A 22-year-old man presents to the emergency department for evaluation of penile
pain of six hours duration. Past medical history is significant for sickle cell disease
. He does not use illicit drugs or take any medications daily. Temperature is 37.0°C (98.6°F), pulse
is 94/min, and blood pressure
is 125/80 mmHg. Physical examination demonstrates an engorged penis
that is painful with manipulation. No urethral
discharge is noted. The testicles
are nontender, and the cremasteric reflex is intact. Which of the following best describes the underlying pathophysiology of this patient’s condition?