• • Spontaneous urethral discharge.
  
• • Burning with urination.
  
• • Purulent or mucoid exudate with urethral stripping.
  
• • More than 5 white blood cells (WBCs) per high-power field of urethral exudate.

Urethral discharge is characterized by abnormal purulent or mucoid secretions from the penis or, rarely, the female urethra. Urethral discharge reflects inflammation of the urethra usually caused by infection. Urethritis is defined as the presence of leukorrhea and urethral inflammation. Clinically, urethritis in men is characterized by urethral discharge and is often accompanied by dysuria. Leukorrhea has been defined as the presence of more than 5 WBCs per high-power field in a urethral swab specimen, using either Gram stain or other cellular stain (eg, Wright or methylene blue).

Urethral discharge can occur in sexually active persons of all ages but is most common in young adults, the age group in which the prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae infection is highest. High rates of urethritis also occur in men who have sex with men. Urethral discharge occurs after urethral infection in persons exposed to infectious agents during oral, vaginal, or anal intercourse.

The most common etiology of urethral discharge is N gonorrhoeae, followed by C trachomatis. These two organisms account for about 40% of cases of urethritis. Although historically urethritis has been differentiated into gonococcal urethritis versus nongonococcal urethritis (NGU), with the discovery of additional causes of urethritis that dichotomy has little clinical relevance. The other major putative organisms that have been associated with sexually transmitted NGU include Mycoplasma genitalium, Trichomonas vaginalis, herpes simplex virus, and adenovirus (see Table 3–1). The role that Mycoplasma hominis and Ureaplasma urealyticum play in urethritis remains unproven.

N Gonorrhoeae

Urethral discharge is most commonly associated with gonorrhea. Infection with these gram-negative diplococci can occur after oral, vaginal, or anal intercourse, with symptoms developing between 1 and 3 days after exposure.

C trachomatis

In early studies that largely relied on culture methods, Chlamydia was found to account for a relatively small proportion of cases of NGU. In three large studies performed at STD clinics in the 1980s and 1990s, Chlamydia was identified in 19–31% of patients. On average one third but in some studies up to 60% of patients with gonococcal urethritis may have coinfection with C trachomatis.

M Genitalium

This organism was first identified as a cause of NGU in 1981. It is very difficult to grow in culture, and diagnostic surveys have been performed in research settings with nucleic acid amplification tests. Some investigators have suggested that M genitalium is responsible for 15–25% of cases of NGU; others cite a much lower percentage. A large review of the literature conducted in 2002 found that patients with NGU were 2.5 times more likely to have M genitalium isolated from their genitourinary tract than patients without urethritis (20% compared with 8%). However, it is difficult to determine the exact relationships between this organism and other urethral pathogens. Although diagnosis of M genitalium infection is currently limited to research settings, commercial assays for M genitalium are in development.

T Vaginalis

Urethritis accompanying Trichomonas infection is usually associated with minimal discharge. Not surprisingly, men with trichomonas-related urethritis are much more likely to have been exposed to women with trichomonas-related vaginitis. One of the more intriguing questions in understanding the epidemiology of Trichomonas infection in men is identification of the anatomic source. Trichomonas infection is very difficult to identify in the urethra in male contacts of women who have trichomoniasis. Several investigators have proposed that Trichomonas is sequestered in the prostate gland and may be a cause of prostatitis.

Herpes Simplex Virus

Up to sixty percent of men with primary herpes infection have associated herpes NGU. A clinical clue to herpes as an etiology is that the urethral inflammatory cells are lymphocytes, and patients present with pain on urination and minimal discharge. Often, patients are treated empirically for NGU; however, because of the natural history of genital herpes (resolution within 5–7 days), the resolution of symptoms is often attributed to treatment for other organisms. Intraurethral herpes infection should be suspected when the primary manifestation is severe dysuria. In these patients, a urethral culture or, if available, a nucleic acid amplification test (polymerase chain reaction) for herpes may be positive. Occasionally, herpetic lesions are seen at the meatus.