Colposcopy

Colposcopy is magnified examination of the cervix, vagina and vulva using a binocular microscope with a light source. The cervix is examined after application of dilute acetic acid, which whitens abnormal epithelium, and after Lugol iodine, which stains normal glycogenated epithelium.

It identifies the abnormal transformation zone and allows targeted biopsy. It is the main investigation after an abnormal cervical screening result.

Usage. It is used for high grade cytology, persistent high risk human papillomavirus, and low grade cytology in selected cases.

Indications. Abnormal cervical screening cytology, positive high risk HPV test with abnormal cytology, persistent low grade abnormality, glandular abnormality, and follow up of previously treated disease.

Preparation and technique. The patient is examined in lithotomy with a speculum, and the cervix is cleaned of mucus. Acetic acid is applied, typically at 3 to 5% concentration, and the cervix is inspected after a short interval. Lugol iodine is applied to identify areas that do not stain. The squamocolumnar junction is assessed for adequacy, since an unseen junction means the examination is incomplete.

Contraindications and precautions. Active pelvic infection and recent heavy bleeding are generally deferred. Pregnancy changes the appearance of the cervix, and colposcopy is performed with caution, with biopsy limited to clear abnormalities. Acetic acid and Lugol iodine can cause stinging and allergy in rare cases.

Interpretation.

• Acetowhite epithelium is a change in the epithelium after acetic acid application, and it is graded by its margins and texture.
• Mosaic and punctation patterns indicate abnormal transformation zones, and atypical vessels are a further sign of higher grade disease.
• Lugol negative areas, meaning areas that do not stain with iodine, suggest abnormal epithelium and are targeted for biopsy.
• Histology grades the abnormality as cervical intraepithelial neoplasia (CIN) 1, 2 or 3, or as adenocarcinoma in situ or invasive disease.

Causes of a false positive appearance. Metaplasia, inflammation, and healing epithelium can appear acetowhite.

Critical values and findings needing immediate action.

• A suspicion of invasive cancer on colposcopy requires biopsy and urgent referral.
• Heavy bleeding after biopsy requires immediate management.

Limitations and artefacts. An inadequate examination, with the squamocolumnar junction not visible, lowers the reliability of a negative finding. Atrophy after the menopause, cervical stenosis and blood obscure the view. Acetic acid can produce false positive appearances in areas of inflammation.

Follow up tests. Histology of directed biopsies, endocervical curettage where the junction is not visible, and repeat cytology or HPV testing at intervals determined by the histology.

Special groups. Adolescents are examined only where clearly indicated, since the cervical screening programme does not usually include them. Post-menopausal women may have atrophy, which is assessed with caution. Pregnancy changes the appearance of the cervix, and biopsy is generally deferred where possible.