Pediatric Surgery, AlSadik Hospital, Qatif, Saudi Arabia
Priapism is defined as a prolonged, non-physiologic, sustained and painful erection.
It is not provoked by sexual stimulation or arousal
It persists after ejaculation and orgasm.
Priapism is an uncommon condition that needs to be recognized early and immediate medical attention is important.
It is considered a true medical and urologic emergency, and early intervention allows the best chance for functional recovery.
Prompt diagnosis and treatment of priapism are important to prevent tissue damage that could result in the inability to get or maintain an erection (erectile dysfunction).
Such a prolonged erection causes physiological changes by 6 h, cellular damage by 24 h, and fibrosis by 36 h, resulting in permanent erectile dysfunction.
Priapism can present in childhood and adolescence.
It is most commonly seen between ages 5 and 10 in boys and ages 20 and 50 in men.
Nocturnal episodes of priapism are more frequent.
Priapism is frequently idiopathic in etiology but it is a known complication of a number of important medical conditions and pharmacologic agents.
More than one-fourth of priapism episodes are caused by sickle cell disease (SCD).
At least one-third of male adults with SCD present with priapism at some point, usually beginning in school age.
Nearly one-fourth of priapism in patients with SCD present during the prepubertal period.
The mean age for the onset of priapism in patients with SCD is 11 years.
In patients with SCD, priapism rarely present for the first time after the third decade of life.
In children nearly all cases of priapism are secondary to sickle cell disease or trauma.
Priapism in childhood commonly presents as a complication of sickle cell disease (SCD) (Figs. 23.1 and 23.2).
Figs. 23.1 and 23.2
Clinical photographs showing priapism in a child
The frequency of priapism in children with SCD varies between 2 and 6 %.
Priapism normally involves the two corpora cavernosa and spares the corpora spongiosum.
Priapism as a complication of SCD can cause persistent impotence, erectile dysfunction and behavioral sexual problems (Figs. 23.3).
Clinical photograph of an adult with priapism
A prior history of priapism makes these patients fear any sexual activities as these may induce an episode of priapism.
In patients with SCD:
Priapism was first reported in SCD patients in 1934.
The most frequent form of priapism in patients with SCD is recurrent self-limited short episodes (stuttering priapism)
Acute episodes of priapism are defined as painful erection and/or persisting more than 4–6 h.
Approximately two-third of patients presenting with an acute attack of priapism report previous intermittent episodes.
Priapism is classified into high or low blood flow.
It is important to differentiate between the two types as this important in terms of treatment and prognosis.
High flow priapism (Nonischemic priapism) is characterized by an increase of arterial supply to the corpora cavernosa while the venous drainage remains normal.
Low flow priapism (Ischemic priapism) is characterized by loss of vascular regulation and the venous drainage is impaired, presumably as a consequence of vascular blockage by deformed red blood cells.
It is estimated that more than 80 % of patients with SCD have low flow priapism and occasionally it may be high flow priapism.
Low-flow priapism is by far the most common type.
High-flow priapism is rare and is usually a result of blunt trauma to the corpora cavernosus resulting in arteriovenous fistula.
The treatment for high-flow priapism is surgical identification and obliteration of fistulas.
Causes of low-flow priapism include the followings:
Hematologic (e.g. sickle cell, leukemia)
Pharmacologic adverse effects (e.g. psychiatric medications)
Therapeutic medications (e.g. oral erectile medications, intracavernous injections)
Others (e.g. surgical, traumatic, neurogenic, infectious)
Management of low flow priapism should achieve resolution as promptly as possible.
Early intervention allows the best chance for functional recovery and minimize the sequelae.
Treatment of low-flow priapism should progress in a stepwise fashion, starting with therapeutic aspiration, with or without irrigation of the corpora. If this fails, intracavernous injection of sympathomimetic drugs is the next step.
Rapid resolution of ischaemic (low flow) priapism prevents permanent cavernosal structural damage and is associated with improved prognosis for potency later in life.
The penis is made up of three corporeal erectile tissues, two corpora cavernosa on the dorsum of the penis and corpora spongiosum ventrally.
The urethra runs within the corpora spongiosum.
The erectile tissue within the corpora contains arteries, nerves, muscle fibers, and venous sinuses lined with flat endothelial cells, and it fills the space of the corpora cavernosa.
The cut surface of the corpora cavernosa looks like a sponge. There is a thin layer of areolar tissue that separates this tissue from the tunica albuginea.
Blood flow to the corpora cavernosa is via the paired deep arteries of the penis (cavernosal arteries), which run near the center of each corpora cavernosa.
Normally, erection occurs in response to physical or psychological stimulation.
Erection is the result of smooth-muscle relaxation and increased arterial flow into the corpora cavernosa, causing engorgement and rigidity.
