B) of the 37 return patients with recurrent erectile dysfunction showed an independent, smaller vein running in almost the same position as the deep dorsal vein even though the latter had been removed in previous surgery. This vein is now identified as the cavernosal vein (Figure 1B).

Cavernosography (Figure 2) done in each of the 9 new patients showed that the deep dorsal vein served as a common vessel receiving blood drained from the corpora cavernosa through numerous emissary veins and from the corpus spongiosum via a number of circumflex veins. This finding correlated well with the dissection in cadavers in whom the deep dorsal vein took on varied course at the proximal end close to the infrapubic angle assuming a railtrack formation or in the shape of "Y" or inverted "Y" with the emissary veins draining from the cavernosal sinusoids. In all the patients, the carvernosal vein was demonstrable in either the early phase of cavernosography (Figure 2A) or in the pharmacocavernosography (Figure 2B) but not in the spongiosography.

View larger version (109K): [in this window] [in a new window]   Figure 2. Preoperative cavernosograms. (A) An early phase of the cavernosograms before the 20 µg of prostaglandin E1 was injected intracavernously. The deep dorsal vein (arrow), as well as the cavernosal vein (arrowhead), are readily seen. The notchlike appearance of the para-arterial vein is conspicuous in the distal portion of the penis. Note the scalp needle in situ and the presence of circumflex veins. (B) Pharmacocavernosogram taken 30 minutes after the intracavernous injection of 20 µg of prostaglandin E1. Note that the deep dorsal vein (arrow) is opacified despite the existing rigid erection. The cavernosal vein (arrowheads), although much smaller, is very close to the sinusoids because of its exceptional proximity to the tunica albuginea. It will be seen readily if the deep dorsal vein is removed.

In the 21 cadavers the circumference of the corpora cavernosa was found to range from 4.71 to 7.15 cm. Circumferences of the deep dorsal vein and the carvernosal vein ranged from 0.6 to 1.3 cm and from 0.2 to 0.76 cm, respectively. Interestingly, in those with the circumference ratio less than 25%, para-arterial veins were quite conspicuous and easy to find. This seems to imply that the sizes of these drainage veins are commensurate with the volume of the corpora cavernosa.

The ratio between the length of the cavernosal vein and that of the deep dorsal vein was greater than 63% in 18 out of the 21 cadavers and less than 41% in the other 3. As shown schematically (Figure 3) the cavernosal vein was found coursing along each corpus cavernosum extending distally to the glans and it is situated between the dorsal artery and the deep dorsal vein but deeper to the latter one and within a different perivascular sheath, lying intimately on the tunica albuginea and receiving direct emissary venous drainage. In all 21 cadavers the cavernosal veins constituted an independent drainage directly into the Santorini's plexus. The cavernosal vein was asymmetrical bilaterally both in its size and course, but they consistently merge into a single channel before entering into the Santorini's plexus. In all the cadavers, 2 sets of para-arterial veins (Figure 4) were found accompanying the dorsal artery. These veins were quite prominent distally with the medial one receiving emissary drainage from the corresponding corpus cavernosum and the lateral one occasionally (in 7 out of the 21 subjects) having its own circumflex vein from the corpus spongiosum. In 17 cadavers the para-arterial veins drained into the deep dorsal vein close to the infrapubic angle and in the other 4 subjects the para-arterial veins entered the pelvis independently.

View larger version (60K): [in this window] [in a new window]   Figure 3. Schematic illustration shows the erection-related vein in the human penis. (A) Lateral view. The deep dorsal vein consistently in the median position receives the blood of the emissary veins from the corpora cavernosa and of the circumflex vein from the corpus spongiosum. It is sandwiched by cavernosal veins, although these lie in a deeper position. Bilaterally, each dorsal artery is sandwiched by its corresponding medial and lateral para-arterial veins. Note that the lateral para-arterial vein merges with the medial vein proximally. The deeper color of the veins indicates the deepest group of the vasculature. (B) Cross section of the mid-portion. Note that there are 7 veins rather than the traditionally described 1, although there are 4 veins at the level of penile hilum because merging takes place in each pair of the nomenclature veins. The erection-related veins are arrayed in an imaginary arc on the dorsal aspect of the tunica albuginea.

