Ultrasonography has gained significant importance in the evaluation of organ systems, and often leads to the diagnosis of diseases and conditions without exposure to ionizing radiation.¹ The use of ultrasonography in the management of erectile dysfunction (ED) is well established and dates back to the early 1990s.² Advances in this technology now allow for submillimeter evaluation of anatomical structures and real-time evaluation of blood flow in small vessels.³ While ultrasonography is now the primary imaging modality used for evaluating anatomical and functional changes of the penis in the setting of ED, its utility and popularity have changed over the last 30 years.

ED is defined as the inability to attain and/or maintain an erection sufficient for sexual satisfaction. ED is generally divided into organic and psychogenic types, and within the organic category ED can be caused by abnormalities in blood flow. Vasculogenic ED is the most common cause of organic ED and accounts for approximately 30%–50% of cases.⁴ Penile arterial insufficiency, venous leak, or a combination of the two define vasculogenic ED and can be diagnosed using imaging modalities. Prior to ultrasound, arteriography and dynamic infusion cavernosometry/cavernosography were the gold standard in diagnosing arterial insufficiency and veno-occlusive disease.⁵ The advent of color duplex Doppler ultrasonography (CDDU) consolidated both studies into 1 and made diagnosing vasculogenic ED a much simpler and conventional process without venous contrast or radiation exposure.

Figure. Longitudinal view of cavernosal artery calcification (arrow).

Penile ultrasonography for the evaluation of ED is done with the patient in the supine position and with the assistance of erectogenic medications injected directly into the corpora cavernosa. In our practice we inject approximately 10 mcg of alprostadil and rarely re-dose in order to minimize the risk for priapism, hematoma, pain, and hypotension. The patient is then given privacy and encouraged to self-stimulate prior to starting the examination. A 12 MHz linear transducer is then used to evaluate penile anatomy and hemodynamics in both the longitudinal and transverse views. Cavernosal artery blood flow is evaluated by placing the probe at the most proximal area of the penis, typically at the penoscrotal junction, in order to minimize the effect intracavernosal pressure has on peak systolic and end diastolic velocities.⁶ We ensure the probe is tilted at an angle of under 60 degrees with respect to the penis in order to capture accurate hemodynamic readings.⁶ A peak systolic velocity (PSV) of >35 cm/s is considered normal, < 25 cm/s is suggestive of arterial insufficiency, and a value between 25 and 35 is considered a gray zone and should be interpreted with caution.³ In younger men, sympathetic overtone from psychological stress can affect the PSV and appear to be within the indeterminate or even low range. The end diastolic velocity of the cavernosal artery is also measured and a value of >5 cm/s suggests a venous leak. Additional values such as the resistive index, systolic rise time, and acceleration time of blood flow within the cavernosal arteries can help paint a more defined picture of flow variations that may be present.⁷ While CDDU provides a detailed assessment of fluid dynamics and anatomical evaluation of the penis, its utility has come into question when evaluating patients with ED.

The 2018 AUA Guideline for ED outlines the conditions in which CDDU can be used to help guide treatment.⁸ The recommendation, based on expert opinion, states that patients who are young, have a strong family history of cardiac illness, history of pelvic trauma, failed prior ED therapies, a strong likelihood of primary psychogenic ED, concomitant Peyronie’s Disease (PD), or have had lifelong ED can benefit from CDDU. In our practice, we most commonly employ CDDU to guide treatment for patients who have failed prior ED therapy and wish to explore alternative treatments. This is especially true for those who are under 40 years of age, have suffered prior pelvic trauma, have undergone prior prostate, bladder, or rectal surgery, or have penile deformities suggestive of PD or have confirmed PD. Penile ultrasonography may also have the added benefit of identifying men at a higher risk for cardiovascular disease, findings that include cavernosal artery calcifications or intimal thickening (see figure). While the frequency in which CDDU is performed has decreased since the widespread adoption of phosphodiesterase type 5 inhibitors, it continues to serve a purpose, but under more defined criteria.³ Ultimately, it is important to ask whether the examination results will guide subsequent medical or surgical treatments, or elucidate early or silent cardiovascular disease.