Merck Manual

Please confirm that you are a health care professional

honeypot link



Geetha Maddukuri

, MD, Saint Louis University

Last full review/revision Jan 2021| Content last modified Jan 2021
Click here for Patient Education
Topic Resources

Priapism is painful, persistent, abnormal erection unaccompanied by sexual desire or excitation. It is most common in boys aged 5 to 10 years and in men aged 20 to 50 years.

Pathophysiology of Priapism

The penis is composed of 3 corporeal bodies: 2 corpora cavernosa and 1 corpus spongiosum. Erection is the result of smooth muscle relaxation and increased arterial flow into the corpora cavernosa, causing engorgement and rigidity.

Ischemic priapism

Most cases of priapism involve failure of detumescence and are most commonly due to failure of venous outflow (ie, low flow), also known as ischemic priapism. Severe pain from ischemia occurs after 4 hours. If prolonged > 4 hours, priapism can lead to corporeal fibrosis and subsequent erectile dysfunction or even penile necrosis and gangrene.

Stuttering priapism is a recurrent form of ischemic priapism with repeated episodes and intervening periods of detumescence.

Nonischemic priapism

Less commonly, priapism is due to unregulated arterial inflow (ie, high flow), usually as a result of formation of an arterial fistula after trauma. Nonischemic priapism is not painful and does not lead to necrosis. Subsequent erectile dysfunction is common.

Etiology of Priapism

In adults, the most common cause (see table Some Causes of Priapism) is

In children, the most common causes are

In many cases, priapism may be idiopathic and recurrent.


Some Causes of Priapism


Suggestive Findings

Diagnostic Approach

  • Alprostadil (injected, intraurethral)

  • Papaverine (injected)

  • Phentolamine (injected)

  • Phosphodiesterase type 5 (PDE-5) inhibitors (avanafil, sildenafil, tadalafil, vardenafil)

Painful ischemic priapism in men with history of treatment for erectile dysfunction

Clinical evaluation

Recreational drugs:

Painful ischemic priapism and psychomotor agitation and anxiety

Clinical evaluation

Sometimes toxicology screen

Other drugs:

  • Beta-blockers (prazosin, tamsulosin, terazosin)

  • Anticoagulants (warfarin)

  • Antihypertensives (nifedipine)

  • Antipsychotics*

  • Corticosteroids

  • Hypoglycemics (tolbutamide)

  • Lithium

  • Methaqualone

  • Trazodone

Painful ischemic priapism in men undergoing treatment for another medical disorder

Clinical evaluation

Hematologic disorders:

Young males, often of African or Mediterranean descent

Complete blood count

Hemoglobin electrophoresis

Locally advanced prostate cancer

Any metastatic disease

Men > 50 with history of increasing symptoms of bladder outlet obstruction


Continuous epidural infusions

Concomitant lower-extremity weakness

CT or MRI of the spine

Trauma (resulting in unregulated arterial inflow or arterial fistula formation)

Nonischemic, nonpainful priapism in men with recent trauma

Penile duplex ultrasonography



Rare causes:



* All atypical antipsychotics may cause priapism.

Evaluation of Priapism

Priapism requires urgent treatment to prevent chronic complications (primarily erectile dysfunction). Evaluation and treatment should be done simultaneously.


History of present illness should cover the duration of erection, presence of partial or complete rigidity, presence or absence of pain, and any recent or past genital trauma. The drug history should be reviewed for offending drugs, and patients should be directly asked about the use of recreational drugs and drugs used to treat erectile dysfunction.

Review of systems should seek symptoms suggesting a cause, including dysuria (urinary tract infections), urinary hesitancy or frequency (prostate cancer), fever and night sweats (leukemia), and lower-extremity weakness (spinal cord pathology).

Past medical history should identify known conditions associated with priapism (see table Some Causes of Priapism), particularly hematologic disorders. Patients should be asked about a family history of hemoglobinopathies (sickle cell disease or thalassemia).

Physical examination

A focused genital examination should be done to evaluate extent of rigidity and tenderness and determine whether the glans and corpus spongiosum are also affected. Penile or perineal trauma and signs of infection, inflammation, or gangrenous change should be noted.

