Tip of the Day!

Further Investigations of Erectile Dysfunction

By Christopher Steidle, M.D.

Penile Biothesiometry

One useful way to evaluate the nerves that carry sensation away from the penis is by the use of a technique called penile biothesiometry. This is a quantitative measure of the vibratory sense of the penis. A biothesiometer consists of a device that vibrates at a known frequency, and it is compared to other parts of the body with known vibration thresholds. This tends to become less reliable in older patients because as men age they tend to lose sensation. Still, it is a reasonable, cost-effective test.

The device is placed on the tip of the finger, and slowly the frequency is increased until the vibration is felt. This is then used as a baseline to compare the vibration sense of the penis as well. It is a useful way to detect early neuropathic disease in younger men, particularly in men with diabetes. It is also used in men who have had circumcisions and complain that the head of the penis has lost sensation.

Duplex Ultrasound

The Duplex ultrasound is a relatively new procedure and probably the single best test to evaluate male erectile dysfunction. Duplex ultrasound combined with an intercavernosal injection has pretty much replaced all other tests that are currently available. This single test can evaluate both the early and late stages of an erection, as well as venous leakage. The technique utilizes a special Doppler ultrasound device that uses a color-type system which assesses the blood flow direction and provides a way to evaluate the volume of flow into and out of the penis.

The technique is fairly simple. It is done by first taking a picture of the flaccid penis. We include the corporal bodies and the spongiosum, which is the spongy layer that surrounds the urethra. There we look for dense areas that may represent Peyronie's disease. We also look for calcifications that can indicate scarring or early blood vessel changes consistent with atherosclerosis. We then induce an erection by injecting prostaglandin. We repeat the study at one-, five-, and fifteen-minute intervals. Using this technique, we are able to image the cavernosal arteries. We measure them both before and after the injection. If the patient responds poorly to this, we sometimes have the patient perform self-stimulation in order to take out of the equation any results of anxiety or embarrassment that may cause a loss of erection and confuse the results.

We are then able to evaluate patients who have arterial disease. Poor arterial dilation indicates poor blood flow in response to the injection. This is compared to data on the normal peak flow velocity and how fast the blood pressure should rise in the artery supplying blood to the penis. We are also able to visually evaluate the erection and document venous leakage. Persistently elevated diastolic flow correlates with venous leakage. Physicians not experienced in performing the tests and interpreting the data should not do these studies.

The blood flow test is particularly useful in patients with Peyronie's disease because it not only assesses how much blood flow is present, but how much bending there is and the presence of other lesions. I generally recommend this test on all patients who are undergoing a penile implant or corrective surgery. This provides good factual information to work with prior to proceeding with the surgical procedure.

Arteriography

Selective arteriography is recommended only for men who are candidates for arterial revasculization. These are usually young, healthy men who have suffered trauma to the penis or to the area under the scrotum known as the perineum. Prior to proceeding with an arteriogram, which is a very invasive procedure, a Duplex Doppler examination showing the presence of poor blood flow and indicating a probable arterial lesion should be performed. If an obstruction is visualized, it is important to document whether there is flow back through the blockage to the point of obstruction so that the patient will be sure to benefit from the procedure.

Microsurgical penile revascularization is an invasive procedure that should only be done in referral centers by experienced physicians. This is not an operation that most urologists do on a regular basis. The procedure performed is generally a microvascular arterial bypass. The objective of the surgery is to increase the blood flow to the corporal body and therefore improve the erections. The best candidates for surgery are men who have poor erections with spontaneous erections absent and in whom all studies indicate a pure arterial component. Patients with other diseases such as diabetes or heavy smokers are poor candidates for this type of operation.

Ideally, arterial surgery should be the way to treat erectile dysfunction since it seems logical that a damaged or blocked artery could easily be bypassed to provide the necessary blood needed to maintain an erection. Unfortunately, this is not the case because the patients who have this distinct arterial lesion are very limited.

Many physicians have spent a lot of time trying to develop an arterial bypass that can improve this condition, and numerous procedures have been developed. Patients who undergo arteriography should be highly motivated and have a complete workup to rule out all other causes of erectile dysfunction, including hormonal problems or venous leaks. Patients should not proceed with arteriography unless they are good candidates for revascularization.

Venous Leakage

Venous leakage is a relatively common cause of erectile dysfunction. An inability to achieve and maintain the full erection occurs because blood leaks out in the presence of an adequate arterial inflow due to a damaged veno-corporo-occlusive mechanism. There are five theorized types of venogenic impotence.

Type 1 is due to the presence of an excessively large number of veins exiting the corporal body. This is probably congenital and is seen in young men with primary erectile dysfunction.

Type 2 is the weakening of the tough outer membrane of the corporal membrane of the corporal body known as the tunica albuginea, resulting in poor compression of the veins, such as in elderly men. I consider this a wear-and-tear phenomenon.

Type 3 is the loss of compliance of the cavernosal smooth muscle because of Peyronie's disease or scarring degeneration in patients with severe hardening of the arteries.

Type 4 is poor relaxation of the cavernous smooth muscle due to inadequate release of the hormones it takes to create an erection. This is typically common in heavy smokers.

Type 5 results from abnormal communications between the corpora cavernosa and the spongiosum due to trauma or a prior procedure to treat priapism. Patients with pure erectile dysfunction on the basis of a venous leak are rare, but many men have venous leakage as a component of their erectile dysfunction. Many years ago, we felt that this was a major problem, and during the early 1980s a great deal of venous leakage surgery was performed. We found that patients with specific venous leakage due to congenital abnormalities or specific trauma type situations do well with these types of operations, but the majority of patients do poorly. We still feel the first choice for patients who have venous leakage is a vacuum erection device or treatment with intercavernosal injections. The only patients who are candidates for a venous leakage operation are patients who have failed simple, noninvasive treatments.

