Penile Doppler Ultrasound Delivers a Fuller Picture of Erectile Issues

When a man with erectile dysfunction comes to urologist Seth Cohen, M.D. because his ED prescription isn't working, Cohen will often administer a penile duplex Doppler ultrasound (PDDU), a noninvasive test that evaluates the arterial damage inside the patient's penis.

If the damage is severe enough that Cohen doesn't think the man is a good candidate for penile injection therapy, he may discuss the possibility of a penile implant. Or, if the penile ultrasound indicates the arteries look healthy, despite not responding to medication, Cohen may offer injection therapy, sparing the man from undergoing implant surgery.

Cohen's example illustrates how useful the PDDU can be in both the diagnosis and treatment of men with erectile difficulties.

The penile ultrasound is similar to most common ultrasounds, said Cohen, an assistant professor of urology and director of sexual medicine at NYU Langone Health. Ultrasounds are good tools to use on the penis because they don't use radiation or transmit much heat, which is why they can be used on the belly of a pregnant woman.

'It's picking up different signal frequencies, whether thicker like muscle or thinner like fat, and then it reads it out on the display machine.'

A PDDU involves placing an ultrasound probe along the side of the penis. Different crystals within the probe measure frequencies within the body.

"It's picking up different signal frequencies, whether thicker like muscle or thinner like fat, and then it reads it out on the display machine," Cohen said.

While most people are familiar with ultrasounds, they may be thrown off by the word "Doppler." We all know about the Doppler weather radar, which shows the rain in our area. In the medical world, a Doppler measures the velocity of flow of a fluid, Cohen explained.

Typically, Doppler is used to measure blood flow within vascular organs. For example, if someone has reconstructive surgery on their leg, a doctor will use the Doppler ultrasound probe to make sure there's continued blood flow in the leg.

When a patient comes to a urologist's office for a penile ultrasound, they are injected with an erectogenic agent (e.g., Trimix) that gives them a full erection. The erection dilates the blood vessels in the penis, particularly the right and left cavernosal arteries. The ultrasound technician or urologist will then put the gel-covered ultrasound probe on the erect penis—the gel is needed for the ultrasound to penetrate the skin.

"We're looking for two types of flow: peak systolic velocity (PSV) and end-diastolic velocity (EDV)," Cohen said.

Blood flow is typically measured in centimeters per second. For peak systolic velocity, 30 centimeters per second or greater of arterial blood flow going into the penis is considered normal arterial function. End-diastolic velocity, which measures blood flow coming out of the penis through the veins, should be less than 3 centimeters per second.

"When you're having an erection, you want maximum blood flow going into the penis so you can get rock hard and minimal blood flow leaking out of the penis," Cohen said, adding that the entire ultrasound procedure takes about 30 minutes.

The most important aspect of the procedure for the medical team is to make sure it has maximally titrated the medication to give a patient a penetration-hardness erection and that all the measurements are performed appropriately, said Helen Bernie, D.O., a urologist and the director of Sexual and Reproductive Medicine at Indiana University Health in Indianapolis.

Bernie and Cohen both said that following the procedure, they talk with patients about the test results and the next steps for treatment.

Bernie uses the PDDU on all of her patients who have Peyronie's disease, which is characterized by fibrous scar tissue, known as plaque, forming under the penile skin and causing curved erections. The ultrasound probe can identify Peyronie's plaque within the shaft of the penis as well as measure curvature and indentation.

"It's going to help you evaluate the degree of deformity and the degree of curvature," Bernie said.

Mondor's disease, an inflammatory disorder typically caused by trauma that results in hard superficial veins in the penis, can also be diagnosed with a penile duplex Doppler ultrasound.

For younger men who have psychogenic or adrenaline-mediated erectile dysfunction, having the PDDU performed and seeing the objective data that their erectile function is fine can give them the confidence they need, Bernie said.

"Sometimes that's all they need to get over that psychological block, and they're able to have erections again, with or without medication," she said.

While the PDDU can help urologists make diagnoses, it's not without its downsides. When administering an erectogenic medication such as Trimix, the doctor doesn't necessarily know what response the patient will have, Cohen said.

"For example, if someone is very anxious in the office, they may have less of a response to the medication, and subsequently, it may throw off the numbers," he said. "It could look like he has more severe arterial disease than he truly does because he's a very anxious guy. I've seen that plenty."

Priapism, or a prolonged erection, is a potential side effect of the erectogenic agent, Bernie said, which is why she makes sure to find out before the ultrasound if patients take any blood pressure medication, because some drugs used to reverse an erection can elevate blood pressure.

'I think it's a very cost-effective, noninvasive procedure that can give you a lot of good information about a man's erectile function.'

"You want to make sure that they've taken their antihypertension medication prior to the procedure," she said, adding that she closely monitors the patient, and if the erection hasn't gone down following the procedure, it can usually be reversed by administering phenylephrine in the office.

While a penile duplex Doppler ultrasound is not a perfect procedure, Cohen said that in the hands of an experienced ultrasound tech or urologist, it can be a very effective tool.

Bernie agreed.

"I think it's a very cost-effective, noninvasive procedure that can give you a lot of good information about a man's erectile function," she said.