Advances have recently been made in both medical and surgical management of priapism, and these offer improvements in the level of care afforded such patients. Further developments can be expected based on ongoing progress, particularly in the area of molecular science, which is the primary source for driving novel therapeutic approaches. Continued action to address the health care administrative concerns of those most commonly affected by priapism, specifically individuals with sickle cell disease, is also appropriate. All successes in these arenas ensure that afflicted individuals avoid the health burdens of priapism and preserve sexual function.
References to priapism as a trivial erection problem misrepresent its importance as a true clinical disorder of male sexual function. The presumably limited frequency and population extent of this disorder largely influences this misconception, although its pathophysiologic obscurity, the dearth of remedies for it, and its self-remitting tendency also are contributing factors in this regard. Unlike the widespread emphasis placed on male erectile dysfunction (ED), less attention has historically been given to priapism despite this erectile disorder also carrying adverse health risks. It is therefore heartening to observe that, at this time when recent advances have been made in the scientific understanding and clinical practice of male ED, a similar aim toward establishing effective, evidence-based therapeutics for priapism is gaining momentum. This article reviews recent clinical developments in the medical and surgical management of priapism and surveys scientific research activity in this rapidly evolving field of study that conceivably will pave the way for further innovations in its treatment. In addition, the relevance of health care administration and policy to this field is evaluated, particularly as this area relates to the sickle cell disease population, and some health care programmatic areas are proposed for improving health outcomes of individuals with priapism.
Disease profile
In a clinical context, priapism connotes abnormally persistent penile erection unrelated to sexual provocation or purpose. An occurrence of 4 hours is often applied as a diagnostic criterion, although the existence of the disorder is accepted for episodes of shorter durations. The penis is readily recognized as the diseased bodily organ, although priapism of the clitoris has also been reported. The abnormality typically involves the main erectile bodies, the corpora cavernosa, although involvement of the corpus spongiosum has also been observed. The disorder represents a dysfunctional process of prolonged genital organ erection.
Many different clinical conditions have been associated with priapism. A basic categorization of these associations is clinically practical and also lends insight into the causal origins of the disorder ( Box 1 ). Categories include hematologic dyscrasias, ED pharmacotherapeutic complications, pharmacologic exposures, nonhematologic malignancies, pelvic or genital trauma, and neurologic conditions. An idiopathic category presently exists, although it is suspected that future scientific investigations of idiopathic presentations will eventually reveal their etiopathogenic sources. Disease associations are additionally relevant for discerning the epidemiology of priapism. A major at-risk population for the disorder consists of individuals with sickle cell disease or other hematologic and coagulative dyscrasias, including thrombophilia and thalassemia. Cohort studies of these populations assign the lifetime probability of developing priapism to be between 29% and 42%. Men with ED receiving vasoactive pharmacotherapies also comprise a major at-risk population, and high rates of priapism occurrences have historically coincided with the clinical introduction of these therapies.
Ischemic priapism
Hematologic dyscrasias
Sickle cell disease, thalassemia, leukemia, multiple myeloma, hemoglobin Olmsted variant, fat emboli associated with hyperalimentation, hemodialysis, glucose-6-phosphate dehydrogenase deficiency
Vasoactive erectile agents
Papaverine, phentolamine, prostaglandin E1, combination therapy
Medications
α-Adrenergic receptor antagonists
Prazosin, terazosin, doxazosin, tamsulosin
Antianxiety agents
Hydroxyzine
Anticoagulants
Heparin, warfarin
Antidepressants and antipsychotics
Trazodone, bupropion, fluoxetine, sertraline, lithium, clozapine, risperidone, olanzapine, chlorpromazine, thioridazine, phenothiazines
Antihypertensives
Hydralazine, guanethidine, propranolol
Drugs (recreational)
Alcohol, cocaine (intranasal and topical), crack cocaine, marijuana
Hormones
Gonadotropin-releasing hormone (in hypogonadal men), testosterone
Infectious (toxin mediated)
Scorpion sting, spider bite, rabies, malaria
Metabolic
Amyloidosis, Fabry disease, gout
Neoplastic (metastatic or regional infiltration)
Prostate, urethra, testis, bladder, colorectal, lung, kidney, penis
Neurogenic
Syphilis, spinal cord injury, cauda equina compression, autonomic neuropathy, lumbar disc herniation, spinal stenosis, cerebral vascular accident, brain tumor, spinal anesthesia, cauda equina syndrome
Anxiety disorders
Anesthesia (general, regional)
Nonischemic priapism
Trauma
Straddle injury, coital injury, pelvic trauma, kick to penis/perineum
Intracavernous injection needle laceration
Penile revascularization surgery
Vasoactive erectile agents/drugs
Neurologic conditions
Treatment-refractory ischemic priapism
NB: Categories are assigned according to the clinicopathologic division of priapism forms.