Corporeal relaxation causes external pressure on the emissary veins exiting the tunica albuginea, trapping blood in the penis and causing erection.
Engorgement of the corpora cavernosa compresses the venous outflow tracts (i.e. subtunical venules), trapping blood within the corpora cavernosa.
Erection is induced by the parasympathetic autonomic nervous system.
This stimulation causes penile blood vessels to relax and expand, increasing blood flow to the spongy tissues in the penis.
The major neurotransmitter that controls erection is nitric oxide, which is secreted by the endothelium that lines the corpora cavernosa. These events occur in both normal and pathologic erections.
Sexual stimulation causes the release of nitric oxide (NO) via stimulation of noradrenergic norcholinergic neurons, provoking a local increase of cyclic GMP (cGMP) by the activation of guanylate-cyclase.
NO-activated intracellular guanylate cyclase, converting guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP), causes relaxation of cavernosal arteries and increased penile blood flow, resulting in erection.
Cyclic GMP then enhances the cellular efflux of calcium and the relaxation of smooth muscle of efferent arteries and of the corpora cavernosa itself. This will lead to an increase in the afferent blood flow.
The draining venules which are located between the corpora cavernosa, are passively compressed by the rigid congested corpora and as a result blood accumulates.
Consequently, the blood-filled penis becomes erect.
The erection process ends by ejaculation and orgasm.
As a result of this, signals are sent to the sympathetic nervous system which determines the vasoconstriction of the efferent arteries of the corpora cavernosa, leading to reduction in the blood inflow.
This will lead to an increase in venous drainage mechanisms and detumescence results. The blood flows out of the penile blood vessels, and the penis returns to its nonrigid (flaccid) state.
Pathophysiologically, priapism can be of either a low-flow (ischemic) or a high-flow (nonischemic) type.
Low-flow priapism, which is by far the most common type, results from failure of venous outflow, whereas high-flow priapism results from uncontrolled arterial inflow.
Clinically, differentiation of low-flow from high-flow priapism is critical, because treatment and prognosis for each is different.
Low-flow priapism may be due to any of the following:
An excessive release of neurotransmitters
Blockage of draining venules (e.g., mechanical interference in sickle cell crisis, leukemia, or excessive use of intravenous parenteral lipids)
Paralysis of the intrinsic detumescence mechanism
Prolonged relaxation of the intracavernous smooth muscles (most often caused by the use of exogenous smooth-muscle relaxants such as injectable intracavernosal prostaglandin E1)
Prolonged low-flow priapism leads to a painful ischemic state, which can cause fibrosis of the corporeal smooth muscle and cavernosal artery thrombosis. The degree of ischemia is a function of the number of emissary veins involved and the duration of occlusion.
Light-microscopy studies conducted early demonstrated that corporeal tissue becomes thickened, edematous, and fibrotic after days of priapism.
Further studies with electron microscopy have demonstrated trabecular interstitial edema after 12 h of priapism and destruction of sinusoidal endothelium, exposure of the basement membrane, and thrombocyte adherence after 24 h of priapism. At 48 h, thrombi were evident in the sinusoidal spaces and smooth-muscle cell.
Histopathologic findings varied from necrosis to fibroblast-like cell transformation. Priapism for longer than 24 h is associated with permanent impotence.
High-flow priapism is the result of uncontrolled arterial inflow from a fistula between the cavernosal artery and the corpus cavernosum. This is generally secondary to blunt or penetrating injury to the penis or perineum causing rupture of a cavernous artery. It is usually not painful.
In priapism, the corpus spongiosum and glans penis are typically not engorged.
Ischemic (low flow) priapism can cause serious complications.
The blood trapped in the penis is deprived of oxygen.
When an erection lasts for longer than 4 h, this oxygen-poor blood can begin to damage or destroy tissues in the penis.
As a result, untreated priapism may cause:
Erectile dysfunction, the inability of the penis to become or stay erect with sexual arousal
Disfigurement of the penis
Sickle cell anemia is the most common cause of priapism in boys (Figs. 23.4 and 23.5).
Figs. 23.4 and 23.5
Clinical photograph showing priapism in two children with sickle cell disease
Priapism can be primary or idiopathic and secondary to other factors.
Factors that can contribute to priapism include the following:
Blood disorders including:
Sickle cell anemia
Oral medications used to treat erectile dysfunction, such as sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra)
Drugs injected directly into the penis to treat erectile dysfunction, such as papaverine
Antidepressants, such as fluoxetine (Prozac) and bupropion (Wellbutrin)
Drugs used to treat psychotic disorders, such as risperidone (Risperdal) and olanzapine (Zyprexa)
Anticoagulant, such as warfarin (Coumadin) and heparin
Alcohol and drug abuse (marijuana or cocaine)
Trauma or injury to the genitals, pelvis or the perineum is a cause of nonischemic (high flow) priapism
Other causes of priapism include:
Spinal cord injury
Poisonous venom, such as venom from scorpions or black widow spiders
Priapism can be idiopathic or can be secondary to a variety of diseases, conditions, or medications.
