Cavernosal artery

Pharmacology Alprostadil induces erection by relaxation of trabecular smooth muscle and by dilation of cavernosal arteries. 

Mechanism of Action A prostaglandin that directly affects vascular and ductus arteriosus smooth muscle and relaxes trabecular smooth muscle. Therapeutic Effect Causes vasodilation dilates cavernosal arteries, allowing blood flow to and entrapment in the lacunar spaces of the penis. 

Alprostadil. Alprostadil is chemically identical to the naturally occurring form of prostaglandin E and acts similar to the endogenous PGE. It induces erection by relaxation of the cavernosal smooth muscle and dilation of cavernosal arteries, which leads to increased arterial inflow and decreased venous outflow. Alprostadil has various systemic... 

Sexual function Unilateral intracavernosal papaverine was associated with increased blood flow and increased cavernosal artery peak systolic velocity on the side of the injection compared with bilateral administration and 5 of 60 patients developed priapism, which was managed successfully with aspiration of blood and irrigation of the corpus cavemosum with isotonic saline [162%... 

Subtunical space Cavernosal artery Erectile tissue... 

Several penile vessels can be identified at greyscale ultrasound as well. In particular, the cavernosal arteries appear as a pair of dots located slightly medially in each corpus cavernosum. On longitudinal scans they present as narrow tubular structures with echogenic wall (Quam et al. 1989). The diameter of the normal cavernosal arteries ranges from 0.3 to 05 mm in the flaccid state and increases to 0.6-1.0 mm after an intracavernosal injection of vasoactive agents (Fig. 5.4). 

During the onset of erection, cavernosal artery pulsation is evident in normal subjects (Lee et al. 1993 Kim 2002). The dorsal arteries are visible in the dorsal aspect of the shaft as anechoic structures with a similar diameter to the cavernosal arteries. As occurs for the cavernosal arteries, also the diameter of the dorsal arteries increases during erection, but to a lesser extent compared with the cavernosal arteries (Lee et al. 1993). Dorsal veins present with less echogenic wall compared to the arteries. 

Fig. 5.4a,b. Normal grey-scale ultrasound anatomy. Longitudinal scans obtained on the ventral aspect of the penis showing the cavernosal artery (open arrows) while flaccid a and during the onset or erection b. The artery presents as a narrow tubular structure with echogenic wall whose diameter increases during erection... 

Common anatomical variations of penile arteries include asymmetry, bifurcated cavernosal artery, multiple cavernosal arteries, presence of recurrent branches, unilateral origin of all cavernosal branches, accessory cavernosal branches, and aberrant origin from the dorsal artery (Fig. 5.5). Occasionally the cavernosal artery consists of multiple short, rapidly tapering segments, periodically reconstituted by perforating vessels from the dorsal penile artery (Juskiewenski et al. 1982 Wahl et al. 1997). 

Fig. 5.5a-c. Anatomical variations of cavernosal arteries at color Doppler ultrasound, a-c Longitudinal scans on the ventral aspect of the penis showing a bifurcated cavernosal artery (arrowheads), b recurrent cavernosal branch (curved arrow), and c accessory cavernosal artery (open arrow)... 

Fig. 5.9a,b. Color Doppler appearance of arterial communications (arrowheads) among the penile arteries. Axial scans on the ventral aspect of the penis, a Communication between the right cavernosal and urethral artery, b Communication between the right dorsal and cavernosal artery... 

A variety of arterial communications is appreciable among the different arteries ofthe penis. In particular, communications between the cavernosal arteries are identified in virtually all patients. Arterial communications between the cavernosal and the urethral artery, between the cavernosal artery and the arteries of the hulb of the corpus spongiosum, and dorsal penile-cavernosal perforators are less common (Fig. 5.9). 

These vessels are either arterovenous shunts connecting the cavernosal arteries with the corpus spongiosum (Wagner et al. 1982) or, more likely. 

At color Doppler ultrasound cavernosal-spongiosal communications are recognized as vessels branching from the cavernosal artery that run to-... 

