Priapismus
Priapism (rarely penile priapism, to differentiate from the very rare clitoral priapism) is a prolonged erection that persists beyond or is not related to sexual stimulation. Imaging, particularly Doppler ultrasound, can help distinguish between ischemic (low-flow) priapism, which is a urologic emergency, and non-ischemic (high-flow) priapism.
Epidemiology
The incidence of priapism is around 0.3-1.5 per 100,000 male person-years . The most common pathophysiologic type is ischemic priapism, accounting for 95% of priapism episodes .
Clinical presentation
Priapism is a full or partial erection that persists beyond or is unrelated to sexual stimulation or desire. Clinical definitions often specify that the erection lasts longer than 4 hours, but episodes of so-called stuttering priapism can be shorter in duration .
Priapism can be differentiated into ischemic and nonischemic types based on the history and physical as well as cavernosal blood gases :
- penis typically fully rigid
- typically painful
- abnormal cavernosal blood gases: hypoxic, hypercarbic, and acidotic
- penis not necessarily fully rigid
- typically painless
- cavernosal blood gases with normal arterial values, not hypoxic or acidotic
A special pattern of recurrent, self-limited episodes of ischemic priapism is known as stuttering priapism .
Pathology
Priapism results from altered penile hemodynamics, whether involving decreased venous outflow or increased arterial inflow. Ischemic, low-flow priapism increases intracavernosal pressure and risks tissue ischemia.
Etiology
In children and adolescents, most cases are associated with sickle cell disease . In adults, most cases are idiopathic . The most common known causes in adults are drug use, perineal trauma, and sickle cell disease . The known causes can be categorized by clinicopathophysiologic types:
- hematologic dyscrasias, such as
- sickle cell disease (most common)
- thalassemia
- hematologic malignancy such as leukemia
- drugs
- recreational drugs (e.g., cocaine)
- vasoactive erectile agents, especially intracavernosal injections (e.g., papaverine, phentolamine, or prostaglandin E1)
- anticoagulants (e.g., heparin, warfarin)
- antihypertensives, especially vasodilators (e.g., hydralazine) and alpha-adrenergic receptor antagonists (e.g., prazosin)
- antidepressants (e.g., trazodone, selective serotonin reuptake inhibitors)
- solid malignancy
- regional infiltration of genitourinary tract malignancy such as prostate or bladder
- metastatic disease to the penis
- traumatic: most commonly due to blunt penile/perineal trauma causing an arteriocavernous fistula
- neurogenic: autonomic imbalance such as due to spinal cord injury or cauda equina syndrome
- post-shunting: iatrogenic or reactive hyperemia after a shunt procedure performed for ischemic priapism
- common in sickle cell disease
Radiographic features
Ultrasound
Ultrasound is the first line imaging modality in evaluation of priapism. A high-frequency transducer (>7 MHz) should be used.
Color and spectral Doppler ultrasound is usually most helpful in distinguishing high-flow priapism from low-flow priapism:
- low-flow priapism (typically ischemic)
- thrombosis of the corpora cavernosa or corpus spongiosum
- decreased/absent color flow or spectral Doppler in the cavernosal artery/arteries
- cavernosal artery velocity <25 cm/s would be considered low velocity, but low velocity flow is technically non-specific
- patients with low but present cavernosal arterial flow tend to require arterial blood gas evaluation
- increased resistive index (RI) of the cavernosal artery
- this can also be seen with a normal erection
- cavernosal artery velocity <25 cm/s would be considered low velocity, but low velocity flow is technically non-specific
- there may be flow in the superficial penile vein
- high-flow priapism (typically non-ischemic)
- an arteriovenous fistula may be visualized
- penile artery Doppler velocities are typically normal (>25 cm/s) or elevated
MRI
MRI is not indicated for emergent evaluation of low-flow priapism due to the time it takes for the scan. It may be used in the non-emergent setting for problem-solving.
- T1: abnormally increased signal in the penile corpora may indicate thrombus
- T2: flow voids in the cavernosa may be present in high-flow priapism
- T1 C+ (Gd):
- post contrast evaluation may be useful for pre-treatment planning of high-flow priapism
- asymmetric cavernosal enhancement may occur with either type of priapism
MRI may be more likely to see associated conditions that may lead to priapism (e.g. malignancy).
Treatment and prognosis
If untreated, priapism can lead to permanent damage with potential erectile dysfunction, and ischemic priapism is a surgical emergency.
Treatments include irrigation with sympathomimetics and surgical shunts. Surgical shunting is considered after failure of intracavernosal sympathomimetics and can be performed proximally or distally:
- proximal shunting involves either an incision of the tunica of the corpora in the base of the penis (corporospongisal) or placement of graft bypass shunting corporal blood to a nearby vein (corporasaphenous)
- distal shunting (cavernoglanular) involves removal or incision of the tunica of the distal tips of the corpora cavernosa with either a biopsy needle or scalpel respectively, to allow drainage into the glans
Penile prosthesis implantation is a last resort.
History and etymology
The term "priapism" derives from a rural Greek fertility god called "Priapus," who sported a permanent erection.
Siehe auch:
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Assoziationen und Differentialdiagnosen zu Priapismus: