What is the appropriate management for a man presenting to the emergency room with vomiting, abdominal pain, and fever?

Management of Acute Abdominal Pain with Vomiting and Fever

Obtain CT abdomen and pelvis with IV contrast as the primary diagnostic imaging study, perform comprehensive laboratory workup including CBC, metabolic panel, and lactate, and initiate empiric broad-spectrum antibiotics if sepsis is suspected while simultaneously assessing for surgical emergencies. 1

Immediate Clinical Assessment

Rapidly evaluate for signs of sepsis and organ failure:

• Check vital signs for hypotension, tachycardia, tachypnea, and fever 1
• Assess for hypoperfusion signs: oliguria, altered mental status, and lactic acidosis 1
• Perform focused abdominal examination for peritoneal signs (rigidity, rebound tenderness, guarding) and absent bowel sounds 1, 2

Critical red flags requiring immediate surgical consultation:

• Peritoneal signs suggesting perforation or ischemia 1, 2
• Hypotension with signs of septic shock 1
• Absent bowel sounds with severe distension 2

Essential Laboratory Studies

Order the following tests immediately:

• Complete blood count to evaluate for leukocytosis, anemia, or thrombocytopenia 2
• Comprehensive metabolic panel including electrolytes, renal function, glucose, and liver enzymes 2
• Lactate level (elevated lactate suggests bowel ischemia or sepsis) 2
• Lipase and amylase if upper abdominal pain predominates 3
• Urinalysis and urine pregnancy test (if applicable) 3

Significantly elevated liver enzymes (AST:ALT ratio >2:1) with gastrointestinal symptoms warrant hospital admission for serial monitoring. 4

Imaging Strategy

CT abdomen and pelvis with IV contrast is the definitive initial imaging study:

• CT changes the leading diagnosis in 49% of cases and alters management in 24-25% of patients 1
• Provides rapid evaluation of the broad differential including appendicitis, diverticulitis, cholecystitis, pancreatitis, bowel obstruction, perforation, and abscesses 1
• Single postcontrast phase is sufficient; oral contrast is not routinely necessary and causes delays 1

Plain abdominal radiographs have limited utility:

• Low sensitivity for detecting sources of abdominal pain and fever 1
• Only useful for detecting free air (perforation) or high-grade bowel obstruction 1

Ultrasound has a limited role unless:

• Right upper quadrant pain suggests biliary pathology (perform formal ultrasound, not just POCUS) 1
• Recent abdominal surgery or abnormal liver function tests are present 1

Differential Diagnosis Priorities

Most common causes in order of frequency:

• Appendicitis (most common single diagnosis) 1
• Acute cholecystitis (especially if right upper quadrant pain) 1, 5
• Small bowel obstruction 1
• Pancreatitis 1
• Diverticulitis 1
• Perforated peptic ulcer 1
• Intra-abdominal abscess 1

Life-threatening diagnoses requiring immediate intervention:

• Bowel ischemia or infarction 1, 2
• Perforated viscus 1
• Emphysematous cholecystitis (mortality 15% vs 4% for non-emphysematous) 5

Antibiotic Therapy

Initiate empiric broad-spectrum antibiotics immediately if:

• Signs of sepsis or septic shock are present 1, 5
• Peritoneal signs suggest intra-abdominal infection 1
• CT demonstrates complicated intra-abdominal infection 1

Appropriate empiric regimen:

• Combination therapy covering gram-negative, gram-positive, and anaerobic organisms 5
• Example: Piperacillin-tazobactam or carbapenem as monotherapy, or ceftriaxone plus metronidazole 5

Risk Stratification for Outcomes

High-risk patients requiring intensive monitoring:

• Advanced age with multiple comorbidities 1
• Presenting in sepsis or septic shock 1
• Immunocompromised status 1
• Significantly elevated lactate or signs of organ dysfunction 1

These patients have very high mortality risk and may require ICU admission; palliative care should be discussed if operative treatment appears futile. 1

Hospital Admission Criteria

Admit to hospital if any of the following:

• Peritoneal signs or suspected surgical emergency 1, 2
• Signs of sepsis or hemodynamic instability 1
• Significantly elevated liver enzymes (AST >250-300) with gastrointestinal symptoms 4
• Inability to tolerate oral intake with dehydration 3
• CT findings requiring intervention or close monitoring 1

Serial monitoring in admitted patients should include:

• Repeat vital signs every 4 hours 1
• Serial liver function tests if initially elevated 4
• Repeat lactate if initially elevated 1
• Surgical re-evaluation if clinical deterioration occurs 1

Common Pitfalls to Avoid

• Do not delay CT imaging for plain radiographs - radiographs have poor sensitivity and delay definitive diagnosis 1
• Do not wait for oral contrast - it delays diagnosis without clear benefit in nonlocalized pain 1
• Do not dismiss elderly patients with normal labs - laboratory tests may be nonspecific despite serious infection in this population 1
• Do not attribute all symptoms to gastroenteritis - one-third of ED patients with abdominal pain have serious pathology requiring intervention 1