Erectile dysfunction (ED) is one of the most common sexual dysfunctions in men. In 1993, the National Institute of Health (NIH) defined ED as “sexual dysfunction in which the male penis is unable to achieve or maintain a sufficient erection for satisfactory sexual intercourse “. The incidence of ED in China is estimated to be about 10%. I. Epidemiology of erectile dysfunction The epidemiology of ED focuses on the distribution of ED in the general and special populations and the risk factors for ED. Due to the traditional avoidance of sexual problems, many patients do not go to the doctor or cannot confess their condition, and related research has also started late, resulting in unsatisfactory epidemiological studies of ED. The main risk factors for ED are age, psychological factors, physical illness, drugs, trauma, surgery and other medical factors, and poor lifestyle. (i) Age As age increases, in addition to a decrease in libido, erectile function will also change significantly; the sensitivity of the penis will also decrease, and the time required for the penis to achieve erection will lengthen; the influence of psychological stimulation on penile erection will decrease, and penile erection will rely more on somatic stimulation; the frequency and duration of penile erection at night will also decrease; at the same time, sexual pleasure during intercourse and the strength and volume of semen during ejaculation will also decrease. (ii) Psychological factors Psychological factors lead to the occurrence of ED through special mechanisms. mmas study found that: the prevalence of moderate ED was 35%, 35% and 15% in men with severe mental depression, temper tantrums and strong desire to rule; the prevalence of severe ED was 16%, 19% and 7.9%. Long-term ineffective treatment of organic erectile dysfunction will increase the psychological burden of patients, the latter will further aggravate the condition, or even transform into the main aspect of the conflict. (iii) Somatic diseases With the development of male science and the application of many new treatment techniques, it is found that purely psychological or purely organic erectile dysfunction is rare, and the vast majority are both. As organic ED is not treated in a timely manner patient psychological pressure aggravated, fear of failure of sexual intercourse, so that ED treatment tends to be more complex. A group of 628 domestic ED patients etiology classification study showed that: psychological accounted for 39%. Organic is 15.8%, and mixed 45.2%. Erectile dysfunction is mainly related to the following physical diseases (its corresponding prevalence is shown in Table 1): cardiovascular disease itself risk factors such as age, high blood lipids, smoking and other risk factors for ED, the study suggests that the cardiovascular status of patients should be evaluated before starting treatment for ED, because ED may be a local manifestation of systemic atherosclerosis. Diabetes can lead to systemic vascular and neuropathy, which may cause ED. studies have found that the higher the total serum cholesterol, the lower the HDL, the greater the likelihood of ED. In addition, chronic renal insufficiency, hyperprolactinemia, adrenal disease, thyroid disease, sclerosis of the penis and other physical diseases can lead to ED. (iv) Drugs Some studies have shown that drug-related ED accounts for 25%, but this information is mostly from clinical experience, case reports, etc., the lack of rigorous evidence-based medical research. Common ED-related drugs are shown in Table 2. Table 2: Common ED-related drugs Drug classification Drugs Diuretics Thiazide diuretics, Antiseptic antihypertensive drugs Colistin, methyldopa, reserpine, β-blockers, guanethidine, isoptin Cardiac drugs Coronary heart, digoxin Antidepressants Tricyclic antidepressants, monoamine oxidase inhibitors, lithium H2-blockers Ranitidine, cimetidine Hormonal drugs Estrogen, progesterone, corticosteroids, cyproterone, gonadotropin-releasing hormone analogues Cytotoxic drugs Cyclophosphamide, methotrexate Anticholinergics Propylamine phosphate, Gastrofluazide Valium Meperidine Other Prolotherapy, NSAIDs (v) Trauma, surgery, and other medical factors Any trauma or surgery that damages the innervation, vascular supply, and androgen source of the penis, including the resulting psychogenic factors, may be a cause of the penis. (vi) Poor lifestyle Some studies suggest that smoking is an independent risk factor for ED and may synergize or enhance the effects of other risk factors, but the