What is the initial diagnostic workup for an 18-year-old female presenting with nausea, abdominal pain, dizziness, and fatigue?

Initial Diagnostic Workup for 18-Year-Old Female with Nausea, Abdominal Pain, Dizziness, and Fatigue

The initial workup must immediately rule out pregnancy with a urine or serum β-hCG test, followed by basic laboratory studies (CBC, comprehensive metabolic panel including liver enzymes, lipase, lactate) and targeted imaging based on clinical findings—this age group requires specific attention to reproductive causes, metabolic derangements, and acute surgical conditions. 1

Immediate Priority: Pregnancy Testing

• Every woman of childbearing age presenting with these symptoms requires pregnancy testing as the first diagnostic step, as pregnancy (including ectopic pregnancy) is the most common endocrinologic cause of nausea and represents a life-threatening emergency if ectopic 1
• Ectopic pregnancy can present with abdominal pain, nausea, dizziness (from blood loss), and fatigue, making it a critical diagnosis that cannot be missed 2

Essential Laboratory Studies

First-Tier Blood Work

• Complete blood count (CBC) to evaluate for infection (elevated WBC), anemia (explaining fatigue and dizziness), or other hematologic abnormalities 3
• Comprehensive metabolic panel including electrolytes, renal function, glucose, and liver enzymes (AST, ALT, bilirubin, alkaline phosphatase) 4
• Lipase to evaluate for pancreatitis, which commonly presents with nausea, vomiting, and abdominal pain 1
• Lactate level if there are any concerning features for bowel ischemia or high-grade obstruction (severe pain, peritoneal signs, or hemodynamic instability) 3

Interpretation of Abnormal Liver Enzymes

• If AST and ALT are significantly elevated (particularly with AST:ALT ratio >2:1), this suggests potential severe liver injury requiring close monitoring and possible hospital admission 4
• The combination of abdominal pain, nausea, and elevated liver enzymes has been associated with higher risk conditions requiring inpatient evaluation 4

History-Specific Red Flags to Elicit

Surgical History and Timing

• Previous abdominal surgery has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction 3
• Last bowel movement and passage of flatus—absence suggests possible obstruction 3
• Timing and character of pain: intermittent crampy pain suggests obstruction, while constant severe pain suggests ischemia or perforation 3

Associated Symptoms

• Fever and elevated WBC raise suspicion for complications such as bowel ischemia, appendicitis, or other infectious/inflammatory processes 3
• Vomiting pattern: bilious versus feculent content (latter suggests distal obstruction) 3
• Dizziness character: orthostatic (suggesting volume depletion from vomiting) versus constant (suggesting anemia or other systemic cause) 1

Reproductive and Menstrual History

• Last menstrual period, sexual activity, contraception use, and possibility of pregnancy 2
• History of pelvic inflammatory disease, endometriosis, or ovarian pathology 3

Physical Examination Priorities

• Vital signs including orthostatic measurements to assess volume status and hemodynamic stability 3
• Abdominal examination for distension, peritoneal signs (guarding, rebound), bowel sounds (absent, high-pitched, or normal), and localized tenderness 3
• Signs of shock (cool, clammy skin, tachycardia, hypotension) suggest critical illness requiring immediate intervention 3
• Pelvic examination if pregnancy test is positive or pelvic pathology suspected 2

Imaging Strategy

CT Abdomen and Pelvis with IV Contrast

• CT is the primary imaging modality for acute abdominal pain with concerning features (peritoneal signs, severe pain, abnormal labs, or high clinical suspicion for surgical pathology) 3
• CT has >90% diagnostic accuracy for small bowel obstruction and can identify the cause, location, and presence of complications like ischemia 3
• No oral contrast is needed in suspected high-grade obstruction as nonopacified fluid provides adequate intrinsic contrast 3
• CT can detect bowel ischemia signs: abnormal bowel wall enhancement, wall thickening, mesenteric edema, ascites, pneumatosis, or mesenteric venous gas 3

When to Avoid Plain Radiography

• Plain abdominal radiographs have low sensitivity and accuracy for acute abdominal pain evaluation and should not be the primary imaging modality 5
• CT provides superior diagnostic information for decision-making and surgical planning 5

Ultrasound Considerations

• Pelvic ultrasound if pregnancy test is positive to evaluate for intrauterine versus ectopic pregnancy 2
• Right upper quadrant ultrasound if biliary pathology suspected (right upper quadrant pain, elevated alkaline phosphatase/bilirubin) 1

Additional Considerations in Young Females

Metabolic and Endocrine Causes

• Consider diabetic ketoacidosis if glucose is elevated (presents with nausea, abdominal pain, fatigue) 1
• Thyroid function tests if chronic symptoms or other signs of thyroid dysfunction 1
• Adrenal insufficiency can present with fatigue, dizziness, nausea, and abdominal pain 1

Functional Disorders

• If initial workup is unrevealing and symptoms are chronic (>3 months), consider functional gastrointestinal disorders, but only after excluding organic pathology 6
• Avoid extensive unnecessary testing in functional disorders once appropriate initial evaluation is complete 6

Criteria for Hospital Admission

• Significantly elevated liver enzymes with gastrointestinal symptoms warrant inpatient monitoring with serial liver function tests 4
• Signs of bowel ischemia, complete obstruction, or peritonitis require immediate surgical consultation 3
• Hemodynamic instability, severe pain unresponsive to analgesia, or inability to tolerate oral intake 3
• Suspected ectopic pregnancy with hemodynamic compromise 2

Common Pitfalls to Avoid

• Failing to obtain pregnancy test first in any woman of childbearing age—this is the single most critical initial test 1
• Ordering plain radiographs instead of CT when clinical suspicion for surgical pathology is moderate to high 5
• Delaying imaging in patients with peritoneal signs or laboratory abnormalities suggesting ischemia (elevated lactate, severe leukocytosis) 3
• Missing extra-abdominal causes: consider inferior myocardial infarction (can present with nausea, abdominal pain, diaphoresis) in patients with cardiac risk factors 3
• Attributing symptoms to functional disorders without first completing appropriate organic disease workup 6