In the United States, the most common cause of priapism in the adult population involves agents used to treat erectile dysfunction.
Internationally, most cases are idiopathic.
The most common cause of priapism in the pediatric population is sickle cell disease (SCD), which is responsible for more than 65 % of cases.
Leukemia, trauma, and idiopathic causes are the causes in 10 % of patients.
Pharmacologically induced priapism is the etiology in 5 % of children.
Among the secondary causes of low-flow priapism are the followings:
Sickle cell anemia – One study found that, in unscreened children with SCD, priapism was the first presentation in 0.5 % of cases.
Fat embolism (from multiple long-bone fractures or intravenous infusion of lipids as part of total parenteral nutrition)
Neurologic diseases that can result in low-flow priapism include the following:
Spinal cord stenosis (i.e. trauma to the medulla)
Autonomic neuropathy and cauda equina compression
Neoplastic disease (metastatic to the penis or obstructive to venous outflow) that can result in low-flow priapism include the following:
Bladder cancer (highest risk)
Hematologic cancer (leukemia)
Pharmacologic causes of low-flow priapism include the following:
Intracavernosal agents – Papaverine, phentolamine, prostaglandin E1
Intraurethral pellets (i.e. medicated urethral system for erection with intracavernosal prostaglandin E1)
Antihypertensives – Ganglion-blocking agents (e.g. guanethidine), arterial vasodilators (e.g. hydralazine), alpha-antagonists (e.g. prazosin), calcium channel blockers
Psychotropics – Phenothiazine, butyrophenones (e.g. haloperidol), perphenazine, trazodone, selective serotonin reuptake inhibitors (e.g. fluoxetine, sertraline, citalopram) 
Anticoagulants – Heparin, warfarin (during rebound hypercoagulable states)
Recreational drugs – Cocaine
Hormones – Gonadotropin-releasing hormone (GnRH), tamoxifen, testosterone, androstenedione for athletic performance enhancement
Herbal medicine – Ginkgo biloba with concurrent use of antipsychotic agents
Miscellaneous agents – Metoclopramide, omeprazole, penile injection of cocaine, epidural infusion of morphine and bupivacaine
Only rare case reports have associated phosphodiesterase-5 enzyme inhibitors such as sildenafil with priapism. In fact, several reports suggest sildenafil as a means to treat priapism and as a possible means of preventing full-blown episodes in patients with sickle cell disease.
High-flow priapism may result from the following forms of genitourinary trauma:
Intracavernous injections resulting in direct cavernosal artery injury
Rare causes of priapism include the following:
Amyloidosis (massive amyloid infiltration)
Gout (one case report)
Carbon monoxide poisoning
Black widow spider bites
Fabry disease (rare association, occasionally noted to be priapism of the high-flow type)
Vigorous sexual activity
Mycoplasma pneumoniae infection (mechanism is thought to be a hypercoagulable state induced by the infection)
23.4 Classification of Priapism
Priapism is a sustained painful erection of the penis often nocturnal or starting in the early hours of the morning.
Priapism develops when there is excess arterial inflow to the penis or when there is persistent venous outflow obstruction to the penis.
Priapism is classified into two main types:
High flow arterial priapism. This is also called non-ischemic priapism.
Low flow priapism. This is also called ischemic priapism.
High flow (non-ischemic) priapism:
This is usually seen following trauma causing injury to the cavernosal artery.
This type of priapism is generally not painful and may manifest in an episodic manner.
The penis in high flow priapism is neither fully rigid nor painful and does not require an emergency treatment.
Characteristics of high-flow priapism include the following:
High flow priapism is characterized by an increase of arterial supply to the corpora cavernosa while the venous drainage remains normal.
An adequate arterial flow and well-oxygenated corpora
The prognosis is better, and secondary impotence is rare (<20 %).
In children high flow priapism is typically caused by post-traumatic arteriocavernosal fistula (from penile, perineal or pelvic trauma), and generally manifests several days after the trauma.
Evidence of blunt or penetrating injury to the penis or perineum especially straddle injury is usually the initiating event.
It can also be caused by:
Intracavernosal injections of vasoactive agents
Scorpion or snake bites
Substance abuse (mainly cocaine, which can cause high or low output priapism)
Therapeutic drugs (especially psychiatric medications with autonomic nervous system effects
Infectious diseases or tumors
Low flow priapism (ischemic):
This is the commonest type
Low flow priapism is characterized by loss of vascular regulation.
Venous drainage is impaired, presumably as a consequence of vascular blockage by deformed red blood cells.
