What are other differential diagnoses for fainting episodes and moderate lower abdominal pain associated with menstruation?

Differential Diagnoses for Fainting Episodes and Moderate Lower Abdominal Pain with Menstruation

The most critical differential diagnoses to consider are ruptured hemorrhagic ovarian cyst with hemoperitoneum, ectopic pregnancy (even with negative β-hCG), hereditary angioedema with abdominal attacks, and severe primary dysmenorrhea with vasovagal syncope. 1, 2, 1

Immediate Life-Threatening Causes Requiring Urgent Evaluation

Ruptured Hemorrhagic Ovarian Cyst with Hemoperitoneum

• Hemorrhagic ovarian cysts account for one-third of gynecologic pain cases in reproductive-aged women and can rupture causing syncope from blood loss. 1, 3
• Syncope in the setting of menstrual-associated abdominal pain should raise immediate concern for intraperitoneal bleeding. 1
• Pelvic ultrasound with Doppler is the first-line imaging modality with 98-100% sensitivity for detecting free fluid and adnexal pathology. 3

Ectopic Pregnancy

• Ectopic pregnancy must be considered even with negative serum β-hCG testing, as pathology-confirmed cases have been documented with negative hCG. 2
• The combination of syncope, abdominal pain, and vaginal bleeding is the classic triad for ruptured ectopic pregnancy. 1, 2
• Serum β-hCG testing is mandatory in all reproductive-aged women with pelvic pain, but a negative result does not definitively exclude ectopic pregnancy in rare cases. 1, 2

Ovarian Torsion

• Ovarian torsion presents with acute severe pain and can cause syncope from vagal stimulation or hypovolemia. 1
• Pelvic ultrasound with Doppler demonstrates enlarged, featureless ovary with absent or decreased blood flow. 3

Menstruation-Specific Differential Diagnoses

Hereditary Angioedema (HAE-C1-INH) with Abdominal Attacks

• Menses precipitate acute HAE attacks in 35.3% of cases, causing severe abdominal pain (VAS >5) with ascites or intestinal edema that can mimic other acute abdominal conditions. 1
• The main differential diagnosis during menses is pelvic endometriosis, particularly if dyspareunia coexists. 1
• Diagnosis is likely when severe abdominal pain improves following specific HAE treatment (icatibant, C1-INH concentrate, ecallantide). 1
• Clinical examination by experienced professionals is recommended, with pelvic ultrasonography or MRI to differentiate from endometriosis. 1

Severe Primary Dysmenorrhea with Vasovagal Syncope

• Primary dysmenorrhea affects up to 90% of reproductive-aged women and causes cramping pain from increased prostaglandin production leading to uterine hypercontractility. 4, 5
• Approximately 10% of women experience debilitating symptoms severe enough to cause syncope through vasovagal mechanisms. 4, 5
• Pain typically begins with bleeding onset and lasts 48-72 hours. 4, 6

Endometriosis

• Transvaginal ultrasound has 98% sensitivity and 100% specificity for rectosigmoid and retrocervical endometriosis, a common cause of secondary dysmenorrhea. 3
• Endometriosis should be suspected when dyspareunia accompanies menstrual pain. 1
• MRI pelvis without and with IV contrast is the next appropriate step for equivocal ultrasound findings. 3

Additional Gynecologic Causes

Pelvic Inflammatory Disease (PID)

• Thick tubal wall and "cogwheel" sign on ultrasound are 100% and 86% sensitive markers respectively for acute PID. 3
• PID accounts for 20% of acute pelvic pain cases and includes tubo-ovarian abscess (93% sensitivity, 98% specificity on ultrasound). 1, 3
• Recent instrumentation, surgery, or sexual activity are common precipitants. 1

Uterine Fibroids

• Acute pain from fibroids occurs from torsion of pedunculated fibroids, prolapse of submucosal fibroids, or acute infarction/hemorrhage in degenerating fibroids. 1
• Fibroids are the second most common cause of acute pelvic pain in reproductive-aged women. 1

Non-Gynecologic Causes to Exclude

Gastrointestinal Pathology

• Appendicitis must be excluded in acute presentations with right lower quadrant pain. 1
• Inflammatory bowel disease, infectious enteritis, and diverticulitis can mimic gynecologic pain. 1
• Mesenteric ischemia should be considered if pain is severe and out of proportion to examination findings, though this is rare in young women. 1

Urologic Causes

• Urinary tract calculi and pyelonephritis can present with lower abdominal pain and syncope from severe pain. 1

Critical Diagnostic Algorithm

Immediate Assessment

1. Obtain serum β-hCG in all reproductive-aged women, but do not exclude ectopic pregnancy based solely on negative result if clinical suspicion is high. 1, 2
2. Perform transvaginal and transabdominal pelvic ultrasound with Doppler as first-line imaging for suspected gynecologic causes. 3
3. Assess hemodynamic stability and signs of acute blood loss (orthostatic hypotension, tachycardia, pallor). 1

When Ultrasound is Equivocal

• MRI pelvis without and with IV contrast is the next appropriate step for detecting endometriosis and characterizing complex adnexal masses. 3
• CT abdomen/pelvis with IV contrast may be necessary if broad differential includes non-gynecologic etiologies, though this exposes patients to unnecessary radiation when gynecologic causes are most likely. 3

Special Considerations for HAE-C1-INH

• Consider HAE-C1-INH if patient has recurrent episodes of severe abdominal pain with menses, family history of angioedema, or history of unexplained abdominal attacks. 1
• Pelvic ultrasonography or MRI should be performed to exclude endometriosis as the primary differential. 1
• Trial of specific HAE treatment can be diagnostic if symptoms improve. 1

Common Pitfalls to Avoid

• Starting with CT instead of ultrasound in reproductive-aged women exposes patients to unnecessary radiation when gynecologic causes are most likely. 3
• Assuming a negative β-hCG definitively excludes ectopic pregnancy in all cases—rare pathology-confirmed cases exist with negative serum hCG. 2
• Dismissing severe dysmenorrhea as "normal" without considering secondary causes like endometriosis or HAE-C1-INH. 1, 3
• Failing to recognize that syncope with menstrual pain suggests either significant blood loss or severe pain with vasovagal response, both requiring urgent evaluation. 1
• Plain radiographs have very limited utility in evaluating pelvic pain and should not be used. 3
• Overlooking HAE-C1-INH in patients with recurrent menstrual-associated abdominal pain, as menses precipitate attacks in over one-third of HAE patients. 1