How should I initially evaluate and manage a 19‑year‑old female presenting with abdominal pain?

Initial Evaluation and Management of Abdominal Pain in a 19-Year-Old Female

Obtain a pregnancy test (serum or urine β-hCG) immediately, followed by transvaginal and transabdominal ultrasound as first-line imaging if gynecologic pathology is suspected; if β-hCG is negative and pain is non-localized or ultrasound is inconclusive, proceed directly to CT abdomen and pelvis with IV contrast. 1, 2

Immediate First Steps

Pregnancy Testing is Mandatory

• Serum or urine β-hCG must be obtained in all women of reproductive age before any imaging or treatment decisions. Failure to do so can result in missed ectopic pregnancy (which carries a positive likelihood ratio of approximately 111 when an adnexal mass is seen without intrauterine gestation), inappropriate radiation exposure, and increased maternal mortality risk. 1, 2

• A positive β-hCG fundamentally changes your diagnostic pathway—it distinguishes pregnancy-related emergencies (ectopic pregnancy, miscarriage, ovarian torsion in pregnancy) from non-pregnancy causes. 1

• A negative β-hCG effectively rules out ongoing pregnancy complications and allows you to pursue broader differential diagnoses including appendicitis, ovarian pathology, pelvic inflammatory disease, and gastrointestinal causes. 1

Assess for Emergency Red Flags

• Evaluate for fever, vaginal bleeding, hemodynamic instability, peritoneal signs, and severe unremitting pain—these indicate potential surgical emergencies requiring immediate intervention. 1

Imaging Algorithm Based on β-hCG Result

If β-hCG is Positive

• Perform immediate transvaginal AND transabdominal ultrasound as the initial imaging modality. This combination provides high diagnostic accuracy without ionizing radiation and is the standard of care recommended by the American College of Radiology. 1, 2

• Ultrasound demonstrates 93% sensitivity and 98% specificity for tubo-ovarian abscess, and reliably identifies ectopic pregnancy when an adnexal mass is visualized without an intrauterine gestation. 1, 2

• Key ultrasound findings to identify:

  • Intrauterine gestational sac with yolk sac or fetal pole confirms intrauterine pregnancy 1
  • Extrauterine gestational sac with yolk sac or fetal pole confirms ectopic pregnancy 1
  • If β-hCG exceeds 2,000 mIU/mL without an intrauterine gestational sac, the probability of ectopic pregnancy rises to approximately 57% 1

• Do not use CT as first-line imaging when β-hCG is positive due to radiation exposure; CT should only be considered if ultrasound is nondiagnostic and non-gynecologic pathology is strongly suspected. 1

If β-hCG is Negative and Gynecologic Etiology Suspected

• First-line transvaginal ultrasound with Doppler imaging is recommended to evaluate for ovarian cysts, ovarian torsion, tubo-ovarian abscess, or other adnexal pathology. 1, 2

• Ultrasound achieves 93% sensitivity and 98% specificity for tubo-ovarian abscess, with characteristic findings including thick-walled (>5 mm) complex adnexal mass, "cogwheel" sign, incomplete septations, and cul-de-sac fluid. 1

• For suspected ovarian torsion, look for enlarged ovary with decreased or absent Doppler flow—this requires urgent surgical consultation. 1

If β-hCG is Negative and Pain is Non-Localized or Ultrasound is Inconclusive

• CT abdomen and pelvis with IV contrast is the preferred imaging study for evaluating generalized or non-localized abdominal pain with a negative pregnancy test. The American College of Radiology specifies that CT pelvis alone is insufficient and must always be combined with abdominal imaging. 1, 2

• Contrast-enhanced CT demonstrates approximately 88% overall accuracy and 89% sensitivity for urgent abdominal and pelvic conditions in adults, significantly outperforming ultrasound (89% versus 70% sensitivity). 1, 2

• CT is specifically indicated when:

  • Ultrasound findings are equivocal or nondiagnostic 1, 2
  • Clinical suspicion for non-gynecologic pathology is high (appendicitis, bowel obstruction, diverticulitis) 1, 2
  • Severe pain persists or worsens despite negative initial workup 1
  • Life-threatening conditions require rapid diagnosis 1

• Retrospective data show CT identified definitive pathology in 36% of pregnant patients with abdominal pain (appendicitis sensitivity ≈92%), and 30% of patients with normal ultrasound had abnormal CT findings leading to surgery. 1

Specific Clinical Scenarios in Young Women

Right Lower Quadrant Pain

• CT abdomen and pelvis with IV contrast is first-line imaging due to 95% sensitivity and 94% specificity for appendicitis, and ability to identify alternative diagnoses in 23-45% of cases. 2

• Ultrasound can be considered first in women of reproductive age to avoid radiation, but has significant limitations: appendix not visualized in 20-81% of cases, sensitivity ranging from 21% to 95.7% depending on operator experience and body habitus, and equivocal results require CT anyway. 2

Suspected Pelvic Inflammatory Disease

• Initiate empiric broad-spectrum antibiotics immediately when minimum criteria are met (uterine + adnexal + cervical motion tenderness), even before culture results, as recommended by the Centers for Disease Control and Prevention. 1

• Coverage must include N. gonorrhoeae, C. trachomatis, gram-negative facultative bacteria, anaerobes, and streptococci. 1

• Obtain cervical cultures for gonorrhea/chlamydia to guide partner treatment, but do not delay antibiotics. 1

• Do not require multiple criteria before treating—requiring two or more findings reduces sensitivity and misses cases that can cause permanent reproductive damage. 1

Common Pitfalls to Avoid

• Never omit pregnancy testing—this is the single most critical error that leads to missed ectopic pregnancies and inappropriate management. 1, 2

• Do not order CT pelvis alone—it provides insufficient coverage for generalized abdominal pain and must be combined with abdominal imaging. 1

• Do not use CT as first-line for gynecologic causes when ultrasound is available—ultrasound provides equivalent or superior accuracy without radiation exposure. 1, 2

• Do not perform non-contrast CT unless specifically evaluating for urolithiasis—IV contrast is essential for detecting inflammatory, vascular, and solid-cystic lesions. 1

• Do not dismiss mild or atypical symptoms in suspected PID—many cases present with nonspecific symptoms like abnormal bleeding or dyspareuria rather than classic findings. 1

• Do not assume non-visualization of appendix on ultrasound equals normal—correlation with clinical presentation is essential, and CT may still be needed. 2