In a 19‑year‑old woman presenting with dysmenorrhea and menstrual bleeding, what are the differential diagnoses and recommended management plan?

Menstrual Pain with Bleeding in a 19-Year-Old: Differential Diagnosis and Management

Immediate Diagnostic Approach

The first mandatory step is to obtain a urine pregnancy test (β-hCG) to rule out pregnancy or ectopic pregnancy, followed by screening for sexually transmitted infections (gonorrhea and chlamydia), as these are the most critical initial evaluations. 1, 2

Essential Laboratory Testing

• Pregnancy test (β-hCG): Mandatory first step to exclude pregnancy-related complications 1, 2
• STI screening: Test for gonorrhea and chlamydia, as pelvic inflammatory disease can cause dysmenorrhea and abnormal bleeding 1
• TSH and prolactin levels: Rule out thyroid disease and hyperprolactinemia, which cause anovulation and irregular bleeding 1, 2
• Coagulation studies: Consider if heavy bleeding or family history of bleeding disorders present 2

Physical Examination Findings to Assess

• Pelvic examination (if sexually active): Look for cervical motion tenderness, adnexal masses, uterine enlargement, or nodularity 3, 4
• Signs suggesting secondary dysmenorrhea: Abnormal uterine bleeding patterns, dyspareunia, noncyclic pain, changes in pain intensity/duration 3

Differential Diagnosis Using PALM-COEIN Classification

The American College of Obstetricians and Gynecologists recommends the PALM-COEIN system to categorize causes systematically 2:

Structural Causes (PALM)

• Polyps: Endometrial polyps causing irregular bleeding 1, 2
• Adenomyosis: Dysmenorrhea with menorrhagia and uniformly enlarged uterus 3
• Leiomyoma: Fibroids causing heavy bleeding and pain 1, 2
• Malignancy/Hyperplasia: Rare in this age group but must exclude 1, 2

Non-Structural Causes (COEIN)

• Coagulopathy: Bleeding disorders (von Willebrand disease, platelet dysfunction) 1, 2
• Ovulatory dysfunction: Most likely diagnosis in young women with irregular bleeding and normal anatomy 2
• Endometrial disorders: Primary endometrial hemostasis defects 1
• Iatrogenic: Hormonal contraceptives, IUDs, anticoagulants 1
• Not yet classified: Other causes 1, 2

Most Likely Diagnosis in This Age Group

Primary dysmenorrhea is the most common cause in adolescents—painful menstruation without pelvic pathology due to increased prostaglandin production causing uterine contractions. 3, 5, 6 However, if symptoms persist despite treatment, endometriosis becomes the leading cause of secondary dysmenorrhea in adolescents 4.

Imaging Considerations

• Transvaginal ultrasound: Perform if secondary dysmenorrhea suspected based on abnormal examination, persistent symptoms despite treatment, or risk factors for structural pathology 7, 3
• Saline infusion sonohysterography: Consider if transvaginal ultrasound inconclusive; has 96-100% sensitivity for intracavitary pathology 1

First-Line Treatment Algorithm

For Primary Dysmenorrhea (No Pathology Identified)

Initiate NSAIDs for 5-7 days during bleeding episodes as first-line therapy, which reduces menstrual blood loss by 20-60%. 7, 8, 1

• NSAID options: Ibuprofen, naproxen, mefenamic acid (500 mg three times daily for 5 days) 7, 3, 9
• Critical caveat: Do NOT use aspirin—it may paradoxically increase bleeding 8
• Timing: Start NSAIDs at onset of menses or just before for maximum effectiveness 3, 9

Second-Line: Add Hormonal Therapy

If NSAIDs alone are insufficient after one cycle, add hormonal contraception 3, 4, 9:

Combined oral contraceptives (COCs) containing 30-35 μg ethinyl estradiol with levonorgestrel or norgestimate are first-line hormonal treatment. 1

• Mechanism: Suppresses endometrial proliferation and prostaglandin production 3, 9
• Alternative: Progestin-only contraception if estrogen contraindicated 1
• Duration: Use for 10-20 days if treating acute bleeding episode 7, 8

Third-Line Options

• Levonorgestrel-releasing IUD (LNG-IUD): Reduces menstrual blood loss by 71-95%; excellent for long-term management 8, 2
• Tranexamic acid: Reduces bleeding by 40-60% but expensive and contraindicated with thromboembolism history 8

Treatment Response Timeline

Reassess after 3-6 months of compliant therapy. 4, 9

• Expected response: Most patients with primary dysmenorrhea improve with NSAIDs and/or hormonal contraceptives 3, 9
• Counseling point: Unscheduled bleeding during first 3-6 months of hormonal therapy is common and generally not harmful 7, 1

When to Investigate for Secondary Causes

If symptoms persist despite 3-6 months of compliant treatment with NSAIDs and hormonal therapy, investigate for secondary dysmenorrhea, particularly endometriosis. 4, 9

Red Flags Requiring Further Investigation

• Persistent pain despite appropriate treatment 4, 9
• Dyspareunia (painful intercourse) 3
• Noncyclic pelvic pain 3
• Abnormal pelvic examination findings 3
• Heavy bleeding requiring pad/tampon change every 1-2 hours 6

Endometriosis Considerations in Adolescents

• Appearance differs from adults: Lesions typically clear or red (not the classic "powder burn" appearance) 4
• First-line treatment: Hormonal contraceptives (same as primary dysmenorrhea) 4
• Laparoscopy: Reserve for patients failing medical management or when diagnosis confirmation needed 4

Common Pitfalls to Avoid

1. Failing to obtain pregnancy test first: Always mandatory regardless of sexual history reported 1, 2
2. Using aspirin for dysmenorrhea: May worsen bleeding 8
3. Inadequate treatment trial: Must ensure 3-6 months of compliant therapy before declaring treatment failure 4, 9
4. Dismissing symptoms: Dysmenorrhea significantly impacts quality of life and school/work attendance; treat aggressively 5, 6
5. Missing STI screening: Pelvic inflammatory disease mimics dysmenorrhea 1
6. Premature surgical intervention: Approximately 90% respond to medical management 3, 9

Monitoring and Follow-Up

• Blood pressure monitoring: For patients on combined hormonal contraceptives 1
• Assess treatment adherence: Non-compliance is common reason for apparent treatment failure 4, 9
• Screen for adverse effects: Particularly with NSAIDs (GI upset) and hormonal contraceptives (thrombotic risk) 1, 9
• Reassess diagnosis: If no improvement after compliant medical therapy, perform transvaginal ultrasound to evaluate for structural pathology 7, 3