Special Investigations - Diagnosis of erectile dysfunction

Blood and urine testing

A key condition to exclude is undiagnosed diabetes mellitus. This is best accomplished by random measurement of blood sugar, as dipstick testing of urine to detect glycosuria does not reliably exclude the diagnosis. Because renal failure is also frequently associated with erectile dysfunction, electrolytes and creatinine should also be measured in addition to liver function tests, especially in those who admit to a high alcohol intake. Documentation of a full blood count and erythrocyte sedimentation rate is also a sensible precaution.

Evaluation of the androgen status of the patient is usually indicated, as some may respond to hormone replacement therapy.
A serum testosterone (best measured as an early-morning sample) and sex hormone binding globulin (SHBG) should be requested. In addition, if the free testosterone level is low, a prolactin level should be measured, as hyperprolactinemia is associated with erectile dysfunction and may be corrected by treatment with bromocriptine.

Some specialists also advocate testing of thyroid function, although this is a relatively unusual cause of erectile dysfunction, at least in younger men. If prostate cancer is a possibility, then a prostate-specific antigen (PSA) test should be requested, especially if treatment with androgen replacement therapy is being contemplated, as this may stimulate occult prostate cancer cells.

Diagnosis of erectile dysfunction History Physical Examination Special Investigations

Nocturnal penile tumescence testing

Although still advocated by some, nocturnal penile tumescence testing is a rather cumbersome way to differentiate psychogenic from organic impotence (Figures 45 and 46). The same information (whether or not an erection develops during sleep) may be gleaned with the use of the snap gauge device or even with a strategically located ring of postage stamps (Figure 47). Only a few laboratories continue to employ nocturnal penile tumescence testing as a routine assessment of patients with erectile dysfunction.

Diagnostic intracorporeal injection

Injection of a vasodilator substance into one or other of the paired corpora cavernosa provides the clinician with two valuable pieces of information. First, it confirms that a normal vasodilatory response is capable of developing (although a failure to respond does not necessarily indicate organic erectile dysfunction, since the response may be inhibited by excessive nervousness). Second, this technique assesses the feasibility of self-injection pharmacotherapy as a treatment option.