View larger version (121K): [in this window] [in a new window]   Figure 4. Photographs of the human penis. (A) At the level of the retrocoronal sulcus. The neurovascular bundle lies intimately on the dorsal aspect of the tunica albuginea (TA). The left dorsal artery (LDA) and the right dorsal artery (RDA) are located at the 3 and 9 o'clock positions, respectively. Note that the distribution of veins looks like a battery of gunshots. The number of veinlets is numerous and may be as high as 29 clinically. The medium septum is incomplete and fenestrated, whereas the intracavernosal pillar (ICP) is arranged laterally. (B) In the mid-pendulous portion. Each dorsal artery is sandwiched with the medial para-arterial vein (MPAV) and lateral para-arterial vein (LPAV), respectively. The central-positioned deep dorsal vein (DDV) is sandwiched with the left cavernosal vein (LCV) and right cavernosal vein (RCV). (C) Cross section at the level of penile hilum. The deep-seated RCV and LCV lie closely to the tunica. The RDA and LDA are thicker in its wall. The medium septum becomes complete earlier. (D) A laterodorsal view of the penis. The DDV trunk (asterisk) is pulled upward with a green suture, whereas the CV remains deeper position within a different perivascular sheath all the way to the glans penis distally and to the infrapubic angle proximally. Note the pubic rami (white diamond). (E) Dorsal view of the penis in another subject. The DDV and CV are tagged with a green suture, whereas the arteries are encased with a reddish suture and the nerves are tagged with a yellow suture. It is clear in the picture that DDV existing bifurcation (asterisk) and CV are separate vessels both at distally and proximally (bottom). The skin level is indicated (arrows). Two of the entering vessels of the Santorini's plexus are retracted with blue sutures.

	Discussion

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The tunica albuginea of the corpora cavernosa is a bilayered structure with multiple sublayers through which emissary veins pass (Hsu et al, 1992), whereas the subtunical venous plexus collects sinusoidal blood via the emissary veins (Banya et al, 1989). No corresponding venous vasculture is found subtunically to the cavernous artery, which is the major arterial supply to the corpora cavernosa. Thereafter, we could regard the sinusoids of the corpora cavernosa as an end-artery organ just like the well-recognized retina and kidney in the human body.

Interestingly, in our dissection, the majority of the emissary veins were found to run in an oblique course between the inner and the outer layers of the tunica albuginea, whereas the arteries took a more direct route through the tunica. The veins, therefore, play a passive and yet overwhelmingly important role in penile erection. It is not unusual to see 2 venous channels of the same emissary vein appearing at the transition between the inner circular and the outer longitudinal layers of the tunica albuginea when a cross section is performed at the bifurcation point of the emissary vein, in which an unusual lateral position as well as tortuous venous routes were demonstrated in a recent study by scanning electron microscopy (Hsu et al, 1994). This earlier finding is further confirmed by the present study.

The neurovascular bundle lies on the dorsal aspect of the corpora cavernosa and it takes on the shape of the tunica albuginea, being convex distally and gradually becoming concave at the proximal end (Baskin et al, 2000). At the level of the retrocoronal sulcus the para-arterial veins, dorsal arteries, and the deep dorsal vein can be seen to lie in the arc of an imaginary line with the cavernosal vein lying deeper to the dorsal artery and the deep dorsal vein in intimate contact with the underlying tunica. Proximally the dorsal artery rises (Figure 4C) above this imaginary line, whereas the deep dorsal vein gradually dives into a position deep to the artery, and the cavernosal vein is maintained in a position deeper to the deep dorsal vein surfing above the tunica albuginea and entering the Santorini's plexus.

