Colposcopy

What is colposcopy?

Colposcopy is the live examination of the cervix during the procedure with a magnifying instrument called a colposcope. The main target of the examination is the transformation zone of the cervix — the area where cell change begins and where, for that reason, precancerous changes are most often seen.

What colposcopy looks for falls under two headings: precancerous cell changes (referred to in guidelines as CIN or SIL) and early-stage cervical cancer.

What happens during the procedure?

Colposcopy is carried out in the position used for a gynaecological examination. The examination rests on magnification and illumination; these are the basic elements of colposcopy.

1. The cervix is brought into view and assessed under magnification.
2. Acetic acid at a concentration of 3–5% (a dilute vinegar solution) is applied to the cervix. Suspicious tissues turn white temporarily; this is called an aceto-white area.
3. Where necessary, Lugol's iodine solution is applied to see whether the tissue takes up the stain.
4. The doctor assesses together the response to the acetic acid, the border characteristics of the lesion (tissue change), the appearance of the surface, its size, the vascular pattern and the uptake of iodine.
5. If there is a suspicious area, a targeted biopsy (a small tissue sample) is taken from it.

Why is a biopsy taken, and from how many places?

Because the colposcopic impression rests on visual assessment, it is known not to be sufficiently certain on its own. For this reason guidelines recommend that a biopsy be taken from every suspicious area seen.

When there is a lesion, targeted biopsies are generally taken from 2 to 4 separate points so that the most advanced disease can be caught. In low-risk people whose colposcopic appearance is normal, avoiding a biopsy is an acceptable approach.

In selected high-risk situations where there is strong evidence in favour of high-grade disease, removal of the whole transformation zone (excision with a loop) may come up immediately after the colposcopy; in that case diagnosis and treatment take place in the same session.

What does colposcopy achieve?

Before colposcopy came into use in the 1970s, almost all women in whom a marked abnormality was found on examination of the cervical cells underwent cone biopsy or removal of the womb for both diagnosis and treatment.

Colposcopy together with targeted biopsy achieved two things at once: correct detection of disease where it is present, and the ability to show safely that it is absent where it is not. The result was a marked reduction in the number of tissue-removal procedures; these are now limited to people in whom a precancerous change has actually been confirmed or who are at high risk of hidden cancer.

What this means in practice is this: changes unlikely to progress can be followed up rather than operated on unnecessarily, while advanced disease is treated in time.

Weighing benefit and risk together

As with every medical procedure, in colposcopy too the benefit and the possible harm must be weighed together within the person's own situation. The main benefit of colposcopy is that precancerous changes and early-stage cancer can be detected correctly.