What is the initial workup and lab orders for a 20-year-old pregnant woman at 16 weeks gestation presenting with abdominal pain, without symptoms of nausea, vomiting, urinary issues, or vaginal bleeding?

From the Guidelines

The initial workup for a 20-year-old pregnant woman at 16 weeks gestation with abdominal pain should include a comprehensive evaluation to rule out both obstetric and non-obstetric causes, starting with a complete blood count (CBC), comprehensive metabolic panel (CMP), urinalysis, and urine culture to assess for infection and evaluate organ function, as well as an obstetric ultrasound to confirm fetal viability and placental location 1. The patient's presentation with abdominal pain at 16 weeks gestation requires a thorough evaluation to determine the cause of the pain and to rule out any potential complications.

• The initial laboratory tests should include:
  • Complete blood count (CBC) to evaluate for infection or inflammation
  • Comprehensive metabolic panel (CMP) to assess organ function
  • Urinalysis and urine culture to evaluate for urinary tract infection
  • C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) to evaluate for inflammation
• An obstetric ultrasound should be ordered to:
  • Confirm fetal viability
  • Evaluate placental location
  • Rule out complications such as placental abruption or cervical insufficiency
• If appendicitis is suspected, an MRI would be the preferred imaging modality over CT scan to avoid radiation exposure 1.
• Pain management with acetaminophen is appropriate while awaiting diagnosis.
• The absence of nausea, vomiting, urinary symptoms, and vaginal bleeding helps narrow the differential diagnosis, but a thorough evaluation remains essential as abdominal pain in pregnancy can indicate serious conditions including preterm labor, appendicitis, ovarian torsion, or urinary tract infection that require prompt identification and management.
• Consider testing for sexually transmitted infections if risk factors are present, and assess fetal heart tones with Doppler ultrasound.
• A step-up approach for diagnosis should be used, tailored to the clinical setting and resources, beginning with clinical and laboratory examination and progressing to imaging examinations if necessary 1.

From the Research

Initial Workup and Lab Orders

The initial workup and lab orders for a 20-year-old pregnant woman at 16 weeks gestation presenting with abdominal pain, without symptoms of nausea, vomiting, urinary issues, or vaginal bleeding, should include:

• A thorough patient history and physical examination to determine the cause of abdominal pain 2
• Laboratory tests, such as complete blood count, blood chemistry, and urinalysis, to rule out any underlying medical conditions 2
• Abdominal ultrasound as the primary imaging investigation to evaluate the cause of abdominal pain 3, 4, 5, 6

Imaging Modalities

• Ultrasound is the recommended initial imaging modality due to its availability, portability, and lack of ionizing radiation 3, 4, 5, 6
• Magnetic Resonance Imaging (MRI) may be used when ultrasound is inconclusive or to further evaluate the cause of abdominal pain 3, 4, 5, 6
• Computed Tomography (CT) scan is generally contraindicated during pregnancy due to radiation teratogenicity, but may be used in life-threatening situations or traumatic injuries 2, 4, 6

Considerations

• The patient's physiologic alterations during pregnancy, including atypical normative laboratory values, should be taken into account when interpreting laboratory results 2
• The risks and benefits of each imaging modality should be carefully considered to minimize harm to the fetus 6