Pathologic basis of disease
Advances in the clinical management of priapism, as for any medical disorder, derive practically from a solid core of knowledge of its pathogenesis. Study of the dynamics and mechanisms of disease involved in priapism conceivably assures the identification of biologic targets toward which therapeutic objectives for the disorder are aimed. Approaches to this investigation include clinical and basic scientific research work.
Clinicopathologic Observations
The natural course of priapism varies, although characteristic clinical patterns and outcomes of the disorder are commonly recognized. The disorder may occur briefly and abate in some individuals with little apparent adverse health consequence, although in others it persists for long durations with major clinicopathologic significance. Two standard forms of priapism are recognized, and this division offers a useful classification system for the disorder. Ischemic priapism, also termed venoocclusive or low-flow priapism, characteristically features absent intracorporal blood flow. This form of priapism represents an actual compartment syndrome localized to the corpora cavernosa and is associated with penile rigidity and pain. Nonischemic priapism, also termed arterial or high-flow priapism, features increased vascular flow within the corpora cavernosa without rendering a compartment syndrome effect. This classification system is also relevant to clinical management. Accordingly, ischemic priapism, which occurs more commonly, represents a medically emergent condition and prompts immediate clinical action, whereas nonischemic priapism, occurring less commonly, can be managed nonemergently.
A major episode of ischemic priapism is generally defined if it has been present for more than a few hours; if it is not treated promptly, pathologic changes of the erectile tissue can be expected, resulting from the prolonged ischemic conditions. Priapism recurrences, in which repeated prolonged erectile events occur but characteristically last less than 3 hours and spontaneously remit, are also observed. These recurrent episodes, often termed stuttering attacks, also are ischemic in quality. A frequent clinical pattern of priapism is the display of recurrences as short-lived episodes that, in time, progress in duration before a major episode occurs. Whether major or recurrent, ischemic priapism implies a risk for development of metabolic derangements in the penis caused by lack of intracorporal circulation. At 4 hours of ischemia, significant acidosis and glucopenia develop in the penis, and thereafter erectile tissue reactivity begins to become irreversibly impaired. Nonischemic priapism follows a distinct natural course that either resolves spontaneously or persists without resolution for extended durations. It also differs pathologically from its ischemic counterpart by maintaining normoxic, metabolically intact intracorporal circulation.
Genital complications of ischemic priapism occur both structurally and functionally. Tissue edema with cellular loss is observed within the penis after several hours of unrelieved ischemia. Penile tissue necrosis and progressive fibrosis represent end-stage pathologic changes. The gross pathologic feature of this course is penile disfigurement, with morphologic defects that range from megalophallic deformity to major penile tissue destruction and sloughing. These changes are responsible for loss of erectile function, directly because of the inability of the penis to achieve physiologic blood engorgement. Complete ED rates of 30% to 90% are documented in men who have experienced major ischemic priapism episodes. As much as a 25% ED rate has been reported in men sustaining recurrent ischemic priapism. Although it is generally believed that individuals with nonischemic priapism escape pathologic effects of the penis that reduce erectile ability, descriptions of ED have been documented for this group. Penile tissue damage associated with the traumatic development of this form of priapism may explain this phenomenon.
Besides its physical complications, the adverse effects of priapism extend to psychosocial and relational realms. Psychological study of the effect of priapism on patients with sickle cell disease has shown its association with despair, embarrassment, and isolation (lack of relationships) as significant health burdens.
Pathophysiology
The pathophysiologic description of priapism has undergone considerable evolution in recent years. Early study of priapism established the features of vascular stasis within the penis and decreased venous outflow from the organ, which correlated with the finding of dark and viscous blood that is surgically drained from the priapic penis. These observations contributed to notions of the ischemic nature of priapism and supported the early hypothesis that penile congestion explained the disorder. This early way of thinking specified the pathophysiology to be that of obstructive processes interfering with penile rheology, a concept modeled by priapism associated with sickle cell disease, in which misshapen erythrocytes were conceived to impede intracorporal blood flow. The causative basis of sickle cell disease–associated priapism, as well as that likely involved in other hematologic dyscrasias, is now suggested to be more scientifically complex than solely a matter of obstructive intravascular phenomena (as described later). The phenomena of venous congestion and heightened blood viscosity within the penis may well be contributive or otherwise simply an effect of the pathophysiologic condition, rather than representing its true cause. However, it remains plausible that mechanical obstruction of blood flow in the penis leading to priapism is causative in some instances of the disorder, such as local primary or metastatic neoplasms involving the penis.
