Erectile Dysfunction

(Impotence)

The inability to develop and sustain an erection sufficient for satisfactory sexual intercourse in 50% or more attempts at intercourse.

Once a rarely discussed topic, erectile dysfunction is now a topic of general conversation. Awareness and openness have been driven in large part by the availability of new treatments and the coverage of these treatments by the media.

Erectile dysfunction may occur from time to time at any age for a variety of reasons. However, the incidence of persistent erectile dysfunction increases with age. The prevalence is about 52% among men aged 40 to 70 and even greater among older men. The prevalence is nearly 95% among men > 70 who have certain medical disorders such as diabetes.

Physiology

Penile erection is accomplished through engorgement of the corpora cavernosa, two spongiform, intercommunicative, highly vascular bodies surrounded by a tough, fibrous sheath (the tunica albuginea). The parenchyma of each corpus cavernosum consists of trabecular smooth muscle with a network of endothelial cells that line vascular spaces and helicine arteries. The combination of vascular engorgement and ischiocavernous muscle contraction leads to rigidity. Erection occurs when arterial blood flow into the corpora cavernosa exceeds venous outflow. The pudendal artery supplies blood to the corpora, and blood flow is controlled by relaxation and contraction of arterial smooth muscle, which in turn is under the influence of a variety of neurotransmitters such as nitric oxide, vasoactive intestinal peptide, and neuropeptide Y. When the smooth muscle relaxes, arterial filling occurs.

Venous drainage occurs through venules below the tunica albuginea. Unlike other venous structures, penile venules have no valves; these venules close by compression against the tunica, as the corpora fill with blood.

The T11 through L2 (sympathetic) nerves, S2 through S4 (parasympathetic) nerves, and somatic nerves (sensory and motor) innervate the penis.

Etiology and Pathogenesis

Causes of erectile dysfunction include vascular, neurologic, and endocrine disorders; structural abnormalities of the penis; the adverse effects of drugs; and psychologic disorders. It is most common to have more than one cause of erectile dysfunction (multifactorial etiology).

Vascular disorders: Of all causes of erectile dysfunction, vascular disorders are the most common among the elderly. This is not surprising for a population in whom atherosclerotic disease is prevalent. Arterial insufficiency, excessive venous outflow, or both can affect sexual function. Arterial disease is the most common finding, especially in elderly men with hypercholesterolemia, diabetes, peripheral vascular disease, or hypertension and in those who smoke. Any impairment of the arterial supply to the corpora cavernosa--such as from atherosclerosis, a clot, or loss of distensibility of a vessel wall--can lead to erectile dysfunction. Venous leakage (excessive venous outflow due to inadequate compression of the venous drainage of the corpora cavernosa) also is common with aging.

Neurologic disorders: Penile sensitivity tends to diminish with age and may contribute to erectile dysfunction, as local stimulation plays a role in erectile response. Peripheral and autonomic neuropathy and the alteration of neurotransmitters due to diabetes can cause erectile dysfunction in the elderly. Rarely, the nerves of the penis are impaired because of lumbar disk disease or, more commonly, surgical procedures such as rectal surgery and prostatectomy. Multiple sclerosis, stroke, and other neurologic diseases can also cause erectile dysfunction.

Endocrine disorders: The most common endocrine disorder in older men is the ADAM (Androgen Deficiency in the Aging Male) syndrome, which is nontumor-related hypogonadism of aging. Relatively uncommon diseases and disorders associated with primary testicular failure (eg, Klinefelter's syndrome, radiation, chemotherapy, or childhood exposure to mumps) can cause erectile problems. Secondary testicular failure due to pituitary or adrenal tumors or other endocrine disorders (eg, hyperprolactinemia due to chronic renal failure) can cause extremely low testosterone levels and, in rare cases, lead to erectile dysfunction. Hyperthyroidism, hypothyroidism, and Cushing's disease are also possible causes of erectile dysfunction.

Structural abnormalities: Peyronie's disease can make intercourse difficult or contribute to venous leaks, which may lead to erectile dysfunction. The disease is characterized by bands or plaques in the tunica albuginea, which lead to a "deformed" erection. Peyronie's disease is not an uncommon cause of erectile dysfunction in the elderly.

Drugs: About 25% of cases of erectile dysfunction are caused by drugs (see Table 115-1), especially antihypertensives (most notably reserpine, -blockers, guanethidine, and methyldopa), alcohol, cimetidine, antipsychotics, antidepressants, lithium, sedative-hypnotics, leuprolide, and hormones such as estrogen and progesterone. In addition, many drugs can impair sexual function in men, especially elderly men, by altering libido (eg, cimetidine, diazepam), inhibiting ejaculatory function (eg, most tricyclic antidepressants such as amitriptyline, clomipramine, doxepin, nortriptyline), or delaying or inhibiting orgasm (eg, selective serotonin reuptake inhibitors such as fluoxetine). However, trazodone has been found to improve libido and facilitate erectile function, but it does not have a specific therapeutic role in erectile dysfunction. Priapism can be an adverse effect.

Psychologic disorders: Among the elderly, most erectile dysfunction is organic rather than psychologic. Psychologic disorders alone probably account for only 10% of cases. However, psychologic and organic factors are often intermixed. Anxiety over an organic cause often aggravates erectile dysfunction. Depression can cause erectile dysfunction, and erectile dysfunction can worsen depression. Elderly men may experience performance anxiety, particularly when having sexual intercourse with a new partner.

Diagnosis

Elderly men may seek help for erectile dysfunction; physicians can make patients feel comfortable by explaining that erectile dysfunction is common and by offering reassurance that effective treatments are available. In private, patients should be asked if they would like to discuss the matter with or without their sexual partner present. It is extremely valuable to have the partner's perspective and to understand the issues that may arise for the partner with resumption of sexual function. Because many men would not otherwise seek medical attention, physicians can use this opportunity to also focus on the management of related disorders (eg, diabetes, hypertension, dyslipidemia, smoking, alcohol abuse). The probability of atherosclerotic disease and the possibility of coronary artery disease should be evaluated.

The physician begins the history by establishing whether the problem does indeed relate to erection, rather than ejaculation, orgasm, or partner-related issues, as well as establishing the setting and frequency with which erectile dysfunction occurs. Assessment should be made as to whether libido is intact. A series of questions can be asked to help assess for androgen deficiency (see Table 115-2). Establishing a history of diabetes, hypertension, or vascular disease is also helpful. A review of all medications used, including over-the-counter drugs, and a review of alcohol use are essential. Assessment for depression, anxiety, and psychologic stress should be performed. The physician should also ask about the sexual partner's health or other issues in the patient's relationships that may affect sexual functioning. Establishing the presence of nocturnal or morning erections is not especially helpful in older men, as it does not necessarily predict either functional ability or organic vs. psychologic causes.

The physical examination should include a search for signs of vascular disease (eg, diminished peripheral and femoral pulses, bruits, skin changes), autonomic neuropathy (eg, absent bulbocavernosus and cremasteric reflexes, orthostatic hypotension), and peripheral neuropathy. The genitalia should be thoroughly examined, checking for testicular atrophy and the plaques or bands that signify Peyronie's disease.

Intracavernosal injection of prostaglandin E₁ to assess penile vascular function is not always diagnostically accurate. For example, severe anxiety may override a response to this test. Abnormal penile brachial artery pressure indexes obtained while the patient is supine and after the patient has exercised (eg, bicycling legs in the air for 3 to 5 minutes) can help establish whether vascular insufficiency is a cause. In men without a history of coronary artery disease or stroke, an abnormal penile brachial pressure index predicts an increased risk of myocardial infarction, stroke, or both.

Bioavailable or free testosterone as well as total testosterone levels should be measured, and other tests performed (eg, CBC, fasting blood glucose, thyroid-stimulating hormone level). Measurement of nocturnal penile tumescence is of little value in distinguishing organic from psychologic erectile dysfunction in elderly men and generally should not be performed.

Treatment

The treatment of erectile dysfunction has changed radically in the past few years. The choice of therapy depends on the patient's goals and desires and on the risks of a given option. The least invasive form of therapy should be the first choice in treatment.

Pharmacotherapy: Drugs are available to treat erectile dysfunction and may be used without regard to the cause of dysfunction, although efficacy may differ. Sildenafil (50 to 100 mg given 1 hour before a sexual encounter) helps produce erections, but only when the patient is sexually stimulated. Sildenafil has relative selectivity for inhibition of type V phosphodiesterase, which inhibits breakdown of cyclic guanosine monophosphate, resulting in vasodilation. However, inhibition of type III and type VI phosphodiesterase may occur, which can affect cardiac function and vision, especially color vision. Because sildenafil can cause severe hypotension when nitrates are used concurrently, it is contraindicated in patients who take nitrates to relieve angina and in those with significant heart disease. Sildenafil can also cause headaches, flushing, and dyspepsia.

Alprostadil (prostaglandin E₁) can be given by intraurethral pellet or intracavernosal injection with or without papaverine phentolamine. Alprostadil causes vasodilation via smooth muscle relaxation and thus improves blood flow, leading to erection. About 5 to 20 minutes after insertion of the pellet or injection, the patient should initiate sexual activity. Under ideal conditions, an erection can last up to 60 minutes. Common adverse effects include a penile burning sensation and aching. Priapism can occur but is less common when the drug is given by intraurethral pellet. Priapism lasting longer than 4 to 6 hours can result in penile ischemic necrosis and fibrosis.

Drugs such as yohimbine have not been shown to be more efficacious than placebo in randomized controlled trials, and use of this drug is not recommended. Testosterone therapy may benefit some men whose erectile dysfunction is due to hypogonadism or when libido is at issue.

Nonpharmacologic measures: Constriction rings, which are made of rubber, slow venous outflow at the base of the penis and may be useful for men who can obtain erections but cannot sustain them. These devices can be purchased from medical supply houses, pharmacies, or stores that sell sexual paraphernalia. Constriction rings can produce local discomfort and, if too tight, difficulty with ejaculation.

Vacuum tumescent devices increase penile engorgement by creating a vacuum or negative pressure, which draws blood into the penis. These devices consist of a plastic cylinder, placed over the flaccid penis, and a pump mechanism. Once an erection occurs, a wide rubber band or ring (constriction ring) is applied at the base of the penis, and the vacuum device is removed. The band retards venous return and helps sustain the erection for up to 30 minutes. Vacuum devices can produce petechiae and make the tip of the penis slightly cooler than usual.

Permanent penile prostheses or implants may be helpful when erectile dysfunction does not respond to other treatment modalities. A prosthesis produces an erection but does not correct phenomena such as impaired penile sensation. Devices that produce a permanent erection include the Small Carrion semirigid rod prosthesis with a silicone sponge interior and the Flexi-Rod II, a hinged modification of the Small Carrion device that allows the penis to appear more physiologically flaccid when not being used for sexual activity. An inflatable prosthesis (AMS 700 CX) is also available. However, the more complicated the device, the greater the risk of mechanical breakdown and infection. Patients should also be aware that if the prosthesis must be removed, the patient could be left with penile scarring and fibrosis, which may lessen response to other therapeutic options.

Penile revascularization surgery (especially arterial) is relatively experimental and has not been found to have high success rates. With venous disease, ligation surgery may afford benefit in the short run, but < 30% of such operations have an effect that lasts > 5 years.

Patient Issues

When the cause of erectile dysfunction is psychologic, reassurance by the physician or the patient's partner may be helpful. However, some psychologic issues such as depression and anxiety may require psychotherapy, counseling, or medication. Medicare pays 50% of the allowable charges for psychotherapy performed by a physician, psychologist, or social worker.