What is the initial workup for a patient presenting with abdominal pain?

Initial Workup for Abdominal Pain

The initial workup for a patient presenting with abdominal pain should include a focused history, physical examination, laboratory testing, and appropriate imaging based on pain location, with contrast-enhanced CT being the most reliable diagnostic tool for nonlocalized abdominal pain when serious pathology is suspected. 1

History and Physical Examination Elements

Key History Components:

• Pain characteristics: onset, duration, location, radiation, quality, severity
• Aggravating/alleviating factors
• Associated symptoms: fever, nausea, vomiting, diarrhea, constipation
• Medical history: previous surgeries, chronic conditions
• Medication use: NSAIDs, antibiotics, immunosuppressants
• For women: last menstrual period, vaginal discharge/bleeding

Physical Examination Focus:

• Vital signs (especially fever and hypotension)
• Abdominal inspection for distension, visible peristalsis
• Auscultation for bowel sounds and bruits
• Percussion for tympany or dullness
• Palpation for tenderness, guarding, rebound, masses
• Rectal examination for masses, tenderness, blood
• Pelvic examination in women of reproductive age

Laboratory Testing

First-line Tests:

• Complete blood count (CBC) with differential
• Basic metabolic panel
• Liver function tests
• Urinalysis
• Pregnancy test for women of reproductive age (before imaging) 1
• C-reactive protein (CRP) - elevated levels significantly predict hospital admission 2

Additional Tests Based on Clinical Suspicion:

• Amylase/lipase for suspected pancreatitis
• Lactate for suspected mesenteric ischemia 1
• Blood cultures if sepsis suspected
• Stool studies if infectious etiology suspected

Imaging Studies Based on Pain Location

Right Upper Quadrant Pain:

• Ultrasonography is the initial imaging test of choice 1
• Consider cholescintigraphy if ultrasound is equivocal
• CT with contrast if ultrasound is inconclusive or complications suspected

Right or Left Lower Quadrant Pain:

• CT of abdomen and pelvis with contrast media is recommended 1
• Consider ultrasonography first in young patients or pregnant women to reduce radiation exposure

Nonlocalized Abdominal Pain:

• CT with IV contrast is typically the imaging modality of choice if serious pathology is suspected 1
• Plain radiography has limited diagnostic value for most abdominal pain but may be helpful for suspected bowel obstruction or perforation 1

Special Considerations

Immunocompromised Patients:

• Clinical signs may be less reliable; fever, leukocytosis, and peritonitis may be mild or absent 1
• Contrast-enhanced CT scan is the most reliable examination to diagnose intraabdominal disease in immunocompromised patients 1
• Test for Clostridioides difficile and its toxin if diarrhea is present 1

Suspected Mesenteric Ischemia:

• CT angiography of abdomen with contrast media is recommended 1
• Elevated lactate and metabolic acidosis are important laboratory findings

Radiation Exposure Concerns:

• Consider ultrasonography as initial imaging for young patients
• Low-dose CT protocols can reduce radiation exposure
• MRI is an emerging technique that avoids ionizing radiation 1

Common Pitfalls to Avoid

• Relying solely on laboratory tests, which may be normal despite serious pathology, especially in elderly patients 1
• Dismissing pain that seems out of proportion to physical findings, which may indicate mesenteric ischemia 1
• Failing to consider gynecological causes in women of reproductive age
• Not performing pregnancy testing before imaging studies in women of childbearing age 1
• Overlooking atypical presentations in elderly or immunocompromised patients 1

By following this systematic approach to the evaluation of abdominal pain, clinicians can efficiently narrow the differential diagnosis and determine appropriate management strategies to reduce morbidity and mortality.