This is the classic type seen in patients with SCD where there is stasis leading to hypoxia and acidosis of venous blood in a normally erected penis. This will lead to sickling of RBCs within the corpora cavernosa venous sinusoids, venous outflow obstruction and engorgement of the corpora cavernosa. The corpora spongiosa and glans of the penis are spared.
The corpora cavernosa becomes rigid and tender to palpation.
This may be further complicated as the fixed resistance maintained by the adventitia of the corpora cavernosa causes a compartment syndrome.
Low-flow priapism is generally painful, although the pain may disappear with prolonged priapism.
Characteristic features of low-flow priapism include the following:
Ischemic corpora as indicated by dark blood upon corporeal aspiration
No evidence of trauma
Low flow priapism is considered a medical and surgical emergency and priapism should be resolved within 6 h of the onset of the episode to minimize the sequelae.
In addition to SCD, low flow priapism can be caused other hematologic diseases with hypercoagulability or hyperviscosity such as leukemia’s and several drugs.
It is important to differentiate between these two types as the management and prognosis are different.
The two types of priapism can be differentiated using color duplex Doppler ultrasonography and analysis of blood aspirated from the corpora cavernosa.
Color Doppler ultrasonography measures blood flow. This typically show little or no blood flow in the cavernosal arteries in those with low flow priapism.
Analysis of blood aspirated from the corpora cavernosa is done at the time of aspiration and irrigation.
In patients with high flow priapism, the aspirated blood:
Is bright red
Has a pO2 >90 % mmHg, pCO2 <40 mmHg and a pH of approximately 7.40.
In patients with low flow priapism, the aspirated blood:
Is dark in color
Has a pO2 <30 mmHg, pCO2 >60 mmHg and a pH <7.25.
Priapism is also classified into two types:
Stuttering priapism: This lasts 2–4 h, often recurrent and may precede a severe attack.
Acute (Severe) priapism: This lasts longer than 4 h and can result in impotence.
23.5 Clinical Features
Priapism causes abnormally persistent erections not related to sexual stimulation.
Priapism symptoms may vary depending on the type of priapism.
There are two main types of priapism: ischemic and nonischemic priapism.
Ischemic, also called low-flow, priapism is the result of blood stasis in the penis.
It’s the more common type of priapism.
Low-flow, ischemic-type priapism is generally painful, although the pain may disappear with prolonged priapism.
It is characterized by ischemic corpora, as indicated by dark blood upon corporeal aspiration; and no evidence of trauma
The history may reveal an underlying cause
Stuttering priapism is unwanted erection off and on for several hours.
Signs and symptoms include:
Unwanted erection lasting more than 4 h
It is characterized by a rigid, painful erection
Rigid penile shaft, but usually soft glans of penis
Usually painful or tender penis
Nonischemic, or high-flow, priapism occurs when too much blood flows into the penis.
This type of priapism is associated with blunt or penetrating injury to the perineum. It may manifest in an episodic manner.
Nonischemic priapism is usually painless.
Signs and symptoms include:
Unwanted erection lasting at least 4 h
Erect but not rigid penile shaft
Patients with high-flow priapism typically have a history of blunt or penetrating trauma to the penis or perineum, resulting in a fistula between a cavernosal artery and the corpus cavernosum.
Clinically, high-flow priapism is characterized by a painless erection; tumescence is typically less marked than in low-flow priapism.
The presence of bright red blood during aspiration is a helpful but not pathognomonic finding of high-flow priapism.
Penile blood gases findings approximate normal arterial values.
Penile duplex ultrasonography with angiographic confirmation helps to identify and locate these fistulae.
Patients with priapism report a persistent erection.
The physical examination detects an erection restricted to the corpora cavernosa. The spongiosum and the glans remain flaccid, except for the rare cases of tricorporal priapism.
Because of the lack of involvement of the periurethral spongiosum, there are normally no micturating problems.
Accompanying symptoms depend on the type of priapism and the duration of engorgement.
Penile priapism generally involves only the paired corpora cavernosa, with the glans and corpora spongiosum remaining flaccid or softly distended without rigidity.
In high flow priapism the erection is less rigid and the penis is pink and pulsatile.
There can be signs of trauma (hematomas, bruises).
It may be possible to resolve the erection compressing the arteriovenous fistula feeder vessel, but the erection will recur immediately after the compression is withdrawn.
In low flow priapism the penis is rigid, extremely painful and seems ischemic: it does not pulse, is pale or grayish and cold. These manifestations are more evident after the episode has evolved for at least 4 h.
In young children, the presence of the Piesis sign (prompt detumescence upon perineal compression with the examiner’s thumb) indicates high-flow priapism.
To provide appropriate treatment, physicians must differentiate between low-flow and high-flow priapism. This is accomplished by taking a thorough history, performing a careful physical examination, and measuring the oxygen content of blood within the corpora cavernosa by penile blood gas analysis.
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