Clinical overview
Colposcopy is the magnified, illuminated examination of the cervix, vagina and vulva used to localise, characterise and biopsy the epithelial abnormalities that precede invasive cervical cancer. It is the diagnostic hinge of the cervical screening programme: screening (cytology or HPV testing) identifies who needs further assessment, but colposcopy decides what the lesion is and where to treat. For a South African registrar this is a high-volume, high-stakes skill. Cervical cancer is the commonest cancer in South African women and one of the leading causes of cancer death, driven by a high background prevalence of HIV — and HIV-positive women progress faster from high-grade lesions to invasive disease. The colposcopist therefore sits at the point where a treatable pre-invasive lesion is either caught and cured or missed and allowed to invade.
"Demonstrate the use of colposcopy" is a doing objective. The examiner is testing whether you can run the clinic safely and competently: set up and use the instrument, apply acetic acid and Lugol's iodine and interpret what they reveal, recognise the transformation zone and judge whether it is fully visible, grade an abnormality, take an adequate directed biopsy, decide between "see-and-treat" and biopsy-then-treat, and — most importantly — know when a colposcopic picture is sinister enough to mandate urgent referral for possible invasion rather than office treatment. This chapter is therefore weighted heavily to Assessment and Management: the practical drill of the examination itself. It pairs directly with cin-management, cervical-screening-sa, cin-pathophysiology, hpv-pathology and cervical-carcinogenesis.
Core knowledge
Figure F10.1 — Transformation zone = the safety decision: TZ types 1–3 and the hidden upper limit — if the upper limit/SCJ is hidden you cannot exclude canal disease; excision (not ablation) when high-risk or not fully visible.
The target: the transformation zone
Cervical neoplasia almost always arises in the transformation zone (TZ) — the band of metaplastic squamous epithelium between the original squamocolumnar junction (SCJ) and the new SCJ, where columnar endocervical epithelium has been progressively replaced by squamous epithelium. This immature metaplastic epithelium is uniquely vulnerable to HPV-driven transformation. Everything the colposcopist does is aimed at seeing this zone completely and assessing whether it harbours abnormality.
The position of the SCJ moves with hormonal status. In a young woman it usually lies on the ectocervix and the whole TZ is visible (an ectocervix picture). After the menopause, and with falling oestrogen, the SCJ retreats up the canal so that the TZ becomes partly or wholly endocervical and invisible to the naked eye. This single anatomical fact underlies the most important judgement in colposcopy: whether the examination is adequate (the whole TZ and the entire lesion are seen) or inadequate (the upper limit cannot be seen).
The TZ is classified into three types, which dictates how — and whether — a lesion can be treated in the office:
| TZ type | Squamocolumnar junction | Excision implication |
|---|---|---|
| Type 1 | Fully ectocervical, completely visible | Shallow ectocervical excision/ablation |
| Type 2 | Has an endocervical component, but fully visible (with manipulation) | Deeper excision, still visible margins |
| Type 3 | Endocervical component not fully visible | Cannot exclude canal disease; long cone/cylindrical excision, or refer |
The two stains and what they mean
Colposcopy relies on two contrast agents applied after a plain saline look:
- Acetic acid (3–5%) is the workhorse. It is thought to reversibly coagulate and dehydrate intracellular nuclear protein; epithelium with a high nuclear-to-cytoplasmic ratio (dysplastic, high-grade) turns dense, opaque white ("acetowhite") and is slow to fade. Low-grade change is thin, translucent and fades quickly. The colposcopist watches the speed of onset, density, persistence and margin of the acetowhite reaction — this dynamic is as informative as the static appearance.
- Lugol's iodine (Schiller's test) stains glycogen-rich mature squamous epithelium dark mahogany-brown. Dysplastic epithelium and columnar epithelium are glycogen-poor and stay pale yellow ("Schiller-positive" / iodine-negative). Lugol's is excellent for delineating lesion borders and for picking up vaginal (VaIN) extension, but it is non-specific (immature metaplasia and atrophic epithelium are also iodine-negative).
Grading systems
You must know both the colposcopic grading vocabulary and the pathology terminology it predicts.
