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Summary Table

Category	Details
Risk Factors	Sickle cell disease/hemoglobinopathy, intracavernosal injection (ICI) of vasoactive agents, hematologic malignancies, use of PDE5 inhibitors or recreational drugs, pelvic/perineal trauma (non-ischemic type), hypercoagulable states, vasculitis
Etiology	Ischemic: impaired venous outflow from corpora cavernosa causing blood stasis, hypoxia, and acidosis. Non-ischemic: unregulated arterial inflow following trauma creating an arterio-lacunar fistula
Patient Presentation	Ischemic: painful, fully rigid erection lasting >4 hours without sexual stimulation. Non-ischemic: painless, partially tumescent (not fully rigid) erection, often with history of perineal/penile trauma
Classic Physical Exam	Ischemic: rigid corpora cavernosa, glans and corpus spongiosum soft, tenderness on palpation. Non-ischemic: partial tumescence without full rigidity, no tenderness
Key Diagnostic Results	Ischemic: aspirated blood is dark; blood gas shows pO2 <30 mmHg, pCO2 >60 mmHg, pH <7.25; CDUS shows absent cavernosal arterial flow. Non-ischemic: aspirated blood is bright red; blood gas resembles arterial blood (pO2 >90, pCO2 <40, pH 7.40); CDUS shows turbulent flow at fistula site
Management	Ischemic (emergency): stepwise approach of aspiration, irrigation with normal saline, intracavernosal phenylephrine injection (200 mcg every 3-5 min, max 1 mg/hour); surgical shunting if refractory; penile prosthesis if >48 hours. Non-ischemic (not an emergency): observation, perineal compression; selective arterial embolization if conservative management fails
Keywords	"Painful erection >4 hours," "dark blood on aspiration," "sickle cell disease with erection," "perineal trauma with painless erection," "acidotic cavernosal blood gas," "absent arterial flow on Doppler"

1. Pathophysiology

Priapism is defined as a persistent erection lasting more than 4 hours in the absence of sexual stimulation (Tata Laksana Disfungsi Seksual Pria IAUI 2023). The underlying mechanism differs fundamentally between the two principal subtypes, and understanding this distinction is what drives both diagnosis and management.

In ischemic (low-flow, veno-occlusive) priapism, the problem is a failure of venous drainage from the corpora cavernosa. Under normal physiology, detumescence occurs when sympathetic tone causes smooth muscle contraction, which reopens venous channels and allows blood to exit. When this mechanism fails, blood becomes trapped within the sinusoidal spaces. As time progresses, the trapped blood undergoes progressive deoxygenation, hypercapnia, and acidosis. This is why aspirated blood is characteristically dark, and the blood gas profile shows pO2 <30 mmHg, pCO2 >60 mmHg, and pH <7.25. If left untreated, the ischemic environment leads to smooth muscle necrosis and corporal fibrosis, which is irreversible and results in permanent erectile dysfunction. This makes ischemic priapism a true urological emergency. Ischemic priapism accounts for more than 95% of all cases (Tata Laksana Disfungsi Seksual Pria IAUI 2023).

In non-ischemic (high-flow, arteriogenic) priapism, the mechanism is entirely different. A traumatic event, most commonly blunt perineal or penile trauma, disrupts a cavernosal artery and creates an arterio-lacunar fistula. This fistula allows unregulated arterial inflow into the sinusoidal spaces, but because venous outflow remains intact, there is no ischemia. The blood within the corpora remains well-oxygenated. This is why the erection is typically only partial (not fully rigid), painless, and not a medical emergency. It accounts for only about 5% of all priapism cases (Tata Laksana Disfungsi Seksual Pria IAUI 2023).

Stuttering (recurrent/intermittent) priapism is a distinct entity characterized by repeated, self-limiting episodes of ischemic priapism that resolve spontaneously but recur over time. If untreated, cumulative episodes lead to progressive corporal fibrosis. Sickle cell disease is the most common underlying cause (Tata Laksana Disfungsi Seksual Pria IAUI 2023).

