Priapism

Authors: Drs Tom F Lue and Alan Shindel University of California San Francisco 2008-09-01

Priapism: Prolonged Erection of the Penis. A guide for men This manuscript reviews priapism, the condition in which a man has a penile erection that is not associated with sexual desire or excitement.

When does a prolonged erection of the penis become a medical problem?

Priapism is the condition where a man has a prolonged and oftentimes painful erection of the penis that is not related to sexual desire or stimulation.[1] Priapism is most often diagnosed after penile erection has persisted for more than 4 hours, although in some men erection associated pain may occur much sooner.  The word “priapism” is derived from the Greek and Roman god Priapus, a minor fertility deity most renowned for his enormous, continuously erect penis.

Priapism can affect boys and men at any age.  Public awareness of this condition has increased in recent years as a result of advertisements for medications that enhance erectile function and warn potential users to beware of erections that last more than four hours.  While this is not a common side effect of such medications, it is a potentially serious one.

There are two types of priapism:

1)     Ischemic Priapism:  Also known as “low flow” or “veno-occlusive” priapism, this is the situation where there is no blood flow into the erectile tissue of the penis.  In ischemic priapism the outflow of blood from the paired erectile bodies of the penis (called corpora cavernosa, located on the topside of the penis) is obstructed.  Because blood cannot escape, it becomes trapped within the corpora cavernosa. Pressure builds up to a point at which no fresh arterial blood can enter the erectile tissues; at that point the corpora cavernosa become a “dead space” with no blood flow.

The shaft of the penis is very hard during ischemic priapism, although the head (glans) of the penis may not be swollen.  This occurs because the erectile tissue in the head of the penis (part of the single corpus spongiosum, which is located on the underside of the penis and contains the urethra [water channel]) is separate from the erectile tissue of the corpora cavernosa.[2]

2)      Non-ischemic Priapism: Also known as “high flow” priapism, this is a rarer condition in which there is excessive flow of blood into the corpora cavernosa due to rupture of a small artery inside the erectile tissues.  This rupture is most commonly the result of blunt injury to the groin, pelvis, or crotch.  In non-ischemic priapism, the penis is enlarged and firm compared to its baseline flaccid (soft) state, but it is usually not as rigid as it would be with normal sexual arousal.[3] 

Why is the difference between ischemic and non-ischemic priapism important?

Ischemic priapism is a medical emergency.  Ischemic priapism can occur for a variety of reasons but the end result is that fresh blood carrying oxygen is not able to enter the corpora cavernosa and waste products from cell activity cannot be cleared from the penis.  The penis is able to tolerate short periods of diminished blood flow (e.g., during normal penile erection).  However, after several hours of continuous erection, cells within the penis are unable to carry on their vital functions due to lack of fresh blood supply.   Cells that cannot carry on vital functions will be damaged and may even die.  As this damage accumulates, a man with ischemic priapism will have increasing pain and will run the risk of severe and permanent injury to his penis.  In some cases, this injury is significant enough to lead to erectile dysfunction (ED), the condition in which a man has difficulty attaining or maintaining an erection sufficient for satisfactory sexual intercourse.[2]  

                                                

Click here to learn about ED and sexual function in men

In non-ischemic priapism, fresh blood is continually getting into the penis.  Although tissue damage may be present from the original injury, pain is typically not present.  In contrast to ischemic priapism, non-ischemic priapism is typically not an emergency but prompt diagnosis and treatment may be beneficial.[3]

What causes ischemic priapism?

Ischemic priapism may occur because of either obstruction of blood flow out of the penis through penile veins or because of failure of the smooth muscle within the spongy erectile tissue of the penis to contract normally.

Click here to see an animation depicting low flow priapism. Animation by William Haun (www.willhaun.com)

Venous Obstruction

For many years, physicians thought that the primary mechanism for ischemic priapism was the trapping of deformed red blood cells in the erectile bodies and veins that drain them.  The most common risk factors for these abnormalities of red blood cell function are diseases like sickle cell disease or thallasemia, although other blood disorders such as leukemia and multiple myeloma have also been associated with ischemic priapism.  Because the sickle cell trait is more common in people of African descent, Africans and African-Americans may have higher rates of priapism than other racial groups.[2]

Although blood disorders are the most common reasons for the venous obstruction-type of ischemic priapism, men with advanced cancers of the pelvic organs (bladder, prostate, or rectum) may also develop priapism due to tumor infiltration of the veins draining the penis.

