Diagnosis of Impotence

A medical examination may indicate neurological, vascular, or hormonal disease, or Peyronie's disease. History of illness, smoking, drug use, and hypertension can be ascertained with a thorough examination of health history. Laboratory tests are performed to identify the underlying cause.

Blood Tests and Urinalysis to Diagnose ED

Blood tests can indicate conditions that may interfere with normal erectile function. These tests measure hormone levels, cholesterol, blood sugar, liver and kidney function, and thyroid function. Excess prolactin (hyperprolactinemea) can lower testosterone levels, which can diminish libido. Both of these levels are measured, as well as levels of other sex hormones. If they are persistently low, an endocrinologist (hormone specialist) should be consulted.

CBC–Complete blood count (CBC) of red cells and white cells is used to evaluate the presence of anemia. A low level of red cells limits the body's utilization of oxygen and can lead to fatigue and general malaise. The level of blood lipids (fats) such as cholesterol and triglycerides may indicate arteriosclerosis, which can reduce blood flow to the penis.

Liver and kidney function tests–Liver and kidney disease can create horomonal imbalances. Blood tests for liver function involves analysis of enzyme and serum creatinine levels, which are indicators of kidney efficiency.

Thyroid function tests–Thyroid hormones regulate metabolism and the production of sex hormones; a deficiency may contribute to impotence.

Urinalysis–Urine is analyzed for protein (albumin), sugar (glucose), and hormone (testosterone) levels that may indicate diabetes mellitus, kidney dysfunction, and testosterone deficiency.

Erectile Function Tests to Diagnose ED

Tests that assess erectile function examine the blood vessels, nerves, muscles, and other tissues of the penis and pelvic region.

Duplex ultrasound–Duplex ultrasound is used to evaluate blood flow, venous leak, signs of artherosclerosis, and scarring or calcification of erectile tissue. Erection is induced by injecting prostaglandin, a hormone-like stimulator produced in the body. Ultrasound is then used to see vascular dilation and measure penile blood pressure (which may also be measured with a special cuff). Measurements are compared to those taken when the penis is flaccid.

Prostate examination–An enlarged prostate, which can be detected with a digital rectal examination (DRE), can interfere with blood flow and nerve impulses in the penis.

Penile nerve function–Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus. Specific nerve tests are used in patients with suspected nerve damage as a result of diabetes or nerve disease.

Nocturnal penile tumescence (NPT)–It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). These erections occur about every 90 minutes and last for about 30 minutes. Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge.

Snap gauge involves wrapping three plastic bands of varying strength around the penis. Erectile function is assessed according to which bands break. Strain gauge involves placing special elastic bands at the base and tip of the penis. These bands stretch during erection and register changes in circumference.

Penile biothesiometry–This test uses electromagnetic vibration to evaluate sensitivity and nerve function in the glands and shaft of the penis. A decreased perception of vibration may indicate nerve damage in the pelvic area, which can lead to impotence.

Vasoactive injection–When injected into the penis, certain solutions cause erection by dilating blood vessels in erectile tissue. Normally, these injections produce an erection lasting about 20 minutes. During this procedure, penile pressure is measured and x-rays may be taken of the penile blood vessels using a special dye (contrast agent).

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 10 Jun 1998

Last Modified: 01 Dec 2011