Differential Diagnosis for Penile Shaft Swelling with Purulent Discharge

Primary Infectious Etiologies

The Centers for Disease Control and Prevention recommends that the two most important bacterial pathogens causing purulent discharge are Neisseria gonorrhoeae and Chlamydia trachomatis, which together account for the majority of urethritis cases in men 1, 2, 3, 4
Gonococcal urethritis presents with purulent discharge and is confirmed by Gram stain showing Gram-negative intracellular diplococci 4
Nongonococcal urethritis (NGU) is characterized by mucopurulent discharge when Gram-negative intracellular organisms cannot be identified on Gram stain 4
C. trachomatis causes 23-55% of NGU cases, with prevalence varying by age group 1, 2, 3
Ureaplasma urealyticum accounts for 20-40% of NGU cases 1, 2, 3
Mycoplasma genitalium is implicated in approximately one-third of nonchlamydial NGU cases 4

The American Urological Association recommends to always exclude penile fracture, which is suspected if there is history of cracking/snapping sound during intercourse, immediate detumescence, and ecchymosis 6
The American Urological Association recommends to always exclude ischemic priapism, which requires immediate intracavernous treatment 6
The American Urological Association recommends to always exclude urethral injury, which is evaluated if blood is present at meatus, gross hematuria, or inability to void 6

The Centers for Disease Control and Prevention recommends to confirm urethritis by documenting mucopurulent or purulent discharge 4
The Centers for Disease Control and Prevention recommends to confirm urethritis by documenting Gram stain showing ≥5 WBCs per oil immersion field on urethral swab 1, 2, 3, 4
The Centers for Disease Control and Prevention recommends specific testing, including Gram stain to identify intracellular Gram-negative diplococci (gonorrhea) 4
The Centers for Disease Control and Prevention recommends specific testing, including nucleic acid amplification tests for N. gonorrhoeae and C. trachomatis on first-void urine 4

The Centers for Disease Control and Prevention recommends to always rule out testicular torsion in patients with scrotal/testicular swelling, especially in younger patients 6
The Centers for Disease Control and Prevention recommends to ensure partner notification and treatment for all sexually transmitted causes to prevent reinfection 1, 2, 3, 4