The cavernous vein, which is regarded as the deep vein system of the penis, has been traditionally described in the literature as being short, running in the proximal portion of the penis (Tudoriu and Bourmer, 1983; Aboseif et al, 1989; Breza et al, 1989), but in our study a venous system was found to course almost the entire length of the corresponding corpus cavernosum, even though it becomes smaller distally. This vein sends a communicating vein, which may be bigger than itself, to the deep dorsal vein and numerous, albeit small, emissary veins proximally to the corpora cavernosa. It is housed within a perivascular sheath different from that of the deep dorsal vein; consequently, it deserves the term of cavernosal vein. Moreover, it leaves the penile tissue and enters independently to the Santorini's plexus; therefore, it should not be regarded as a branch of the deep dorsal vein. Once the deep dorsal vein is completely removed, the cavernosal vein becomes more readily identifiable. Distally, the cavernosal vein is prone to bleeding during surgery if its removal is attempted, not only because of its relationship to the sinusoids but also because of its fragility. In addition, the close proximity of the cavernosal vein to the corpus cavernosum can make it difficult for the surgeon to distinguish venous from arterial bleeding during surgical manipulation. The anatomical relationship of the cabernosal vein to the sinusoids mimics a grapevine with cluster of grapes and irreversible intracavernosal fibrosis may result if cauterization is applied to the venous stump of the emissary vein during surgery. Not surprisingly, erectile dysfunction may ultimately ensue.

The para-arterial veins that were found consistently in all the cadavers in this study have not been previously reported in the literature. These veins were prominent in the pendulous portion of the penis, with the medial one communicating with the glanular sinusoids and cavernosal vein, and the lateral one communicating with the glans and, in some cases, with the corpus spongiosum directly via its own circumflex vein. These para-arterial veins became greatly engorged when the cavernous sinusoids were squeezed after filling with methylene blue solution. This implies that a substantial amount of sinusoidal blood can drain into these veins via the emissary veins. Thus, both the cavernosal and the para-arterial veins play an important role in the circulation of the cavernosal sinusoids.

The number of veinlets at the level of the retrocoronal sulcus varied greatly and could be numerous. This retrocoronal plexus could be seen to merge variedly with the deep dorsal vein, the cavernosal vein, or the para-arterial veins. Such extensive and varied venous communications would imply that collateral circulation could readily develop if the stripping of these veins were not complete. During cadaver dissection, these veinlets are very susceptible to injury from instruments because of their thin walls. In our experience during surgery, having an assistant compress the cavernosal and the glanular sinusoids to control bleeding facilitates surgical dissection and hemostasis.

The dorsal artery spreads out laterally gradually as it goes distally. At the level of the retrocoronary sulcus the left and the right arteries are located at the 3 and 9 o'clock positions respectively; however, the dorsal artery may send branches to course centrally at the 11 to 1 o'clock positions (Figure 4A). During dissection, the use of a microscope is very helpful in differentiating the artery from the vein without the necessity of special stain.

In penile anatomy, it is commonly believed that a single deep dorsal vein and a pair of dorsal arteries are located between the tunica albuginea and Buck's fascia. This seems to provide an exception in human anatomy in that the number of veins is less than the number of arteries. However, in this study, it was found that each of the dorsal arteries is sandwiched by a medial and a lateral para-arterial vein, and the deep dorsal vein is accompanied by the cavernosal veins, which are housed in their own perivascular sheath. Hence, the penile vascular system still complies with the general rule in the body in that the number of veins is normally greater than that of the arteries.

	Acknowledgments

 
We would like to thank Prof S. M. Wang, Chairman of the Department of Anatomy, National Taiwan University, and Associate Prof T. H. Fong, Chairman of the Department of Anatomy, College of Medicine, Taipei Medical University, who made cadaver specimens available for this work.

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