- IFCPC 2011 terminology (International Federation for Cervical Pathology and Colposcopy) is the modern descriptive standard. It records: adequacy, SCJ visibility, TZ type; then grade 1 (minor) changes — thin acetowhite, fine mosaic, fine punctation, irregular/geographic borders — versus grade 2 (major) changes — dense acetowhite, rapidly appearing and slow to fade, coarse mosaic, coarse punctation, sharp borders, "inner border" sign, "ridge/cuffed gland openings"; then non-specific findings; then explicit features suspicious for invasion (atypical vessels, fragile bleeding, irregular surface, exophytic lesion, necrosis, ulceration).
- The older Reid Colposcopic Index (RCI) scores four features (margin, colour, vessels, iodine staining) 0–2 each to predict low- versus high-grade.
Histology is reported either as CIN 1/2/3 or in the newer LAST / WHO two-tier system as LSIL (≈ CIN 1) and HSIL (≈ CIN 2–3). See cin-pathophysiology for the biology and cin-management for the treatment thresholds.
Assessment
Before the speculum: counselling, consent and timing
Explain what colposcopy is, that it is essentially a magnified Pap examination with a low-power microscope that does not enter the body, that vinegar/iodine will be painted on, and that small biopsies may sting briefly. Obtain informed consent for examination, biopsy and — if you run a see-and-treat clinic — possible same-visit excision. Document HPV/cytology result, HIV status and ART, parity, contraception, smoking, and last menstrual period. Colposcopy is best in the follicular phase but is not contraindicated at any time; pregnancy is not a contraindication (see Red flags). A chaperone is mandatory.
Setting up and the systematic look
- Position the woman in lithotomy; insert the largest comfortable bivalve speculum and bring the cervix into clear view, suctioning or swabbing mucus.
- Focus the colposcope (working distance ~20–25 cm; magnification typically 6–16×) and examine first under white light, then with the green (red-free) filter which makes vessels appear black and accentuates abnormal vascular patterns (punctation, mosaic, atypical vessels).
- Plain saline look: assess gross appearance, leukoplakia (white before acetic acid — biopsy it, never ablate blindly), and the vascular pattern.
- Apply acetic acid, wait the full 60 seconds and beyond, and watch the reaction develop. Identify the SCJ, define the TZ, locate every acetowhite area and grade it. Manipulate to see the canal (endocervical speculum/forceps) to judge the upper limit.
- Apply Lugol's iodine to map lesion borders and screen the vagina.
- Take directed biopsies from the most abnormal area(s) — from the acetowhite, coarse-vessel, sharp-bordered region nearest the SCJ, not from the centre of an obvious cancer (sample the edge) and not from normal-looking epithelium.
The adequacy judgement
For every colposcopy, you must record three things: is it adequate (was the examination satisfactory — cervix clearly seen, not obscured by bleeding/inflammation/atrophy)? is the SCJ fully visible? and what is the TZ type (1/2/3)? An inadequate colposcopy — most often a non-visible SCJ in an older or post-treatment woman — means the lesion may extend into the canal beyond view. You cannot reassure such a woman with a negative ectocervical biopsy; she needs an excisional diagnostic procedure (a "diagnostic cone/LLETZ") rather than ablation. In atrophic post-menopausal women, a short course of topical oestrogen before repeat colposcopy can bring the SCJ down and improve adequacy.
Estimating grade colposcopically
Build a mental gestalt: low-grade lesions are thin, snow-white, fade fast, have feathery/geographic borders and fine, regularly-spaced punctation or mosaic. High-grade lesions are dense, oyster-white, appear quickly and linger, have sharp straight borders, show coarse punctation/mosaic with widely and irregularly spaced vessels, an "inner border" (a sharper white lesion inside a paler one), and "cuffed crypt openings". Invasion is signalled by atypical vessels (corkscrew, comma, hairpin, bizarre branching with abrupt calibre change), surface irregularity, friability and contact bleeding, ulceration, necrosis, or a frankly exophytic/nodular mass.
