madman
Super Moderator
High-frequency US, with a linear transducer and gray-scale, color, and spectral Doppler US techniques, is the primary imaging modality for evaluation of the penis. It can allow delineation of anatomy and assessment of dynamic blood flow; it is easily available and non invasive or minimally invasive; it is cost effective; and it is well tolerated by patients. US assessment after pharmacologic induction of erection is an additional tool in assessing patients with suspected vasculogenic impotence, and also in selected patients with penile trauma and suspected Peyronie disease. Penile injuries, life-threatening infections, and vascular conditions such as priapism warrant rapid diagnosis to prevent long-term morbidities due to clinical misdiagnosis or delayed treatment. US can facilitate a timely diagnosis in these emergency conditions, even at the point of care such as the emergency department, which can facilitate timely treatment. In addition, color and spectral Doppler US are valuable applications in the follow-up of patients treated with endovascular revascularization procedures for vasculogenic erectile dysfunction. Image optimization and attention to meticulous techniques including Doppler US is vital to improve diagnostic accuracy. Radiologists should be familiar with the detailed US anatomy, pathophysiologic characteristics, scanning techniques, potential pitfalls, and US manifestations of a wide spectrum of vascular and nonvascular penile conditions to suggest an accurate diagnosis and direct further management. The authors review a range of common and uncommon abnormalities of the penis, highlight their key US features,discuss differential diagnosis considerations, and briefly review management.
Penile Anatomy
Physiology of Penile Erection
Penile erection is a complex phenomenon that is dependent on the coordinated interaction of the arterial, veno sinusoidal and autonomic nervous systems. In the flaccid state, the smooth muscles are in a tonic state, the cavernous sinusoids are collapsed, and the cavernous venules are open. The emissary veins drain the sinusoidal spaces into dorsal veins, and a low-velocity flow can be detected at US.
Erection of the penis is initiated by neuronal impulses that lead to relaxation of smooth muscle and dilatation of the cavernosal arteries, which in turn causes increased blood flow to the cavernosa. These, together with compression of cavernous venules between dilated sinusoid spaces and the unyielding tunica albuginea, results in reduction of venous outflow. This leads to an imbalance between arterial inflow and venous drainage that causes and maintains turgidity of the corpora and rigid erection. Five stages of erection have been defined: latency, tumescence, full erection, rigid erection, and detumescence (Fig S1). Specific physiologic and Doppler US changes and spectral waveforms (Fig 5) occur during each of these stages. A thorough understanding of the stages facilitates accurate interpretation of the Doppler US findings in patients with penile abnormalities, including suspected ED.
US Protocol and Technique
Classification of Penile Abnormalities
Nonvascular Abnormalities
Peyronie Disease
Trauma
Infection
Tumors and Tumor like Lesions
Foreign Body
Vascular Abnormalities
Venous Thrombosis
Priapism
Erectile Dysfunction
ED has a high prevalence and incidence worldwide and can substantially affect physical and psychosocial health. ED can have vascular and nonvascular causes (eg, neurogenic, psychogenic, or hormonal), and penile US with Doppler US is an excellent tool for identification and classification of organic causes of ED. However, with the introduction of oral phosphodiesterase inhibitors, Doppler US studies for evaluation of ED are used substantially less frequently and are indicated mainly in patients who do not respond to a trial of medication or for whom there is high suspicion for a remediable vascular cause that is amenable to intervention (35–37).
In addition, penile Doppler US may suggest the presence of silent coronary artery disease in men presenting with ED, because ED has been reported to be a marker of endothelial dysfunction and an early manifestation of cardiovascular disease (38,39).
Doppler US assessment can accurately suggest the diagnosis of vasculogenic impotence due to arterial or venous disease or can exclude a vascular cause. Pharmacologic induction of erection is necessary for accurate assessment of the hemodynamic changes that occur during erection that are reflected on the Doppler US images.
After the initial gray-scale and Doppler US evaluation of the penis, erection is induced by intracavernosal injectionof a vasoactive drug into the lateral aspect of one of the cavernosa along the proximal one-third of the penis. Prostaglandin E1 is the most common vasoactive agent used, with a dosage of 10–20 μg (40).