incidence of ED is not dependent on current or lifetime smoking. Alcohol consumption can increase desire but may decrease sexual function. The likelihood of ED is also increased in men with long-term drug use. Second, the physiology of penile erection In essence, the process of penile erection is a series of neurovascular activity, the nerves that control penile erection and relaxation are mainly sympathetic and parasympathetic nerves. When there is no sexual stimulation, sympathetic nerve is the main action, arterial smooth muscle contracts, penile cavernous trabeculae also contract, trabecular space is empty, arterial inflow is obviously reduced and basically balanced with venous outflow, and the penis is in a weak state; when sexual stimulation parasympathetic nerve is the main action, arterial smooth muscle diastole, arterial inflow increases sharply, while penile cavernous trabeculae relax, trabecular space expands, and the penis is in a weak state. Compressing the small submembranous veins, the venous outflow decreases and the penis erects. Erections are classified as reflex erections, psychogenic erections and nocturnal erections. A reflex erection is an erection produced by sensory stimulation through the pubic nerves and sacral sex centers. Reflex erection is accomplished by nerve reflexes, and the afferent nerves of its reflex arc are the dorsal penile nerve and the perineal nerve, and the efferent nerve is the parasympathetic nerve of the sacral region. Injuries to the spinal cord, spinal nerve roots, pelvic nerve, perineal nerve, and cavernous nerve can lead to the loss of transmitting erection; the effect of spinal cord injury on erectile function is related to the height of the injury; injuries above the thoracic segment of the spinal cord have little effect, while injuries to the following parts can have serious effects and even lead to the loss of reflex erection. Psychogenic erection is an erection of the penis caused by the sexual awareness generated by the brain. Psychogenic erections are synergistic with reflex erections. Psychogenic erections are more common in young people and gradually decrease with age. Nocturnal erection, also known as nocturnal penile tumescene (NPT) is an erection of the penis that occurs during the rapid eye movement phase of sleep. NPT occurs in all healthy men, including infants and older men , and the mechanism of NPT has not been discovered, but most researchers believe it is related to the transmission of information from the central nervous system to the sacral parasympathetic plexus during sleep. The presence or absence of NPT is an important aspect of clinical differentiation between psychological erectile dysfunction and organic erectile dysfunction. In general, penile erectile function decreases with increasing age. As age increases, the penis may require stronger stimulation to achieve an erection, and there is a tendency for the intensity of orgasm and the frequency of sexual intercourse to diminish, as well as a longer interval between erections. However, as age increases, the incidence of various diseases and the use of various drugs increase accordingly, so it is sometimes difficult to distinguish whether the changes in erectile dysfunction are caused by old age or by diseases or drugs. The diagnosis of erectile dysfunction can be made by taking a detailed medical history, conducting a physical examination and the necessary laboratory tests to diagnose ED. (i) Medical history Because of the influence of traditional concepts, ED patients are often difficult to talk about their condition, so the patient’s consultation environment should be quiet and comfortable, and the urologist or male physician should seek the patient’s trust in order to obtain objective and detailed clinical information. The current medical history should answer the following three questions: ⒈ in addition to ED, whether the patient is combined with other sexual dysfunction? Clinically, ED patients are often accompanied by premature ejaculation, and some patients also have ejaculatory abnormalities and hypoactive sexual desire and other sexual dysfunction. What is the degree of erectile dysfunction? This is mainly based on the International Index of Erectile Function 5 (IIEF-5). Is it psychological ED or organic ED? The past history should be reviewed for psychosomatic, cardiovascular system, endocrine system, neurological system, and genitourinary system, among which cardiovascular system and endocrine system are the most important. In addition, the patient’s