What is the likely diagnosis and first‑line management for colicky abdominal pain that occurs with menses in a woman without red‑flag features?

Primary Dysmenorrhea: Diagnosis and First-Line Management

For colicky abdominal pain occurring with menses in a woman without red-flag features, the diagnosis is primary dysmenorrhea, and first-line treatment is NSAIDs (ibuprofen 400–800 mg every 6–8 hours or naproxen 440–550 mg every 12 hours) started at the earliest onset of pain and continued for 48–72 hours during menstruation. 1, 2, 3

Diagnostic Criteria

Primary dysmenorrhea is a clinical diagnosis requiring:

• Cramping, colicky suprapubic pain that begins at or shortly after the onset of menstrual flow 4, 5
• Pain duration of 48–72 hours, most severe during the first or second day of menstruation 4, 6
• Onset at or shortly after menarche in adolescence 4, 5
• Normal pelvic examination with no identifiable pelvic pathology 3, 7

Associated symptoms may include headache, nausea, diarrhea, back pain, and fatigue, but these are supportive rather than required for diagnosis. 6

When Additional Testing Is NOT Required

No diagnostic evaluation is necessary when the patient presents with:

• Typical cramping pain limited to menstruation 5, 7
• Age-appropriate onset (adolescence to early 20s) 4
• Normal physical examination 3
• No alarm features (see below) 1

Pregnancy testing (serum β-hCG) must be performed in all reproductive-age patients before confirming the diagnosis, even if contraception is reported. 1

Red-Flag Features Requiring Further Evaluation

Proceed to imaging and extended work-up if any of the following are present:

Alarm Feature	Implication	Next Step
Pain that does not improve after 2–3 cycles of appropriate NSAID therapy	Suggests secondary dysmenorrhea	Transvaginal ultrasound [1]
Abnormal pelvic examination findings	Possible structural pathology	Transvaginal ultrasound [1]
Deep dyspareunia or severe dysmenorrhea	Endometriosis or adenomyosis	MRI pelvis (90% sensitivity, 91% specificity for endometriosis) [1]
Fever	Pelvic inflammatory disease	Transvaginal ultrasound; empiric antibiotics if cervical motion tenderness present [8,1]
Mid-cycle or continuous pain	Ovarian pathology or endometriosis	Transvaginal ultrasound with Doppler [1]
Pain pattern changes abruptly	New pathology	Transvaginal ultrasound [1]

First-Line Pharmacologic Treatment

NSAIDs (Preferred Initial Therapy)

Start ibuprofen 400 mg every 4–6 hours (maximum 3200 mg/day) or 600–800 mg every 6–8 hours with food, beginning at the earliest onset of pain (ideally at the first sign of cramping or bleeding). 1, 2, 3

• Alternative: Naproxen 440–550 mg every 12 hours for 5–7 days during symptomatic periods 1
• Mechanism: NSAIDs inhibit prostaglandin synthesis, reducing uterine hypercontractility and ischemia 4, 3, 7
• Expected response: Significant pain relief in 80–82% of patients 1, 5
• Duration: Continue for 48–72 hours (the typical duration of primary dysmenorrhea pain) 4, 6

Critical dosing principle: Do not under-dose NSAIDs; use the full therapeutic dose from the outset. 1

When NSAIDs Fail or Are Contraindicated

Add combined oral contraceptives as second-line therapy if:

• NSAIDs provide inadequate relief after 2–3 menstrual cycles 1, 3
• The patient desires contraception 4, 5
• NSAIDs are contraindicated (e.g., peptic ulcer disease, renal impairment) 3

Mechanism: Oral contraceptives suppress endometrial growth, reducing menstrual flow and prostaglandin production. 4

Approximately 10% of patients fail both NSAIDs and hormonal contraception, which should trigger evaluation for secondary causes (endometriosis, adenomyosis, pelvic inflammatory disease). 1, 5

Adjunct Non-Pharmacologic Measures

The following may be used in combination with NSAIDs, not as replacements:

• Topical heat application to the lower abdomen or back 1, 3, 6
• Acupressure at LI4 and SP6 points 1
• Topical peppermint essential oil 1
• Regular aerobic exercise 6

Management Algorithm

1. Confirm the diagnosis clinically (typical colicky menstrual pain, normal examination, no alarm features) 3, 5, 7
2. Perform pregnancy test (β-hCG) 1
3. Initiate ibuprofen 400–800 mg every 6–8 hours at the earliest onset of pain, continued for 48–72 hours 1, 2, 4
4. Reassess after 2–3 menstrual cycles:
   • If pain resolves or improves significantly → continue NSAIDs as needed 3
   • If pain persists despite adequate NSAID dosing → add oral contraceptives (if acceptable to patient) 1, 3
   • If pain persists after 2–3 cycles of combined therapy → obtain transvaginal ultrasound to exclude secondary causes 1
5. Refer to gynecology if imaging reveals endometriosis, adenomyosis, or other structural pathology, or if empiric therapy fails after 3–6 months 1, 7

Common Pitfalls to Avoid

• Do not delay NSAID initiation while awaiting diagnostic work-up in patients with typical symptoms 1
• Do not under-dose NSAIDs; prescribe the full therapeutic dose (ibuprofen 400–800 mg, not 200 mg) 1
• Do not continue ineffective therapy beyond 2–3 cycles without imaging 1
• Do not omit pregnancy testing, even if the patient reports reliable contraception 1
• Do not assume normal inflammatory markers exclude pelvic inflammatory disease; approximately 20% of patients with acute pelvic pain from PID have no fever 1
• Do not prescribe opioids for primary dysmenorrhea; they are contraindicated in functional pain disorders 9