Abnormal Uterine Bleeding

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Core Mechanism: Abnormal Uterine Bleeding (AUB) is defined as bleeding from the uterine corpus that is irregular in volume, frequency, or duration in the absence of pregnancy. Normal menstruation occurs every 28 (±7) days, lasts up to 7 days, and involves approximately 35 mL of blood loss. Blood loss exceeding 80 mL is considered pathologic.
• The Cellular/Hormonal Breakdown: During a normal cycle, estrogen drives endometrial proliferation, while progesterone (secreted by the corpus luteum post-ovulation) matures and stabilizes the lining. In Dysfunctional Uterine Bleeding (DUB)—the most common non-structural cause—the patient experiences anovulatory cycles. The lack of ovulation means no corpus luteum forms, leading to an absence of progesterone. This results in unopposed estrogen stimulation, creating a massively thickened, fragile, and unstable endometrium that sloughs off irregularly, unpredictably, and often profusely.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Stabilization: Assess ABCs, establish two large-bore IVs, and initiate aggressive crystalloid resuscitation if the patient exhibits tachycardia, hypotension, or orthostasis.
• First-Line Pharmacotherapy (Severe Bleeding):
• Conjugated Equine Estrogen (Premarin): 25 mg IV every 4 to 6 hours (up to 4 doses total) until bleeding diminishes. Note: Co-administer antiemetics, as high-dose estrogen causes severe nausea.
• Combined OCPs: Monophasic combined oral contraceptive pill, 1 tab PO QID.
• Alternative Agents (If Estrogen is Contraindicated):
• Tranexamic Acid (TXA): 1300 mg PO TID.
• Progestins: Medroxyprogesterone acetate 10 mg PO or Norethindrone 5 mg PO.
• Mechanical Tamponade: If life-threatening hemorrhage is refractory to medical therapy, initiate intrauterine tamponade by inserting a 26-French Foley catheter or Bakri balloon transvaginally into the uterus and inflating the balloon with 30 to 60 mL of normal saline.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• "Can't-Miss" Mimics & Etiologies:
• Ectopic Pregnancy / Complications of Pregnancy: The absolute first condition to rule out in any woman of reproductive age.
• Gynecologic Malignancy: Endometrial or cervical cancer, especially critical in postmenopausal women presenting with new bleeding.
• Coagulopathy: Conditions such as von Willebrand disease, immune thrombocytopenia, or iatrogenic bleeding from anticoagulants.
• Prioritized Diagnostic Workup:
• Quantitative/Qualitative $\beta$-hCG: Mandatory and non-negotiable first step in all women with a uterus and ovaries.
• CBC & Coagulation Profile: Check hemoglobin/hematocrit to quantify acute anemia, platelets, and PT/PTT/INR to rule out coagulopathy.
• Type and Screen: Obtain Rh status; administer RhoGAM if the patient is pregnant and Rh-negative.
• The PALM-COEIN Matrix: Systematically evaluate for Polyps, Adenomyosis, Leiomyoma, Malignancy (Structural) and Coagulopathy, Ovulatory dysfunction, Endometrial, Iatrogenic, Not otherwise classified (Nonstructural).

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Transvaginal Ultrasound (TVUS): The gold-standard imaging modality. Visually assess for structural causes like uterine fibroids (leiomyomas), polyps, or retained products of conception.
• Endometrial Stripe Thickness: On TVUS, scrutinize the endometrial thickness. In postmenopausal women presenting with AUB, an endometrial thickness of < 4 to 5 mm reliably excludes endometrial cancer. A thickened stripe mandates urgent outpatient endometrial biopsy.
• The Sterile Speculum Exam: You must physically visualize the cervix to confirm the blood is of uterine origin. Clear the vaginal vault of blood and clots using sponge forceps. Actively look for vaginal lacerations, cervical masses, or products of conception stuck in the cervical os.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• Clinical Disposition Criteria:
• Unstable / Admit: Hemodynamic compromise (HR > 110 bpm, SBP < 90 mm Hg, or orthostatic HR rise > 30 bpm), hemoglobin < 9 g/dL, profuse continuous bleeding, or underlying severe coagulopathy.
• Stable / Discharge: Normal vital signs, reassuring hemoglobin/hematocrit, and bleeding that has slowed or stopped. Discharge with strict return precautions and mandatory Gynecology follow-up within 10 days for an endometrial biopsy if the patient is older and at high risk for cancer.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Deadly Cognitive Trap (Administering Estrogen to the Wrong Patient): Giving IV Premarin to a patient with contraindications. Critical Action: You must explicitly verify the patient has no history of venous thromboembolism (VTE/DVT/PE), thrombophilia, vascular disease, or estrogen-dependent malignancy before giving high-dose estrogen.
• Deadly Cognitive Trap (Blind Vaginal Packing): Placing standard gauze packing in the vagina to stop heavy uterine bleeding. Correction: Routine vaginal packing is strongly discouraged as it increases the risk of infection and dangerously masks ongoing occult blood loss. Use direct intrauterine balloon tamponade (Foley/Bakri) instead.
• Diagnostic Pitfall (Misinterpreting "Cervical Shock"): A pregnant patient presents with heavy bleeding, profound hypotension, and a paradoxical bradycardia. Critical Action: Do not just push fluids. This is cervical shock caused by vagal stimulation from tissue (products of conception) stuck in the cervical os. You must perform a speculum exam and remove the tissue with sponge forceps, which will rapidly resolve the shock.

7. MCQ MASTERCLASS (Written Exam Tips)

• The VTE Distractor: A board question describes a 32-year-old female with profuse AUB, a negative pregnancy test, and a past medical history of a DVT. The question asks for the best medical therapy. The distractor is "IV Conjugated Estrogen." Correction: Estrogen is strictly contraindicated here. The correct answer will be Oral Tranexamic Acid or Oral Medroxyprogesterone.
• The Primary Step Buzzword: When asked for the "most appropriate initial step" or "first diagnostic test" in any female from ages 10 to 55 with abdominal pain or vaginal bleeding, the answer is always Urine Pregnancy Test (hCG), even if they deny sexual activity.
• The Postmenopausal Rule-Out: A 65-year-old woman has new vaginal bleeding. A transvaginal ultrasound shows an endometrial thickness of 3 mm. What does this indicate? Answer: An endometrial thickness < 4-5 mm effectively rules out endometrial cancer.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Initial Assessment Hook: "Given the patient's profuse vaginal bleeding, my immediate priority is to determine her hemodynamic stability and pregnancy status. I will secure the ABCs, place two large-bore IVs, initiate crystalloid resuscitation, and order a STAT quantitative hCG, CBC, coagulation panel, and a Type and Screen."
• The Exam & Diagnostic Command: "The pregnancy test is negative, confirming true Abnormal Uterine Bleeding. I will perform a sterile speculum examination to clear any clots from the vaginal vault, assess the cervical os, and rule out local vaginal trauma or cervical masses. I will also obtain a bedside transvaginal ultrasound to evaluate for structural abnormalities like fibroids or endometrial thickening, utilizing the PALM-COEIN framework."
• The Resuscitation & Disposition Pivot: "Because she remains hypotensive and actively bleeding, and she has no personal history of VTE or estrogen-dependent malignancies, I will administer 25 mg of IV conjugated equine estrogen and an antiemetic. If the hemorrhage does not abate, I will place a 26-French Foley catheter into the uterus and inflate it with 30 mL of normal saline for mechanical tamponade, and consult Gynecology emergently for potential surgical intervention."