Why residual endometrium always survives: Ablation devices destroy the functional layer to roughly 6 mm depth, but the uterine cornua and lower uterine segment are anatomically difficult to reach fully. Post-ablation hysteroscopy consistently reveals distorted, scarred cavities with residual endometrial pockets, documented in Vilos et al. 2026 (narrative review of 86 post-ablation endometrial cancers spanning four decades).

• Oderkerk et al. (Int J Gynecol Cancer 2022, PMID 36375895): Meta-analysis, 11 studies, 29,102 women. EC incidence 0.0–1.6%; summary ~0.1%. This is LOWER than the general population rate of 2–3%.
• Bhattacharya et al. (Health Technol Assess 2011, PMID 21535970): 11,299 women post-ablation; EC incidence 0.02%.
• Vilos et al. (Cancers 2026): 43 ECs in 39,795 women at median 8.5-year follow-up = 0.11%. Ninety percent were Stage I, caught early because unexpected bleeding triggered evaluation.

Ablation + unopposed or under-progestinized estrogen = estrogen-sensitive endometrial islands with insufficient progestogen protection. Six months of possible inadequate progestin cover is exactly this scenario. The absolute risk is low (~0.1% baseline), but evaluation is warranted. Duration matters more than months (years drive most cases), but ruling out existing pathology is the right call given this history.

• Oral micronized progesterone: 200 mg/day x 12–14 days/month (sequential) OR 100 mg/day continuous = adequate endometrial protection at established standard doses.
• Noncontinuous EPT carries RR 1.2 for endometrial hyperplasia vs. continuous EPT; continuous carries no increased risk.
• No NAMS 2022 protocol specifically addresses post-ablation surveillance; general surveillance principles apply.

• Direct statement: "Combined HRT regimens should be used in women who have undergone endometrial ablation who wish to take HRT."
• The "estrogen-only after subtotal hysterectomy" exception does NOT extend to ablation. Combined HRT remains mandatory regardless of ablation status.

• Bleeding beyond 4–6 months on HRT: TVU + endometrial biopsy where appropriate.
• Hysteroscopy where clinically indicated or bleeding persists.
• Surveillance accuracy via 6-monthly ultrasound alone has acknowledged limitations post-ablation.

• Oral MP 200 mg/day x 12–14 days/month: adequate sequential protection for up to 5 years.
• Oral MP 100 mg/day continuous: adequate continuous combined protection.
• Transdermal MP: does NOT provide adequate endometrial protection (insufficient systemic absorption).
• Current regimen of 200 mg/day continuous = double the established continuous protective dose. Robust endometrial protection going forward.

Post-ablation anatomy changes how every diagnostic modality performs. Intrauterine adhesions, cavity distortion, and cervical stenosis each affect the tools differently. Here is what the evidence shows specifically for post-ablation uteri.

This prospective study systematically compared diagnostic accuracy in post-ablation women and established the benchmark data still cited today. SHG failed to distend the cavity adequately in the majority of subjects; TVU stripe was measurable in only 71%. This is the foundation for understanding why post-ablation surveillance requires different tools than standard endometrial monitoring.

• WHIMS (WHI Memory Study, women age 65+): CEE alone or CEE+MPA = 49–76% increased dementia risk. Wrong window, initiated years after menopause.
• WHIMSY (age 50–55, correct window): No increased cognitive risk. Confirms timing is critical.
• Meta-analysis through 2023: HRT initiated within 10 years of FMP = decreased later-life Alzheimer's risk. Greatest risk reduction with estrogen-only regimens.

• Saleh RN et al. (Alzheimer's Research & Therapy 2023; 113 citations), EPAD cohort n=1,906: APOE4 HRT users had the highest delayed memory scores (p-interaction=0.009). APOE4 HRT users had 6–10% larger entorhinal cortex and amygdala volumes (p-interaction=0.002–0.005). Earlier HRT = larger hippocampal volumes ONLY in APOE4 carriers, not non-carriers. APOE4 is the genotype that benefits most from timely estrogen.
• Ambikairajah A et al. (Human Brain Mapping 2024), UK Biobank n=207,595: APOE4/E4 homozygous HRT users showed slightly smaller hippocampal volumes (~1–2 years extra aging equivalent) but no meaningful cognitive impact detected. Caveat: cross-sectional; healthy user bias possible.
• Watts A et al. (IGNITE trial, Innovation in Aging 2025): Earlier menopausal HRT initiation = greater white matter volume. APOE4 carriers had smaller estrogen-receptor-rich brain regions, suggesting greater vulnerability to estrogen deficiency.

APOE4 impairs amyloid-beta clearance and synaptic plasticity. Estrogen receptors (ERα, ERβ) are highly expressed in the hippocampus and entorhinal cortex, exactly where APOE4 causes its earliest damage. Estrogen supports neuronal plasticity, reduces neuroinflammation, and protects the blood-brain barrier. For an APOE4 carrier, estrogen deficiency compounds genetic vulnerability. Replacement during the critical window addresses that compounding directly.

