Factors that prevent the erectile tissue from fully filling with blood usually have to do with problems of arterial blood flow to the penis. Factors that tend to prevent initiation of an erection usually involve the nerve supply or can be psychological. No matter what the causes of erectile dysfunction, we need to keep in mind the basic principles of the nerve and blood vessel mechanisms discussed in the previous chapters. No one who has failed to initiate or maintain an erection on one occasion can keep from thinking "what if the erection fails the next time they want to have sexual intercourse. On the other hand, it is virtually impossible that impotence, even with an underlying physical cause, won't have an impact on a man's psychological well-being. Although the psychological component remains a very important factor in diagnosis and treatment, we now know that at least 80 percent of men who seek medical care for erectile dysfunction will have primary physical problems. However, after twenty-five years of advances in the understanding of neurogenic and vascular physiology, we have much better knowledge of the mechanisms of erectile dysfunction. The noted sex therapy experts Masters and Johnson reported that 90 percent of impotent men suffered from a psychological problem.

The causes of male erectile dysfunction fall into two general categories: physical (or organic), and psychological. In the next chapter, we will look at the specific causes of erectile dysfunction, and then in the following chapters we will review the various treatments now commonly available. We have also seen that male erectile dysfunction is just one of several problems that come under the category of male sexual dysfunction. With the availability of the new noninvasive oral medication, Cialis, we expect more men to come forward with this symptom. We have seen in this chapter that impotence, now commonly referred to as erectile dysfunction, is defined as the inability to initiate and maintain an erection adequate for normal intercourse. Along this same vein, as patients are now well aware of Cialis and its benefits, hopefully they will be less hesitant to bring up their problems with erectile dysfunction to their primary care doctor. Most men complaining of erectile dysfunction have at least one, and sometimes several, of the following problem areas: blood flow problems, nerve problems, diabetes, prior surgery, drugs, pelvic trauma or pelvic radiation, Peyronie's disease, and psychological problems. We can easily see that a breakdown in any one of these areas can result in erectile dysfunction. Factors that lead to loss of the erection before orgasm and ejaculation tend to involve failure of the venous occlusive mechanism that, as we have seen, traps blood in the penis and thus maintains the erection.