What is the appropriate workup for pelvic pain in a 40‑year‑old woman?

Workup for Pelvic Pain in a 40-Year-Old Woman

Begin with immediate serum β-hCG testing to determine pregnancy status, followed by transvaginal and transabdominal ultrasound as first-line imaging for suspected gynecologic causes, or CT abdomen/pelvis with IV contrast if non-gynecologic etiology is more likely. 1, 2

Immediate Laboratory Assessment

Serum β-hCG is mandatory as the first test in all reproductive-age women presenting with pelvic pain, as this single result fundamentally determines the entire diagnostic pathway and imaging strategy. 1, 2 A negative β-hCG essentially excludes pregnancy-related causes (ectopic pregnancy, spontaneous abortion) and permits use of ionizing radiation if needed, while a positive result immediately prioritizes pregnancy complications and eliminates CT as a first-line option due to fetal radiation exposure. 2

Additional initial labs should include:

• Urine culture even with negative urinalysis, as dipstick cannot detect all clinically significant bacteria 2
• Complete blood count and inflammatory markers if infection suspected 3
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis 3

Critical History Elements

Document specific pain characteristics that guide the differential diagnosis:

• Pain timing relative to menstrual cycle: Cyclical pain suggests endometriosis or adenomyosis, while non-cyclical pain points toward ovarian cysts, pelvic inflammatory disease, or non-gynecologic causes 1, 4
• Duration: Acute (<3 months) versus chronic (≥6 months) pain have different differential diagnoses 2, 3
• Associated symptoms: Dyspareunia, dysuria, fever, nausea/vomiting, or vaginal discharge help distinguish gynecologic from non-gynecologic etiologies 2, 3
• Sexual history and recent instrumentation: Pelvic inflammatory disease accounts for 20% of acute pelvic pain cases 1
• History of endometriosis or adenomyosis, as these are primary causes in this age group 1

Imaging Algorithm Based on Clinical Suspicion

If Gynecologic Etiology Suspected (β-hCG Negative)

Transvaginal ultrasound combined with transabdominal ultrasound is the first-line imaging modality, providing superior evaluation of pelvic structures without radiation exposure. 1, 2 The American College of Radiology designates this as "usually appropriate" for initial imaging. 5, 1

• Transvaginal ultrasound provides superior spatial resolution for detailed evaluation of ovaries, fallopian tubes, and uterus, with 93% sensitivity for tubal involvement and 90% for ovarian involvement in pelvic inflammatory disease 5
• Transabdominal ultrasound provides anatomic overview and larger field of view for free fluid and overall pelvic architecture 5, 1
• Color and spectral Doppler should be included as standard components to evaluate vascularity and distinguish cysts from solid masses 1

MRI pelvis without and with contrast is recommended when:

• Ultrasound identifies an abnormality requiring further characterization 1
• Endometriosis is specifically suspected based on cyclical rectal pain or deep dyspareunia, where MRI demonstrates 90.3% sensitivity and 91% specificity 4
• Adenomyosis evaluation is needed, as MRI provides greatest soft-tissue detail 5

If Non-Gynecologic Etiology Suspected

CT abdomen/pelvis with IV contrast should be the initial imaging study when gastrointestinal or urologic causes are strongly suspected, providing 89% sensitivity for urgent diagnoses compared to 70% for ultrasound alone. 1, 2 CT is superior for detecting appendicitis, diverticulitis, inflammatory bowel disease, urinary calculi, and pyelonephritis. 2

If β-hCG Positive

Ultrasound is mandatory as first-line imaging, and CT is contraindicated due to fetal radiation exposure. 2 Transvaginal ultrasound demonstrates 99% sensitivity and 84% specificity for ectopic pregnancy when β-hCG levels are >1,500 IU/L. 5 The classic "tubal ring" sign has high specificity for ectopic pregnancy. 5

Common Diagnostic Pitfalls to Avoid

• Never skip β-hCG testing even if the patient reports contraceptive use or recent menses, as approximately 40% of ectopic pregnancies are misdiagnosed at initial presentation 3
• Do not assume gynecologic origin, as 15-25% of pelvic pain has gastrointestinal or urologic causes 1
• Plain radiographs have no role in pelvic pain evaluation and should not be ordered 1, 2
• Consider musculoskeletal causes, as pelvic floor myofascial pain is found in 50-90% of patients with chronic pelvic pain 6
• Screen for trauma history and psychiatric comorbidity, as these significantly influence pain severity and treatment response 6, 7

Key Differential Diagnoses by Frequency

Gynecologic causes (most common in this age group):

• Ovarian cysts (most common gynecologic cause) 1
• Pelvic inflammatory disease (20% of acute cases) 1
• Endometriosis and adenomyosis (especially if chronic/recurrent pain) 1, 4
• Adnexal torsion 5, 1

Non-gynecologic causes:

• Appendicitis, diverticulitis, inflammatory bowel disease 2
• Urinary calculi, pyelonephritis 2
• Musculoskeletal/pelvic floor dysfunction 6