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[Conditions](https://durgical.com/en/conditions/) · [Pelvis](https://durgical.com/en/anatomy/region/pelvis/)

# Chlamydia infection

Chlamydia is a common sexually transmitted bacterial infection that usually causes no symptoms but can lead to pelvic inflammatory disease and infertility.

Updated 2026-10-30

## Structures involved

Tap one to see what it is and open it in 3D.

- [Cervix](https://durgical.com/en/anatomy/cervix-of-uterus/)
- [Urethra (female)](https://durgical.com/en/anatomy/female-urethra/)
- [Uterine tubes](https://durgical.com/en/anatomy/uterine-tube/)
- [Endometrium](https://durgical.com/en/anatomy/endometrium/)
- [Ampulla of uterine tube](https://durgical.com/en/anatomy/ampulla-of-uterine-tube/)
- [Vagina](https://durgical.com/en/anatomy/vagina/)
- [Rectum](https://durgical.com/en/anatomy/rectum/)

## Microorganisms that cause it

- [Chlamydia trachomatis](https://durgical.com/en/microbiology/chlamydia-trachomatis/)

## Why it happens

- [Outcomes of acute inflammation: resolution, abscess, scar or chronic inflammation](https://durgical.com/en/general-pathology/outcomes-of-acute-inflammation-resolution-abscess-scar-or-chronic-inflammation/)
- [Uterine tube](https://durgical.com/en/histology/uterine-tube/)
- [Cervix and vagina: the transformation zone](https://durgical.com/en/histology/cervix-and-vagina-the-transformation-zone/)

## What it is

A sexually transmitted infection caused by Chlamydia trachomatis that affects men and women. It is usually silent but can infect the [cervix](https://durgical.com/en/anatomy/cervix-of-uterus/), urethra, [rectum](https://durgical.com/en/anatomy/rectum/) and eyes and lead to pelvic inflammatory disease and infertility.

## Who gets it

The most frequently reported bacterial sexually transmitted infection in many countries, most common under age 25; most infections cause no symptoms. In Medellín, Colombia, PCR found it in 4.1% of asymptomatic women attending cervical cytology at three centres. This page shows the female model; male genital parts are in the male [pelvis](https://durgical.com/en/anatomy/region/pelvis/) region.

## Causes

- Chlamydia trachomatis serovars D–K (genital infection)
- Serovars L1–L3: lymphogranuloma venereum
- Spread by vaginal, anal or oral sex, and from mother to newborn at birth

## Risk factors

- Age under 25
- New or multiple sexual partners
- Inconsistent condom use
- Previous sexually transmitted infection
- Partner with a sexually transmitted infection

## Pathophysiology

Chlamydia is an obligate intracellular bacterium with two forms: the infectious elementary body enters columnar cells and becomes a replicating reticulate body, then many elementary bodies are released. The slow, often silent inflammation it causes in the cervix and [uterine tubes](https://durgical.com/en/anatomy/uterine-tube/) leads to scarring; repeated infections increase tubal damage.

## Classification

- Lower genital tract: cervicitis, urethritis, proctitis
- Upper genital tract: pelvic inflammatory disease, perihepatitis in women; epididymitis in men
- Lymphogranuloma venereum (serovars L1–L3)
- Extragenital: conjunctivitis; neonatal conjunctivitis and pneumonia
- Reactive arthritis

## Symptoms and signs

- No symptoms in most women and many men
- Women: vaginal discharge, bleeding after sex or between periods, dysuria, lower abdominal pain
- Mucopurulent cervicitis with a friable cervix
- Men: urethral discharge (often clear or scant) and dysuria; testicular pain with epididymitis
- Rectal infection: discharge, pain or bleeding, often silent
- Lymphogranuloma venereum: painless ulcer, then painful inguinal nodes or severe proctitis

## Red flags

- Pelvic pain, dyspareunia or cervical motion tenderness (pelvic inflammatory disease)
- Positive pregnancy test with pain or bleeding (exclude ectopic pregnancy)
- Testicular pain and swelling
- Right upper quadrant pain (Fitz-Hugh–Curtis perihepatitis)
- Painful inguinal nodes or severe proctitis (lymphogranuloma venereum)

## Diagnosis

**Clinical**
Suspected from symptoms, examination or sexual history, but mostly found by screening people at risk.

**Tests**
Nucleic acid amplification tests (NAAT) on vaginal swabs (often self-collected) or first-void urine, plus rectal and pharyngeal swabs by exposure; pregnancy test; testing for gonorrhoea, HIV, syphilis and hepatitis B.

