How should persistent abdominal pain be evaluated and managed in a 17‑year‑old female?

Evaluation and Management of Persistent Abdominal Pain in a 17-Year-Old Female

Obtain a urine or serum β-hCG immediately, then proceed with transvaginal and transabdominal ultrasound as the first-line imaging modality, followed by contrast-enhanced CT abdomen and pelvis if ultrasound is nondiagnostic or if a non-gynecologic cause is suspected. 1, 2, 3

Initial Assessment

Mandatory First Step: Pregnancy Testing

• Failure to obtain β-hCG testing can result in missed ectopic pregnancy (which carries a positive likelihood ratio of 111 when an adnexal mass is seen without intrauterine gestation), unnecessary radiation exposure, and increased maternal mortality risk. 4, 1, 2
• Approximately 40% of ectopic pregnancies are misdiagnosed at the initial visit, making pregnancy testing non-negotiable in all reproductive-age females. 5

Critical History Elements

• A complete pelvic examination is always indicated for lower abdominal pain to identify pelvic inflammatory disease, ovarian mass or torsion, ectopic pregnancy, or other gynecologic pathology. 4
• Characterize pain onset (sudden vs. gradual), location (localized vs. diffuse), radiation pattern, aggravating/relieving factors, and associated symptoms (fever, vaginal discharge, bleeding, urinary symptoms, diarrhea). 1, 5
• Sexual activity history is essential, as sexually active adolescents have higher likelihood of pelvic inflammatory disease and ectopic pregnancy. 4, 2
• Menstrual history including last menstrual period, cycle regularity, and dysmenorrhea patterns. 5

Essential Laboratory Workup

• Complete blood count to assess for leukocytosis indicating infection or inflammation. 1
• Comprehensive metabolic panel including liver function tests. 1
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis. 1
• Cervical cultures for Neisseria gonorrhoeae and Chlamydia trachomatis if pelvic inflammatory disease is suspected, though treatment should not be delayed awaiting results. 2

Imaging Algorithm

If β-hCG is Positive

• Perform transvaginal AND transabdominal ultrasound immediately as the initial imaging modality. 4, 2
• Ultrasound demonstrates 99% sensitivity and 84% specificity for ectopic pregnancy when β-hCG levels exceed 1,500 IU/L. 4
• Key ultrasound findings include: presence or absence of intrauterine gestational sac with yolk sac/fetal pole (confirms intrauterine pregnancy), extrauterine gestational sac (confirms ectopic), or adnexal mass without intrauterine pregnancy (highly suggestive of ectopic). 4, 2
• Endometrial thickness <8 mm virtually excludes normal intrauterine pregnancy; thickness ≥25 mm virtually excludes ectopic pregnancy. 4
• If β-hCG exceeds 2,000 mIU/mL without visualization of an intrauterine gestational sac, the probability of ectopic pregnancy rises to approximately 57%. 2

If β-hCG is Negative and Gynecologic Etiology Suspected

• Transvaginal ultrasound with Doppler imaging is the first-line modality, demonstrating 93% sensitivity and 98% specificity for tubo-ovarian abscess. 4, 2
• Specific ultrasound findings for pelvic inflammatory disease include: thick wall >5 mm, cogwheel sign (present in 86% of acute cases), incomplete septa (present in 92% of tubal inflammatory disease), and cul-de-sac fluid. 4
• For ovarian torsion, look for asymmetrically enlarged ovary with decreased or absent Doppler flow, twisted vascular pedicle on multiplanar imaging, and abnormal ovarian enhancement. 4
• Ultrasound demonstrates 98% sensitivity and 100% specificity for rectosigmoid endometriosis. 4

If β-hCG is Negative and Non-Gynecologic Etiology Suspected

• Contrast-enhanced CT abdomen and pelvis is the preferred imaging modality, demonstrating approximately 88% overall accuracy and 89% sensitivity for urgent abdominal and pelvic conditions. 4, 1, 3
• CT changes the leading diagnosis in 49% of patients with nonlocalized abdominal pain and alters management in 42% of cases. 4, 3
• CT pelvis alone is insufficient and must always be combined with abdominal imaging to avoid missing pathology. 4, 1
• Single-phase IV contrast-enhanced examination is typically sufficient; pre-contrast and post-contrast images are not required for initial diagnosis. 4, 3

If Initial Imaging is Nondiagnostic

• Proceed to contrast-enhanced CT abdomen and pelvis if ultrasound findings are equivocal or nondiagnostic. 4, 1
• Retrospective data show that 30% of patients with normal ultrasound had abnormal CT findings requiring surgery. 4
• MRI abdomen and pelvis without IV contrast is an alternative when radiation exposure is a concern, though it has limited availability in emergency settings. 4, 3

Management Based on Diagnosis

Pelvic Inflammatory Disease

• Initiate empiric broad-spectrum antibiotics immediately when minimum criteria are met (uterine + adnexal + cervical motion tenderness), even before culture results. 2
• Coverage must include N. gonorrhoeae, C. trachomatis, gram-negative facultative bacteria, anaerobes, and streptococci. 2
• Approximately 15% of untreated chlamydia infections progress to pelvic inflammatory disease, which can cause permanent reproductive damage. 2, 5

Ovarian Torsion

• Urgent surgical consultation is required if ultrasound demonstrates an enlarged ovary with decreased or absent Doppler flow. 2

Ectopic Pregnancy

• Immediate obstetric consultation for methotrexate versus surgical management. 2

Tubo-Ovarian Abscess

• Ultrasound sensitivity of 93% and specificity of 98% support immediate initiation of broad-spectrum antimicrobial therapy. 2

Critical Pitfalls to Avoid

• Never proceed with CT imaging without pregnancy testing—this leads to delayed diagnosis of ectopic pregnancy and unnecessary fetal radiation exposure. 1, 2
• Do not require multiple criteria before treating suspected pelvic inflammatory disease—requiring two or more findings reduces sensitivity and misses cases that cause permanent reproductive damage. 2
• Do not use CT as first-line imaging for suspected gynecologic causes—ultrasound provides equivalent or superior diagnostic accuracy without radiation exposure. 4, 2, 3
• Do not order CT pelvis alone—it provides insufficient coverage and must be combined with abdominal imaging. 4, 1
• Do not rely on conventional radiography, as it has limited diagnostic value (49% sensitivity for bowel obstruction, low sensitivity for abscess) and rarely changes management. 4, 1, 3
• Do not dismiss mild or atypical symptoms—many pelvic inflammatory disease cases present with nonspecific symptoms like abnormal bleeding or dyspareunia rather than classic findings. 2
• Do not delay imaging in clinically deteriorating patients while pursuing additional non-diagnostic tests. 1, 3
• Pap testing is not indicated until age 21 years (except in HIV-positive or immunosuppressed patients), and speculum examination is not required before prescribing most forms of contraception. 4