The pathophysiology of nonischemic priapism is characterized as having a traumatic basis. The mechanism fundamentally involves excessive arterial inflow to the penis, resulting from structural damage of its arterial circulation. Physical trauma to the penis classically involves a straddle injury to the perineum, although other forms of genital trauma, including needle lacerations associated with intracavernosal pharmacotherapy for ED, have also been described. The pathognomonic feature of this form of priapism is the formation of a fistula between the cavernosal artery and lacunar spaces of the cavernous tissue. This defect then allows blood to bypass the helicine arteriolar bed, which regularly serves as a vascular resistance mechanism in the penis. A nonischemic priapism variant is recognized in which a high-flow hemodynamic state of the cavernosal arteries exists in the absence of fistula formation. This variant commonly is observed as a refractory presentation of priapism after medical or surgical treatment of ischemic priapism, and in similar fashion to the fistula type of nonischemic priapism ostensibly results from cavernosal arterial dysregulated inflow.
Recent discoveries in priapism research suggest that the pathogenesis of ischemic priapism is explained by molecular science and involves altered vascular homeostatic actions in the penis coupled with deficient erection control mechanisms. A dysregulatory erection physiology hypothesis equates with the evolution of understanding in this field. The range of dysregulatory erection physiologic mechanisms likely exists at multiple control levels of penile erection, including central and peripheral neurotransmission, paracrine agency within the corporal tissue, as well as the hormonal axis. Major molecular determinants of erection physiology are currently proposed to be principally involved, and recent descriptions have centered on aberrant nitric oxide (NO), RhoA/Rho-kinase and adenosine signaling pathways as primary mechanisms acting at a local penile level. Consistent with other factors contributing to the pathophysiology of the condition, ongoing investigative work has centered on mechanisms of ischemia-reperfusion injury, inflammation and oxidative stress, and tissue fibrosis. Scientific progress in this field exemplifies the rapidly changing molecular science of erection physiology, and, as much as this evolution has led to the introduction of new therapies for ED, similar innovations in molecularly based clinical therapeutics for priapism are anticipated.
Pathologic basis of disease
Advances in the clinical management of priapism, as for any medical disorder, derive practically from a solid core of knowledge of its pathogenesis. Study of the dynamics and mechanisms of disease involved in priapism conceivably assures the identification of biologic targets toward which therapeutic objectives for the disorder are aimed. Approaches to this investigation include clinical and basic scientific research work.
Clinicopathologic Observations
The natural course of priapism varies, although characteristic clinical patterns and outcomes of the disorder are commonly recognized. The disorder may occur briefly and abate in some individuals with little apparent adverse health consequence, although in others it persists for long durations with major clinicopathologic significance. Two standard forms of priapism are recognized, and this division offers a useful classification system for the disorder. Ischemic priapism, also termed venoocclusive or low-flow priapism, characteristically features absent intracorporal blood flow. This form of priapism represents an actual compartment syndrome localized to the corpora cavernosa and is associated with penile rigidity and pain. Nonischemic priapism, also termed arterial or high-flow priapism, features increased vascular flow within the corpora cavernosa without rendering a compartment syndrome effect. This classification system is also relevant to clinical management. Accordingly, ischemic priapism, which occurs more commonly, represents a medically emergent condition and prompts immediate clinical action, whereas nonischemic priapism, occurring less commonly, can be managed nonemergently.
A major episode of ischemic priapism is generally defined if it has been present for more than a few hours; if it is not treated promptly, pathologic changes of the erectile tissue can be expected, resulting from the prolonged ischemic conditions. Priapism recurrences, in which repeated prolonged erectile events occur but characteristically last less than 3 hours and spontaneously remit, are also observed. These recurrent episodes, often termed stuttering attacks, also are ischemic in quality. A frequent clinical pattern of priapism is the display of recurrences as short-lived episodes that, in time, progress in duration before a major episode occurs. Whether major or recurrent, ischemic priapism implies a risk for development of metabolic derangements in the penis caused by lack of intracorporal circulation. At 4 hours of ischemia, significant acidosis and glucopenia develop in the penis, and thereafter erectile tissue reactivity begins to become irreversibly impaired. Nonischemic priapism follows a distinct natural course that either resolves spontaneously or persists without resolution for extended durations. It also differs pathologically from its ischemic counterpart by maintaining normoxic, metabolically intact intracorporal circulation.
