If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.
This month’s stumper
A 15-year-old boy with no past medical history is brought to the emergency department with a five-hour history of right testicular pain. He states that the pain began after football practice this afternoon, but does not remember any trauma. He appears to be in a significant amount of pain. His blood pressure is 128/80 mm Hg and pulse is 110 beats per minute. Physical examination shows an erythematous, swollen right scrotum with significant tenderness to palpation on that side. Cremasteric reflex is absent on the right side. Urinalysis is negative.
Which of the following is the most appropriate next step in the management of this patient?
A. CT of the abdomen.
B. Doppler ultrasound scan.
C. Surgical exploration.
D. Testicular biopsy.
E. Voiding cystourethrogram.
The correct answer is C.
Kaplan Medical explains why
This patient has torsion of the right testicle. In any patient with testicular swelling and pain, surgical exploration should be performed as soon as possible. Delay in the diagnosis of testicular torsion can result in loss of that testis due to absent blood flow. If the diagnosis is delayed more than six hours without intervention, there is a significant risk of necrosis.
If treated in less than six hours, there is an almost 100 percent chance of saving the testicle. This rate decreases to 70 percent if treatment takes place after less than hours; 20 percent if treatment takes place after less 24 hours; and 0 percent if treatment takes place after 24 hours. Doppler ultrasound scan may delay the treatment and jeopardize the viability of the testicle.
Why the other answers are wrong
Choice A: CT scan of the abdomen will not be helpful in assessing this patient's scrotum.
Choice B: Doppler ultrasound scan can confirm the diagnosis by showing the presence or absence of blood flow to the testicle. However, if suspicion is high, immediate untwisting is advised in order to prevent infarction and subsequent testicular loss with or without sterility. Treatment of testicular torsion should not be delayed for a diagnostic test.
Choice D: Testicular biopsy is not part of the evaluation of testicular torsion.
Choice E: Voiding cystourethrogram is a procedure used to diagnose vesicoureteral reflux. This test is used as part of the workup of a child with a urinary tract infection.
Tips to remember
- Testicular torsion is a surgical emergency.
- Treatment is geared toward restoring perfusion to the affected testis.
For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.