Special populations
- HIV-positive women: higher prevalence, larger and multifocal lesions, faster progression, more frequent recurrence after treatment, and more vaginal (VaIN) extension — examine the vagina carefully with Lugol's, have a low threshold for excision over ablation, and ensure ART is optimised. Screening and follow-up are more frequent per the SA programme (see Management and cervical-screening-sa).
- Pregnancy: the cervix is hyperaemic, the TZ everts (often a Type 1 picture), and decidual/metaplastic change can mimic neoplasia — colposcopy in pregnancy is a consultant-level examination to exclude invasion, not to treat CIN.
Management
Translating colposcopy into a decision
Colposcopy is a means, not an end — the deliverable is a management decision for the woman in the chair.
- Normal/adequate colposcopy after a minor screening abnormality (e.g. low-grade cytology, HPV-positive low-grade): no high-grade lesion seen, SCJ visible → reassure and return to programme surveillance (repeat HPV/cytology at the recommended interval). Do not ablate normal epithelium.
- Colposcopic low-grade (LSIL/CIN 1): usually regresses, especially in the young. Conservative surveillance is generally preferred over immediate treatment; biopsy to confirm if the picture or cytology is discordant.
- Colposcopic high-grade (HSIL/CIN 2–3): treat. In the TZ, excision is generally preferred over ablation because it yields a specimen for histology that excludes occult invasion and confirms margins.
- Suspicion of invasion: do not attempt office ablation; take a biopsy of the lesion edge (or proceed to diagnostic excision/EUA per local protocol) and refer urgently to gynae-oncology for staging — see cervical-carcinogenesis and pregnancy-and-neoplasia.
Excisional and ablative techniques
- LLETZ / LEEP (large-loop excision of the transformation zone) is the standard office excisional treatment: a wire loop under blood-modified electrosurgical current removes the TZ and lesion as a histological specimen, with the loop size and depth chosen to match the TZ type (a Type 3 TZ needs a deeper "cylindrical"/cone-shaped excision, sometimes a top-hat). Understand the electrosurgical principles — blend cutting/coagulation, dispersive plate, fluid/instrument safety.
- Cold-knife conisation is reserved for suspected microinvasion/glandular disease or where thermal artefact at the margin would compromise interpretation.
- Ablation (thermal/cryo/cold-coagulation) destroys tissue without a specimen, so it is only permissible when: the colposcopy is adequate, the SCJ and whole lesion are fully visible (Type 1 TZ), there is no glandular abnormality and no suspicion of invasion, and (ideally) biopsy has confirmed the grade. WHO's screen-and-treat strategy uses thermal ablation widely as a cheap, portable, single-visit option.
See-and-treat
In a see-and-treat model the woman with a high-grade screening result and a colposcopic high-grade lesion is treated by LLETZ at the first colposcopy visit, without a prior diagnostic biopsy. This reduces loss to follow-up — a major advantage in the South African context where return rates are imperfect — but risks over-treating women who would have had low-grade or no disease. It is appropriate when the cytology is high-grade and the colposcopic lesion is convincingly high-grade; it is not appropriate for low-grade referrals, where it causes substantial overtreatment, nor where invasion is suspected.
South African context
South Africa is transitioning toward HPV-DNA primary screening (informed by the South African DiaVACCS trial) but the long-standing public-sector programme has been cytology-based, screening women from age 30, three smears at 10-yearly intervals. HIV-positive women are screened at HIV diagnosis and more frequently thereafter (≈3-yearly), regardless of age. The SA source of truth for the screening-and-colposcopy pathway is the SASOG / BetterGyn cervical screening guideline (2024) alongside the NDoH National Cervical Cancer Screening / Prevention and Control Policy — confirm the exact interval and triage algorithm against the current document before quoting numbers. The colposcopy service sits within the levels of care: screening and many LLETZ/thermal-ablation procedures happen at district/regional level, while suspected invasive disease is referred to a regional/tertiary gynae-oncology unit. SA's prevention effort also rests on the school-based HPV vaccination programme (girls 9–14 since 2014) and aligns to the WHO 90-70-90 cervical cancer elimination targets — see cervical-screening-sa and hpv-pathology. Excised tissue must always go to histology (NHLS), and the woman must be enrolled in a test-of-cure / colposcopic follow-up pathway, because residual/recurrent disease — especially in HIV-positive women — is common and the test of cure (HPV at follow-up) is the most sensitive recurrence detector.
