What is the appropriate initial management for a patient with abdominal pain and a fever of 100.2 °F (38 °C)?

Initial Management of Abdominal Pain with Low-Grade Fever

Obtain CT abdomen and pelvis with IV contrast immediately as your first-line diagnostic test, start broad-spectrum antibiotics if intra-abdominal infection is suspected, and provide pain control without delay. 1, 2

Immediate Assessment and Risk Stratification

Check hemodynamic stability first – assess for hypotension, tachycardia, or signs of peritonitis (rigid abdomen, severe tenderness), as these require immediate surgical consultation rather than extended workup. 2 Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop. 2

Mandatory Initial Testing

• Pregnancy test (β-hCG) is mandatory in all women of reproductive age before any imaging to rule out ectopic pregnancy – never proceed with CT without this test. 2
• Complete blood count (CBC) to assess for leukocytosis indicating infection or inflammation. 1, 2
• C-reactive protein (CRP) has superior sensitivity and specificity compared to white blood cell count for identifying surgical disease. 1
• Comprehensive metabolic panel including liver function tests to evaluate organ function and hepatobiliary pathology. 2

Imaging Strategy

CT abdomen and pelvis with IV contrast is the gold standard initial imaging study for nonlocalized abdominal pain with fever. 1, 2 This approach is strongly supported by the American College of Radiology guidelines and changes the leading diagnosis in 49-51% of cases, alters admission decisions in 24-25%, and modifies surgical plans in 25% of patients. 1, 2

Why CT with Contrast is Superior

• Doubles the detection rate of cholecystitis/cholangitis compared to non-contrast imaging. 1, 2
• Increases identification of pelvic inflammatory disease by 280% after imaging is performed. 1, 2
• Detects pseudomembranous colitis in 88% of cases, supporting diagnosis of C. difficile infection. 2
• Enables CT-guided percutaneous drainage of intra-abdominal abscesses when identified. 2

Alternative Imaging Considerations

• Upright chest X-ray should be obtained first if you suspect perforated viscus (rigid abdomen, severe peritonitis) – it detects pneumoperitoneum in 75-80% of cases within minutes and immediately directs management toward surgery. 3
• Ultrasonography is preferred only for right upper quadrant pain specifically suggesting hepatobiliary disease. 2
• Rapid MRI protocols achieve 99% accuracy for renal abscesses and 86% sensitivity/100% specificity for ovarian torsion when these specific conditions are suspected. 2

Antibiotic Therapy

Initiate broad-spectrum antibiotics immediately once intra-abdominal infection is diagnosed or considered likely. 2 Do not delay antibiotics while awaiting imaging results if clinical suspicion is high.

Timing Guidelines

• For septic shock: administer antibiotics as soon as possible, ideally within the first hour of recognition. 2
• For patients without septic shock: start antimicrobial therapy in the emergency department before definitive source control. 2
• Maintain satisfactory drug levels during any source control intervention (surgery or drainage). 2

Pain Management

Provide immediate pain relief without withholding medication while awaiting diagnosis – pain control facilitates better physical examination without affecting diagnostic accuracy. 1

• Oral NSAIDs (ibuprofen) for mild-to-moderate pain if no contraindications exist. 1
• Intravenous opioid analgesics titrated to effect for severe pain. 1

Most Likely Diagnoses to Consider

Based on the presentation of abdominal pain with fever of 100.2°F (38°C), prioritize these conditions:

High-Priority Surgical Emergencies

• Appendicitis (including perforated appendicitis with abscess) – most common surgical emergency, with atypical presentations possible. 1
• Intra-abdominal abscess – presents with fever, diffuse or localized pain, and possible back pain from retroperitoneal extension. 1
• Perforated viscus – if rigid abdomen and severe peritonitis are present, obtain upright chest X-ray first to detect pneumoperitoneum. 3
• Diverticulitis – especially in older adults with left lower quadrant pain. 2

Other Important Considerations

• Cholecystitis/cholangitis – right upper quadrant pain suggests hepatobiliary disease. 2
• Small bowel obstruction – accounts for 4-5% of acute abdominal pain cases; ask about last bowel movement and passage of gas (85% sensitivity, 78% specificity if prior abdominal surgery). 2
• Pelvic inflammatory disease – in women of reproductive age. 2
• Inflammatory bowel disease complications – Crohn's disease with abscess or perforation. 1

Critical Pitfalls to Avoid

• Never proceed with CT in reproductive-age women without pregnancy testing – this leads to delayed diagnosis of ectopic pregnancy and unnecessary fetal radiation exposure. 2
• Do not assume normal initial labs exclude serious pathology – proceed to appropriate imaging if clinical suspicion remains high. 2
• Do not delay imaging in clinically deteriorating patients while pursuing additional non-diagnostic tests. 2
• Do not skip upright chest X-ray if perforated viscus is suspected – going straight to CT wastes time when free air can be detected in minutes. 3
• Recognize that elderly patients may have atypical symptoms and require more thorough evaluation even if laboratory tests are normal; 15% of elderly patients with bacteremia are afebrile. 2

Disposition and Follow-Up

• Instruct patient to return immediately if severe or progressive pain develops, fever persists beyond 48-72 hours of treatment, or new symptoms appear. 1
• Monitor for persistent fever, leukocytosis, or failure of symptoms to improve – these indicate high risk of ongoing intra-abdominal infection requiring additional intervention. 1
• Close clinical and radiological surveillance at 12-24 hour intervals is crucial if non-operative management is attempted for uncomplicated conditions. 4