What is the recommended approach to assess and manage acute abdominal pain, including initial evaluation for emergent intra‑abdominal pathology and stepwise analgesic therapy?

Management of Acute Abdominal Pain

Initial Stabilization and Risk Stratification

Immediately assess hemodynamic stability by checking for hypotension, tachycardia, oliguria, altered mental status, and signs of shock—these findings mandate urgent surgical consultation and aggressive investigation for life-threatening pathology. 1, 2

• Obtain intravenous access and begin fluid resuscitation when the patient is hypotensive or tachycardic 2
• Assess mental status promptly, as obtunded patients have unreliable abdominal examinations 2
• In suspected septic shock from an intra-abdominal source, start resuscitation and empiric broad-spectrum antibiotics immediately without waiting for imaging 1, 2

Focused History: Red Flags for Emergent Pathology

Pain disproportionate to physical findings is the classic presentation of mesenteric ischemia and requires immediate CT angiography. 2

Critical red flags requiring emergent evaluation: 2

• Sudden onset pain suggests perforation, embolic event, or aortic dissection
• Syncope with abdominal pain indicates ruptured AAA or ectopic pregnancy
• Back radiation raises suspicion for AAA or pancreatitis
• Hematemesis, melena, or hematochezia denote significant GI bleeding
• Fever combined with peritoneal signs points to perforated viscus or advanced infection
• Atrial fibrillation is present in ~50% of mesenteric embolism cases

Physical Examination Priorities

A rigid, board-like abdomen with guarding indicates peritonitis from perforation and requires immediate surgical consultation. 2

Systematic examination approach: 1, 2

• General appearance: Writhing movements suggest colic; a still, rigid abdomen suggests peritonitis
• Auscultation (before palpation): Absent bowel sounds indicate ileus/peritonitis; high-pitched sounds indicate obstruction
• Percussion: Loss of liver dullness suggests perforation; tympany indicates obstruction
• Palpation: Begin away from painful area, assess for guarding, rebound tenderness, rigidity, masses, and hernias
• Special signs: Positive psoas sign increases likelihood of appendicitis 1; Murphy's sign indicates cholecystitis 2

Critical pitfall: Elderly, immunosuppressed, or obtunded patients may exhibit minimal abdominal findings despite life-threatening pathology. 1, 2

Immediate Bedside and Laboratory Testing

Obtain serum lactate immediately—elevated levels indicate mesenteric ischemia, sepsis, or shock and require urgent intervention. 2

Essential immediate tests: 2

• Point-of-care ultrasound for free intraperitoneal fluid, AAA, or ectopic pregnancy
• Electrocardiogram to rule out inferior MI presenting as epigastric pain
• Complete blood count (leukocytosis suggests infection; anemia indicates bleeding)
• Serum lactate and blood gas analysis
• Pregnancy test mandatory for all women of childbearing potential
• Liver function tests and serum lipase for hepatobiliary disease and pancreatitis
• Type and screen when major bleeding or operative intervention anticipated

Imaging Strategy

CT abdomen/pelvis with IV contrast is the gold standard with >95% sensitivity for perforation, ischemia, and abscesses—obtain immediately (<30 minutes) for hemodynamic instability, suspected AAA, or mesenteric ischemia. 1, 2, 3

Imaging algorithm: 1, 4, 2

• Omit imaging when diffuse peritonitis is obvious and immediate laparotomy is indicated
• Focused ultrasound first-line for suspected cholecystitis, AAA, ectopic pregnancy, or pediatric appendicitis
• CT with IV contrast for all other acute presentations requiring definitive diagnosis
• Staged approach: If ultrasound is inconclusive for appendicitis or diverticulitis, proceed to CT 1, 4
• MRI preferred for pregnant patients with inconclusive ultrasound (94% sensitivity, 96% specificity for appendicitis) 1, 4
• Timing: Urgent imaging (1-2 hours) for sepsis, severe pain, or high suspicion of surgically correctable pathology 2

CT performance: Likelihood ratio+ of 45 and likelihood ratio- of 0.09 for solid organ injuries (sensitivity 98%, specificity 98%); lower for hollow organ lesions (sensitivity 85%, specificity 96%). 1

Antibiotic Initiation

Administer empiric broad-spectrum antibiotics before imaging when septic shock from a presumed intra-abdominal source is identified. 2

Antibiotic principles: 1, 2

• Start antibiotics after confirming or strongly suspecting complicated intra-abdominal infection
• Select agents according to local epidemiology and resistance patterns
• Ensure therapeutic drug levels before any definitive source-control procedure
• Duration depends on clinical response and CRP levels 1
• Reserve antifungals for high-risk patients (bowel perforation, recent steroid treatment) 1

Do not routinely administer antibiotics in inflammatory bowel disease patients—only give for superinfection, intra-abdominal abscesses, or sepsis. 1

Surgical Consultation Triggers

Immediate surgical team activation is required for peritonitis with hemodynamic instability, free intraperitoneal air, or mesenteric ischemia—mortality rises hourly without rapid intervention. 2

Specific indications for urgent/emergent surgery: 1, 2

• Peritonitis with hemodynamic instability
• Free intraperitoneal air on imaging
• Mesenteric ischemia (arterial, venous, or non-occlusive)
• Ruptured AAA
• Strangulated hernia or bowel obstruction with ischemia
• Life-threatening hemorrhage
• Any complicated intra-abdominal infection requiring source control

Stepwise Analgesic Therapy

Early analgesia does not obscure diagnosis and should be provided promptly to improve patient comfort and cooperation with examination. 5, 6

Analgesic approach:

• Initiate analgesia early in evaluation—does not interfere with diagnostic accuracy 5, 6
• Titrate opioids or NSAIDs based on pain severity and hemodynamic stability
• Reassess pain response and physical findings after analgesia administration

High-Risk Patient Factors

Elderly patients with accumulated risk factors (advanced age, high disease severity, sepsis/septic shock) have very high mortality risk—actively discuss palliative care when operative treatment appears futile. 1

Risk stratification considerations: 1

• Advanced age, immunosuppression, malignant disease, and pre-existing comorbidities increase failure risk
• High-risk scores (ASA, APACHE, SOFA) predict poor outcomes
• Delay in intervention >24 hours significantly worsens prognosis
• Healthcare-associated IAI carries higher risk than community-acquired

Common Pitfalls to Avoid

Never assume a normal abdominal exam excludes serious disease in elderly or immunosuppressed patients—these populations require a lower threshold for advanced imaging. 2, 3

Critical errors: 2

• Delaying antibiotics in septic patients to obtain cultures first worsens outcomes
• Missing mesenteric ischemia by focusing only on more common conditions
• Attributing all symptoms to known chronic illnesses without ruling out acute pathology
• Relying exclusively on CT for hollow organ injuries (sensitivity only 85%) 1