What is the appropriate diagnostic and management approach for a patient presenting with abdominal pain, considering their demographic and medical history?

Differential Diagnosis and Diagnostic Approach for Abdominal Pain

Initial Triage and Critical Assessment

Begin by immediately assessing hemodynamic stability and identifying life-threatening conditions before pursuing an extensive differential diagnosis. 1

• Hypotension, severe pain out of proportion to exam findings, or signs of peritonitis require immediate surgical consultation rather than extended diagnostic workup. 1
• Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop. 1
• The combination of fever, tachycardia, and tachypnea predicts serious complications including anastomotic leak, perforation, or sepsis. 1

Differential Diagnosis by Pain Location

Pain location is the most valuable starting point for narrowing your differential diagnosis. 2, 1

Right Upper Quadrant Pain

• Primary consideration: Acute cholecystitis 2
• Other considerations: Hepatobiliary disease, complicated pancreatic processes, pneumonia 2

Right Lower Quadrant Pain

• Primary consideration: Appendicitis 2
• Other considerations: Ovarian torsion, ectopic pregnancy (in women of reproductive age), inflammatory bowel disease 2

Left Lower Quadrant Pain

• Primary consideration: Diverticulitis 2
• Other considerations: Inflammatory bowel disease, colitis 3

Diffuse/Nonlocalized Pain

The differential is broader and includes: 2

• Pneumonia
• Gastrointestinal perforation or inflammation
• Bowel obstruction or infarction
• Abscesses anywhere in the abdomen
• Mesenteric ischemia
• Tumor
• Small bowel obstruction
• Pancreatitis

Key Historical Features to Elicit

Specific pain characteristics and associated symptoms significantly narrow the differential: 1

• Ripping, tearing, stabbing, or sharp quality pain suggests aortic dissection 1
• Colicky pain indicates bowel obstruction as the bowel attempts to overcome occlusion 1
• The triad of abdominal pain, constipation, and vomiting suggests sigmoid volvulus 1
• Asking about the last bowel movement and passage of gas has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction in patients with prior abdominal surgery 1
• Vomiting occurs earlier and more prominently in small bowel obstruction versus large bowel obstruction 1
• Approximately 25% of acute mesenteric ischemia patients have occult blood in stool 1

Physical Examination Findings

The jumping test (heel-drop test) detects peritoneal irritation without direct palpation: 4

• Have the patient stand on tiptoes and then drop suddenly onto their heels 4
• A positive jumping test suggests peritoneal irritation requiring urgent evaluation, often with CT imaging for nonlocalized pain 4
• A negative test does not exclude serious pathology—avoid relying solely on this test to exclude conditions like bowel ischemia, particularly in elderly patients or those with chronic distension 4

Mandatory Laboratory Testing

β-hCG testing is mandatory in all women of reproductive age before proceeding with any imaging to rule out ectopic pregnancy. 2, 1, 5

Additional essential laboratory tests include: 1, 5

• Complete blood count (CBC) to assess for leukocytosis indicating infection or inflammation
• Comprehensive metabolic panel (CMP) including liver function tests to evaluate hepatobiliary pathology and organ function
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis
• Serum lipase (more specific than amylase for diagnosing pancreatitis)

For suspected mesenteric ischemia, consider lactate and D-dimer 5

Imaging Strategy Based on Pain Location

The American College of Radiology Appropriateness Criteria provide evidence-based imaging recommendations: 2

Right Upper Quadrant Pain

• Ultrasonography is the initial imaging study of choice (rating 9/9) 2
• Consider cholescintigraphy or CT if ultrasonography is equivocal 2

Right Lower Quadrant Pain (Suspected Appendicitis)

• CT of abdomen and pelvis with contrast media is the initial imaging study of choice (rating 8/9) 2
• Ultrasonography with graded compression may be appropriate (rating 6/9), particularly in children to avoid radiation 2

Left Lower Quadrant Pain (Suspected Diverticulitis)

• CT of abdomen and pelvis with contrast media is recommended 2
• Patients with typical symptoms and no suspected complications may not require imaging 2

Diffuse/Nonlocalized Abdominal Pain

• CT of abdomen and pelvis with IV contrast is the preferred initial imaging study, as it changes the leading diagnosis in 51% of patients and alters admission decisions in 25% of cases 2, 1

Common Diagnoses and Their Imaging Recommendations

The most common causes of abdominal pain beyond appendicitis include: acute cholecystitis, small-bowel obstruction, pancreatitis, renal colic, perforated peptic ulcer, cancer, and diverticulitis 2

Specific imaging recommendations: 2

• Acute pancreatitis: Ultrasonography of abdomen; consider CT if ultrasonography is nondiagnostic or patient is critically ill
• Cholecystitis: Ultrasonography of abdomen
• Appendicitis: CT of abdomen and pelvis with contrast media
• Diverticulitis: CT of abdomen and pelvis with contrast media
• Small bowel obstruction: CT of abdomen and pelvis with contrast media; conventional radiography may be appropriate for initial evaluation
• Mesenteric ischemia: CT angiography of abdomen with contrast media
• Nephrolithiasis: CT of abdomen and pelvis without contrast media

Special Population Considerations

Women of Reproductive Age

• Always consider gynecologic conditions including ectopic pregnancy, ovarian torsion, or pelvic inflammatory disease 2, 1
• Transvaginal and transabdominal ultrasonography is recommended for suspected ectopic pregnancy or ovarian torsion 2

Elderly Patients

• Elderly patients may have atypical symptoms and require more thorough evaluation, even if laboratory tests are normal 2, 1
• Many laboratory tests are nonspecific and may be normal despite serious infection 2

Immunocompromised Patients

• Should be considered for intra-abdominal infection if they present with evidence of infection from an undetermined source 1
• Typical signs of abdominal sepsis may be masked, diagnosis may be delayed, and mortality rate is high 2

Post-Bariatric Surgery Patients

• Often present with atypical symptoms 1
• Tachycardia is the most critical warning sign 1

Critical Pitfalls to Avoid

• Never proceed with CT imaging in reproductive-age women without pregnancy testing, as this leads to delayed diagnosis of ectopic pregnancy and unnecessary fetal radiation exposure 2, 1, 5
• Do not order conventional radiography routinely, as it has limited diagnostic value and rarely changes management 2, 1
• Do not assume normal initial labs exclude serious pathology in patients with high clinical suspicion—proceed to appropriate imaging 1
• Do not delay imaging in clinically deteriorating patients while pursuing additional non-diagnostic tests 1
• Avoid overuse of CT scans to minimize ionizing radiation exposure, especially in young patients 2

When to Initiate Treatment

For patients with septic shock, antibiotics should be administered as soon as possible. 1

• For patients without septic shock, antimicrobial therapy should be started in the emergency department once intra-abdominal infection is diagnosed or considered likely 1
• Satisfactory antimicrobial drug levels should be maintained during a source control intervention 1
• Begin rapid intravascular volume resuscitation immediately when hypotension is identified 1