Excessive relaxation of smooth muscle of the corpora cavernosa

The muscles within the spongy erectile tissue of the penis are designed to relax during sexual stimulation to permit blood to enter the penis. This blood fills the erectile tissue and causes it to press against venous channels that normally drain the penis; pressure against these veins keeps the blood from leaving and maintains the hardness of the penis. Under normal conditions, after sexual intercourse or when sexual arousal has passed, these same muscles contract, which leads to opening of the venous channels and the resumption of blood flow out of the penis.  This is the process by which penile erection goes away under normal circumstances.

A number of drugs may impair the ability of these muscles to contract.  In most cases, this impairment is minor, but in some circumstances the impairment may be abnormally robust.  In these cases, persistent trapping of blood may lead to prolonged compression of the venous outflow tracts and cessation of blood inflow. The resulting lack of fresh blood may further impair the ability of the muscle to contract, resulting in ischemic priapism.

The most common drugs associated with priapism include 

1)      Drugs designed to cause penile erection

a.       Papaverine, Phentolamine, Prostaglandin: These medications are used alone or in combination as a penile injection to produce a rigid erection in men with ED.  While these drugs are generally safe, some men are very sensitive to them.  Other men may take an overdose in the hopes of producing a more durable and/or rigid erection.  In some cases this may lead to excessive smooth muscle relaxation and ischemic priapism.

b.      Phosphodiesterase Type 5 Inhibitors (PDE5I): These are the oral medications commonly used to treat ED around the world.  The risk of priapism with these medications is much lower than with penile injections but it is still a potential concern, particularly when they are used in men with mild ED at baseline or combined with other ED treatment.

2)      Some antidepressants such as trazodone.

3)      Some blood pressure medications such as propranolol and hydralazine.

4)     Some psychiatric medications such as thioridazine and some selective serotonin reuptake inhibitors (SSRIs).

5)      Cocaine.[2]

While medications and drugs represent the most common causes of impaired smooth muscle contraction leading to priapism, injuries and lesions of the nervous system, most commonly spinal cord injuries, have also been associated with ischemic priapism.  This type of neurologically driven priapism is thought to most commonly occur through transmission of abnormal signals to the smooth muscle of the penis via the cavernous nerves (which carry signals from the central nervous system to the penis).  This may impair the ability of these muscles to contract.

While a risk factor for ischemic priapism can be determined in many cases, oftentimes no distinct reason for the problem can be identified.  In these cases the condition must be considered “idiopathic” (meaning unknown cause).

What causes non-ischemic priapism? 

Non-ischemic priapism is most often the result of a rupture of a branch of the cavernous artery (which supplies blood to the penis) followed by uncontrolled pooling of blood in the corpora cavernosa.

This condition differs from ischemic priapism in that the artery supplying blood to the erectile tissue bursts and therefore is no longer under control of the cavernous nerves. In most of these cases, the veins draining the erectile tissue are able to shunt (divert) enough of this increased blood flow back to the body.  Because of this, fresh blood is able to continuously enter the corporal bodies and the tissues are therefore provided with oxygen and nutrients.  Therefore, pain and tissue damage typically do not occur with non-ischemic priapism.[3]

The most common cause of non-ischemic priapism is blunt trauma to the penis, groin, or “crotch” from a fall or impact.  Persistent erection does not typically develop immediately but may appear the following morning or even several days later.  It is thought that this delayed presentation is due to the fact that men are usually not sexually excited after a trauma and the penis will be soft, with minimal blood flow.  During sleep, most men have several penile erections.  In a man with a penile artery that has been weakened by trauma, the added pressure from penile erection may cause the damaged artery to rupture (or “blow up”), leading to non-ischemic priapism which presents some time after the initial injury.  

