Advanced diagnostic tests

There are several advanced diagnostic tests that can be recommended in cases were a diagnosis remains unclear or if a surgical option is being considered. Most serve to confirm the presence and degree of a physical problem or organic ED.

Blood, Hormonal Testing

Basic evaluation of blood sugar, cholesterol and as testosterone levels may be indicated if these were not previously performed. Some decline in testosterone levels can be expected with age, however there is very little evidence indicating that this age-related decline affects sexual performance.  

Sleep monitoring

A test that is no longer considered very useful in the majority of patients complaining of ED, may be useful in a young patient where the diagnosis of psychogenic ED is suspected. If erections occur and are documented by the device, the patient’s ED is most likely psychogenic. However the lack of demonstrable erections is non-diagnostic. A lack of erections could simply mean that the man has not slept well, which occurs because wearing the device is uncomfortable, and interfere with sleep. 

Penile injection and measurement test

Performed by injecting the base of the penis with with an FDA approved medication such as alprostadil (Prostaglangin E-1). This very useful test and must be performed on all patients prior to penile prosthesis implantation. It allows the physician to evaluate the capacity of the penis to become erect and is also an indirect evaluation of the integrity of the erectile tissues of the penis. The amount of medication required to obtain a maximal response is an indication of the severity of the ED and helps determine whether the patient is likely to benefit from medical treatment. In addition the physician is able to examine the penis during erection and note any abnormality such as plaques or curvature seen in Peyronie’s disease. Measurements of the stretched penis is obtained before and after injection and the erection is obtained. The measurement of the penis erect after the penile injection test predicts the size of the implanted penis when Dr. Eid performs the penile implant.

Duplex sonography-pulsed Doppler study

A duplex ultrasound is a test to see how blood moves through the arteries and veins in the body. It combines traditional ultrasound with doppler ultrasound. Traditional ultrasound uses sound waves that bounce off blood vessels to create images. Doppler ultrasound records sound waves reflecting off moving objects (example: blood cells), to measure their speed and other aspects of how they flow.

This procedure involves the injection of a drug combination of Papaverine and Phentolamine (or an injection of Prostaglandin E-l) into the penis. The drugs cause a dilation of the blood vessels supplying the penis, thus causing an erection. Men with diseased blood vessels which may be caused by high blood pressure, arteriosclerosis, diabetes, etc., will not develop a full erection. Men with abnormal veins will also not develop a full erection. The purpose of this examination is to take a close look at the arteries of the penis. Therefore, the test will tell us whether the erectile dysfunction is due to arterial vascular disease.

The ultrasonography part of the procedure involved measuring the penile arteries before and after the injection of the medication. If the arteries were normal, we expect them to dilate. The Pulsed Doppler is utilized to look at the increase in blood flow. An increase in blood flow will occur if narrowing of the larger arteries supplying blood to the penile arteries is present. A venous leak is considered when no erection is noted despite normal arterial dilation and normal blood flow. 

As with medical tests there are possible complications. Approximately 5% of men will develop a small bruise at the injection site which will resolve within 7 to 10 days and cause no further problems. Dizziness has been reported, though it is rare, but this is resolved by lying down for a short period. Some might develop a full erection which can last for many hours. If this occurs, we will have to inject an additional medication to bring the erection down. 

Combining the penile injection test with duplex ultrasonograpy will provide additional information on the cause of the dysfunction as well as further evaluated the erectile muscle of the penis. This test uses real-time ultrasonography to visualize the cavernosal ateries and muscle tissue, allowing for the detection of abnormalities such as fibrosis and calcifications of the erectile muscle as well as change in the measurements of the diameter of each cavernosal artery in response to the penile injection. 

At the same time, the pulsed Doppler ultrasound records and measures actual blood flow into the penis. This combined ultrasound/Doppler test provides information about patency of arteries, thickening of the arterial walls and or presence of a “venous” leak, which would prevent trapping and storing of blood in the penis sufficient to maintain an erection. Measuring the ratio of blood flow into the penis while the heart is pumping versus when it is at rest can assess this. This measurement is called the resistive index, and is based on the observation that in a normal erect penis, the pressure inside the erectile chamber of the penis exceeds the pressure in the arteries when the heart is at rest, and therefore no blood should be flowing into the penis. If blood flow occurs in this situation, the diagnosis of “venous leak” is confirmed.   

Additional more invasive tests such a Dynamic Infusion Cavernosometry and Cavernosograpy as well as Arteriography are no longer utilized and are mentioned here for historical purposes. The data obtained from these expensive and invasive procedures are of very limited use and do not alter the treatment options, especially since venous ligation surgery and arterial bypass surgeries are never successful.

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