Priapism is a persistent erection that occurs without sexual arousal and lasts for an extended period, typically more than four hours. It is considered a medical emergency in some forms, as prolonged erections can lead to tissue damage. High flow priapism is a less common but distinct type of this condition.
Understanding High Flow Priapism
High flow priapism, also known as non-ischemic or arterial priapism, results from an unregulated and excessive flow of arterial blood into the penile erectile tissues, known as the corpora cavernosa. This occurs due to the formation of an arteriovenous fistula, an abnormal connection between an artery and the spongy spaces within the penis, allowing arterial blood to bypass normal blood flow regulation and leading to a sustained erection.
It differs significantly from low flow priapism, which is caused by impaired venous outflow, leading to blood becoming trapped and deoxygenated within the penis. Unlike low flow priapism, high flow priapism typically does not cause pain because the blood within the corpora cavernosa remains well-oxygenated, preventing tissue damage from lack of oxygen. The erection in high flow priapism may not be fully rigid.
Causes of High Flow Priapism
The most frequent cause of high flow priapism is trauma to the perineum or penis. Such injuries can lead to the rupture of a cavernosal artery or one of its branches, subsequently forming an arteriovenous fistula.
Less common causes of high flow priapism include iatrogenic factors, which are complications arising from medical procedures. This can occur after penile injection therapy or surgical interventions. In some instances, no clear cause can be identified, and these cases are referred to as idiopathic.
Diagnosing High Flow Priapism
The diagnostic process for high flow priapism begins with a thorough physical examination and a detailed patient history. Distinguishing high flow from low flow priapism is important because their treatments differ.
A key diagnostic tool is penile duplex ultrasonography, which can visualize blood flow within the penis and identify the arteriovenous fistula. This imaging technique can also measure blood flow velocities, helping to confirm the presence of increased arterial inflow. Additionally, penile blood gas analysis may be performed. In high flow priapism, this analysis typically shows normal or near-normal oxygen levels, contrasting with the low oxygen levels seen in low flow priapism. Angiography, a more invasive imaging technique, may be utilized to precisely locate the fistula and plan for treatment, particularly if embolization is considered.
Treatment Options
The primary treatment for high flow priapism is selective arterial embolization. This minimally invasive procedure involves blocking the specific artery that is supplying the arteriovenous fistula. The procedure is often highly effective, with resolution rates reported around 75%.
Unlike low flow priapism, which often requires immediate intervention due to the risk of tissue damage, high flow priapism typically does not necessitate urgent treatment. Conservative management, including perineal compression and ice application, may be attempted initially, as spontaneous resolution occurs in approximately 60% of cases. If conservative measures fail, selective arterial embolization is then pursued. Surgical ligation of the fistula is an alternative treatment option, but it is generally reserved for cases where embolization is not feasible or has failed, as it carries a higher risk of complications like erectile dysfunction.