Many people have attempted surgery for venous leakage. A host of different procedures attempt to make the diagnosis. All these techniques basically try to measure the pressures required to make blood leak out of the corporal bodies. Cavernosography is the technique of injecting dye into the corporal body to identify a leaking blood vessel. Prostaglandin is first injected to create an erection and then dye, which potentially identifies the site of the leakage. The results of these diagnostic procedures have not been dramatic.

When it has been determined that the patient is a good candidate for repair, the idea of treatment is to find the vein that is the source of the leakage and then tie it off. If the leaking vessel is near the base of the body, then an incision is made over that area. We feel that good candidates for venous surgery are those who have identified a localized leak and who have had a complete workup to rule out all the obvious causes for erectile dysfunction, including the Duplex Doppler examination. Surgical candidates should be nonsmokers, young, and have no other medical problems. A preoperative X-ray examination called the cavernosogram should identify the site of the leaking vessel.

The complications with this type of operation are numerous, as with all operations. They include numbness of the penis, scarring, a shortening or twisting of the penis, and painful erections.

Dynamic Infusion Cavernosometry and Cavernosography

Dynamic infusion cavernosometry is a technique in which fluid is pumped into the penis at a known rate and pressure. This procedure helps us to define the veno-occlusive function during an erection. To do this test we administer prostaglandin E-1. We measure the rate of infusion required to get a rigid erection and then use this to help find how severe the venous leak is. As an adjunct to this procedure, we then instill contrast material, and this is termed a cavernosogram. We then use X rays to measure and to visualize any leaking vessels. This is particularly applicable in men who have Type 1 or Type 5 venous leaks.

Nocturnal Penile Tumescence Testing

Nocturnal penile erections have been associated with rapid eye movement (REM) sleep. Nocturnal penile tumescence (NPT) helps maintain erections by providing oxygenation to the penis. During REM sleep, men normally have several erections each night, each one lasting up to an hour. Thus, during the erection, the corporal bodies are exposed to the same oxygen level that the rest of the body experiences for up to four hours per day. In men who have poor penile blood flow, and therefore poor erections, this does not occur, hastening the development of scar tissue and loss of corporal smooth muscle. Therefore, nocturnal erections are extremely important for the maintenance of good erectile functioning. As men age, these episodes become fewer and shorter. Nocturnal penile tumescence monitoring is useful in patients who report a complete absence of erections but in whom a psychological component is suspected.

Before the advent of the newer techniques using the rigiscan, physicians used the postage stamp test. Basically, a series of stamps was placed around the base of the penis. If the patient awoke the next morning with the stamps unbroken, this indicated an organic problem. However, if the stamps were broken, this was felt to be a psychological problem. Following the postage stamp test was the development of the snap gauge, a Velcro band placed around the base of the penis that had three colored plastic film elements. Each film ruptured at a specific known force. It took 10 ounces of radial force to rupture the blue tab, 15 ounces to rupture the red tab, and 20 ounces to rupture the clear tab. These snap gauge results were reasonable. However, there was no way to measure rigidity. When the criteria for the snap gauge was carefully examined, it was found that half the men who broke two to three films actually had no rigidity by visual inspection. Because of this, it has lost some favor and it has been mostly supplanted by the rigiscan.

The rigiscan allows us to measure continuous tumescence monitoring, but it also provides rigidity information during the times when the patient is achieving an erection. In addition, it gives detailed information about how often the erections occur, for what period of time, and the rigidity and change in diameter. Rigidity is measured by placing a loop around the base of the penis, which is tightened every thirty seconds with a force of 2.8 Newtons. It records three sessions, and then it is downloaded into a computer. The newest version of the rigiscan uses software that can calculate an entire evening of tumescence and rigidity data into rigidity activity units and tumescence activity units. Several different types of patterns are measured by the rigiscan, including dissociation which is seen with Peyronie's disease. This pattern shows how the base of the penis gets hard and the tip past the areas of the Peyronie's plaque has poor rigidity and tumescence.

Another pattern, termed uncoupling, occurs when there is good tumescence on both the base and tip, but poor rigidity. While rigiscan testing doesn't give an exact diagnosis, it can be extremely useful.

NPT studies are not perfect. Some problems, including sleep disorders and depression, can cause abnormal readings. This should be recognized when performing the study. Testing prior to surgery demonstrates that the patient does indeed have erectile dysfunction. If the patient has complications or needs surgery, such as repairing the implant, testing protects the patient against cases in which an insurance company attempts to avoid payment for a service and in medical malpractice. An NPT study supports the urologist's diagnosis of erectile dysfunction.

It is important to tailor the workup to the individual needs of the patient.

Take-Home Points

When lab tests are ordered during the workup of erectile dysfunction, it is important to know what the physician is looking for prior to having a test. Ordering every test on every patient is not necessary. If a physician orders every test without an explanation, find another physician. 

Prior to proceeding with venous leakage surgery, it is important that you have an adequate diagnosis. This necessitates a minimal workup: a Duplex Doppler ultrasound examination and a cavernosogram. 

Rigiscan testing is not for all patients with erectile dysfunction, but if there is any question as to cause, it is a useful test. Prior to having a rigiscan, be sure that your insurance carrier recognizes this as a covered service. 

Before proceeding with a surgical procedure on the penis, it is recommended to have a rigiscan to document poor erectile functioning, especially prior to a penile implant. 
Only candidates for microvascular reconstructive surgery should undergo arteriography. Microvascular reconstructive surgery should be limited to very experienced surgeons.
 


"Copyright © 1998 NTC/Contemporary Publishing Group. From The Impotence Sourcebook, by arrangement with The RGA Publishing Group."