Ischemic Priapism Due to Impaired Venous Outflow
The correct answer is B: Impaired penile venous outflow. This patient has acute ischemic priapism secondary to sickle cell disease, where sickling of red blood cells obstructs venous drainage from the corpora cavernosa, creating a compartment syndrome-like state with resultant tissue hypoxia and acidosis 1, 2.
Pathophysiology Confirmed by Clinical Findings
The diagnosis is definitively established by the corporal blood gas results showing:
- pH 7.21 (normal 7.40, ischemic <7.25) 1
- PO2 26 mm Hg (normal >90, ischemic <30) 1
- PCO2 68 mm Hg (normal <40, ischemic >60) 1
These values confirm ischemic (low-flow) priapism, which results from blockage of venous outflow by sickled erythrocytes, leading to blood stasis, anoxia of cavernosal smooth muscle, and subsequent tissue damage 3, 4. The rigid corpora cavernosa with soft glans is pathognomonic for ischemic priapism affecting only the erectile bodies while sparing the corpus spongiosum 1, 2.
Why Other Options Are Incorrect
Option A (Fibrosis of tunica albuginea): This is a consequence of chronic, untreated priapism or Peyronie's disease, not the acute cause. Fibrosis develops after prolonged ischemia damages smooth muscle, which is then replaced by scar tissue 3.
Option C (Impaired parasympathetic activity): Decreased parasympathetic activity would prevent erection, not cause it. Priapism represents a failure of detumescence, not excessive tumescence signaling 5.
Option D (Increased arterial inflow): This describes non-ischemic (high-flow) priapism, typically from trauma creating an arteriovenous fistula. Blood gas would show bright red blood with PO2 >90 mm Hg and normal pH, not the dark, acidotic blood seen here 1, 4, 5.
Option E (Increased sympathetic activity): Increased sympathetic tone promotes detumescence through alpha-adrenergic vasoconstriction. This is why phenylephrine (an alpha-agonist) is used to treat ischemic priapism 1, 6.
Critical Clinical Context
In sickle cell disease, recurrent vaso-occlusive crises cause sickling in the low-oxygen, low-pH environment of the corpora cavernosa, mechanically obstructing venous drainage 1. This creates a vicious cycle: stasis → hypoxia → acidosis → further sickling → worsening obstruction 2, 4. The 6-hour duration places this patient at significant risk for permanent erectile dysfunction, as smooth muscle edema and atrophy begin as early as 6 hours, with irreversible damage highly likely after 36 hours 1, 6.
Immediate Management Required
This is a urologic emergency requiring immediate intracavernosal phenylephrine (100-500 mcg/mL, maximum 1000 mcg in first hour) with corporal aspiration, which has a 43-81% success rate 6, 7. Do not delay urologic intervention for systemic sickle cell treatments alone, as this guarantees erectile dysfunction 1, 7. Standard sickle cell management should occur concurrently with, not instead of, direct penile intervention 1, 8.