Penile conditions: Pathology review

Jacob is a 32 year old male who comes to the emergency department because of a painful, sustained erection, which has lasted five hours now. Upon further questioning, Jacob tells you that he takes antidepressant medications. You immediately order a penile arterial blood gas analysis, which reveals decreased concentration of oxygen, increased concentration of carbon dioxide, and decreased arterial pH.

Next you see Tafari, a 55 year old male of African descent. Tafari is worried because he developed a lesion on the glans penis about six months ago, and it won’t go away. Upon physical examination, you notice that the lesion looks bright red and has well-defined borders. Finally, you decide to perform an excisional biopsy to remove and analyze the lesion.

Okay, based on the initial presentation, both Jacob and Tafari seem to have some form of penile condition.

Now, the penis is made of three long cylindrical bodies: the corpus spongiosum that surrounds the penile urethra, and the two corpora cavernosa that are made of erectile tissue. The corpora cavernosa are wrapped in a fibrous coat called the tunica albuginea, and each corpus cavernosum is made up of blood-filled spaces called the cavernosal spaces. These spaces are lined with endothelial cells surrounded by smooth muscle. Running down the center of each corpus cavernosum is a large artery called the deep artery, which gives off smaller arteries that supply the cavernosal spaces. Next, blood gets drained from these spaces by small emissary veins, which drain into the deep dorsal vein. This vein then carries the blood back into the systemic circulation.

Now, for your exams, some high yield penile conditions you must absolutely remember include Peyronie disease, priapism, and squamous cell carcinoma of the penis.

Let’s start with Peyronie disease, which refers to an abnormal curvature of the penis. For your exams, make sure you don’t confuse this disease with a penile fracture, where penile injury may result in rupture of the corpora cavernosa, leading to an abnormal penile curvature. In contrast, the cause of Peyronie disease is not fully understood, however, it’s thought to be associated with repeated microtrauma during sexual intercourse. This is followed by local inflammation and collagen deposition creating a fibrous plaque in the tunica albuginea.

The most common symptoms of Peyronie disease include a visibly curved penis that may progress or stabilize over time. This is often accompanied by penile pain and erectile dysfunction, where an individual is unable to develop or maintain an erection. Keep in mind that this may increase the risk for psychiatric conditions, like anxiety or depression. Diagnosis of Peyronie disease is usually clinical, and treatment involves injections of collagenase, which helps degrade collagen within the lesion, once the curvature gets stabilized. In more severe cases, surgical repair might be recommended.

Next is priapism, which refers to a prolonged penile erection that occurs in the absence of sexual arousal, often lasts for more than four hours, and is not relieved by ejaculation. For your exams, remember that there are two main types of priapism: ischemic or low-flow priapism and nonischemic or high-flow priapism. What helps you set these two apart clinically is that in the case of ischemic priapism, the erection is painful and rigid, in contrast to nonischemic priapism, where the erection is typically painless and not fully rigid.

Now, the most common and high yield type is ischemic or low-flow priapism, which occurs when there’s insufficient venous drainage from the corpora cavernosa. This means that blood can’t leave through the veins, so it backs up, slowing down the blood flow through the arterial side as well! As a result, less oxygenated blood gets to the penis, which leads to ischemia.

Now, insufficient venous drainage is often due to blockage of draining venules. An important cause for your exams is sickle cell disease, where sickled red blood cells get stuck in the walls of those venules, clogging up blood flow. So, if a test question mentions a child with priapism, think of sickle cell disease! On the other hand, the most common cause of priapism among adults are medications, including antidepressants like trazodone, and phosphodiesterase-5 or PDE-5 inhibitors like sildenafil, which are used to treat erectile dysfunction.

Now, there’s also nonischemic or high-flow priapism, which is less common. Here, the problem is excessive cavernous arterial inflow from a fistula that connects the deep artery and corpus cavernosum. Usually, this occurs as a result of genital trauma or penetrating injury.