Emergency Medicine · Urologic Emergencies
The facts most likely to be tested
Ischemic (low-flow) priapism is a urologic emergency characterized by a rigid, painful erection with absent cavernous blood flow.
Sickle cell disease and leukemia are the most common hematologic causes of ischemic priapism due to venous outflow obstruction.
Intracavernosal injection of vasoactive agents like papaverine or alprostadil is the most common iatrogenic cause of ischemic priapism.
Cavernosal blood gas analysis in ischemic priapism reveals hypoxia (pO2 < 30 mmHg), hypercapnia (pCO2 > 60 mmHg), and acidosis (pH < 7.25).
Non-ischemic (high-flow) priapism is typically caused by perineal trauma resulting in a cavernosal artery-corpus cavernosum fistula and is generally painless.
First-line treatment for ischemic priapism is aspiration of the corpora cavernosa followed by intracavernosal injection of a sympathomimetic agent like phenylephrine.
Delayed treatment of ischemic priapism beyond 4–6 hours leads to irreversible fibrosis and permanent erectile dysfunction.
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A 22-year-old male with a history of sickle cell disease presents to the emergency department complaining of a painful, persistent erection that began 8 hours ago. On physical examination, the penis is rigid and tender to palpation. A cavernosal blood gas is performed, which demonstrates a pO2 of 20 mmHg, pCO2 of 70 mmHg, and a pH of 7.15. The patient has no history of recent trauma or medication use.
What is the most appropriate initial management for this patient?
Aspiration of the corpora cavernosa and intracavernosal phenylephrine injection
The patient presents with classic signs of ischemic priapism, confirmed by the blood gas findings; immediate decompression and sympathomimetic therapy are required to prevent permanent fibrosis.
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Etiology / Epidemiology
Common in Sickle Cell Disease and patients using PDE-5 inhibitors or trazodone.
Clinical Manifestations
Persistent, painful erection >4 hours; ischemic type is rigid, tender corpora cavernosa.
Diagnosis
Gold standard is cavernosal blood gas; ischemic shows pH <7.25, pO2 <30 mmHg, pCO2 >60 mmHg.
Treatment
First-line is phenylephrine intracavernosal injection; avoid epinephrine due to systemic risk.
Prognosis
Delayed treatment (>24h) leads to permanent erectile dysfunction due to fibrosis.
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Epidemiology & Etiology
Primary causes include Sickle Cell Disease (most common in children) and medication-induced cases. Common pharmacologic triggers include trazodone, prazosin, and sildenafil. It is a urologic emergency requiring immediate intervention to prevent long-term damage.
Pertinent Anatomy
The penis contains two corpora cavernosa and one corpus spongiosum. Priapism involves the corpora cavernosa, which are responsible for rigidity. The corpus spongiosum and glans are typically spared in ischemic priapism.
Pathophysiology
Ischemic (low-flow) priapism results from venous outflow obstruction leading to compartment syndrome. Stasis causes hypoxia, hypercapnia, and acidosis within the cavernosa. Prolonged ischemia triggers irreversible fibrosis and smooth muscle necrosis.
Clinical Manifestations
Patients present with a painful, rigid erection lasting >4 hours. Ischemic priapism is characterized by tender, rigid corpora with a soft glans. Red flags include systemic toxicity or history of perineal trauma, which may suggest high-flow (arterial) priapism.
Diagnosis
Perform cavernosal blood gas analysis to differentiate ischemic from non-ischemic types. Ischemic findings include pH <7.25, pO2 <30 mmHg, and pCO2 >60 mmHg. A penile duplex ultrasound is used to assess blood flow velocity in suspected high-flow cases.
Treatment
Initial management involves aspiration of the corpora followed by irrigation with saline. If unsuccessful, inject phenylephrine (alpha-agonist) directly into the corpora. Contraindications include systemic hypertension or severe cardiovascular disease. If refractory, surgical distal shunts are required.
Prognosis
Prognosis is time-dependent; permanent erectile dysfunction occurs in nearly 100% of cases if duration exceeds 24 hours. Patients require close follow-up to monitor for cavernosal fibrosis and potential penile prosthesis placement.
Differential Diagnosis
High-flow priapism: painless, non-rigid, history of trauma
Peyronie disease: fibrous plaque causing curvature, not sustained erection
Penile fracture: sudden 'pop' sound followed by detumescence and hematoma
Spinal cord injury: may cause neurogenic priapism
Leukemic infiltration: rare cause of persistent priapism