A penile ultrasound is a non-invasive medical imaging procedure that uses high-frequency sound waves to generate pictures of the internal structures of the penis. It focuses on assessing the two main erectile bodies, the corpora cavernosa, and surrounding structures like the cavernosal arteries and the tunica albuginea. The primary goal of the examination is to evaluate blood flow dynamics and tissue structure to diagnose various underlying conditions.
Diagnostic Applications
The penile ultrasound is a precise tool for investigating conditions, most commonly those related to the vascular system. For men experiencing difficulty achieving or maintaining a firm erection, the ultrasound determines if the problem is due to insufficient blood flow into the penis or excessive blood flow out of it. The procedure is also used for assessing structural abnormalities, such as the plaques that form in Peyronie’s disease. Imaging allows for precise measurement of the size, location, and calcification of these fibrous plaques, assisting in monitoring the condition’s progression and guiding treatment decisions.
Preparation for the Dynamic Test
The most informative penile ultrasound is often the dynamic study, which requires preparation to assess blood flow during an induced erection. Patients are instructed to avoid certain medications, such as those for erectile dysfunction, before the test, as these can interfere with the results. Preparation involves an intracavernosal injection (ICI) of a vasoactive drug, such as prostaglandin E1 (alprostadil), to induce a temporary erection. This drug relaxes the smooth muscles in the penile arteries, increasing blood flow into the corpora cavernosa.
The Step-by-Step Procedure
The dynamic ultrasound procedure begins with the patient lying down comfortably. The technician applies a water-based gel to the skin to ensure the transducer can transmit sound waves effectively. Initial imaging is performed in B-mode, which uses gray-scale images to map the internal anatomy and check for pre-existing plaques or tumors.
Following the initial scan, the vasoactive medication is administered through a fine needle into one of the corpora cavernosa. The injection is quick and is typically given at the side of the penile shaft. The patient rests briefly while the drug takes effect and the erection develops.
The dynamic phase begins as the erection progresses, with the technician using the Doppler mode of the ultrasound machine. Doppler technology measures the speed and direction of blood flow. Measurements of specific parameters, such as Peak Systolic Velocity (PSV) and End-Diastolic Velocity (EDV), are taken at five-minute intervals for up to 25 to 30 minutes.
Interpreting the Findings
The data collected during the dynamic scan translates directly into diagnostic information about the cause of functional problems. The Peak Systolic Velocity (PSV) is the primary indicator of arterial health. A PSV value greater than 30 centimeters per second indicates normal arterial inflow. If the PSV is less than 25 centimeters per second, it suggests arterial insufficiency, an inflow problem that limits the amount of blood reaching the erectile tissue.
The End-Diastolic Velocity (EDV) assesses the integrity of the veno-occlusive mechanism. When the veins properly trap the blood during erection, the EDV should be low, ideally less than 5 centimeters per second. A persistently elevated EDV, often above 5 centimeters per second, indicates veno-occlusive dysfunction, or a venous leak, where blood escapes prematurely. For structural issues like Peyronie’s disease, gray-scale images confirm the presence and size of plaques, and the Doppler aspect indicates if the condition has affected blood flow.