Priapism in Children

23.1Introduction

•Priapism is defined as a prolonged, nonphysiologic, 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).

•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).

•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:

–Idiopathic

–Hematologic (e.g. sickle cell, leukemia)

–Pharmacologic adverse effects (e.g. psychiatric medications)

–Therapeutic medications (e.g. oral erectile medications, intracavernous injections)

–Neoplastic

–Others (e.g. surgical, traumatic, neurogenic, infectious)

Fig. 23.3 Clinical photograph of an adult with priapism

•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.

23.2Pathophysiology

•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 smoothmuscle 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).

•Priapism can be primary or idiopathic and secondary to other factors.