Priapism is a prolonged, painful, and persistent erection that occurs without sexual stimulation or arousal, typically defined as lasting four hours or longer. This condition is a true medical emergency that requires immediate attention to prevent severe, permanent damage to the penis. Delaying treatment based on self-diagnosis or waiting for the erection to subside naturally can lead to irreversible tissue destruction. The following information details the different types of this condition, the timeline of tissue damage in an untreated episode, and the necessary emergency medical interventions.
Defining Priapism and Recognizing the Emergency
Priapism is categorized into two primary types: ischemic (low-flow) and non-ischemic (high-flow). Ischemic priapism, which accounts for the majority of cases, is a urological emergency because it involves a failure of blood to drain from the corpora cavernosa. This entrapment of blood creates a painful, rigid erection, though the glans (tip) of the penis usually remains soft.
The trapped blood is deoxygenated, leading to a state of hypoxia and local acidosis that starves the penile tissues. Common underlying causes for this urgent condition include sickle cell disease, certain psychiatric medications, and intracavernosal injections used for erectile dysfunction. Any erection lasting beyond the four-hour mark is considered ischemic priapism and necessitates an immediate emergency room visit.
In contrast, non-ischemic priapism is a less urgent situation caused by uncontrolled, excessive arterial blood flow into the penis, usually due to trauma to the perineum or penis. This high-flow state often results from a rupture in a penile artery, creating a fistula that bypasses the normal flow-regulating mechanisms. The resulting erection is typically less rigid, not painful, and the blood remains oxygenated because flow is continuous, minimizing the risk of immediate tissue death.
The Progression of Tissue Damage in Untreated Priapism
The most severe consequences are seen in untreated ischemic priapism, where the lack of oxygen leads to cellular destruction within the corpora cavernosa. Within the first four to six hours, the trapped, stagnant blood becomes severely deoxygenated, leading to cellular hypoxia and local acidosis. This environment begins to stress the delicate smooth muscle cells that line the erectile tissue chambers.
As the condition persists past 12 hours, microscopic examination reveals trabecular interstitial edema, where fluid accumulates between the smooth muscle bundles. The prolonged lack of fresh blood flow causes damage to the sinusoidal endothelium, the specialized lining of the blood spaces in the corpora cavernosa. This destruction exposes the underlying basement membrane, encouraging platelet adherence and the formation of microscopic blood clots within the chambers.
By 24 hours, the damage progresses to the point of smooth muscle cell necrosis due to the sustained ischemia. The specialized erectile smooth muscle, which is necessary for the flaccid and erect states, is replaced by non-functional fibrous tissue. If the ischemic episode lasts 36 hours or more, the likelihood of extensive, permanent fibrosis increases. This irreversible scarring replaces the elastic tissue with stiff, inelastic collagen, leading to a loss of the penis’s ability to fully relax and also to shorten and curve during erection.
Emergency Medical Interventions and Long-Term Outcomes
Treatment for ischemic priapism must be initiated without delay. The first-line intervention is corporal aspiration, where a needle is inserted into the corpus cavernosum to drain the trapped, deoxygenated blood and relieve pressure. If aspiration alone is unsuccessful, the physician will perform an intracavernosal injection of an alpha-adrenergic agonist, such as phenylephrine.
This medication constricts the arteries that supply blood to the penis and relaxes the smooth muscle, encouraging the stagnant blood to drain out. If the priapism has lasted longer than 48 hours or is refractory to these conservative measures, a surgical shunt procedure becomes necessary. This involves creating a small channel between the corpus cavernosum and another structure, like the glans penis or corpus spongiosum, to manually bypass the blocked venous outflow.
The long-term outcome of priapism is correlated with the duration of the ischemic event. For episodes resolved within 24 hours, the chance of recovering normal erectile function is higher. However, for cases lasting 36 hours or more, the risk of permanent erectile dysfunction (ED) is substantial, often exceeding 50% due to the extensive corporal fibrosis that occurs. In severe, neglected cases where fibrosis and shortening are significant, a penile prosthesis may be required to restore the ability to achieve a functional erection.