Priapism is a medical condition characterized by a prolonged erection of the penis that persists for hours beyond or is unrelated to sexual stimulation. The erection is often painful and does not subside after orgasm. The condition is considered a medical emergency, particularly for the more common ischemic type, due to the risk of permanent penile tissue damage and erectile dysfunction if not treated promptly. The name derives from Priapus, the Greek god of fertility, who was often depicted with a permanent, oversized erection.
Classification
Priapism is primarily classified into two main types based on blood flow dynamics:
- Ischemic Priapism (Low-Flow Priapism): This is the more common and serious form, resulting from insufficient venous outflow from the penis. It is characterized by a rigid, often painful erection. The lack of blood flow leads to hypoxia (lack of oxygen) and acidosis (build-up of acidic waste products) within the erectile tissue, which can cause permanent damage if not quickly resolved.
- Non-Ischemic Priapism (High-Flow Priapism): This less common type results from uncontrolled arterial inflow into the penis, typically due to a fistula (abnormal connection) between an artery and the corpus cavernosum. It is usually less rigid, often not painful, and does not typically lead to tissue damage as blood flow is maintained. It often arises from trauma.
Causes
The causes of priapism vary depending on the type:
Ischemic Priapism:
- Sickle Cell Disease: This is the most common cause in children and a significant cause in adults, where sickled red blood cells can obstruct venous outflow.
- Medications:
- Drugs used to treat erectile dysfunction (e.g., intracavernosal injections, oral PDE5 inhibitors like sildenafil, tadalafil, vardenafil).
- Antidepressants (e.g., trazodone).
- Antihypertensives (e.g., alpha-blockers like prazosin).
- Antipsychotics.
- Anticoagulants.
- Hematologic Conditions: Leukemia, thalassemia.
- Neurological Conditions: Spinal cord injury, cauda equina syndrome.
- Illicit Drug Use: Cocaine, marijuana.
- Metabolic Conditions: Fabry disease.
- Idiopathic: In some cases, no clear cause can be identified.
Non-Ischemic Priapism:
- Trauma: Blunt trauma to the perineum or penis (e.g., straddle injury) is the most common cause, leading to arterial rupture and the formation of an arteriovenous fistula.
- Medical Procedures: Rarely, iatrogenic injury during penile procedures.
Symptoms
- Ischemic Priapism:
- Persistent, rigid erection lasting more than four hours.
- Significant pain and tenderness in the penis.
- The corpora cavernosa (main erectile chambers) are engorged and firm, while the glans penis (head) and corpus spongiosum (tissue around the urethra) may be soft.
- Non-Ischemic Priapism:
- Persistent erection that is usually less rigid and often non-painful.
- The erection may be sustained for days or weeks.
- Often has a history of trauma, with the priapism sometimes developing hours or days after the injury.
Diagnosis
Diagnosis is based on a combination of patient history, physical examination, and diagnostic tests:
- Patient History: Inquiring about duration, pain, recent trauma, medication use, and underlying medical conditions.
- Physical Examination: Assessing the rigidity and tenderness of the penis.
- Corpus Cavernosum Blood Gas Analysis: This is the most crucial test to differentiate between ischemic and non-ischemic types. Ischemic priapism will show low oxygen tension, high carbon dioxide tension, and acidosis, while non-ischemic will have arterial-like oxygen levels.
- Doppler Ultrasound: Used to assess blood flow within the penis. It can identify the presence or absence of flow, differentiate between high and low flow, and locate arteriovenous fistulas in non-ischemic cases.
- Arteriography: May be used for non-ischemic priapism to precisely locate the arterial fistula before embolization.
Treatment
Treatment goals are to detumesce the penis and prevent long-term complications. The approach varies significantly by type:
Ischemic Priapism (Medical Emergency):
- Aspiration and Irrigation: The first-line treatment involves aspirating old, deoxygenated blood from the corpus cavernosum, followed by irrigation with saline solution.
- Intracavernosal Injection of Alpha-Adrenergic Agonists: Phenylephrine, a vasoconstrictor, is injected directly into the penis to constrict the arterial inflow and relax the smooth muscle, allowing blood to drain.
- Surgical Shunt Procedures: If aspiration and medication fail, surgical creation of a shunt (a connection between the corpus cavernosum and another venous system) is performed to allow blood to drain. Various types of shunts exist (e.g., corporo-spongiosal, corporo-saphenous).
- Management of Underlying Cause: For sickle cell patients, aggressive hydration, oxygenation, and sometimes blood transfusions are essential.
Non-Ischemic Priapism:
- Observation: Many cases of non-ischemic priapism resolve spontaneously.
- Selective Arterial Embolization: If the condition is persistent or bothersome, a minimally invasive procedure can be performed to identify and occlude the problematic arterial fistula using coils or other embolic agents. This preserves potency.
- Surgical Ligation: Rarely, if embolization fails, surgical ligation of the fistula may be considered.
Prognosis and Complications
The prognosis for priapism heavily depends on its type and how quickly it is treated.
- Ischemic Priapism: If not treated promptly, ischemic priapism can lead to severe and permanent complications, including:
- Erectile Dysfunction (ED): This is the most common and feared long-term complication, occurring due to damage to the cavernosal smooth muscle and nerves from prolonged hypoxia. The longer the erection persists, the higher the risk of irreversible ED.
- Penile Fibrosis: Scar tissue formation within the corpora cavernosa, leading to penile shortening, curvature, and painful erections.
- Gangrene: In very rare, severe, and neglected cases, tissue necrosis can occur.
- Non-Ischemic Priapism: The prognosis for erectile function is generally excellent, as the blood supply to the tissue is maintained. Complications are rare, though the persistent erection can be bothersome.