What are the possible causes of a heavy, recurrent menorrhagia with clots and left iliac fossa discomfort in a woman whose period began on [DATE], with initial cramps, brief resolution, and no pain, dizziness, or new medications?

Heavy Menstrual Bleeding with Clots and Left Iliac Fossa Pain: Differential Diagnosis

This presentation of heavy recurrent menstrual bleeding with clots, left-sided pelvic discomfort, and no systemic symptoms most likely represents either a structural uterine abnormality (polyp, fibroid, or adenomyosis) or ovulatory dysfunction, though a bleeding disorder must also be considered given the severity of bleeding. 1, 2

Immediate Clinical Assessment Priorities

The workup should focus on three key diagnostic categories using the PALM-COEIN classification system 2:

Structural Causes (PALM):

• Endometrial polyps - particularly likely given age >40 if applicable 3
• Adenomyosis - can cause heavy bleeding and pelvic discomfort
• Leiomyoma (fibroids) - especially submucosal types; most common in women <40 3
• Malignancy/hyperplasia - must be excluded, especially if risk factors present

Non-Structural Causes (COEIN):

• Coagulopathy - von Willebrand disease affects up to 20% of women with heavy menstrual bleeding 4, 5
• Ovulatory dysfunction - common cause in reproductive-age women 2
• Endometrial disorders - primary hemostatic defects

Key Diagnostic Red Flags in This Case

The specific features that narrow the differential:

• Clots ≥1 inch diameter - highly predictive of true heavy menstrual bleeding and suggests possible bleeding disorder 5
• "Flooding" pattern (filling 2 super pads in hours) - indicates blood loss likely >80mL per cycle 4, 5
• Left iliac fossa pain - suggests possible structural pathology (fibroid, endometriosis, or rarely endometriosis-related bleeding 6)
• Recurrent pattern after brief resolution - suggests either structural lesion or coagulopathy rather than simple ovulatory dysfunction

Essential Workup Algorithm

Laboratory tests needed immediately:

1. Hemoglobin/hematocrit - assess for anemia from blood loss 5, 7
2. Ferritin - low ferritin is predictive of heavy menstrual bleeding 5
3. Pregnancy test (β-hCG) - mandatory first step to exclude pregnancy complications 8
4. TSH and prolactin - screen for ovulatory dysfunction 2, 7

Coagulation screening is indicated given the severity of bleeding with large clots and flooding pattern 8, 9:

• von Willebrand factor antigen and activity
• Factor VIII level
• Complete blood count with platelet count
• Consider PT/PTT if family history suggests coagulopathy

Imaging - transvaginal ultrasound is first-line 1, 2:

• Assess endometrial thickness and structural abnormalities
• Evaluate for fibroids, polyps, adenomyosis
• If endometrium cannot be fully visualized, proceed to saline infusion sonohysterography (96-100% sensitivity) or hysteroscopy 2

Most Likely Diagnoses in Order of Probability

1. Structural uterine pathology (50% probability) - Given the left-sided discomfort and recurrent heavy bleeding pattern, this suggests a focal lesion like a fibroid or polyp 3

2. Ovulatory dysfunction (30% probability) - Common in reproductive-age women, though the left-sided pain is less typical 2

3. Bleeding disorder (20% probability) - The severity of bleeding with large clots and flooding pattern warrants investigation, as adolescents and women with treatment-refractory bleeding have higher rates of coagulopathy 8, 9

Critical Pitfalls to Avoid

• Do not assume this is "just a heavy period" - the flooding pattern and clot size indicate pathologic bleeding requiring investigation 5
• Do not delay coagulation testing - bleeding disorders are underdiagnosed in women with heavy menstrual bleeding, and early diagnosis changes management 4, 8
• Do not rely on patient's subjective assessment alone - women's perception of blood loss often doesn't correlate with actual volume 3
• Left iliac fossa pain during menses could rarely indicate endometriosis with vascular involvement - though uncommon, endometriosis infiltrating the uterine artery can cause acute bleeding 6

When to Refer Urgently

• Hemodynamic instability (though absent here)
• Severe anemia requiring transfusion
• Confirmed or suspected bleeding disorder - refer to hematology 5, 9
• Structural abnormality requiring surgical intervention - refer to gynecology
• Endometrial sampling cannot be completed or shows concerning pathology 1

Endometrial biopsy should be considered if: patient has risk factors for endometrial hyperplasia/cancer (age >45, obesity, PCOS, unopposed estrogen exposure) 1, 2