2. Classification and Clinical Manifestation

Feature	Ischemic (Low-Flow)	Non-Ischemic (High-Flow)	Stuttering
Proportion of cases	>95%	~5%	Subset of ischemic
Mechanism	Impaired venous outflow	Unregulated arterial inflow via fistula	Recurrent episodes of venous outflow failure
Corpora cavernosa rigidity	Fully rigid (typical)	Rarely fully rigid	Fully rigid during episodes
Pain	Typical (severe)	Rare	Present during episodes
Onset	Spontaneous or drug-induced	Post-traumatic	Recurrent, self-limiting
Blood gas on aspiration	Abnormal (dark blood, pO2 <30, pCO2 >60, pH <7.25)	Normal/arterial (bright red, pO2 >90, pCO2 <40, pH 7.40)	Abnormal during acute episodes
CDUS findings	Absent cavernosal arterial flow	Normal arterial flow with turbulent flow at fistula site	Absent flow during episodes
Hematologic disorders	Sometimes	Rare	Common (sickle cell disease)
History of ICI	Sometimes	Sometimes	Less common
Perineal trauma	Rare	Typical	Rare
Urgency	Emergency	Not an emergency	Each acute episode is treated as emergency
Risk of erectile dysfunction	High (smooth muscle necrosis)	Low	Cumulative risk with repeated episodes

3. Diagnostic Workup

Test	Purpose	Key Findings
Comprehensive history	Determine duration, pain severity, prior episodes, medications, substance use, sickle cell/hemoglobinopathy status	Strong recommendation (Tata Laksana Disfungsi Seksual Pria IAUI 2023)
Physical examination	Assess genitalia, perineum, abdomen; determine rigidity and tenderness	Rigid, tender corpora = ischemic; partial tumescence, non-tender = non-ischemic
Corporal blood gas analysis	Differentiate ischemic from non-ischemic	Best initial differentiating test. Ischemic: pO2 <30, pCO2 >60, pH <7.25. Non-ischemic: resembles arterial blood
Color duplex ultrasonography (CDUS) of penis and perineum	Assess cavernosal blood flow; detect fistula	Ischemic: absent arterial flow. Non-ischemic: normal flow + turbulent flow at fistula
CBC with differential, platelet count, coagulation profile	Evaluate for hematologic disorders	Screen for sickle cell, leukemia, coagulopathy
Hemoglobinopathy screening	Identify sickle cell disease or thalassemia in at-risk patients	Strong recommendation for ischemic priapism in at-risk populations
Penile MRI	Assess smooth muscle viability in prolonged or refractory ischemic priapism	Weak recommendation; helps predict whether smooth muscle is viable or necrotic
Pudendal arteriography	Pre-procedural mapping before embolization	Performed only when embolization is planned for non-ischemic priapism

The first step in evaluating any priapism is a thorough history (strong recommendation, Tata Laksana Disfungsi Seksual Pria IAUI 2023). The history must include the duration of erection, the presence and severity of pain, any prior episodes and their treatment, current erectile function, use of vasoactive medications or recreational drugs, and a review for sickle cell disease, hemoglobinopathy, hypercoagulable states, vasculitis, and history of pelvic/perineal trauma.

Physical examination of the genitalia, perineum, and abdomen is the next step (strong recommendation). In ischemic priapism, the corpora cavernosa are fully rigid and tender, while the glans penis and corpus spongiosum remain soft. In non-ischemic priapism, the penis is only partially tumescent and typically non-tender.

The critical differentiating test is corporal blood gas analysis from aspirated blood (strong recommendation). This is the best initial test to distinguish ischemic from non-ischemic priapism. The reference blood gas values from the IAUI 2023 guideline are:

Source	pO2 (mmHg)	pCO2 (mmHg)	pH
Normal arterial blood (same as non-ischemic priapism)	>90	<40	7.40
Normal mixed venous blood	40	50	7.35
Ischemic priapism (first aspiration)	<30	>60	<7.25

Color duplex ultrasonography (CDUS) of the penis and perineum should be performed before aspiration to differentiate ischemic from non-ischemic priapism (strong recommendation, Tata Laksana Disfungsi Seksual Pria IAUI 2023). In ischemic priapism, there is absent cavernosal arterial flow. In non-ischemic priapism, arterial flow is preserved and turbulent flow can be identified at the fistula site.

Laboratory workup (strong recommendation) includes CBC with differential, platelet count, and coagulation profile. In children, a comprehensive evaluation of all possible causes is required. Hemoglobinopathy screening is strongly recommended in patients with ischemic priapism who are at risk for sickle cell disease or thalassemia.

MRI of the penis is a weak recommendation, reserved for prolonged or refractory ischemic priapism as an adjunct to predict smooth muscle viability. This is useful when deciding between shunting procedures and immediate prosthesis implantation.

Pudendal arteriography is only indicated when arterial embolization is planned for non-ischemic priapism (strong recommendation).

