What is the appropriate workup and management for a 22‑year‑old woman presenting with two weeks of low abdominal pain?

Workup and Management of a 22-Year-Old Woman with Two Weeks of Lower Abdominal Pain

Begin with transvaginal and transabdominal ultrasound as the first-line imaging modality, followed by CT abdomen and pelvis with IV contrast if ultrasound is nondiagnostic or clinical suspicion remains high for surgical pathology. 1, 2

Initial Clinical Assessment

History Focus

• Pain characteristics: Determine exact location (right vs. left lower quadrant, midline, or diffuse), onset pattern, radiation, aggravating/relieving factors, and relationship to menstrual cycle 2
• Associated symptoms: Fever, vaginal bleeding or discharge, urinary symptoms, bowel changes, nausea/vomiting 2, 3
• Gynecologic history: Last menstrual period, sexual activity, contraception use, history of sexually transmitted infections, prior pelvic surgeries 2
• Red flags: Signs of peritonitis, hemodynamic instability, or acute abdomen requiring urgent surgical evaluation 3

Physical Examination

• Abdominal examination: Assess for peritoneal signs, rebound tenderness, guarding, masses 3
• Pelvic examination: Bimanual examination to assess for cervical motion tenderness, adnexal masses or tenderness, uterine size and mobility 2, 3

Essential Laboratory Testing

Obtain the following tests immediately: 2

• Urine pregnancy test or serum β-hCG: Critical first step for any sexually active woman of reproductive age, as approximately 40% of ectopic pregnancies are misdiagnosed at initial presentation 2
• Complete blood count: Assess for leukocytosis (infection) or anemia (hemorrhage) 2
• Urinalysis with culture: Rule out urinary tract infection or pyelonephritis 2
• STI testing: Chlamydia and gonorrhea, as approximately 15% of untreated chlamydia infections lead to pelvic inflammatory disease 2

Imaging Algorithm

First-Line: Ultrasound

Transvaginal ultrasound (with transabdominal ultrasound) is the initial imaging modality of choice for evaluating lower abdominal pain in young women, offering high sensitivity without radiation exposure. 1, 2, 4, 5

• Advantages: Excellent for detecting ovarian pathology (cysts, torsion), pelvic inflammatory disease, ectopic pregnancy, appendicitis, and uterine abnormalities 4, 5
• Sensitivity for appendicitis: Bedside ultrasound demonstrates 90% sensitivity and 95% specificity for acute appendicitis 1

Second-Line: CT Abdomen and Pelvis with IV Contrast

If ultrasound is nondiagnostic or clinical suspicion remains high, proceed to CT with IV contrast. 1, 2, 4

• CT is the most useful examination for lower quadrant pain, accurate regardless of body habitus, and guides appropriate management 1
• IV contrast improves detection of bowel wall pathology, pericolic abnormalities, vascular pathology, and intraabdominal fluid collections 1
• CT sensitivity for appendicitis: 95% sensitivity and 94% specificity 6

Third-Line: MRI Abdomen and Pelvis

Consider MRI if both ultrasound and CT are nondiagnostic or for further characterization of complex masses. 2, 4, 7

• MRI is particularly useful for characterizing adnexal masses and evaluating for malignancy in indeterminate cases 7
• Less sensitive for extraluminal air and urinary calculi compared to CT 1

Differential Diagnosis by Location

Right Lower Quadrant Pain

Most urgent considerations: 1, 2, 4

• Appendicitis: Most common surgical emergency in this age group
• Ovarian torsion: Requires urgent surgical intervention to preserve ovarian function
• Ruptured ovarian cyst: May cause acute hemorrhage
• Ectopic pregnancy: Life-threatening if ruptured
• Pelvic inflammatory disease: Can lead to tubo-ovarian abscess

Left Lower Quadrant Pain

Key considerations (though less common in this age group): 1

• Diverticulitis is uncommon in 22-year-olds but should be considered
• Ovarian pathology (cyst, torsion)
• Pelvic inflammatory disease
• Urolithiasis or pyelonephritis

Bilateral or Midline Pain

Consider: 2, 4

• Pelvic inflammatory disease (most common with bilateral pain and cervical motion tenderness)
• Endometriosis
• Uterine leiomyoma degeneration
• Urinary tract infection or interstitial cystitis

Management Based on Findings

Urgent Surgical Conditions (Immediate Consultation)

• Ectopic pregnancy with rupture or hemodynamic instability 2
• Ovarian torsion (requires detorsion within 4-8 hours to preserve ovarian function) 4
• Appendicitis (surgical intervention within 24 hours reduces perforation risk) 6
• Ruptured hemorrhagic ovarian cyst with hemodynamic compromise 4

Medical Management

• Pelvic inflammatory disease: Outpatient treatment with ceftriaxone 500 mg IM once plus doxycycline 100 mg PO BID for 14 days (if hemodynamically stable without tubo-ovarian abscess) 2
• Simple ovarian cysts: Conservative management with repeat ultrasound in 6-8 weeks for physiologic cysts <5 cm 4
• Urinary tract infection/pyelonephritis: Appropriate antibiotic therapy based on culture results 2

Common Pitfalls to Avoid

• Do not dismiss the possibility of ectopic pregnancy without a pregnancy test, as 40% are initially misdiagnosed 2
• Do not delay imaging when clinical suspicion for surgical pathology is high; subacute presentation does not exclude urgent conditions 3
• Do not skip ultrasound and proceed directly to CT in young women, as ultrasound provides excellent diagnostic information without radiation exposure 5
• Do not assume pelvic inflammatory disease without STI testing, as other causes of bilateral pain must be excluded 2
• Do not order MRI as first-line imaging for acute evaluation, as it is time-consuming and less sensitive for certain urgent conditions 1