Sexual Dysfunction in Men and Women With Chronic Kidney Disease

2.1

Vascular System

Normal erections require blood to flow from the hypogastric arterial system into specialized erectile chambers, including the paired corpora cavernosae flanking the penile urethra and the corpus spongiosum at the glans penis. As blood flow accelerates, the pressure within the intracavernosal spaces increases dramatically to choke off penile venous outflow from emissary veins. This combination of increased intracavernosal blood flow and reduced venous outflow allows a man to acquire and maintain a firm erection.

Studies in patients with chronic kidney disease have shown that vascular causes of erectile dysfunction are common. Decreased arterial inflow has been demonstrated to result from occlusive disease of the cavernosal artery. Erectile dysfunction can also result from occlusive disease in the more proximal ileac and pudendal arteries by producing a pelvic arterial steal syndrome. This syndrome results from blood being diverted from the corpus cavernosa to meet the oxygen requirements of the pelvis. In addition to reductions in arterial inflow many patients have evidence of venoocclusive dysfunction. Such abnormalities lead to venous leakage and therefore inability to achieve or maintain an erection.

Erectile dysfunction in nonuremic men has been identified as a marker of atherosclerosis and endothelial dysfunction in other vascular beds to include the coronary circulation. Erectile dysfunction is more common in men with evidence of coronary endothelial dysfunction as compared to those with normal function. Such patients have increased circulating levels of the nitric oxide synthase inhibitor, asymmetric dimethylarginine (ADMA), suggesting a reduction of endogenous nitric oxide activity may be responsible for the abnormal vascular behavior. It is likely that a similar relationship exists between erectile dysfunction and vascular disease in uremic men given the high frequency of both disorders.

2.2

Neurologic System

Significant portions of chronic kidney disease patients display abnormalities in the function of the autonomic nervous system. Such derangements are due to comorbid conditions such as diabetes but also result directly from uremic toxicity. Given the importance of the sympathetic and parasympathetic nervous system in normal sexual function, disturbances in the autonomic nervous system are likely to participate in the genesis of erectile dysfunction. Reductions in nocturnal penile tumescence (NPT) and the frequency of sexual intercourse are positively correlated with disturbances in autonomic function as assessed by the valsalva maneuver.

2.3

Endocrine System

While adequate penile blood flow and intact neural input are prerequisites for an erectile response, the endocrine system plays an integral role in normal male sexual function ( Table 16.2 ). In men with chronic kidney disease disturbances in the pituitary–gonadal axis can be detected with only moderate reductions in the glomerular filtration rate and progressively worsen as kidney failure progresses. These disorders rarely normalize with initiation of hemodialysis or peritoneal dialysis and, in fact, often progress. By comparison, a well-functioning kidney transplant is much more likely to restore normal sexual activity, although some features of reproductive function may remain impaired.