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]
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.
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]
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]
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:
- American Urological Association Guidelines for the treatment of Priapism: (http://www.auanet.org/guidelines/priapism.cfm
- 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
Priapism - A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References by ICON Health Publications
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[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