A 38-year-old woman presents with menorrhagia and pelvic pain for 8 months. On clinical examination, the uterus is enlarged, firm, and irregular. Pelvic ultrasound shows multiple hypoechoic lesions within the myometrium with preserved endometrial echo. What is the most appropriate next investigation to confirm the diagnosis and assess fibroid burden before planning treatment?

Explanation

## Investigation of Choice for Fibroid Uterus Confirmation and Assessment ### Why MRI Pelvis is the Gold Standard **Key Point:** MRI pelvis with contrast is the most accurate imaging modality for confirming uterine fibroids and assessing fibroid burden, location, and degenerative changes before treatment planning. **High-Yield:** MRI provides: - Superior soft tissue characterization (differentiation of fibroids from adenomyosis) - Exact fibroid location (submucosal, intramural, subserosal) - Number and size of fibroids - Assessment of junctional zone and endometrial cavity distortion - Detection of red degeneration or cystic changes - Evaluation of myometrial invasion ### Comparison of Imaging Modalities | Feature | Ultrasound | MRI | CT | Hysteroscopy | |---------|-----------|-----|----|--------------| | **Sensitivity for fibroids** | 90–95% | 99–100% | 85–90% | Only submucosal | | **Characterization** | Good | Excellent | Moderate | Visual only | | **Adenomyosis differentiation** | Poor | Excellent | Poor | Not applicable | | **Fibroid location mapping** | Moderate | Excellent | Moderate | Limited | | **Radiation exposure** | None | None | Yes | None | | **Cost** | Low | High | Moderate | Moderate | | **Time to diagnosis** | Immediate | 30–45 min | 15–20 min | Procedure dependent | **Clinical Pearl:** While transvaginal ultrasound is the first-line screening tool (cost-effective, no radiation), MRI is mandatory before definitive treatment (myomectomy, hysterectomy, uterine artery embolization) because it provides the surgical roadmap and rules out adenomyosis, which changes management strategy. ### When Each Modality is Used 1. **Transvaginal ultrasound** — Initial diagnosis, assessment of submucosal extension 2. **MRI** — Preoperative staging, complex cases, adenomyosis exclusion, treatment planning 3. **Hysteroscopy** — Evaluation and management of submucosal fibroids causing abnormal uterine bleeding 4. **CT** — Rarely used; reserved for incidental findings or when MRI is contraindicated **Mnemonic: SMART for MRI in Fibroids** — **S**oft tissue detail, **M**ultiple fibroid mapping, **A**denomyosis exclusion, **R**adiation-free, **T**reatment planning.