Click here to see an animation depicting trauma as a factor in producing non-ischemic priapism. Animation by William Haun (http://www.willhaun.com)

What are signs of priapism and how is it evaluated by a health care provider?

The most important sign of priapism is persistent penile erection in the absence of sexual excitement.  A man who has an erection that has lasted more than four hours should seek immediate medical attention even if he is not yet experiencing pain.  Even if four hours have not passed a man should consider seeking medical attention if he has an erection that is painful and persistent despite lack of sexual arousal.

Embarrassment keeps some men from seeking prompt medical consultation.  This is unfortunate because tissue damage from ischemic priapism accumulates with time, and the longer a man waits to seek help the higher the chances that he will have long term problems with erectile function.  Time is of the essence in the treatment of ischemic priapism and better results can be expected when treatment is started quickly.[1]

The first and most important step for a health care provider evaluating priapism is to determine whether the condition is ischemic or non-ischemic. Usually this information can be gleaned by a medical history and physical examination alone.  Ischemic priapism is suspected when the patient has penile pain, has used a medicine known known to be associated with ischemic priapism, has sickle cell disease or another blood abnormality, and/or when physical exam reveals a fully erect penis. Non-ischemic priapism is suspected when there is no or minimal pain, a history of trauma, and physical exam reveals a penis that is only partially erect.[1]

A brief but thorough physical exam is performed with particular attention paid to the penis and the other organs of the male genitalia (scrotum and groin area).  To confirm the diagnosis, it is routine for a provider to draw a small sample of blood from the penis to test for oxygen content and acidity.  Other tests that might be useful include simple blood and urine tests (to rule out blood abnormalities or recent drug use) and color duplex ultrasound examination of the penis to assess blood flow.[1]

How is ischemic priapism treated?

If a specific cause for ischemic priapism is identified, therapy should be directed towards the root cause.  Intravenous fluids, pain medications, and supplemental oxygen have been the traditional treatments of choice for men with priapism associated with sickle cell disease.  Blood transfusion has also been commonly used to treat sickle cell associated priapism, although recent research has cast some doubt on whether this is an effective treatment for ischemic priapism.[4]  In the case of priapism from advanced pelvic cancer, treatment with radiation or chemotherapy may be helpful.[5]  It is important to emphasize that while treatment of any underlying condition is a key component of managing the problem of ischemic priapism, it should not delay treatment that is intended specifically to reverse penile erection.[6]

Medical Treatments for Ischemic Priapism

Some physicians have suggested that oral administration of medications such as terbutaline (an asthma medication) or a decongestant like pseudoephrine can be used to treat priapism.  However, few studies have shown a convincing benefit from this type of treatment.  Men with erections that have lasted more than four hours should not try to manage the problem at home with over-the-counter medicines; this may delay their evaluation by a medical professional.[2]

      

Corporal irrigation (evacuation of old blood from the penis) is a simple intervention that often produces softening of the erect penis and relief of pain.  In this procedure, a small needle is inserted into either the head or shaft of the penis and sterile saline is flushed in and out of the penis to clear old, sludged blood.  Typically a “penile block” of local anesthetic is administered before this treatment to minimize patient discomfort.  While corporal irrigation is an important intervention, in most cases this procedure is insufficient by itself to completely reverse the process of ischemic priapism.[2]

Click here to see an animation of corporal irrigation. Animation by William Haun (www.willhaun.com)

Direct injection of a class of medications called alpha agonists (medications that cause contraction of smooth muscles) into the penis is a mainstay in the treatment of ischemic priapism and is oftentimes given with or without corporal irrigation.  Alpha agonists (the most commonly used example is phenylephrine) act by contracting the cavernous arteries and smooth muscles inside the erectile bodies of the penis.  This process decreases pressure on the veins that normally drain the penis and permits blood to exit through them.  In many cases the injection is repeated over the course of several minutes until the penis is notably softer.  Injection of these medications is generally safe but can cause significant increases in blood pressure.  Close monitoring for symptoms of dizziness and headache and repeated measurement of blood pressure and heart rate are required while this therapy is being administered to people with high blood pressure or heart disease. [2]

Click here to see an animation of corporal injection therapy. Animation by William Haun (www.willhaun.com)

In some cases of priapism, particularly those that have lasted for more than a day, medical management as detailed above may not be sufficient to reduce the erection.  In these situations, a procedure called a shunt may be required. [2]

What are shunt procedures for ischemic priapism?

