By definition, nonspecific urethritis is a urethritis in which no specific organism can be identified—it is a nongonococcal urethritis. The same clinical features are caused by infection with Chlamydia—chlamydial urethritis. The only way to detect the difference is to find no organismal cause in the former, and to have a positive test for Chlamydia in the latter. The test for Chlamydia used to be a serologic one but it has now been superseded by a very accurate PCR test. Patients with NSU present with a urethral discharge of clear, mucoid fluid (shown in Fig. below). The urethritis may be painless; more often it is painful, but less painful than gonorrhea.
Nonspecific urethritis. A urethral discharge of clear, mucoid fluid. Marked acute inflammation of the urethral meatus is present as well, which is a little unusual.