4. Management & Treatment

Ischemic Priapism (Emergency)

Step	Intervention	Details	Recommendation Strength
1	Penile aspiration	Local anesthesia; insert 16-18G wing needle through glans into corpora cavernosa or via lateral approach bilaterally; aspirate until bright red (arterial) blood is obtained	Strong
2	Corporal irrigation	Irrigate with 0.9% normal saline	Strong
3	Intracavernosal sympathomimetic injection	Phenylephrine 200 mcg every 3-5 minutes until detumescence (maximum dose: 1 mg in 1 hour)	Strong
4 (if steps 1-3 fail)	Repeat aspiration + sympathomimetic before surgery	Repeat the above steps before considering surgical intervention	Strong
5a (<24 hours)	Distal shunt +/- tunneling (T-shunt)	First-line surgical option	Weak
5b (24-48 hours, no necrosis)	Distal shunt; if failed, consider peno-scrotal decompression	MRI penis to assess necrosis	Weak
5b (24-48 hours, necrosis present)	Penile prosthesis implantation	Consider early implantation	Weak
5c (>48 hours)	Penile prosthesis implantation	Prosthesis may be preferred over proximal shunting in delayed presentation	Weak

Non-Ischemic Priapism

Step	Intervention	Details	Recommendation Strength
1	Observation + perineal compression	Conservative first-line; consider androgen deprivation therapy (ADT) in adults only	Weak
2 (if conservative fails)	Selective arterial embolization	Use temporary embolization materials first	Strong (for embolization); Weak (for temporary materials)
3 (if recurrence after embolization)	Repeat embolization with temporary or permanent agents	For recurrent non-ischemic priapism	Weak
4 (last resort)	Surgical ligation of fistula	Only when repeated embolization has failed	Weak

Stuttering Priapism

Phase	Intervention	Details	Recommendation Strength
Acute episode	Manage as ischemic priapism	Same stepwise approach	Strong
Prevention	Hormonal therapy (GnRH agonist/antagonist, antiandrogens)	Do NOT use before sexual maturity is reached	Weak
Prevention	PDE5 inhibitor	Start only when penis is in flaccid state	Weak
Refractory cases	Digoxin, alpha-adrenergic agonists, baclofen, gabapentin, or terbutaline	Only for frequent, uncontrolled recurrence	Weak

Ischemic priapism is a urological emergency and must be treated as soon as possible, ideally within 4 to 6 hours (strong recommendation, Tata Laksana Disfungsi Seksual Pria IAUI 2023). The management follows a stepwise approach, and the clinician should advance to the next step only when the current one fails.

Step 1: Aspiration and irrigation. After administering local anesthesia to the penis, a 16-18G wing needle is inserted through the glans into the corpora cavernosa (or through the lateral aspect bilaterally). Dark, deoxygenated blood is aspirated until bright red arterial blood is obtained. The corpora are then irrigated with 0.9% normal saline.

Step 2: Intracavernosal sympathomimetic injection. If aspiration alone does not achieve detumescence, phenylephrine is injected intracavernosally at a dose of 200 mcg every 3 to 5 minutes until detumescence occurs. The maximum dose is 1 mg within 1 hour (Tata Laksana Disfungsi Seksual Pria IAUI 2023). Phenylephrine can cause hypertension and should be used with caution in patients with cardiovascular disease. Heart rate and blood pressure monitoring is recommended during and for 1 hour after injection. Phenylephrine is contraindicated in patients with a history of cerebrovascular disease and significant hypertension. In pediatric patients, the dose must be reduced.

For priapism secondary to ICI with vasoactive agents, the aspirated blood should be replaced with an intracavernosal sympathomimetic injection as the first step (strong recommendation).

Step 3: If still refractory, repeat the aspiration and sympathomimetic injection before considering surgery (strong recommendation).

Step 4: Surgical intervention. When aspiration and injection fail, the approach depends on the duration of priapism. For priapism lasting less than 24 hours, a distal shunt (such as a T-shunt) with or without tunneling is performed first. For 24 to 48 hours, MRI of the penis can help assess whether smooth muscle necrosis has occurred. If no necrosis is present, a distal shunt is attempted; if necrosis is confirmed, penile prosthesis implantation should be considered. For priapism lasting more than 48 hours, prosthesis implantation is generally preferred over proximal shunting (Tata Laksana Disfungsi Seksual Pria IAUI 2023).

If a proximal shunt has been performed previously and failed, or if the patient does not wish to proceed with immediate prosthesis, proximal shunting remains an option for cases under 48 hours (weak recommendation).

Important post-surgical consideration: If a shunt has already been performed, prosthesis implantation should be delayed to minimize the risk of infection and implant erosion (strong recommendation). The type of implant depends on the clinical situation, surgeon experience, availability, and cost. If a malleable prosthesis is placed initially, it can later be replaced with an inflatable prosthesis (strong recommendation).

