Erectile physiology, etiology, work-up and treatment of erectile dysfunction, psychological counselling

One of the essential recommendations to come from a National Institute of Health Consensus Development Conference on Impotence held in December 1992 was to educate health care providers and the public on aspects of human sexuality, sexual dysfunction, and availability of successful treatment. Impotence, or to use the more appropriate term, erectile dysfunction, affects approximately 30 million American men. It is only over the last decade that the rigors of a more scientific approach to this dysfunction of the corporeal cavernosal tissue have begun to unlock some of the causes of and treatment for this disorder. This effort was the result of interaction between multidisciplined clinical specialists, and basic scientists.

Anatomy and physiology
An erection is a psychosomatic-dependent event -an integration of several mutually occurring actions in several different systems (vascular, endocrine, and neurologic). Three sets of peripheral nerves have a role in erectile function: thoracolumbar sympathetic, sacral parasympathetic and sacral somatic. The most important neurotransmitter in initiation of penile erection may be nitric oxide, also known as endothelium-derived relaxing factor. The spongy erectile tissue is located in paired cylinders, called corpora cavernosa, which are located on the dorsum of the penis. The internal pudendal artery, which generally arises from the anterior division of the hypogastric or internal iliac artery, is usually the source for the penile arteries (Fig.1). The corpora cavernosal sinus tissue is supplied by a slightly eccentric central vessel (the cavernosal artery), which is derived from the pudendal artery, and branches to form the helicine arteries (Fig.2). The sinus spaces drain into a system of venules that coalesce on the outer surface of the cavernous tissue just beneath the tunica albuginea or lining of the corpus cavernosum. These venules form a number of veins traversing the tunica albuginea called emissary veins, which usually drain into the circumflex veins on the outer surface of the tunica albuginea, that in turn drain into the deep dorsal vein of the penis located in the dorsal midline of the penile shaft (Fig. 2, 3A). Functionally, in the flaccid condition, there is a high-resistance, low-flow arterial state in the cavernous tissue, primarily regulated by the contracted smooth muscles surrounding the cavernous spaces. Intracavernous pressure in this flaccid state is usually equal to resting venous pressure. With the initiation of erection, relaxation of the sinus and arterial smooth muscle occurs and a low-resistance system is produced with blood flow increasing to 6 -10 times that of the flaccid state. As the sinus spaces expand, the subtunical venules are collapsed beneath the tunica albuginea. The emisary veins are also further collapsed by the expanding tunica albuginea so that venous efflux is markedly decreased and intracavernous pressure rises to 80 to 100 mm Hg, which is the pressure necessary for rigidity (Fig.3B).

Diagnosis
The causes of male erectile dysfunction have traditionally been separated into two broad areas, organic and psychogenic. For the most part, this is a rather difficult distinction because the impact of this disorder on the psychological state of the patient is devastating and can make treatment directed at a specific physical defect difficult. Similarly, psychological disease such as depression may result in changes in the internal chemical milieu that produce a true organic effect on the cavernosal tissue. Organic causes of impotence can be classified as hormonal, neurogenic, vascular (arteriogenic or venogenic), or muscular, the latter involving disease of the smooth muscle of the cavernous sinus or tissue.

It is impossible to discuss diagnostic steps without stressing how this process is tailored for each individual and his partner. Not every step is necessary for each patient. The various diagnostic steps will be presented as information about what is available for the modern evaluation of this disorder. As with other disease evaluations, taking a history of the disorder for each individual is paramount before making any further diagnostic plans (Table 1). Physical evaluation should concentrate on the genital and rectal examination (Table 2). An evaluation of the psychological status of the patient is a crucial early step in the diagnostic process.

Laboratory studies generally obtained in all patients are serum testosterone and prolactin levels and urinalysis. Other laboratory tests are tailored to the patient and include: complete blood count and serum chemical profile in the patient who has not had these recently; fasting blood sugar or glycosylated hemoglobin in patients with a family history of diabetes or who have this disease and are unsure of their current disease control; lipid profiles in patients with family history of lipid disorders or with other vascular disease history, and certain other endocrine evaluations when history or physical examination suggests the possibility of an endocrine disease. Many consider the evaluation of nocturnal erection mandatory by either a home monitoring machine or in a formal sleep laboratory. All agree that these studies are useful in patients when a psychological cause is thought to be the primary etiology of the erectile dysfunction, or a major sleep disorder is suspected from the history.

Measuring the erectile response of the patient to an intracavernous injection of a smooth muscle relaxant has become an important tool in the evaluation of erectile dysfunction. A full erectile response that lasts for thirty minutes is usually indicative of no major vascular nor sinus smooth muscle disease. A lack of response does not definitely establish organicity of the erectile dysfunction. Some patients with psychologic-based impotence or patients who are apprehensive in the testing situation will not respond with a full erection. Other more sophisticated diagnostic studies, some of which are, more invasive are listed in Table 3. These other tests are more important for those patients who are considered candidates for more invasive therapeutic choices (e.g., arteriography if you are considering a revascularization procedure). As mentioned above, the diagnostic workup is directly controlled by the therapeutic goal decisions made by the patient and his partner.