Fig. 5.12a-f. Normal waveform changes in the cavernosal arteries during the onset of erection, a Phase 0. Monophasic flow with minimal or no diastolic flow occurring in the flaccid state, b Phase 1. Increased systolic and diastolic flow, c Phase 2. Dicrotic notch appearance at end systole and progressive decrease of the diastolic flow, d Phase 3. End diastolic flow disappearance, e Phase 4. Diastolic flow reversal, f Phase 5. Reduction of the systolic peak during rigid erection... 

Also in these vessels characteristic changes are recognized reflecting waveform changes within the cavernosal arteries (Bertolotto et al. 2002). In particular, within the corpus cavernosum caverno-sal-spongiosal communications have arterial wave-... 

Gain and power settings should be optimized so that all structures of the penis are appreciable. Harmonic imaging and 3D reconstruction techniques can be used, if available, but they are not mandatory for the diagnosis even though they can offer a more detailed image of the small post-cavernosal arteries, which are frequently compromised in subjects with diabetes or systemic arterial disease. 

Topical applications of drugs can increase PSV by 15 to 22 cm/s (Kim and McVary 1995). Also the mean cavernosal artery diameter has been reported to increase by 0.9 to 1.1 mm. The highest flow veloc-... 

Following identification at color Doppler ultrasound, the cavernosal vessels are interrogated. Pulse-wave (PW) duplex Doppler is turned on putting the sample volume on the cavernosal arteries. The spectral analysis is preferably performed at the base of the penis where the Doppler angle is particularly favorable (between 30° and 50°) and the flow velocity shows major reproducibility and correctness (Mills and Sethia 1996). The flow velocity must be measured repeatedly (at least three times) at the same level and the mean value reported. Functional studies have shown a progressive decrease of blood velocity in the cavernosal arteries from the base to the glans penis... 

The morphological aspects to define with grey-scale ultrasonography are the presence of calcifications and kinking of the cavernosal arteries diameter and size changes of the cavernosal arteries before and after pharmacological injection distension and texture of the erectile tissue evaluated before and during erection. 

In older patients, and in those suffering from diabetes or chronic renal failure, microcalcifications in the wall of the cavernosal arteries are frequently detectable and are the expression of calcium deposits in atheromatous endothelial plaques (Fig. 6.2) or in the tunica media as observed in subjects on chronic hemodialysis (Fig. 6.3). 

Measurement of the diameter changes in the cavernosal arteries after drug injection is clinically more useful since it expresses the stiffness of the arterial wall. In normal subjects there is normally a 75 to 120% increase in size of the vessels whose diameter is of 0.5-0.7 mm at rest and 1-1.2 mm after stimulation. This measurement is performed using the maximum electronic magnification of the scanner to reduce errors due to incorrect positioning of the electronic calipers (Chiou et al. 1999). 

Fig. 6.4. Transversal scan. Asymmetric distension of the corpora cavernosa secondary to obstruction of the left cavernosal artery...

Fig. 6.2. Longitudinal scan. Thickening of the cavernosal artery wall with calcifications (arrowheads) in a patient with diabetes...

Fig. 6.3. Longitudinal scan. Diffuse small calcifications of the cavernosal arteries (arrowheads) in a patient in chronic hemodialysis...

Fig. 6.5. Longitudinal scan. Reduced distension with calcifications (arrowheads) and stenosis of the cavernosal artery in severe arteriogenic erectile dysfunction...

Color imaging is fundamental to identify the cavernosal arteries and to detect the presence and direction of flow, especially in patients with reduced distension of the vessel (Fig. 6.5) after drug stimulation (Mancini et al. 2000). The vessel kinkings, stenosis... 

Because of extensive arterial lesions, the flow in the elicine arteries is reduced (Fig. 6.9), and sometimes the distal part of the cavernosal arteries is not visualized because of reduced flow velocity (Sarteschi et... 

Fig. 6.6. Color Doppler in transversal scan after pharmaco-stimulation showing differences in size between the cavernosal arteries. The left artery (curved arrow) is smaller in diameter with reduced flow velocity...

Fig. 6.7. Transversal scan. Complete obstruction of the right cavernosal artery with no flow detectable ( ). Normalappearing left cavernosal artery (curved arrow)...

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