What is the differential diagnosis for a 25-year-old female with lower abdominal pain and severe cramping that started 2 weeks prior and worsened with the onset of menstruation?

Differential Diagnosis for Lower Abdominal Pain with Prolonged Cramping

The most likely diagnosis in this 25-year-old with two weeks of severe cramping that worsened with menstruation is primary dysmenorrhea, though the prolonged duration (two weeks before menses) raises concern for secondary causes including endometriosis, ovarian cysts, or pelvic inflammatory disease. 1, 2

Primary Differential Diagnoses

Gynecological Causes (Most Likely)

Primary Dysmenorrhea

• Defined as cramping lower abdominal/pelvic pain occurring just before or during menstruation without underlying pelvic pathology, typically lasting 1-3 days 2, 3
• However, the two-week duration before menses is atypical and suggests this may not be simple primary dysmenorrhea 3
• Caused by increased endometrial prostaglandin production resulting in increased uterine tone and stronger contractions 3
• Prevalence rates as high as 90% in reproductive-aged women 3

Secondary Dysmenorrhea - Endometriosis

• Must be considered given the prolonged pain duration extending well before menstruation 2, 4
• One of the most common diagnoses in reproductive-aged women with acute pelvic pain 4
• Warrants prompt gynecology referral if suspected 2
• Transvaginal ultrasound has sensitivity of 98% and specificity of 100% for rectosigmoid and retrocervical endometriosis 1

Ovarian Cysts

• Common cause of acute pelvic pain in reproductive-aged women 4
• Can cause pain that worsens cyclically with hormonal changes 1
• Pelvic ultrasound with Doppler is first-line imaging to assess for cysts, masses, or torsion 5

Pelvic Inflammatory Disease (PID)

• One of the most common diagnoses in reproductive-aged women with acute pelvic pain 4
• Thick tubal wall and "cogwheel" sign on ultrasound are sensitive markers (100% and 86% respectively) of acute disease 1
• Tubo-ovarian abscess has 93% sensitivity and 98% specificity on pelvic ultrasound 1

Pelvic Congestion Syndrome

• Chronic pelvic pain caused by engorged and refluxing pelvic veins 6
• Estrogen overstimulation is a contributing factor 6
• Ultrasound findings include engorged periuterine/periovarian veins ≥8 mm with low-velocity flow and retrograde ovarian vein flow 6

Non-Gynecological Causes (Less Likely Given Timing)

Appendicitis

• Common cause of acute pelvic pain but typically presents with right lower quadrant localization 4
• Would not typically correlate with menstrual timing 1

Urinary Tract Pathology

• Urolithiasis or urinary tract infection should be considered 4
• Less likely given the menstrual correlation 1

Recommended Diagnostic Approach

Initial Workup

• Pregnancy test (urine or serum β-hCG) is mandatory in all reproductive-aged women with pelvic pain 1, 4
• Transvaginal and transabdominal pelvic ultrasound with Doppler is the first-line imaging modality for suspected gynecologic causes 1, 7, 5
• STI screening may be helpful to rule out PID 2

Advanced Imaging if Ultrasound Inconclusive

• MRI pelvis without and with IV contrast is the next appropriate step for equivocal ultrasound findings 5
• MRI is superior for detecting endometriosis and characterizing complex adnexal masses 5
• CT abdomen/pelvis with IV contrast should be reserved for suspected non-gynecological causes 1, 7

Critical Clinical Pitfalls

Duration Red Flag

• The two-week pre-menstrual pain duration is highly atypical for primary dysmenorrhea and strongly suggests secondary causes 2, 3
• Do not dismiss this as "just bad cramps" without imaging evaluation 1

Avoid Diagnostic Delays

• Approximately 10% of women with dysmenorrhea do not respond to standard NSAID/hormonal therapy, indicating secondary causes 3
• Endometriosis is often underdiagnosed and requires high clinical suspicion 2

Imaging Selection Error

• Plain radiographs have very limited utility in evaluating pelvic pain and should not be used 7
• Starting with CT instead of ultrasound in reproductive-aged women exposes patients to unnecessary radiation when gynecologic causes are most likely 1, 7