The general examination should note any psychomotor agitation, and the head and neck examination should look for pupillary dilation associated with stimulant use. The abdomen and suprapubic area should be palpated to detect any masses or splenomegaly, and a digital rectal examination should be done to detect prostatic enlargement or other pathology. Neurologic examination is useful to detect any signs of lower-extremity weakness or saddle paresthesias that might indicate spinal pathology.

Red flags

The following findings are of particular concern:

  • Pain

  • Priapism in a child

  • Recent trauma

  • Fever and night sweats

Interpretation of findings

In most cases, the clinical history reveals a history of drug treatment for erectile dysfunction, illicit drug use, or a history of sickle cell disease or trait; in these cases, no testing is indicated.

In patients with ischemic priapism, physical examination typically reveals complete rigidity with pain and tenderness of the corpus cavernosa and sparing of the glans and corpus spongiosum. By contrast, nonischemic priapism is painless and nontender, and the penis may be partially or completely rigid.


If the cause is not obvious, screening is done for hemoglobinopathies, leukemia, lymphoma, urinary tract infection, and other causes:

  • Complete blood count

  • Urinalysis and culture

  • Hemoglobin electrophoresis in blacks and men of Mediterranean descent

Many clinicians also do drug screening, intracavernosal arterial blood gas testing, and duplex ultrasonography. Penile duplex ultrasonography will show little or absent cavernosal blood flow in men with ischemic priapism and normal to high cavernosal blood flow in men with nonischemic priapism. Ultrasonography may also reveal anatomic abnormalities, such as cavernous arterial fistula or pseudoaneurysm, which usually indicate nonischemic priapism. Occasionally, MRI with contrast is useful to demonstrate arteriovenous fistulas or aneurysms.

Treatment of Priapism

Treatment is often difficult and sometimes unsuccessful, even when the etiology is known. Whenever possible, patients should be referred to an emergency department; patients should preferably be seen and treated urgently by a urologist. Other disorders should be treated. For example, priapism often resolves when sickle cell crisis is treated. Measures used to treat priapism itself depend on the type.

Ischemic priapism

Treatment should begin immediately, typically with aspiration of blood from the base of one of the corpora cavernosa using a nonheparinized syringe, often with saline irrigation and intracavernous injection of the alpha-receptor agonist phenylephrine. For phenylephrine injections, 1 mL of 1% phenylephrine (10 mg/mL) is added to 19 mL of 0.9% saline to make 500 mcg/mL; 100 to 500 mcg (0.2 to 1 mL) is injected every 5 to 10 minutes until relief occurs or a total dose of 1000 mcg is given. Before aspiration or injection, anesthesia is provided with a dorsal nerve block or local infiltration.

If these measures are unsuccessful or if priapism has lasted > 48 hours (and is thus unlikely to resolve with these measures), a surgical shunt can be created between the corpus cavernosum and glans penis or corpus spongiosum and another vein.

Stuttering priapism

Stuttering priapism, when acute, is treated in the same way as other forms of ischemic priapism. There is a report of several cases caused by sickle cell disease that responded to a single oral dose of sildenafil. Treatments that may help prevent recurrences of stuttering priapism include antiandrogen therapy with gonadotropin-releasing hormone agonists, estrogen, bicalutamide, flutamide, phosphodiesterase type-5 inhibitors, and ketoconazole. The goal of antiandrogen therapy is to decrease the plasma testosterone level to < 10% of normal. Digoxin, terbutaline, gabapentin, and hydroxyurea have also been tried with some success.

Nonischemic priapism

Conservative therapy (eg, ice packs and analgesics) is usually successful; if not, selective embolization or surgery is indicated.

Refractory priapism

If other treatments are ineffective, a penile prosthesis can be placed.

Key Points

  • Priapism requires urgent evaluation and treatment.

  • Drugs (prescription and recreational) and sickle cell disease are the most common causes.

  • Acute treatment is with alpha agonists, needle decompression, or both.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Test your knowledge

Minimal Change Disease
Spontaneous remission in patients with minimal change disease (MCD) occurs in 40% of cases. Approximately 80 to 90% of cases respond to initial therapy with corticosteroids. It is important to continue therapy for another 2 weeks after remission and change to a maintenance regimen to lower the possibility of relapse of MCD. For those patients who do not respond to corticosteroid therapy, which of the following is the most appropriate next step in treatment? 
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID