Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Urethritis

What Is It?

Urethritis is an inflammation of the urethra, which is the tube that carries urine out of the body. Urethritis is usually caused by a sexually transmitted infection. Much less often, it is the result of an injury from an instrument such as a urinary catheter or exposure to an irritating chemical such as an antiseptic or a spermicide.

Doctors usually classify sexually transmitted (infectious) urethritis into two categories: gonococcal urethritis, caused by gonorrhea bacteria, and nongonococcal urethritis, caused by bacteria other than gonorrhea.

Gonococcal urethritis, commonly called clap, is caused by Neisseria gonorrhoeae bacteria. Gonorrhea infections are passed from person to person during sexual activity (vaginal, oral and anal intercourse). The U.S. Centers for Disease Control (CDC) estimates that there are 700,000 new cases of gonorrhea each year. However, only half of them are reported. Many who are infected do not seek treatment.

Nongonococcal urethritis is caused by all sexually transmitted bacteria other than N. gonorrhea. The most frequent cause is Chlamydia trachomatis bacteria, which cause the sexually transmitted disease Chlamydia. Nongonococcal urethritis is the most common form of sexually transmitted infection in the United States, with an estimated 4 million new cases each year. In addition to C. trachomatis,, other possible infectious causes of nongonococcal urethritis include Ureaplasma urealyticum, Mycoplasma genitalium and Trichomonas vaginalis.