Conclusion
US is typically the first-line imaging tool to evaluate the penis. It provides valuable information for detection, characterization, and management of penile pathologic conditions. Penile Doppler US studies with pharmacologic induction of erection continue to be crucial in the evaluation of patients with suspected vasculogenic impotence who have not responded to medical treatment. Furthermore, Doppler US can be important in the follow-up of patients to assess response to treatment and identify treatment failure. Radiologists should be familiar with Doppler US techniques, understand the limitations of the modality, and be able to interpret the wide spectrum of vascular and nonvascular abnormalities that are encountered on US images.
Penile Anatomy
Physiology of Penile Erection
Penile erection is a complex phenomenon that is dependent on the coordinated interaction of the arterial, veno sinusoidal and autonomic nervous systems. In the flaccid state, the smooth muscles are in a tonic state, the cavernous sinusoids are collapsed, and the cavernous venules are open. The emissary veins drain the sinusoidal spaces into dorsal veins, and a low-velocity flow can be detected at US.
Erection of the penis is initiated by neuronal impulses that lead to relaxation of smooth muscle and dilatation of the cavernosal arteries, which in turn causes increased blood flow to the cavernosa. These, together with compression of cavernous venules between dilated sinusoid spaces and the unyielding tunica albuginea, results in reduction of venous outflow. This leads to an imbalance between arterial inflow and venous drainage that causes and maintains turgidity of the corpora and rigid erection. Five stages of erection have been defined: latency, tumescence, full erection, rigid erection, and detumescence (Fig S1). Specific physiologic and Doppler US changes and spectral waveforms (Fig 5) occur during each of these stages. A thorough understanding of the stages facilitates accurate interpretation of the Doppler US findings in patients with penile abnormalities, including suspected ED.
US Protocol and Technique
Classification of Penile Abnormalities
Nonvascular Abnormalities
Peyronie Disease
Trauma
Infection
Tumors and Tumor like Lesions
Foreign Body
Vascular Abnormalities
Venous Thrombosis
Priapism
Erectile Dysfunction
ED has a high prevalence and incidence worldwide and can substantially affect physical and psychosocial health. ED can have vascular and nonvascular causes (eg, neurogenic, psychogenic, or hormonal), and penile US with Doppler US is an excellent tool for identification and classification of organic causes of ED. However, with the introduction of oral phosphodiesterase inhibitors, Doppler US studies for evaluation of ED are used substantially less frequently and are indicated mainly in patients who do not respond to a trial of medication or for whom there is high suspicion for a remediable vascular cause that is amenable to intervention (35–37).
In addition, penile Doppler US may suggest the presence of silent coronary artery disease in men presenting with ED, because ED has been reported to be a marker of endothelial dysfunction and an early manifestation of cardiovascular disease (38,39).
Doppler US assessment can accurately suggest the diagnosis of vasculogenic impotence due to arterial or venous disease or can exclude a vascular cause. Pharmacologic induction of erection is necessary for accurate assessment of the hemodynamic changes that occur during erection that are reflected on the Doppler US images.
After the initial gray-scale and Doppler US evaluation of the penis, erection is induced by intracavernosal injectionof a vasoactive drug into the lateral aspect of one of the cavernosa along the proximal one-third of the penis. Prostaglandin E1 is the most common vasoactive agent used, with a dosage of 10–20 μg (40).
Conclusion
US is typically the first-line imaging tool to evaluate the penis. It provides valuable information for detection, characterization, and management of penile pathologic conditions. Penile Doppler US studies with pharmacologic induction of erection continue to be crucial in the evaluation of patients with suspected vasculogenic impotence who have not responded to medical treatment. Furthermore, Doppler US can be important in the follow-up of patients to assess response to treatment and identify treatment failure. Radiologists should be familiar with Doppler US techniques, understand the limitations of the modality, and be able to interpret the wide spectrum of vascular and nonvascular abnormalities that are encountered on US images.
