A 28-year-old nulliparous woman with heavy menstrual bleeding is evaluated. Coagulation studies are normal. Pelvic ultrasound shows a normal uterus and ovaries. Endometrial biopsy reveals proliferative endometrium with increased vascularity and edema but no structural lesions. Which single finding best distinguishes dysfunctional uterine bleeding (DUB) from bleeding due to coagulopathy in this patient?

Explanation

## Distinguishing Dysfunctional Uterine Bleeding from Coagulopathy ### Key Discriminating Feature **Key Point:** A **normal coagulation profile combined with abnormal endometrial vascularity and local hemostatic defects** is the hallmark that distinguishes DUB from systemic coagulopathy. ### Comparative Table | Feature | DUB (Anovulatory) | Coagulopathy | |---------|-------------------|---------------| | **Coagulation Studies** | Normal (PT, aPTT, fibrinogen, platelet count) | Abnormal (prolonged PT/aPTT, low fibrinogen, thrombocytopenia) | | **Endometrial Vascularity** | Increased, abnormal (local defect) | Normal or secondary to bleeding | | **Structural Pathology** | None | None (primary bleeding disorder) | | **Endometrial Biopsy** | Proliferative or secretory (depending on cycle phase) | Normal histology | | **Mechanism** | Local endometrial hemostatic defect (↓ progesterone, ↑ prostaglandins, ↓ vasopressin) | Systemic platelet/coagulation factor deficiency | | **Response to Hormonal Therapy** | Excellent | Poor; requires factor replacement | ### Pathophysiology of DUB **High-Yield:** DUB is a **diagnosis of exclusion** characterized by: 1. **Anovulation** → absent progesterone secretion 2. **Unopposed estrogen** → endometrial proliferation without orderly shedding 3. **Local endometrial defects:** - Increased vascularity and vascular fragility - Abnormal angiogenesis - Reduced vasopressin and increased prostaglandins (PGE₂, PGF₂α) - Impaired local hemostasis despite normal systemic coagulation **Mnemonic: COPE** — Coagulation normal, Ovulation absent, Pathology excluded, Endometrial defect (local) ### Why Normal Coagulation Profile is Discriminatory **Clinical Pearl:** The presence of **normal coagulation studies in a patient with heavy menstrual bleeding** immediately excludes coagulopathy as the primary cause and points toward DUB or structural pathology. When imaging is also normal, DUB becomes the diagnosis. In contrast, coagulopathy (von Willebrand disease, factor deficiencies, thrombocytopenia) will show **abnormal coagulation parameters** — this is the key discriminator. ### Why Other Features Are Non-Discriminatory - **Absence of structural pathology:** Both DUB and coagulopathy present without structural lesions on imaging - **Proliferative endometrium:** Both can show proliferative endometrium; this reflects the cycle phase, not the underlying cause - **Heavy menstrual bleeding:** Both conditions present with menorrhagia; this is the symptom, not the discriminator [cite:Park 26e Ch 10; Munro MG. Classification of abnormal uterine bleeding. Best Pract Res Clin Obstet Gynaecol. 2018;46:3-14]