Genital complications of ischemic priapism occur both structurally and functionally. Tissue edema with cellular loss is observed within the penis after several hours of unrelieved ischemia. Penile tissue necrosis and progressive fibrosis represent end-stage pathologic changes. The gross pathologic feature of this course is penile disfigurement, with morphologic defects that range from megalophallic deformity to major penile tissue destruction and sloughing. These changes are responsible for loss of erectile function, directly because of the inability of the penis to achieve physiologic blood engorgement. Complete ED rates of 30% to 90% are documented in men who have experienced major ischemic priapism episodes. As much as a 25% ED rate has been reported in men sustaining recurrent ischemic priapism. Although it is generally believed that individuals with nonischemic priapism escape pathologic effects of the penis that reduce erectile ability, descriptions of ED have been documented for this group. Penile tissue damage associated with the traumatic development of this form of priapism may explain this phenomenon.
Besides its physical complications, the adverse effects of priapism extend to psychosocial and relational realms. Psychological study of the effect of priapism on patients with sickle cell disease has shown its association with despair, embarrassment, and isolation (lack of relationships) as significant health burdens.
Pathophysiology
The pathophysiologic description of priapism has undergone considerable evolution in recent years. Early study of priapism established the features of vascular stasis within the penis and decreased venous outflow from the organ, which correlated with the finding of dark and viscous blood that is surgically drained from the priapic penis. These observations contributed to notions of the ischemic nature of priapism and supported the early hypothesis that penile congestion explained the disorder. This early way of thinking specified the pathophysiology to be that of obstructive processes interfering with penile rheology, a concept modeled by priapism associated with sickle cell disease, in which misshapen erythrocytes were conceived to impede intracorporal blood flow. The causative basis of sickle cell disease–associated priapism, as well as that likely involved in other hematologic dyscrasias, is now suggested to be more scientifically complex than solely a matter of obstructive intravascular phenomena (as described later). The phenomena of venous congestion and heightened blood viscosity within the penis may well be contributive or otherwise simply an effect of the pathophysiologic condition, rather than representing its true cause. However, it remains plausible that mechanical obstruction of blood flow in the penis leading to priapism is causative in some instances of the disorder, such as local primary or metastatic neoplasms involving the penis.
The pathophysiology of nonischemic priapism is characterized as having a traumatic basis. The mechanism fundamentally involves excessive arterial inflow to the penis, resulting from structural damage of its arterial circulation. Physical trauma to the penis classically involves a straddle injury to the perineum, although other forms of genital trauma, including needle lacerations associated with intracavernosal pharmacotherapy for ED, have also been described. The pathognomonic feature of this form of priapism is the formation of a fistula between the cavernosal artery and lacunar spaces of the cavernous tissue. This defect then allows blood to bypass the helicine arteriolar bed, which regularly serves as a vascular resistance mechanism in the penis. A nonischemic priapism variant is recognized in which a high-flow hemodynamic state of the cavernosal arteries exists in the absence of fistula formation. This variant commonly is observed as a refractory presentation of priapism after medical or surgical treatment of ischemic priapism, and in similar fashion to the fistula type of nonischemic priapism ostensibly results from cavernosal arterial dysregulated inflow.
Recent discoveries in priapism research suggest that the pathogenesis of ischemic priapism is explained by molecular science and involves altered vascular homeostatic actions in the penis coupled with deficient erection control mechanisms. A dysregulatory erection physiology hypothesis equates with the evolution of understanding in this field. The range of dysregulatory erection physiologic mechanisms likely exists at multiple control levels of penile erection, including central and peripheral neurotransmission, paracrine agency within the corporal tissue, as well as the hormonal axis. Major molecular determinants of erection physiology are currently proposed to be principally involved, and recent descriptions have centered on aberrant nitric oxide (NO), RhoA/Rho-kinase and adenosine signaling pathways as primary mechanisms acting at a local penile level. Consistent with other factors contributing to the pathophysiology of the condition, ongoing investigative work has centered on mechanisms of ischemia-reperfusion injury, inflammation and oxidative stress, and tissue fibrosis. Scientific progress in this field exemplifies the rapidly changing molecular science of erection physiology, and, as much as this evolution has led to the introduction of new therapies for ED, similar innovations in molecularly based clinical therapeutics for priapism are anticipated.
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