What is the most likely diagnosis in a reproductive‑age woman presenting with heavy menstrual bleeding and abdominal cramping?

Most Likely Diagnosis: Uterine Fibroids (Leiomyomas)

In a reproductive-age woman presenting with heavy menstrual bleeding and abdominal cramping, uterine fibroids (leiomyomas) are the most likely diagnosis, followed closely by adenomyosis as a differential consideration.

Diagnostic Reasoning

The clinical presentation of heavy menstrual bleeding (HMB) with abdominal cramping in reproductive-age women points to structural uterine pathology. Based on the PALM-COEIN classification system, structural causes (PALM) include polyps, adenomyosis, leiomyomas, and malignancy 1.

Primary Differential Diagnoses by Probability:

Uterine Fibroids (Leiomyomas):

• Most common benign tumor in reproductive-age women 2
• Classic presentation includes heavy and prolonged uterine bleeding with pelvic pain/cramping 2
• Approximately 50% of women consulting for heavy menstrual bleeding have uterine abnormalities, with fibroids being most common in women under 40 years 3

Adenomyosis:

• Second most likely structural cause
• Presents with heavy menstrual bleeding and dysmenorrhea (painful cramping) 4
• Often coexists with fibroids, making diagnosis challenging 4
• Can be asymptomatic but symptomatic patients typically have both HMB and significant cramping 4

Endometrial Polyps:

• More common in women over 40 years 3
• Less likely to cause significant cramping compared to fibroids or adenomyosis

Diagnostic Workup Algorithm

Step 1: Initial Clinical Assessment

• Menstrual history specifics: Duration of bleeding (>8 days suggests HMB), cycle regularity, volume assessment
• Pain characteristics: Timing with menses (dysmenorrhea suggests adenomyosis), constant vs. cyclical
• Risk stratification: Age, reproductive desires, anemia symptoms

Step 2: Physical Examination

• Abdominal examination for palpable masses
• Speculum examination to exclude cervical/vaginal sources
• Bimanual pelvic evaluation to characterize uterine size, shape, contour irregularities, and mobility 2

Step 3: Laboratory Testing

• Hemoglobin level to assess for anemia 2
• Pregnancy test to exclude pregnancy-related bleeding 1

Step 4: Imaging (First-Line)

Transvaginal ultrasound (TVUS) is the initial and most appropriate imaging modality 1, 5

• Can accurately identify fibroids, adenomyosis, and polyps
• 3-dimensional TVUS superior to 2-dimensional for adenomyosis diagnosis 4

Step 5: Advanced Imaging (If Needed)

Pelvic MRI with diffusion-weighted imaging when 1:

• TVUS cannot completely visualize the uterus or endometrium
• Patient body habitus limits ultrasound
• Presence of multiple fibroids obscures endometrial visualization
• Need to differentiate adenomyosis from fibroids
• MRI provides superior tissue characterization and multiplanar capability 1

Step 6: Endometrial Sampling Considerations

Consider endometrial biopsy if 1:

• Age >40-45 years with new-onset or changing bleeding pattern
• Risk factors for endometrial hyperplasia/cancer present
• Imaging cannot adequately assess endometrium

Common Diagnostic Pitfalls

1. Assuming anovulatory bleeding without imaging: While ovulatory dysfunction is common, structural pathology exists in ~50% of cases 3. Always obtain imaging in reproductive-age women with persistent HMB.

2. Missing coexistent pathology: Adenomyosis and fibroids frequently coexist 4. Both conditions may contribute to symptoms and affect treatment planning.

3. Inadequate ultrasound evaluation: Uterine position, body habitus, and presence of fibroids can limit TVUS visualization 1. Don't hesitate to proceed to MRI when ultrasound is suboptimal.

4. Overlooking bleeding disorders: In adolescents and young women with HMB since menarche, consider coagulopathy (19.4% of adolescent HMB) 6, though less likely with new-onset symptoms in established reproductive years.

Clinical Context

The combination of HMB with cramping specifically suggests:

• Fibroids cause cramping through uterine distension, increased contractility during menstruation, and mechanical effects
• Adenomyosis causes dysmenorrhea through ectopic endometrial tissue within myometrium responding to hormonal cycles
• Simple ovulatory dysfunction typically causes HMB without significant cramping

The presence of abdominal cramping alongside HMB makes structural uterine pathology (fibroids or adenomyosis) significantly more likely than purely hormonal causes 4, 5.