Chapter 19: Priapism in Sickle Cell Disease

Overview

Priapism is defined as a prolonged penile erection, either long beyond sexual stimulation or, more typically, unrelated to sexual stimulation or interest.¹ The condition is relatively uncommon, with a reported incidence of 0.34 to 1.5 cases per 100,000 male patients per year.^2,3 Estimations of incidence are likely to vary by region, however, because the proportion of the population with sickle cell disease or sickle cell trait will vary. Although priapism has many causes, the lifetime risk of a patient with sickle cell disease developing an episode of priapism is between 29% and 42%.⁴ In the United States, using the Nationwide Emergency Department Sample, Stein et al⁵ estimated a total of 9991 encounters per year, with 27.9% of these encounters leading to admission. They estimated a total cost of $123,860,432 dollars per year in the United States for treatment related to priapism, with 86.8% of these charges stemming from inpatient admission.⁵

In the sickle cell patient population, priapism can be a recurrent issue that severely impairs quality of life in a particularly young group of patients. For a subset of these patients, recurrent ischemic priapism, or stuttering priapism, may occur weekly or even daily.^6,7 In one study, a third of children and adolescents with priapism regard this as the worst complication of the disease.⁸ Patients experiencing priapism have reported embarrassment, worry, and social isolation as a consequence of these painful erections.⁹ Furthermore, because recurrent ischemic priapism often begins as a nocturnal erection, patients awaken earlier than usual with a painful erection resulting in daytime fatigue that impairs concentration and ability to perform at school or in the workplace.⁹ Finally, these patients experience recurrent hospitalizations, significant medical costs, and, in the most devastating cases, erectile dysfunction as a result of priapism.

Priapism is divided into subtypes classified as ischemic (low flow), stuttering (recurrent intermittent), and nonischemic (high flow). The vast majority of patients presenting with priapism present with ischemic priapism, as is the case in patients with sickle cell disease. An estimated 95% of cases are ischemic.¹⁰

Pathophysiology

Penile Anatomy

The penis is composed dorsally of 2 paired erectile bodies, the corpora cavernosa, and ventrally the corpus spongiosum, which contains the urethra (Figure 19-1A). The glans penis is an extension of the corpus spongiosum.¹¹ The corpora cavernosa are ensheathed by a thick collagenous connective tissue layer called the tunica albuginea.¹¹ Within the corpora cavernosa lies the erectile tissue itself, which is a network of smooth muscle bundles forming endothelium-lined sinusoidal spaces (Figure 19-1B).¹¹ There is a septum between the 2 corpora cavernosa; however, it is freely permeable distally, allowing for communication between these 2 vascular spaces.¹¹