## Most Common Cause of AUB with Normal Structural Findings **Key Point:** When structural and coagulation abnormalities are excluded (normal ultrasound, normal coagulation studies), **ovulatory dysfunctional uterine bleeding** (now termed **ovulatory AUB** in the FIGO classification) is the most common cause of abnormal uterine bleeding. **High-Yield:** The FIGO classification divides AUB into **structural** (PALM: Polyps, Adenomyosis, Leiomyomas, Malignancy) and **non-structural** (COEIN: Coagulopathy, Ovulatory dysfunction, Endometrial, Iatrogenic, Not yet classified). Ovulatory dysfunction is the most common non-structural cause. ### Classification of Dysfunctional Uterine Bleeding (DUB) | Type | Mechanism | Prevalence | Characteristics | |------|-----------|-----------|------------------| | **Ovulatory DUB** | Abnormal endometrial hemostasis despite normal ovulation | ~70% of DUB cases | Regular or slightly irregular cycles; heavy/prolonged flow; normal coagulation | | **Anovulatory DUB** | Absent corpus luteum → unopposed estrogen → proliferative endometrium | ~30% of DUB cases | Irregular, unpredictable cycles; often in adolescents or perimenopausal women | ### Pathophysiology of Ovulatory AUB 1. **Abnormal prostaglandin metabolism** — increased PGE~2~ and PGF~2α~ in endometrium → increased vasodilation and myometrial contractions 2. **Impaired endometrial hemostasis** — reduced platelet aggregation, abnormal fibrinolysis, reduced vasoconstriction 3. **Increased fibrinolytic activity** — elevated tissue plasminogen activator (tPA) and reduced plasminogen activator inhibitor (PAI-1) 4. **Abnormal angiogenesis** — increased vascular density and fragility in endometrium 5. **Normal ovulation and luteal phase** — distinguishes this from anovulatory DUB **Clinical Pearl:** Ovulatory DUB typically presents with **regular or predictable menstrual cycles** with **excessive flow or duration**, whereas anovulatory DUB presents with **irregular, unpredictable bleeding**. This distinction is crucial for diagnosis. ### Why This Case Represents Ovulatory AUB - **Normal pelvic examination** → excludes structural pathology - **Normal transvaginal ultrasound** → rules out fibroids, polyps, adenomyosis, malignancy - **Normal coagulation studies** → excludes von Willebrand disease and other bleeding disorders - **Chronic heavy menstrual bleeding** (3 years) with **nulliparity** → consistent with ovulatory dysfunction - **Age 32** → reproductive age, less likely to be anovulation (which peaks in adolescence and perimenopause) **Mnemonic:** **PALM-COEIN** — FIGO classification of AUB: - **PALM** (Structural): **P**olyps, **A**denomyosis, **L**eiomyomas, **M**alignancy - **COEIN** (Non-structural): **C**oagulopathy, **O**vulatory dysfunction, **E**ndometrial, **I**atrogenic, **N**ot yet classified ### Management Approach ```mermaid flowchart TD A[AUB in reproductive-age woman]:::outcome --> B{Structural findings<br/>on ultrasound?}:::decision B -->|Yes| C[PALM diagnosis<br/>Fibroids, polyps, etc.]:::outcome B -->|No| D{Coagulation<br/>abnormality?}:::decision D -->|Yes| E[Coagulopathy<br/>vWD, platelet disorder]:::outcome D -->|No| F{Regular cycles?}:::decision F -->|Yes| G[Ovulatory AUB<br/>Most common]:::action F -->|No| H[Anovulatory AUB<br/>Adolescent/perimenopausal]:::action G --> I[Treatment: NSAIDs,<br/>hormonal contraceptives,<br/>tranexamic acid]:::action ``` **High-Yield:** First-line treatment for ovulatory AUB includes: 1. **NSAIDs** (mefenamic acid, ibuprofen) — reduce prostaglandins and bleeding by 20–50% 2. **Combined oral contraceptives** — suppress endometrial proliferation and reduce flow by 40–50% 3. **Tranexamic acid** — antifibrinolytic, reduces flow by 40–60% 4. **Levonorgestrel IUD** — local progestin, reduces flow by 60–90% [cite:Williams Obstetrics 26e Ch 38; FIGO Classification of Abnormal Uterine Bleeding]
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