If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 2 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.  

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A 45-year-old man consults a physician because of a four-week history of low back pain that radiates to the scrotum, dysuria and pain on defecation. The patient is treated with trimethoprim-sulfamethoxazole, but symptoms recur one week after antibiotic therapy is stopped. The physician decides to start ciprofloxacin, but the symptoms again recur after cessation of the antibiotic. Today, the patient appears ill. He has shaking chills and sweats. Rectal examination demonstrates an enlarged prostate with areas of tenderness and fluctuance.

Which of the following is the most likely diagnosis?

A. Acute bacterial E. coli cystitis.

B. Benign prostatic hyperplasia.

C. Chronic nonbacterial prostatitis.

D. Multidrug-resistant urinary tract infection (UTI).

E. Prostatic abscess.

F. Prostatodynia.

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The correct answer is E.

This patient has a prostatic abscess. The typical patient age is 40 to 60 years, somewhat younger than the ages at which benign prostatic hyperplasia (BPH) and prostate cancer become major problems. Infecting organisms include aerobic gram-negative bacilli and Staphylococcus aureus. Prostatic abscess should be suspected when a man develops repeated UTI which seems to get better with antibiotic therapy, only to recur after therapy ends. The most important diagnostic clue, if detectable, is the presence of a fluctuant mass that is felt in the prostate on rectal examination.

Some patients have only prostatic enlargement or even no findings on physical examination. Patients may have normal urine, although it is more usual for an organism to be cultured at some point. Prostatic ultrasound may be helpful if abscess is suspected. This can allow for needle-guided drainage of the abscess fluid. Any prostatic fluid obtained at the time of the drainage procedure can sent for culture. This will further guide antibiotic therapy. A few cases are even picked up at the time of prostatic resection for BPH or other disease.

Choice A: Acute bacterial E. coli cystitis is rare in men, and it would not show any of the prostatic findings that this patient has.

Choice B: BPH can cause urinary obstruction predisposing for bladder infection, but the prostate would not be fluctuant.

Choice C: Chronic nonbacterial prostatitis can cause symptoms resembling UTI but would not cause a fluctuant prostate.

Choice D: Urine cultures with antibiotic sensitivity are necessary to establish the diagnosis of multidrug-resistant UTI. UTI presents with urgency, dysuria, and frequency. It does not present with a fluctuant mass on examination of the prostate.

Choice F: Prostatodynia is a noninfectious, noninflammatory condition of younger men that can mimic prostatitis, but it would not cause a fluctuant prostate.

  • Prostatic abscess should be suspected in patients who have recurrent UTI that initially improves but recurs after the antibiotic is discontinued.
  • Prostatic abscess is characterized by a tender prostate with a fluctuant mass that is felt on examination. Patients are often ill-appearing with shaking chills and are febrile.
  • Treatment is evacuation of the abscess by a transurethral or perineal route, followed by appropriate antibiotics.

For more prep questions on USMLE Steps 1, 2 and 3, view other posts in this series.

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