Treatment
Today the focus of the physician who treats erectile dysfunction is to identify the probable primary etiologies of the condition in the individual patient and to design a therapeutic regimen that will deal with the physical and psychological aspects of the disease. Successful treatment for male erectile dysfunction depends on the motivations and goals of the patient and his partner.

Rarely an endocrine or hormonal primary etiology is found and this problem is best managed by the endocrinologist. Treatment may consist of parenteral testosterone therapy or therapy directed at specific endocrine disease. If the patient is a diabetic with poor control of his disease, sometimes return of this control will improve erectile function. Treatment of other conditions such as prostatitis, sleep disorders or hyperlipidemia sometimes leads to improvement in sexual function. Modification of medications, such as certain antihypertensives, or avoidance of substances such as tobacco and other drugs may be the most appropriate therapeutic intervention. Success with such oral medications, such as vitamin E or yohimbine has been anecdotal or not statistically verified in placebo-controlled trials. Intraurethral delivery of vasoactive agents is currently being studied. If psychological disease or disorder is the underlying etiology, the psychiatrist or sexual therapist becomes the primary caregiver for the patient and his partner.

Vacuum/constriction devices are a therapeutic choice for almost any type of erectile dysfunction. They have become very popular as the first choice of therapy with very little risk for the patient, since these are purely external devices. Proper expectations from the devices and ongoing availability of the physician to answer questions about the device are important for success of this treatment.

lntermittent home self-injection therapy with smooth muscle relaxants is the only accepted pharmaceutical therapy directed at the cavernosal tissue. The agents most commonly used for injection therapy are papaverine with or without phentolamine, prostaglandin E-1, or a combination of the three. These agents relax arterial and sinus smooth muscle tissue converting the corpora cavernosa to a low resistance, high flow system, and mimicking natural erection. Priapism (prolonged erection) and intracavernous fibrosis are the potential complications from this type of therapy, but with proper controlled use, these complications are neither common nor serious. This therapy has become quite popular worldwide and has proven effective for patients with neurogenic impotence (who are quite sensitive to very low doses of the medication), medication-associated impotence, diabetes mellitus, minor or even moderate arteriogenic erectile dysfunction, and, under some controlled situations for patients with primarily psychogenic erectile dysfunction.

Penile prostheses have been available as a treatment option for almost two decades now and have been placed in approximately 250,000 men in the United States. They are basically inflatable or noninflatable rigid or semi-rigid devices. The material that makes up most of these devices is solid silicone, not gel; polyurethanes are contained in one product. They are reliable (particularly with improved engineering) and resistant to wear. Nevertheless, they are prosthetics and are not guaranteed for life. Reoperation because of mechanical or surgical complications such as infection realistically occurs in 10-15% of patients over a 5-10 year period. Since this therapy is essentially non-reversible, the patient and partner should be carefully told what the prosthesis can and cannot do, and the risks of reoperation and infection. Studies of patient and partner satisfaction, although infrequently reported in the literature, indicate high satisfaction for these prosthetic devices.

Vascular surgery, either arterial revascularization or venous ablation surgery, have been presented as an option for treatment in a highly selected group of patients. Long-term success with this type of surgical intervention is still lacking and, for the most part, this surgery should be performed in centers with experience in this type of procedure.

The Future
What we know today about erectile dysfunction has only begun to scratch the surface. Some of the basic physiology and anatomy of the corpora cavernosa tissue remains to be discovered; pathophysiological details of erectile dysfunction are needed, particularly in regards to the function and integrity of the sinusoidal smooth muscle. The epidemiology of and risk factors for erectile dysfunction are also poorly understood.

Suggested Readings

de Groat WC, Steers WD. Neuroanatomy and neurophysiology of penile erection. In: Tanagho EA, Lue TF, McClure RD, eds. Contemporary Management of Impotence and Infertility. Baltimore: Williams and Wilkins; 1988:3-27.

Krane RJ, Goldstein I, de Tejada IS. Impotence. N Engl J Med 1989;321:1648-1659.

Lewis RW. Erectile dysfunction. In: Stein B, ed. Practice of Urology 1993 UPDATE. Pennsylvania: W. W. Norton & Company; 1993:21-38.

Lue TF. Impotence: a patient's goal-directed approach to treatment. World J Urol 1990;8:67-74.

Lue TF. Tanagho EM. Physiology of erection and pharmacological management of impotence. J Urol 1987; 137:829-836.