medications, history of trauma or surgery and whether the patient smokes and drinks alcohol are also asked. In order to quantify the degree of erectile dysfunction, researchers have designed various questionnaires, among which the currently commonly used ones are the Brief Male Sexual Function Inventory for Urology (1995) designed by O’Leary and the IIEF designed by Rosen in 1997. In 1998, Rosen simplified the 15 questions of the IIEF into 5 questions: 3 questions about erectile function, 1 question about overall satisfaction with sexual life, and 1 question about patients’ confidence in penile erection and maintaining penile erection, which is the well-known IIEF-5 (see Table 5). According to IIEF-5, erectile dysfunction can be classified into: >21 points, no erectile dysfunction; 12-21 points, mild erectile dysfunction; 8-11 points, moderate erectile dysfunction; 5-7 points, severe erectile dysfunction, also called complete erectile dysfunction. the sensitivity of IIEF-5 is 98% and the specificity is 88%. (ii) Physical examination The main observations are the patient’s body shape, hair and subcutaneous fat distribution, secondary sexual characteristics and the presence of gynecomastia feminization. Blood pressure and pulses of the extremities, and the presence of hepatosplenomegaly should also be measured. Neurological examinations of the lower abdomen, lower extremities, perineum and penis, such as pain and temperature sensation and bulbocavernosal reflexes, should be performed. Attention should be paid to checking the size and shape of the patient’s penis, whether there is any abnormality in the foreskin, and carefully palpating the penile corpus cavernosum; checking the size and texture of the patient’s testicles, whether there is testicular syringomyelia, varicocele, etc.; performing anal finger diagnosis to check the condition of the prostate gland. (iii) Laboratory tests Routine blood, urine, fasting blood sugar, liver and kidney function and lipid measurements are helpful in detecting diabetes, liver and kidney disorders and hyperlipidemia. In addition, some special tests are still needed. 1 Endocrine function test Whether hormone test as a routine examination is still controversial, some researchers pointed out that patients with erectile dysfunction do not need to routinely conduct hormone test, only patients with obvious loss of libido and the appearance of related signs to conduct hormone test. The main hormone tests are: (1) testosterone (2) prolactin (3) LH and FSH (4) thyroid hormone (5) GnRH stimulation test (6) clomiphene stimulation test (7) HCG stimulation test. 2 Penile vascular function tests mainly include (1) penile brachial index (PBI): PBI > 0.75 in normal men, and may be between 0.6 and 0.7 under 40 years old; PBI < 0.6 indicates possible arterial blood supply disorders. (2) Intracavernous injection test (ICI): commonly used drugs include poppies, phentolamine and prostaglandin E1 (PGE1). The grading criteria for this method: E0, no penile swelling; E1, beginning of penile swelling; E2, moderate penile swelling; E3 full penile swelling; E4, full penile swelling with moderate hardness; E5, full penile swelling with full hardness. If the penile erection reaches E4 to E5, no more drug is administered; if the penile erection is at E0 to E3, the dosage is increased by 1 ml, 2 ml and 3 ml (up to 3 ml) until the penile erection reaches E4 to E5. If the penile erection can reach E4 to E5 level when the dosage is 0.25 to 0.5 ml, it indicates normal penile vascular function; if the penile erection can reach E4 to E5 level only when the dosage is 0.5 to 3 ml, it indicates penile artery or penile cavernous body dysfunction; if there is no response, i.e. E0 to E3 level, it indicates penile vein or penile cavernous body dysfunction. (3) Color Duplex Ultrasonography (CDU): to detect the maximum systolic flow rate (PSV), end-diastolic flow rate (EDV) and impedance index (RI) of the penile artery. PSV is an important index to assess the blood supply of the penile artery, and its normal value is defined by some researchers as >25 cm/s, and some as ＞EDV is an important index to assess the closing function of the dorsal penile vein, and the normal value of EDV should be <5 cm/s. Above this value, it suggests that the closing function of the dorsal penile vein may be incomplete. The mean value of RI in normal men is 0.99; the mean value of RI in simple arterial insufficiency is 0.96, which is slightly lower than normal, but there is no statistically significant difference