Post-ablation absolute EC risk is ~0.1%. Ninety percent of cases are Stage I when detected. The neuroprotective benefit for APOE4 carriers in the critical window is well-supported and potentially substantial. The math strongly favors continuing estrogen with adequate progestogen protection (already in place at current dose) and appropriate baseline monitoring. This is a clinical conversation with her gynecologist, not a reason to stop estrogen.

Risk context: Baseline post-ablation EC risk ~0.1%. Six months of possible estrogen-only exposure adds modest additional risk. Evaluation is warranted and straightforward.

1. Transvaginal ultrasound (TVU)- First-line. Note stripe thickness, echogenicity, hematometra, suspicious lesions. Understand that a thin, normal-appearing stripe is partially reassuring but does NOT rule out pathology post-ablation (adhesions can mask cornual endometrium).
2. Endometrial biopsy (Pipelle)- Attempt even if TVU appears normal. Successful negative biopsy is reassuring. A FAILED Pipelle (11–23% of post-ablation women) is NOT a negative result, it means the cavity could not be sampled. Failed = proceed to Step 3.
3. Office hysteroscopy + directed biopsy- If: any abnormal TVU, failed Pipelle, any bleeding/spotting/cyclic pelvic pain, or persistent clinical concern. Gold standard at ~93.9% success post-ablation. May need ultrasound guidance if cervical stenosis is present.
4. MRI- Reserve for non-diagnostic findings requiring myometrial characterization, suspected adenomyosis, or hematometra assessment. Not a primary tool.

Do NOT use SIS/SHG as primary post-ablation evaluation, adequate cavity distension occurs in only 16–40% of post-ablation women.

• 200 mg/day continuous oral micronized progesterone = double the established continuous protective dose (100 mg/day per NAMS 2022). Robust endometrial protection going forward. BMS 2026 confirms combined HRT is correct post-ablation. The regimen is appropriate.

• Annual gynecologic visit with bleeding pattern review.
• Repeat TVU if clinically indicated while on HRT.
• Endometrial biopsy if unscheduled bleeding occurs beyond 4–6 months on HRT.

For confirming whether residual endometrium has proliferated or become hyperplastic, MRI cannot replace tissue sampling. It doesn't diagnose hyperplasia, that requires a biopsy. What MRI does well post-ablation: maps residual endometrium location, detects hematometra (trapped blood), identifies hematosalpinx, assesses adenomyosis, and shows myometrial invasion depth if cancer is suspected. Use it as an anatomic roadmap, not a replacement for hysteroscopy.

Start with without-contrast (CPT 72195). T2-weighted imaging without gadolinium is the standard for post-ablation uterine assessment, it shows the junctional zone, endometrial stripe, hematometra, cornual pockets, and adhesion patterns. Add contrast (CPT 72197, with and without) only if cancer staging or myometrial invasion depth is clinically suspected based on prior findings. For anatomic screening: no contrast needed. Ask for: "pelvic MRI without contrast, T2 sagittal/axial/coronal sequences for post-ablation uterine assessment."

Denver market median across all 36 providers = $972. Hospital-based facilities (Presbyterian/St Luke's, UCHealth) run $1,600–$3,500. Avoid for cash-pay. Freestanding centers are 60% cheaper.

• Script: "I'm a cash-pay patient. I need a pelvic MRI without contrast for uterine evaluation: I've had an endometrial ablation and I need to assess for residual endometrium. Do you need a physician order, or can I self-refer? What is your cash-pay price for CPT 72195?"
• If they need a diagnosis code: N85.00 (endometrial hyperplasia, unspecified) or N93.9 (abnormal uterine bleeding) or Z09 (follow-up after completed treatment).
• Ask: Is the radiologist interpretation report included in the quoted price, or billed separately?
• Ask: Is this a 1.5T or 3T magnet? (3T gives sharper junctional zone; 1.5T is adequate but 3T is preferable for uterine evaluation.)
• Colorado self-referral: Most freestanding imaging centers do NOT require a physician order for cash-pay patients in Colorado. You can often book directly.

1. Try office hysteroscopy + biopsy first- actual tissue, gold standard, cheaper than MRI at many OB/GYN offices. Ask your gynecologist about in-office hysteroscopy as a cash-pay procedure.
2. If you want MRI for anatomic mapping first: Call Radiology Assist ($375 all-in, includes report) or Health Images Castle Rock ($350–$750). Request CPT 72195 (without contrast). Or check sesamecare.com/Denver for current provider listings.
3. Bring MRI images on CD to hysteroscopy: The radiologist's report + images help the gynecologist navigate post-ablation scarring and identify where to direct the biopsy scope.