**Imaging**
Not needed for uncomplicated infection; pelvic ultrasound if PID with abscess is suspected.

## Differential diagnosis

- Gonorrhoea
- Mycoplasma genitalium infection or trichomoniasis
- Urinary tract infection
- Bacterial vaginosis
- Herpes simplex infection (ulcers)
- Inflammatory bowel disease (proctitis)

## Goal of treatment

Cure the infection, prevent complications such as pelvic inflammatory disease and infertility, and stop transmission by treating partners.

## Treatment

**Medical**
A course of a tetracycline is first-line in most guidelines; a macrolide is an alternative, and in pregnancy the regimen is chosen from drugs considered safe.

**Medical**
Lymphogranuloma venereum is treated with a longer course of a tetracycline.

**Follow-up**
Partner notification and treatment, avoiding sex until both partners finish treatment, retesting after about three months for reinfection, and test of cure in pregnancy.

## Drugs for this condition

- [Azithromycin](https://durgical.com/en/pharmacology/azithromycin/)
- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Complications

- Pelvic inflammatory disease
- Tubal infertility, ectopic pregnancy and chronic pelvic pain
- Fitz-Hugh–Curtis perihepatitis
- Epididymitis
- Reactive arthritis
- Neonatal conjunctivitis and pneumonia
- Increased risk of HIV acquisition

## Prognosis

Antibiotics cure the infection in almost all cases, but reinfection is common; tubal damage from earlier or repeated infections may be permanent.

## Prevention

- Consistent condom use
- Regular screening of sexually active women under 25 and others at risk
- Partner treatment
- Screening in pregnancy where recommended
- Sexual health education

## Test yourself

Think of the answer, then tap the question to see it.

## Why is chlamydia screening recommended for young sexually active women?

Most infections cause no symptoms but can silently damage the uterine tubes, causing infertility and ectopic pregnancy.

## What are the two developmental forms of Chlamydia trachomatis?

The infectious extracellular elementary body and the replicating intracellular reticulate body.

## Which serovars of Chlamydia trachomatis cause lymphogranuloma venereum?

Serovars L1, L2 and L3.

## What is the preferred diagnostic test for genital chlamydia?

Nucleic acid amplification testing (NAAT) on a vaginal swab or first-void urine.

## Which antibiotic class is first-line for uncomplicated chlamydia in most guidelines?

A tetracycline, with a macrolide as an alternative.

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## Related conditions

- [Gonorrhoea](https://durgical.com/en/conditions/gonorrhoea/)
- [Pelvic inflammatory disease](https://durgical.com/en/conditions/pelvic-inflammatory-disease/)
- [Ectopic pregnancy](https://durgical.com/en/conditions/ectopic-pregnancy/)
- [Syphilis](https://durgical.com/en/conditions/syphilis/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Trichomoniasis](https://durgical.com/en/conditions/trichomoniasis/)
- [Bacterial vaginosis](https://durgical.com/en/conditions/bacterial-vaginosis/)
- [Epididymitis](https://durgical.com/en/conditions/epididymitis/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Chlamydia trachomatis Infection](https://www.ncbi.nlm.nih.gov/books/NBK537286/) (StatPearls (NCBI Bookshelf), 2026); [Prevalence of Chlamydia trachomatis in an asymptomatic female population attending cervical cytology services of three healthcare centers in Medellín, Colombia](https://europepmc.org/article/PMC/PMC7666851) (Biomedica: revista del Instituto Nacional de Salud, 2020) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/conditions/chlamydia-infection/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/chlamydia-infection/