Diagnosing priapism

Priapism is a painful (and often embarassing) condition that physicians may need to manage from time to time. In this video, from our Emergency Procedures Masterclass (Part 2), we'll review the anatomy of the penis in preparation for learning how to perform a dorsal nerve penile block. You'll learn about the areas you need to avoid when injecting a block, why you don't need to inject both sides of the penis, and how to differentiate ischemic from non-ischemic priapism, in order to refer your patient quickly and avoid permanent erectile dysfunction.

In this course, you will learn a variety of procedures used in emergency medicine. These procedures will help you to diagnose and treat common infections, injuries, and other problems, such as joint infections, dislocations, soft tissue abscesses, and priapism. You’ll also cover the ultimate airway rescue procedure—the cricothyrotomy. This masterclass is a companion to the Emergency Procedures Masterclass (Part 1).

So what is priapism? Priapism is a prolonged penis erection lasting over four hours in the absence of sexual stimulation. It's named after Priapus, God of Fertility in Greek mythology. Let's quickly review the anatomy of the penis. The urethra where the urine and semen travel through is surrounded by the corpus spongiosum.

Remember this anatomy when we get into the treatment, because we don't want to inject anything in this area. There are two nerves on the dorsum of the penis that innervate it. The location of these is important for performing a dorsal nerve penile block. And finally, there are multiple layers of connective tissue surrounding the corpora, including the outer buck’s fascia and the inner tunica albuginea.

Erection of the penis is achieved by engorgement of the corpora cavernosa by increased arterial flow and decreased venous return. There are two of these in the penis, but it's important to note that they are connected to each other. So that's why you don't have to inject both sides of the penis when we discuss treatment in the next lesson.

There are two types of priapism. The first and most common almost 95% of cases, is ischemic priapism, caused by painful venous engorgement of the corpora cavernosa. This is the kind of priapism we will be discussing in this chapter. The second and really rare type is non-ischemic priapism, which is caused by increased arterial inflow to the penis, usually from trauma causing arteriocavernosal fistula, and these are typically not painful.

Ischemic priapism is a urologic emergency because it's really painful and can lead to permanent erectile dysfunction. This happens as the pressure in the penis approaches the arterial pressure and venous return is diminished. At this point, there's no new blood flow to the penis, and the blood in the penis becomes hypoxic and acidotic.

Rarely, the stagnant blood can even clot. If there's ever a question about ischemic versus non-ischemic priapism, a blood sample from the corpora cavernosum will confirm ischemia by having high lactate, low pH, and low PaO2. But this is rarely ever needed. Because in the absence of trauma and presence of pain, you're definitely dealing with an ischemic priapism.

There are lots of causes of ischemic priapism. The most common reason I've treated in my career, his use of impotence medications, mostly the kind that the patients directly inject into the penis to achieve an erection right before sex. Lots of other medications can lead to priapism like psychiatric medications, certain blood pressure medications, hormones, illicit drugs like cocaine, lots of them.

But all these vasoactive medications result in promoting blood flow to the penis and decreasing venous outflow. The other important category of patients that can develop priapism are patients with sickle cell disease. The prevalence of priapism in men with sickle cell disease is up to 40%. And of those affected, 30% will develop erectile dysfunction. Now that you know the anatomy and causes of priapism in the next Medmastery lesson, we'll talk about the approach and the tools needed to treat priapism.