Discussion

Pathophysiology

The mechanism by which erection occurs involves smooth muscle relaxation, which is regulated by adrenergic bers, myogenic, and endothelium-derived factors (such as prostaglandin and endothelin). Non-adrenergic non-cholinergic (NANC) nerves release nitric oxide (NO) and parasympathetic nerves release acetylcholine, both actions that result in increased cyclic GMP (cGMP) concentration and smooth muscle relaxation. With smooth muscle relaxation, blood lls the corpora cavernosa, which in turn compresses the subtunical venules preventing venous outfow. cGMP is hydrolyzed by phosphodiesterase type 5 (PDE5), which contracts the smooth muscle and reverses this process, allowing for penile detumescence. ED can occur with the disruption of any of the steps in this process, including nerve dysfunction, decreased arterial infow, or inelasticity of the smooth muscle of the penis so that venous outfow cannot be compressed.

Evaluation

Evaluation of ED requires a comprehensive history, including history of present illness, past medical history, past surgical history, medication history, social history, and family history, along with a focused physical exam [2]. Components of the history that are essential to capture include the onset of ED, persistence of the problem, maximal penile rigidity, sustainability of the erection, nocturnal erectile function, libido, ejaculatory function, and orgasm sensation. Another set of important questions centers around the patient and his partner’s sexual dynamics, including frequency of sex and whether spontaneity is important. Questions of past medical history should examine for vascular or neurologic risk factors, diabetes, and coronary artery disease. Past surgical history should focus on any surgical procedures that may compromise penile neural innervation or blood fow (such as radical pelvic surgery). Medications being taken should be completely documented to ensure offending medications are not the etiology for ED. Social history should evaluate for illicit drug and tobacco use. Family history should be taken to determine if the patient is at risk for vascular or neurologic disorders that may contribute to ED. Components of the physical exam important to perform include general body habitus evaluation, evaluation for gynecomastia, testicular volume and consistency, penile stretch, and penile pathology evaluation (i.e., tunica albuginea plaque). In addition to a thorough history and physical examination, validated questionnaires are recommended to document the severity of the disease, to measure treatment ef cacy, and to guide future treatment options [2].

Laboratory evaluation should be performed to aid in diagnosis of the etiology and for treatment optimization for ED. An early morning total testosterone level should be obtained [2]. Men with low testosterone levels should be counseled that ED treatments coupled with testosterone replacement may be more effective than