“Shunting” is the medical term for diversion of any fluid into an alternate drainage path.  In the case of ischemic priapism, shunting refers to diverting blood from the corpora cavernosa by creating a connection between these paired organs and either the corpus spongiosum or a vein.  Because it requires a surgical procedure, shunts are considered an option of last resort for those cases of severe, painful priapism that do not respond to less invasive treatments as detailed above.[2] It is important to note that in the case of priapism the shunt is a connection between natural tissues of the body rather than a foreign substance that is implanted to divert blood flow.  These shunts may last forever or they may spontaneously close off as a part of normal healing.

Some simple shunts may be done under local anesthesia in the clinic or emergency room.  More invasive shunts may require regional anesthesia (such as a spinal block) or even general anesthesia in the operating room.  There are three types of shunts for priapism, which are discussed below in increasing order of invasiveness.  

1)      Distal shunts: These shunts create a connection to permit direct blood flow from one or both of the corpora cavernosa to the erectile tissue inside the glans (head) of the penis.  The simplest versions involve inserting a needle through the head of the penis into the corpora cavernosa, thus creating a connection.  Some variants of this procedure are done though a small incision on the head of the penis.

2)      Proximal shunts: These shunts create a connection between the corpora cavernosa and the lower portion of the corpus spongiosum.  These are most commonly done through an incision in the perineum (also known as the “taint,” the area between the scrotum and anus).

3)      Venous Shunts: These shunts are made between the corpora cavernosa and a vein such as the saphenous vein (which runs on the inside of the thigh) or the dorsal vein of the penis (located on the top side of the penis).

At our institution, we favor a procedure known as the T-shaped shunt, which is created by passing scalpel through the head of the penis into the corpora cavernosa after a local anesthetic is administered to the patient.  In cases of priapism that do not resolve after this intervention, passage of a small, sterile metal rod through the incision can open up the connection between the base of the corpora and the erectile tissue of the head of the penis to re-establish circulation.  These procedures are routinely performed at our clinic or the emergency room with high success rates with respect to resolution of pain.

In priapism of more than two days duration, shunt procedures may not completely resolve the erection due to inflammation and swelling.  An ultrasound examination can be used to determine if normal blood flow has resumed after shunting.  Alternatively, repeat sampling of blood to assess the oxygen content within the penis can be used to assess response to treatment. 

How is recurrent (“stuttering”) priapism treated?

Patients with recurrent (“stuttering”) priapism suffer recurrent episodes of ischemic priapism as often as several times per week, resulting in significant disruptions to everyday life.  Some men with recurrent priapism can be taught to inject their penis with the same alpha-agonist type medicines used by physicians.  This treatment allows patients to avoid coming into the hospital or clinic, but it is not a viable option for every patient.  

Men who cannot self-treat, or for whom self-treatment does not work, may consider androgen ablation, which is the process of blocking the production of the male hormone testosterone.  Testosterone is intimately associated with erectile function and suppression of this hormone has helped many men with severe stuttering priapism.[7]  The most common means of androgen ablation is an intermittent (monthly or every three months) injection of a medication that suppresses the pituitary gland hormone responsible for stimulating the testicles to produce testosterone.

                                                                                                     

Suppression of testosterone reduces a man’s libido and sleep erections, but may not inhibit sexual erections.  Testosterone is important for mood and various aspects of physical health such as bone and muscle maintenance; long term suppression of testosterone production may have an impact on these health factors as well as potentially unforeseen effects on other body systems.  For these reasons, androgen ablation is usually stopped after six months and re-instituted only if ischemic priapism recurs. This type of treatment should NOT be utilized in boys who have not gone through puberty, since it might irreversibly inhibit the normal process of male development.

