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Anomalous vascular anastomoses between the peripenile circulation and the erectile tissues of the CCP result in shunts that allow blood from the CCP to exit the erectile tissues and destroy the integrity of the closed hydraulic system necessary for complete erection [27]. Vascular shunts may occur as a congenital anomaly or form following an injury that disrupts the integrity of the tunica albuginea of the penis. Regardless of etiology, when erection is stimulated at a test breeding or with an electroejaculator, partial erection and protrusion of the glans penis is initiated followed by loss of intrapenile pressure and failure to achieve full erection.

Vascular anastomoses between the CCP and extracorporeal vasculature found in the distal free portion of the penis are usually multiple and result from congenital flaws in the integrity of the tunica albuginea [28]. As blood escapes through these distally located shunts at the time of sexual stimulation, “blushing” of the preputial tissues may be observed as blood from the CCP enters the venous circulation beneath the preputial skin. A presumptive diagnosis may be made following observation of a test mating or attempts to induce erection with an electroejaculator. Confirmation requires demonstration of the shunts with radiographic contrast studies in which radiopaque contrast media are injected directly into the CCP as serial radiographs are taken. In the normal penis the contrast media remain within the CCP until eventually exiting at the crura of the penis (Figure 15.12). Visualization of the contrast media within the peripenile vasculature outside the CCP is diagnostic (Figure 15.13). Demonstration of anomalous vessels in the distal portion of the penis may be enhanced by occlusion of the distal peripenile vessels by application of a tourniquet to the penis proximal to the location of the shunt(s) [29]. Unlike acquired vascular shunts of the CCP, congenital shunts are seldom amenable to surgical correction.

Figure 15.12 Normal cavernosogram. Contrast media injected into the CCP at the level of the free portion of the penis remain within the CCP. The ventral canals and cavernous spaces are clearly outlined.

Figure 15.13 Cavernosogram demonstrating multiple shunts from distal cavernous spaces to the peripenile vasculature.

Source: Courtesy of Robert L. Carson and Dwight Wolfe.