Red flags / pitfalls
- Treating without a diagnosis of the upper margin. An inadequate colposcopy (Type 3 TZ, SCJ not seen) treated by ablation may leave high-grade or invasive disease deep in the canal. Inadequate examination = excision, not ablation (or refer).
- Never ablate a lesion you have not assessed for invasion. Atypical vessels, friability, an irregular/exophytic surface, ulceration or necrosis = suspected cancer: biopsy the edge and refer to gynae-oncology urgently. Do not "treat and hope".
- Sampling error. Biopsy the most abnormal area near the SCJ, under green-filter and Lugol guidance; a biopsy from the wrong spot gives false reassurance.
- Discordance is a warning, not a nuisance. High-grade cytology with a normal/low-grade colposcopy means the lesion is hidden (canal/vagina) or missed — re-examine the canal and vagina, consider diagnostic excision; do not simply discharge.
- Leukoplakia (white before acetic acid) can hide invasion under keratin — always biopsy, never ablate blindly.
- Pregnancy is not a time for office treatment of CIN. Colposcopy in pregnancy is to exclude invasion; treat after delivery unless cancer is suspected. This is a consultant-level examination.
- The atrophic post-menopausal cervix gives a poor, often inadequate examination and iodine-negative epithelium that mimics dysplasia — a course of topical oestrogen first improves the picture.
- Over-treatment harms. Excessive or repeated/deep excision is associated with increased risk of subsequent preterm birth and cervical insufficiency (relevant to cervical-cerclage and preterm-birth-and-pprom) — match excision depth to TZ type and do not over-treat low-grade disease, especially in young women who may regress.
- HIV-positive women are the group most likely to have multifocal, vaginal-extending, recurrent disease — examine the whole lower tract, favour excision, optimise ART, and follow up tighter.
The "suspected invasion" drill (make this unmistakable)
If at colposcopy you see atypical/bizarre vessels, an irregular friable or exophytic surface, contact bleeding, ulceration or necrosis: STOP — do not ablate and do not attempt office excision of an obvious tumour. Take a biopsy of the lesion edge to confirm tissue diagnosis, document the findings and a clinical FIGO impression, ensure haemostasis, and refer urgently to a gynae-oncology unit for examination under anaesthesia and staging. Treating a cancer as if it were CIN delays definitive care and worsens outcome.
Evidence anchors
- SASOG / BetterGyn Cervical Cancer Screening Clinical Guideline (2024) and the NDoH National Cervical Cancer Screening / Prevention and Control Policy — the South African source of truth for the screening-to-colposcopy-to-treatment pathway (HPV-primary transition informed by DiaVACCS; cytology-based legacy programme: screen from age 30, three smears 10-yearly; HIV-positive women at diagnosis then ≈3-yearly). Confirm exact intervals/algorithm against the current PDF before quoting.
- WHO Cervical Cancer Elimination Strategy (2020) — 90-70-90 by 2030; WHO endorsement of the single-dose HPV schedule (2022); WHO screen-and-treat using thermal ablation as a single-visit option.
- ESGO/ESTRO/ESP Guidelines for cervical cancer — Update 2023 — staging (FIGO 2018), management of pre-invasive and early invasive disease, and the principles distinguishing pre-invasive lesions suitable for excision from invasive disease requiring oncology referral.
- WHO Classification of Tumours of the Female Genital Tract, 5th ed (2020) / LAST terminology — LSIL/HSIL replacing CIN 1–3 in pathology reporting.
- IFCPC 2011 colposcopic terminology and the Reid Colposcopic Index — standard colposcopic teaching for adequacy, TZ typing and grading; flagged as non-guideline canon.
- South African disease burden and HIV-driven progression context: Saving Mothers / national cancer statistics framing; HIV care per SA HIV/ART Consolidated Guidelines (2023, TLD).