A 23-year-old male graduate student at a major university experiences mild dysuria and an occasional scant, whitish urethral discharge for several days. He then develops a low-grade fever and tenderness in the region of his scrotum. The tenderness becomes increasingly uncomfortable and painful over the next 24 hrs, so he goes to the student clinic on his campus for advice. Vital signs are normal, except for a mild fever (38ºC). Examination of his scrotum reveals unilateral pain and marked tenderness, with swelling and erythema. There are no other remarkable physical findings. A history is taken and the student indicates that he has been sexually active with several different partners during the past few weeks and that he doesn't like to use condoms.

Question 2.1: What is your preliminary diagnosis?

The dysuria and discharge suggest a mild urethritis. The patient's history of unprotected sexual intercourse with multiple partners could indicate that he has a sexually transmitted urethritis. If so, the scrotal symptoms may be evidence of bacterial epididymitis, most likely as a result of an infection ascending from the urethra.

Question 2.2: What tests should you perform?

A urinalysis and urine culture should be ordered because a urinary infection is suspected. A culture and Gram stain of the urethral discharge (urethral smear) might provide helpful information. Given the likelihood of an STD, you may also want to test for sexually transmitted pathogens.

Test Results

The urine and urethral smear cultures are negative. PMNs are present in the urethral smear, but there are no free bacterial cells. Bacterial cells are not present in a Gram stain of the urine sample either. Lab tests for Neisseria gonorrhoeae and Treponema pallidum are negative.

Question 2.3: What is the most likely causative agent?

Chlamydia trachomatis is the most likely causative agent for at least two reasons. In the U.S., it now causes > 70% of epididymitis cases in sexually active young males, so there is a high statistical probability of infection by this microbe. Moreover, C. trachomatis is an intracellular pathogen that will not grow in lab cultures for bacteria and that is seldom recognizable in Gram stains of urine specimens. Of course, these negative test results do not demonstrate the presence of C. trachomatis; they are simply consistent with that diagnosis. Various methods are now available to confirm a C. trachomatis infection, and these have been discussed in detail in previous cases.

Question 2.4: What other microbes cause this disease?

Most epididymitis cases in sexually active young men that are not caused by C. trachomatis are caused by Neisseria gonorrhoeae. Some patients are co-infected with both agents. In contrast, typical UTI bacteria are the most important cause of epididymitis in men who are older than 35, who have underlying urologic disease, who recently have undergone urinary surgery, or who recently have been subjected to urinary catheterization. Typical UTI bacteria include Escherichia coli and other members of the Enterobacteriaceae, along with aerobic Gram-negative rods (especially Pseudomonas aeruginosa in nosocomial cases). Coliform bacteria are principal causative agents of epididymitis in pre pubertal boys, typically as a complication of some underlying urologic disease. Coliform-related epididymitis also occurs in homosexual men, as a result of anal intercourse. Mycobacterium tuberculosis causes epididymitis during genitourinary tuberculosis (TB), a form of TB that results from hematogenous spread after a pulmonary infection and that accounts for 15% of extrapulmonary TB cases. In addition to the usual STD agents, cytomegalovirus (CMV), Salmonella, and Toxoplasma have been reported to cause epididymitis in AIDS patients. Various other bacteria and parasites are known to cause epididymitis infrequently.

Question 2.5: What other conditions should be considered in a case like this?

Unlike this case, many cases of C. trachomatis epididymitis are accompanied by asymptomatic urethritis, so there is no dysuria or urethral discharge. When there is no immediate evidence of urinary infection, one must also consider testicular torsion, tumor, or trauma. Testicular torsion, a surgical emergency, usually occurs in the second or third decade of life and produces a sudden onset of pain, elevation of the testicle within the scrotal sac, and rotation of the epididymis from a posterior position to an anterior position. Torsion can be diagnosed with a radionuclide (99Tc) scan, Doppler flow study, or surgical exploration. Testicular tumor or chronic infection (e.g., in tuberculosis) ought to be considered when a patient with symptoms typical of epididymitis does not respond to appropriate antimicrobial therapy.

Question 2.6: How can this case be treated?

Ice packs and scrotal elevation can be used to help to relieve the pain. One can also resort to analgesia with acetaminophen, with or without codeine, or NSAIDS. The recommended antibiotic treatment for sexually active young men is doxycycline (100 mg PO bid) or tetracycline (500 mg PO qid) for 10 days, to cover both gonococci and chlamydiae.