What are the usual outcomes for men with ischemic priapism?

A general rule of thumb is that the risk of long term problems, such as penile shortening or erectile dysfunction, after an episode of ischemic priapism increases the longer the duration of penile erection.  For this reason, it is very important that men who think they might have priapism seek medical evaluation as quickly as possible.  Men who have multiple recurrent episodes of priapism are also at increased risk of long term ED, with the risk increasing with each episode.

In nine out of 10 cases, a single episode of ischemic priapism that is diagnosed and treated within 24 hours of onset can be managed without surgery and with nearly complete recovery of baseline erectile function.[8]  Most men who have priapism that lasts more than 24 hours will develop some degree of ED.  In cases of priapism that last more than two or three days, the chance of recovering normal erectile function is very small.[9]  In these men, medications that bring about penile erections are rarely useful and surgical implantation of a penile pump may be necessary to restore erectile function.[10]  This implantation may occur during the priapism episode or at a later date.

How is non-ischemic priapism treated?

Given that non-ischemic priapism does not cause tissue damage, conservative management with pain medication as needed is usually the treatment of choice.  In some cases, non-ischemic priapism may resolve spontaneously.[2] In other men, the moderate degree of penile erection induced by non-ischemic priapism is not too troublesome and they choose to live with it.[11]

Although some men choose to live with non-ischemic priapism, others are bothered by it due to discomfort or erectile dysfunction.  Since non-ischemic priapism almost always occurs during sleep erections when the increased blood flow “blows out” the damaged artery within the corpus cavernosum, therapy aimed at reducing sleep erections is an effective way to heal the ruptured artery. At our institution, we have successfully treated a number of men with non-ischemic priapism by androgen ablation therapy similar to what is done for men with stuttering ischemic priapism (see above).

For more immediate results, a procedure called selective angioembolization may be used to treat non-ischemic priapism.  This procedure is similar to a cardiac catheterization beacuse it is performed through a small catheter placed into the femoral artery near the groin.  Using x-ray guidance, this catheter is advanced into the area of the artery that supplies the penis and an intravenous dye is injected to locate the area of arterial rupture.  After the rupture is located, a piece of absorbable foam or a clot derived from the patient’s own blood is passed through the catheter to obstruct the connection and block the abnormal blood flow.[3]  This procedure is generally safe and well tolerated, although possible risks include worsening of erectile function, infection, and failure to reverse priapism.[12] 

After angioembolization, it is recommended that patients follow-up with repeat physical examination and color Doppler ultrasound examination of the penis to confirm that the ruptured artery has healed.  In cases where angioembolization fails or where non-ischemic priapism has lasted longer than six months, a surgical approach to tying off the ruptured artery using ultrasound guidance may definitively resolve the problem.  X-ray guidance as used for angioembolization cannot typically be utilized during this type of approach.  For this reason, surgical repair of high-flow priapism should only be contemplated after six months have passed and an ultrasound has confirmed that a pseudocapsule (a rind of tissue) has formed around the connection since the procedure will fail if there is no pseudocapsule to help the surgeon locate the ruptured artery.

What are the usual outcomes for men with non-ischemic priapism?

The outcomes for men with non-ischemic priapism are generally much better than those with ischemic priapism. However, because most cases of non-ischemic priapism are caused by blunt injury to the base of the penis, damage associated with the original injury can result in erectile dysfunction or scarring even if the priapism is successfully treated.

New directions in the treatment of priapism

Research into the mechanisms and treatments of priapism continues.  Although progress is sometimes slow, new developments may improve the way health care providers are able to care for men with this very serious and personal health issue.

An intriguing recent study has suggested that daily treatment with low dose phosphodiesterase type 5 inhibitors (PDE5I) may be a novel means to treat priapism.  PDE5Is are most commonly used to cause erections in men with ED.  While it seems counterintuitive to treat prolonged erections with a medication designed to cause erections, a very small preliminary study has suggested that this therapy may be useful for men with stuttering ischemic priapism.  It is thought that low dose treatment with PDE5I may increase production of the enzyme phosphodiesterase type 5 (PDE5).   PDE5 is a protein in the penis that is responsible in part for reversing erections.  An increase in PDE5 in the penis should, in theory, decrease the tendency of the penis to become erect. 