between the two; the mean value of RI in simple venous occlusion insufficiency is 0.71; in both arteriovenous abnormalities, RI is 0.63. (4) Cavernosometry (CM): Diagnosis of CM The main indicators are the perfusion flow rate to induce erection (IF), the perfusion flow rate to maintain erection (MF), IF/IM and the pressure drop difference (PLC). In normal men, MF is <10 ml/min and usually <5 ml/min; if MF >10 ml/min, it indicates venous occlusion insufficiency, and MF >40 ml/min, it indicates significant venous occlusion insufficiency. (5) Penile cavernosography (Cavernosography) (6) Selective penile arteriography 3 Neurological testing for erectile dysfunction mainly includes (1) corpus cavernosum electromyogram (cc-EMG) (2) sympathetic skin responses, (3) sacral reflex latency (SRL) (4) cotical pudendal evoked potentials (CPEPs), etc. 4 Nocturnal penile tumescence test (NPT) Health Nocturnal penile tumescence (NPT) is the best method to distinguish psychological erectile dysfunction from organic erectile dysfunction because psychological factors such as emotional tension and anxiety that affect erectile function do not exist during sleep. The normal value of NPT varies depending on the method of measurement. the main methods of NPT measurement are: (1) Paper tape or Snap-Gauge test. (2) Hardness tester (Regiscan) Regiscan can observe not only the swelling of the penis during erection at night, but also the hardness of the penis during erection. regiscan is a non-invasive test, and its normal reference values are: the frequency of erection is 3-6 times per night, the duration of each erection is 10-15 minutes, the swelling is >2~3 cm, and the hardness is more than 70%. V. Treatment of penile erectile dysfunction Nowadays, the first-line treatment of ED is psychotherapy, oral medication and negative pressure suction device; the second-line treatment is transurethral drug delivery and intracavernosal injection therapy; penile prosthesis implantation is the third-line therapy. 1.Psychotherapy The most important heart treatment at present is sexy concentration training, which aims at relieving the anxiety of both sides, improving communication and exchange between both sides, so as to gradually improve the sexual function of both sides. Sexual concentration training mainly includes three stages: non-genital organs sexual concentration training stage, genital organs sexual concentration training stage and penile penetration training stage. The efficiency of sexy concentration training for erectile dysfunction is 21~81%; however, the effect of psychosexual treatment is not good for those who have low sexual desire, poor relationship between both parties or both parties do not have strong desire for treatment. 2, oral medication Oral medication is currently the preferred method of treatment of ED, phosphodiesterase type V (PDE5) inhibitors are currently the first choice of drugs used to treat ED. Its role is to relax the cavernous smooth muscle, so as to treat penile erectile dysfunction, the efficiency of 78%, the side effects of dizziness, headache, flushing, nasal congestion, gastrointestinal symptoms, visual impairment, etc.; can not be combined with NO preparations such as nitroglycerin class. Cardiac patients should be used with caution. 3.Vacuum suction device. The use of negative pressure to make the penis distended, with an elastic ring placed in the penis root to prevent venous blood flow back, to maintain the erection state. This device is suitable for elderly patients with cisplastic lesions. Side effects include numbness of the penis, decreased orgasm, difficulty in ejaculation, and painful sensation. 4, intracavernosal drug self-injection Initially, poppy bases or phentolamine alone or in combination are used to achieve more satisfactory results, but about 2% to 6% will have abnormal erectile comorbidity is a concern. 5.Surgical treatment is applicable to both venous and arterial erectile dysfunction. Penile vein surgery includes deep dorsal penile vein ligation, penile pedicle vein ligation, sciatic cavernous muscle folding, urethral cavernous body stripping, internal iliac vein ligation, etc. 6.Penile prosthesis is an effective method to treat erectile dysfunction, which is suitable for patients with organic and some psychological erectile dysfunction whose treatment by other methods is ineffective. The prosthesis mainly includes semi-rigid rod-shaped penile prosthesis, expandable three-part prosthesis, expandable two-part prosthesis, expandable single-part prosthesis.