Perioperative anticoagulation may reduce the recurrence of priapism (weak recommendation).

For sickle cell-related priapism, the penile management is identical to idiopathic ischemic priapism. Supportive measures include intravenous hydration, supplemental oxygen with bicarbonate alkalinization, and exchange transfusion, but these should not delay the initial treatment of the penis (strong recommendation, Tata Laksana Disfungsi Seksual Pria IAUI 2023).

Non-ischemic priapism is not an emergency. The first-line approach is conservative management with perineal compression at the site of the fistula. Androgen deprivation therapy may be considered in adults only (weak recommendation). If conservative management fails, selective arterial embolization is performed, initially using temporary embolization materials (strong and weak recommendations, respectively). If priapism recurs after embolization, the procedure can be repeated using temporary or permanent agents. Surgical ligation of the fistula is a last-resort option when repeated embolization fails (weak recommendation).

5. Differential Diagnosis & Distractors

Differential	Why It Looks Similar	Key Discriminator
Non-ischemic priapism (when the vignette is ischemic)	Both present with prolonged erection >4 hours	Ischemic: painful, fully rigid, dark blood on aspiration, acidotic blood gas, absent arterial flow on CDUS. Non-ischemic: painless, partially rigid, bright red blood, normal blood gas, history of trauma
Ischemic priapism (when the vignette is non-ischemic)	Both involve prolonged erection	Non-ischemic: painless, history of perineal trauma, arterial blood gas values, turbulent flow at fistula on CDUS
Nocturnal penile tumescence (sleep-related erection)	Patient wakes up with erection	Normal sleep erections resolve spontaneously within minutes, are not painful, and do not last >4 hours
Pharmacologically induced erection (normal response to ICI or PDE5i)	Erection occurs after drug use	Normal pharmacologic erection resolves within 1-2 hours; priapism is diagnosed when erection persists beyond 4 hours despite no ongoing stimulation
Sickle cell vaso-occlusive crisis (without priapism)	Patient with sickle cell disease, pain	Vaso-occlusive crisis causes pain in bones and abdomen, not an isolated rigid painful erection. Priapism in sickle cell is a localized veno-occlusive event in the penis
Stuttering priapism (vs. single episode ischemic)	Both involve painful rigid erection	Stuttering priapism is characterized by recurrent, self-limiting episodes that resolve and recur; treatment includes prevention of future episodes with hormonal therapy or PDE5i (started when flaccid)
Peyronie's disease with erection difficulty	Both can present with abnormal erection and pain	Peyronie's involves a palpable plaque, curvature, and pain during erection that resolves with time; the erection itself is not prolonged beyond 4 hours

6. Traps and High-Yield Pearls

The most common way students get priapism questions wrong is by confusing ischemic and non-ischemic subtypes and consequently choosing the wrong management. The vignette will often contain one or two distinguishing features that must be identified quickly. Pain and full rigidity point to ischemic. A history of perineal trauma with a painless, partially tumescent erection points to non-ischemic. Blood gas analysis is the confirmatory differentiator, and the cutoff values (pO2 <30, pCO2 >60, pH <7.25 for ischemic) must be memorized.

A second common trap is failing to recognize that ischemic priapism is an emergency while non-ischemic is not. Students may rush to embolization in non-ischemic cases (which is premature; conservative management is tried first) or delay intervention in ischemic cases (which causes irreversible damage). The management of ischemic priapism is strictly stepwise: aspiration first, then irrigation, then phenylephrine injection, then repeat before surgery. Skipping steps or going directly to surgery is incorrect unless prior steps have explicitly failed.

A third trap involves sickle cell disease. The question may present a child or young adult with sickle cell disease and priapism, and the student may be tempted to prioritize hematologic management (hydration, exchange transfusion, oxygen). While these supportive measures are important, the IAUI 2023 guideline emphasizes that penile management must not be delayed for systemic treatment. The penile protocol is identical to idiopathic ischemic priapism.

The phenylephrine dosing detail is another testable point: 200 mcg every 3-5 minutes with a ceiling of 1 mg in 1 hour, contraindicated in cerebrovascular disease and significant hypertension. Students who confuse this with epinephrine or adrenaline may select a wrong answer.

Finally, the decision tree for surgery hinges on duration. Under 24 hours: distal shunt. Between 24 and 48 hours: check for necrosis with MRI. Over 48 hours: prosthesis implantation is generally favored. If a shunt has already been performed, prosthesis implantation should be delayed to reduce infection risk. The core competency being tested is the ability to match the correct intervention to the duration and refractoriness of the priapism, while applying the stepwise management principle accurately.

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