Causes of Penile Discharge in Males
Penile discharge in males is most commonly caused by sexually transmitted infections, with Chlamydia trachomatis and Neisseria gonorrhoeae being the primary pathogens responsible for urethritis. 1, 2
Primary Infectious Causes
Sexually Transmitted Pathogens
Chlamydia trachomatis accounts for 23-55% of nongonococcal urethritis (NGU) cases and is the most common cause of urethral discharge in sexually active men, though this proportion has been declining over time 1, 3
Neisseria gonorrhoeae causes gonococcal urethritis, presenting with purulent discharge that is typically more profuse than chlamydial discharge 1, 4
Mycoplasma genitalium and Ureaplasma urealyticum are increasingly recognized causes of NGU, with U. urealyticum accounting for 20-40% of NGU cases 1, 3, 4
Trichomonas vaginalis causes 2-5% of NGU cases and should be considered, particularly in persistent or recurrent urethritis 3, 4
Less Common Infectious Causes
Herpes simplex virus can cause urethritis with discharge, though ulcerative lesions are more characteristic 4
Adenovirus has been identified as a rare cause of urethritis 4
Enteric organisms (particularly Escherichia coli) cause urethritis in men who are the insertive partner during anal intercourse 1
Clinical Presentation Patterns
Gonococcal vs. Nongonococcal Urethritis
Gonococcal urethritis typically presents with mucopurulent or purulent discharge that is more profuse and symptomatic 1, 2
Chlamydial urethritis often presents with mild or absent symptoms, with discharge being less profuse and more mucoid; many infections are completely asymptomatic 1, 2
Dysuria (painful urination) accompanies discharge in both gonococcal and nongonococcal urethritis 1, 2
Anatomic Site Variations
- Rectal discharge occurs in men who engage in receptive anal intercourse, with C. trachomatis and N. gonorrhoeae being the primary pathogens; most rectal infections are asymptomatic 1, 2
Critical Diagnostic Distinctions
Urethritis vs. Urinary Tract Infection
In young sexually active men with penile discharge, urethritis from STIs should be the primary consideration, as UTIs are uncommon in this population without anatomic abnormalities. 5
UTIs in males are caused by enteric bacteria like E. coli and present with dysuria plus bladder/suprapubic discomfort without urethral discharge 5
STI-related urethritis presents with mucopurulent/purulent discharge as the distinguishing feature 5
Men over 35 years with urogenital symptoms are more likely to have UTIs from enteric organisms, while men 14-35 years typically have STI-related causes 5
Diagnostic Approach
Confirmation of Urethritis
Urethritis is confirmed by demonstrating ≥5 polymorphonuclear leukocytes per oil immersion field on urethral Gram stain, or ≥10 white blood cells per high-power field in first-void urine 1, 3
Pathogen Identification
Nucleic acid amplification tests (NAATs) on first-void urine or urethral swabs are the preferred method for detecting N. gonorrhoeae and C. trachomatis, with superior sensitivity compared to culture 1, 5
Gram stain showing Gram-negative intracellular diplococci provides presumptive diagnosis of gonorrhea 1
If M. genitalium or T. vaginalis are suspected (persistent/recurrent urethritis), specific testing should be requested, as these are not detected by standard STI panels 3
Important Clinical Pitfalls
Coinfection Considerations
Dual infection with C. trachomatis and N. gonorrhoeae is common, requiring empiric treatment for both pathogens even when only one is detected 1, 4, 6
All patients with urethritis should undergo syphilis serology and HIV testing, as STIs frequently coexist 1
Asymptomatic Infections
The majority of chlamydial infections in men are asymptomatic or minimally symptomatic, yet these men can transmit infection to partners 1
Asymptomatic infections are more common with chlamydia than gonorrhea 1
Partner Management
Sexual partners with last contact within 60 days of symptom onset (or diagnosis if asymptomatic) must be evaluated and treated simultaneously to prevent reinfection. 3