Dr. med. Dirk Manski

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Non-Gonococcal Urethritis (NGU)

Review-Literature: (CDC Guidelines, 2006) (Schneede et al., 2003).


A non-gonococcal urethritis is an infectious urethritis, which is not caused by Neisseria gonorrhoeae.


Increasing incidence, nowadays more frequent than gonorrheal urethritis.

Causes (Pathogens) of Non-Gonococcal Urethritis

Chlamydia trachomatis:

Most often cause of NGU. Chlamydia are gram-negative obligate intracellular pathogens, urethritis is caused by serotypes D–K.


The extracellular form of Chlamydia are elementary bodies (diameter 0.3 μm), the intracellular multiplication creates intracellular inclusion bodies.


Mycoplasma cause 20% of NGU. Important species are Mycoplasma genitalis and Ureaplasma urealyticum. Mycoplasma are bacteria without cell wall, they grow optional anaerobic and as extracellular parasites on epithelial cells.


Lack of a cell wall. For Microscopy use Giemsa staining. Size between 0.1–0.6 μm.

Gram-positive bacteria:

Enterococci in 15%, Streptococci in 12%, Staphylococcus aureus in 5%.

Trichomonas vaginalis:

an anaerobic, parasitic flagellated protozoan, rare cause of urethritis (<1%).

Uncertain etiology:

in 20–30%.

Signs and Symptoms


Incubation period 1–5 weeks. Men complain of glassy or purulent discharge from the urethra, Dysuria and burning in the urethra. Women complain of vaginal discharge, dysuria or abdominal pain (sign of progression to pelvic inflammatory disease). The extent of the symptoms is very variable, men and women may be asymptomatic.


Ascending infections may lead to complications: in men epididymitis and in women pelvic inflammatory disease (PID). Women face a 20% risk for PID due to urethritis with chlamydia. The consequences of PID are infertility by tubal occlusion (12% for the first PID, 35% after three and more PID). After PID, there is an increased risk for ectopic pregnancies. Neonates may be infected by their mother (Pneumonia or chlamydial conjunctivitis).

Reiter syndrome:

HLA-B-27 associated, autoimmune reaction with arthritis, conjunctivitis, balanitis, fever and rashes with cornification at the palms and soles (fig. keratoderma blenorrhagicum). The symptoms develop after a urethritis or gastroenteritis. Due to a mixed infection, the Reiter syndrome is also possible due to gonorrhea.

Keratoma blennorrhagicum due to Reiter syndrome

Fig. Keratoma blennorrhagicum: Reiter syndrome (e.g., after urethritis) may result in excessive cornification of the palms or soles. Figure from Dr. M. F. Rein, Public Health Image Library, Center for Disease Control and Prevention, USA, https://phil.cdc.gov/.

Fitz-Hugh-Curtis syndrome:

Peritoneal infection in women due to ascending pelvic inflammatory disease, usually right-sided abdominal pain because of an infection of the liver capsule.


Urethral swab:

should be done 4 h after voiding with inoculation of different culture media:

Two microscope slides:

for Gram stain (gonococcus) and Giemsa stain (Chlamydia), if a microscopic pathogen detection is sought. Over 4 leukocytes/field with high power microscopy are typically in purulent urethritis [fig. microscopy of gonorrhea].

Blood agar plates:

to detect Enterococcus, Streptococcus, Staphylococcus aureus ...

Special media:

to detect gonococci Martin-Lewis plates or Thayer-Martin agar should be used. Stuart medium is appropriate to detect Mycoplasma and Ureaplasma. The detection of Chlamydia is done with direct DNA evidence from the swab or seldom by growing in McCoy cell culture.

Further pathogen collection:

swab specimens collected from anus, pharynx, cervix, depending on history and symptoms.

Study of the sexual partner:

to avoid a ping-pong-infection a detailed history and examination of any sexual partner is necessary.

Urine analysis:

after the urethral swab is collected, an urine culture from midstream should be started.

Serologic diagnosis:

to exclude Syphilis, inappropriate for Chlamydia.

Treatment of Urethritis

Antibiotic Therapy:

Ciprofloxacin 500 mg p.o. or Ofloxacin 300 mg p.o., followed by doxycycline 100 mg p.o. 1-0-1 for 7 days. This regimen is effective against most pathogens causing urethritis. Alternative: Azithromycin 1 g p.o. once.

Recurrent urethritis should be treated with Erythromycin 500 mg p.o. 1-1-1-1 for three weeks, Ureaplasma urealyticum is most likely responsible for the recurrence.

Prevention of urethritis:

Use of condoms, treatment with intravaginal nonoxynol-9 containing Spermacides, antibiotic prophylaxis after sexual intercourse, treatment of newborns eyes with antibiotic ointment.

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Center for Disease Control and Prevention.: Sexually transmitted diseases treatment guidelines 2006.
in: MMWR
2006; 55 (No. RR-11): 1–93.

Schneede u.a. 2003 SCHNEEDE, P. ; TENKE, P. ; HOFSTETTER, A. G.: Sexually transmitted diseases (STDs)-a synoptic overview for urologists.
In: Eur Urol
44 (2003), Nr. 1, S. 1–7

  Deutsche Version: nichtgonorrhoische Urethritis.