Encouraging results have been obtained in the small preliminary study of seven men, and most of the men in this study have been able to engage in sexual intercourse.[13] Although PDE5I may represent an exciting new means of therapy for priapism, more studies are needed before this treatment should be considered outside of a research setting.                                                                                                                  

Conclusions

Erections that last four hours or longer are a serious matter.  Ischemic priapism is a urologic emergency and demands prompt medical evaluation to minimize the risk of long term loss of erectile function.  Non-ischemic priapism may be managed conservatively although treatment options are available for men who desire resolution of the problem.  A number of risk factors for priapism have been identified.  Further research will hopefully continue to improve the treatments available for men with this disabling condition.

Additional internet resources:

1. American Urological Association Guidelines for the treatment of Priapism: (http://www.auanet.org/guidelines/priapism.cfm
2. UCSF Deparment of Urology: (http://www.ucsfhealth.org/adult/medical_services/urology/male_sexual/conditions/priapism/signs.html)

Books on priapism:


Priapism - A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References by ICON Health Publications

REFERENCES 

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[1] Berger R, Billups K, Brock G, Broderick GA, Dhabuwala CB, Goldstein I, et al.  Report of the American Foundation for Urologic Disease (AFUD) Thought Leader Panel for evaluation and treatment of priapism. Int J Impot Res. 2001 Dec;13 Suppl 5:S39-43.

[2] Pryor J, Akkus E, Alter G, Jordan G, Lebret T, Levine L et al.  Priapism. J Sex Med 2004 Jul;1:116-20.

[3] Bastuba MD, Saenz de Tejada I, Dinlenc CZ, et al. Arterial priapism: diagnosis, treatment and long-term followup.  J Urol. 1994 May;151(5):1231-7

[4] Merritt AL, Haiman C, Henderson SO.  Myth: blood transfusion is effective for sickle cell anemia-associated priapism.  CJEM.  2006Mar;8(2):119-22

[5] Chan PTK, Begin LR, Arnold D, Jacobson SA, Corcos J, Brock GB.  Priapism secondary to penile metastasis: A report of two cases and a review of the literature.  J Surg Oncol. 1998 May;68:51-9

[6] Montague DK, Jarow J, Broderick GA, Dmochowski RR, Heaton JPW, Lue TF, et al. Guideline on the management of priapism.  Linthicum, MD.  American Urologic Association Education and Research, Inc., 2003
[7] Dahm P, Rao DS, Donatucci CF.  Antiandrogens in the treatment of priapism. Urology. 2002 Jan;59(1):138.

[8] Kulmala RV, Lehtonen TA, Tammela TL.  Preservation of potency after treatment for priapism.  Scand J Urol Nephrol 1996;30:313-6

[9] El-Bahnasawy MS, Dawood A, Farouk A.  Low-flow priapism: risk factors for erectile dysfunction. BJU Int. 2002 Feb;89(3):285-90.

[10] Sundaram CP, Fernandes ET, Ercole C, Billups KL.  Management of refractory priapism with penile prostheses.  Br J Urol 1997 Apr;79(4):659

[11] Hakim LS, Kulaksizoglu H, Mulligan R, Greenfield A, Goldstein I. Evolving concepts in the diagnosis and treatment of arterial high flow priapism. J Urol. 1996 Feb;155(2):541-8.
[12] Sandock DS, Seftel AD, Herbener TE, Goldstein I, Greenfield AJ.  Perineal abscess after embolization for high-flow priapism.  Urology. 1996 Aug;48:308-11.

[13] Burnett AL, Bivalacqua TJ, Champion HC, Musicki B.  Feasibility of the use of phosphodiesterase type 5 inhibitors in a pharmacologic prevention program for recurrent priapism.  J Sex Med. 2006 Nov;3(6):1077-84