What is the approach to diagnosing and managing abdominal pain?

Approach to Abdominal Pain

Begin by determining the anatomic location of pain, as this directly guides your imaging choice and differential diagnosis, then rapidly assess for red flags requiring immediate intervention. 1, 2

Initial Clinical Assessment

Vital Signs and Red Flags

• Check vital signs immediately to identify hemodynamic instability (tachycardia, hypotension), fever, or tachypnea, which suggest bleeding, sepsis, or serious infection 1, 2
• Peritoneal signs (rigid abdomen, rebound tenderness) indicate perforation or ischemia and require urgent surgical evaluation 1, 2
• Pain out of proportion to physical findings strongly suggests mesenteric ischemia, a surgical emergency 1, 2
• Abdominal distension with vomiting indicates bowel obstruction 1, 2
• Fever with severe pain suggests infection, abscess, or perforation 1

Physical Examination Essentials

• Always examine hernia orifices and surgical scars to avoid missing incarcerated hernias 1
• Look for Murphy's sign (pain with right upper quadrant palpation during inspiration) suggesting cholecystitis 2
• Assess for signs of peritonitis, which may indicate intestinal ischemia or perforation 2

Mandatory Laboratory Testing

Obtain β-hCG testing in ALL women of reproductive age before any imaging to avoid missing ectopic pregnancy 1, 3, 2

Initial Laboratory Panel

• Complete blood count (CBC) to assess for leukocytosis indicating infection or inflammation 3, 2
• Comprehensive metabolic panel including liver function tests (ALT, AST, alkaline phosphatase, bilirubin) 3
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis 3
• Serum lipase (more specific than amylase) for suspected pancreatitis 3

Additional Tests Based on Suspicion

• Lactate and D-dimer if mesenteric ischemia is suspected 3, 2
• Blood cultures if sepsis is suspected 3

Imaging Strategy by Pain Location

Right Upper Quadrant Pain

Ultrasonography is the initial imaging study of choice for right upper quadrant pain, as acute cholecystitis is the primary diagnostic consideration 4, 3, 2

Right Lower Quadrant Pain

Computed tomography (CT) of abdomen and pelvis with contrast is recommended for evaluating right lower quadrant pain, particularly for suspected appendicitis 4, 3, 2

• Consider ultrasound first in young patients to minimize radiation exposure before proceeding to CT 4, 2
• Always consider ectopic pregnancy in women of reproductive age 1

Left Lower Quadrant Pain

CT of abdomen and pelvis with contrast is recommended, especially for suspected diverticulitis in older adults 4, 2

• Consider sigmoid volvulus, particularly with history of chronic constipation 1

Epigastric or Diffuse Pain

CT of abdomen and pelvis with contrast is the optimal choice, especially with fever or suspicion of serious illness 2

• Consider upper GI series if gastritis, peptic ulcer disease, or GERD is suspected 2
• Evaluate for pancreatitis with serum lipase 3

Pelvic Pain

CT of abdomen and pelvis with contrast is the most appropriate initial imaging 2

Differential Diagnosis Framework

By Location

• Right upper quadrant: cholecystitis, choledocholithiasis, cholangitis, hepatobiliary pathology 1
• Right lower quadrant: appendicitis (most critical to exclude), ectopic pregnancy 1
• Left lower quadrant: diverticulitis (leading consideration in older adults), sigmoid volvulus 1
• Epigastric/diffuse: peptic ulcer disease, gastritis, pancreatitis 1

By Mechanism

• Bowel obstruction: adhesions (55-75%), hernias (15-25%), colorectal cancer (60% of large bowel), volvulus (15-20% of large bowel) 1
• Inflammatory/infectious: appendicitis, cholecystitis, diverticulitis, pancreatitis, pelvic inflammatory disease 1
• Vascular: mesenteric ischemia (arterial or venous thrombosis) 1

Critical Pitfalls to Avoid

• Failing to obtain β-hCG in women of reproductive age delays diagnosis of ectopic pregnancy 1, 3
• Overlooking hernia orifices and surgical scars during examination misses incarcerated hernias 1
• Dismissing atypical presentations in elderly patients leads to missed diagnoses, as symptoms may be subtle even with serious pathology 1, 2
• Over-relying on normal laboratory values early in disease can lead to missed diagnoses 1
• Conventional radiography has limited diagnostic value and should not be routinely ordered 4, 3

Special Populations

Women of Reproductive Age

Always consider gynecologic conditions: ectopic pregnancy, ovarian torsion, pelvic inflammatory disease 2

Elderly Patients

Symptoms may be atypical and require more thorough evaluation even if laboratory tests are normal 2

Immunocompromised Patients

A more extensive workup may be necessary 3

Radiation Exposure Considerations

• Use ultrasonography as initial study for suspected appendicitis before CT to minimize radiation, especially in young patients 4, 2
• Consider low-dose CT rather than standard-dose CT when appropriate 4
• Avoid overuse of CT scans to minimize ionizing radiation exposure 2