A 28-year-old nulliparous woman with menorrhagia undergoes pelvic MRI. Imaging reveals a 4 cm lesion in the fundus with low T2 signal intensity, a well-defined pseudocapsule, and a normal junctional zone. Her coagulation profile is normal. Which single finding best distinguishes this presentation from von Willebrand disease as a cause of her abnormal uterine bleeding?

Explanation

## Fibroid-Related Bleeding vs. Coagulopathy (von Willebrand Disease) ### The Critical Distinction **Key Point:** The presence of a **localized structural lesion** on imaging is the single most important discriminator between fibroid-related menorrhagia and systemic coagulopathy. ### Comparative Framework | Aspect | Fibroid (Structural) | von Willebrand Disease (Coagulopathy) | |--------|---------------------|----------------------------------------| | **Imaging Finding** | Discrete lesion with pseudocapsule | Normal uterus, no structural lesion | | **Junctional Zone** | Preserved, normal | Normal | | **Myometrial Architecture** | Intact except at fibroid site | Completely normal | | **Coagulation Studies** | Normal | Abnormal (↓ vWF, ↓ Factor VIII, ↑ PT) | | **Mucocutaneous Bleeding** | Absent | Often present (epistaxis, gum bleeding, easy bruising) | | **Age of Onset** | Typically after fibroid develops | Often from menarche or earlier | | **Response to Hormonal Therapy** | Variable; depends on fibroid size | Often responds well | **High-Yield:** A **normal pelvic ultrasound or MRI excludes structural pathology** and should prompt investigation for coagulopathy. Conversely, **imaging evidence of a fibroid confirms a structural cause**, even if coagulation studies are normal (fibroids can cause bleeding independent of hemostatic defects). ### Clinical Pearl **Clinical Pearl:** The presence of a structural lesion on imaging is pathognomonic for fibroid-related bleeding in this context. von Willebrand disease presents with a normal pelvis but abnormal coagulation studies and often a lifelong bleeding history. ### Why Imaging is the Discriminator - **Fibroids** cause bleeding through mechanical distortion of the endometrium, increased vascularity, and abnormal hemostasis at the lesion site. - **von Willebrand disease** causes bleeding through a systemic hemostatic defect; the uterus is structurally normal. **Mnemonic:** **FIBROID = FOUND** (imaging finds it); **vWD = FUNCTIONAL** (defect in function, not structure). [cite:Park 26e Ch 9; Harrison 21e Ch 181]