What are the possible causes of pelvic pain in a 25‑year‑old woman with irregular menstrual cycles?

Pelvic Pain with Irregular Periods in a 25-Year-Old Woman

In a 25-year-old woman presenting with pelvic pain and irregular menstrual cycles, endometriosis is the most likely diagnosis and should be the primary consideration, as it is the leading cause of cyclical pelvic pain in reproductive-age women and commonly presents with menstrual irregularities. 1, 2

Primary Gynecologic Causes to Consider

Endometriosis (Most Likely)

• Endometriosis is the most common cause of cyclical pelvic pain in women of reproductive age and characteristically presents with pain that correlates with the menstrual cycle 1, 2
• This estrogen-dependent condition causes chronic pain and typically affects women during their reproductive years, making it the top differential in this age group 3
• Pain patterns to specifically ask about include: dysmenorrhea (painful periods), dyspareunia (painful intercourse), dyschezia (painful bowel movements during menses), and cyclical rectal pain 4, 1
• MRI pelvis is the preferred imaging modality if deep pelvic endometriosis is suspected, with 90.3% sensitivity and 91% specificity 4

Adenomyosis

• Adenomyosis causes dysmenorrhea and diffuse pelvic pain, though it is more commonly encountered in older reproductive-age women 3, 1
• Unlike endometriosis, adenomyosis typically presents with diffuse pelvic pain rather than the sharp, cyclical pattern characteristic of endometriosis 4
• High-resolution transvaginal ultrasound and MRI can establish this diagnosis with high accuracy 5

Ovarian Cysts

• Hemorrhagic ovarian cysts are among the most commonly diagnosed gynecologic conditions presenting with acute pelvic pain 6
• Functional ovarian cysts can cause irregular menstrual cycles and pelvic discomfort 2
• Transvaginal ultrasound is the primary imaging modality for diagnosis 2

Pelvic Inflammatory Disease (PID)

• PID remains a frequent cause of pelvic pain in reproductive-age women and can present as chronic inflammatory disease 3, 7
• Critically, PID does not follow menstrual cyclicity, so if pain is strictly cyclical with menses, PID becomes less likely 4
• Look for fever, cervical motion tenderness, purulent discharge, and risk factors including multiple sexual partners or history of sexually transmitted infections 6

Less Common but Important Gynecologic Causes

Uterine Fibroids

• Fibroids can present with heavy menstrual bleeding, pelvic pressure, and pain 2
• Degenerating fibroids can cause acute pain episodes 6
• Transvaginal ultrasound is the primary diagnostic tool 2

Ovarian Torsion

• Though less frequent, ovarian torsion presents with acute severe pain and requires urgent surgical intervention 6
• Consider this diagnosis if pain is sudden-onset, severe, and associated with nausea/vomiting 6

Non-Gynecologic Causes to Exclude

Gastrointestinal

• Inflammatory bowel disease can manifest as chronic pelvic pain and should be considered if gastrointestinal symptoms predominate 8, 3
• Appendicitis must be excluded in acute presentations, particularly with right lower quadrant pain 8, 6

Urologic

• Urinary tract pathology including cystitis or urethral disorders can cause pelvic pain 8, 3
• Ask specifically about dysuria, frequency, urgency, and hematuria 8

Musculoskeletal

• Pelvic girdle pain and myofascial pain are common causes but typically lack menstrual cyclicity 8, 3
• These conditions do not worsen with menses and are not associated with irregular periods 4

Algorithmic Diagnostic Approach

Step 1: Characterize the pain pattern

• If pain is cyclical and correlates with menstruation → endometriosis is most likely 1, 2
• If pain is constant without menstrual relationship → consider PID, adhesions, or non-gynecologic causes 4, 7
• If pain is positional (worse with standing) → consider pelvic congestion syndrome 4

Step 2: Identify associated symptoms

• Heavy menstrual bleeding → fibroids or adenomyosis 2
• Fever, discharge, cervical motion tenderness → PID 6
• Gastrointestinal symptoms during menses → endometriosis with bowel involvement 4
• Dyspareunia → endometriosis or adenomyosis 1, 5

Step 3: Initial imaging

• Transvaginal ultrasound is the first-line imaging modality for all structural gynecologic disease 2
• If endometriosis is suspected and ultrasound is non-diagnostic, proceed to MRI pelvis 4, 5

Step 4: Definitive diagnosis

• Endometriosis requires surgical diagnosis via laparoscopy for definitive confirmation 1, 7
• Adenomyosis can be diagnosed definitively with MRI or ultimately requires hysterectomy for pathologic confirmation 1, 5

Critical Pitfalls to Avoid

• Do not assume all pelvic pain in young women is "normal menstrual cramps" – endometriosis is frequently underdiagnosed, leading to years of unnecessary suffering 5
• Do not overlook non-gynecologic causes – systematic evaluation of gastrointestinal, urologic, and musculoskeletal systems is essential to avoid missed diagnoses 8, 3
• Do not dismiss irregular periods as benign – the combination of pelvic pain and menstrual irregularity significantly increases the likelihood of structural gynecologic disease 1, 2
• Do not delay imaging – transvaginal ultrasound should be performed early in the evaluation to identify ovarian cysts, fibroids, or other structural abnormalities 2