paraphrase and avoid AI patterns: This is the most likely diagnosis given the clinical presentation. The patient is a sexually active 24-year-old male with unilateral (left-sided) testicular pain and swelling, gradual symptom onset, urethral discharge, dysuria, and positive findings on urinalysis (leukocyte esterase and >10 WBCs). The presence of a preserved cremasteric reflex and a normal vertical lie of the testicle further supports epididymitis rather than testicular torsion. The infectious etiologymost likely due to Chlamydia trachomatis or Neisseria gonorrhoeae in this age groupis consistent with his sexual history and urinary symptoms