What is the initial assessment and management plan for acute abdominal pain?

Initial Assessment and Management of Acute Abdominal Pain

The initial assessment of acute abdominal pain requires a detailed history, thorough physical examination, appropriate laboratory tests, and targeted imaging based on pain location, with CT abdomen and pelvis with IV contrast being the preferred initial imaging modality for adults with nonlocalized abdominal pain. 1, 2

Clinical Evaluation

History

• Pain characteristics:

  • Onset (sudden vs. gradual)
  • Location and radiation
  • Quality (sharp, dull, cramping)
  • Severity
  • Timing (constant vs. intermittent)
  • Aggravating/alleviating factors 2

• Associated symptoms:

  • Nausea/vomiting
  • Change in bowel habits
  • Fever
  • Urinary symptoms
  • Gynecological symptoms in women 2

Physical Examination

• Vital signs: Tachycardia is a significant warning sign, especially after bariatric surgery 1
• Abdominal examination:
  • Inspection for distension
  • Auscultation for bowel sounds
  • Palpation for tenderness, guarding, rigidity
  • Percussion for shifting dullness (ascites)
  • Rebound tenderness (peritoneal irritation)

Caution: Severe abdominal pain out of proportion to physical examination findings should be assumed to be acute mesenteric ischemia until proven otherwise 2

Red Flags Requiring Immediate Surgical Consultation

• Fever, hypotension, tachycardia, tachypnea with hypoxia
• Decreased urine output
• Signs of shock or multi-organ failure
• Rigid abdomen or peritoneal signs 1

Laboratory Tests

First-line Tests

• Complete blood count
• Comprehensive metabolic panel (electrolytes, renal and liver function)
• C-reactive protein (CRP) and/or procalcitonin
• Serum lactate levels
• Blood gas analysis
• Urinalysis
• Pregnancy test in women of childbearing age 1, 2

Note: High CRP levels are predictive of both early and late postoperative complications after bariatric surgery, but a normal CRP level alone does not rule out complications 1

Imaging Studies

Based on Patient Population:

Adults with Nonlocalized Abdominal Pain

• CT abdomen and pelvis with IV contrast is the first-line imaging modality 1, 2
  • High sensitivity (>95%) for appendicitis and diverticulitis
  • Can identify other potential causes of abdominal pain (e.g., colon cancer)
  • Oral contrast is often not necessary and may delay diagnosis 2

Children with Suspected Appendicitis

• Ultrasound as initial imaging modality
• If ultrasound is equivocal/indeterminate, proceed to either:
  • MRI (preferred to avoid radiation exposure)
  • CT (if MRI unavailable) 1

Pregnant Women

• Ultrasound as initial imaging modality (sensitivity 96.7%, specificity 85.7%)
• If ultrasound is equivocal, proceed to:
  • MRI without contrast (to avoid radiation exposure) 1, 2

Right Upper Quadrant Pain

• Ultrasound is the preferred initial imaging modality
  • High sensitivity for gallbladder pathology and hepatic lesions 2

Suspected Mesenteric Ischemia

• CT Angiography (CTA) should be performed without delay
  • Should include arterial and venous phases
  • No oral contrast (may be harmful)
  • Every 6-hour delay doubles mortality 2

Initial Management

1. Stabilization:

   • Correction of fluid and electrolyte abnormalities
   • Hemodynamic support if needed 2

2. Pain management:

   • Early administration of analgesia is recommended and does not impair diagnostic accuracy 3

3. Thromboprophylaxis:

   • Low molecular weight heparin for hospitalized patients 2

4. Antibiotics:

   • Only when infection is suspected or confirmed
   • Clinical improvement should be seen within 3-5 days 2

5. Surgical consultation:

   • Early involvement of surgical team when surgical abdomen is suspected
   • Mandatory surgical exploration without delay in patients with signs of shock and multi-organ failure 1

Special Considerations

Post-Bariatric Surgery Patients

• Tachycardia is the most sensitive sign of surgical complications
• Classic signs of peritoneal irritation may be absent due to body habitus
• Combination of fever, tachycardia, and tachypnea is a significant predictor of anastomotic or staple line leak 1

Elderly Patients

• May present with atypical symptoms
• Higher risk for serious conditions like bowel obstruction, diverticulitis, and mesenteric ischemia 4

Women of Reproductive Age

• Consider gynecological causes:
  • Ectopic pregnancy
  • Pelvic inflammatory disease
  • Adnexal torsion 4

By following this systematic approach to acute abdominal pain, clinicians can efficiently narrow the differential diagnosis and determine the appropriate management plan, ultimately improving patient outcomes.