What is the diagnostic approach for a patient presenting with fevers, low back pain, and hepatomegaly, including labs and imaging?

Diagnostic Approach for Fevers, Low Back Pain, and Hepatomegaly

For patients presenting with fevers, low back pain, and hepatomegaly, the diagnostic approach should focus on liver abscess as the primary consideration, with initial evaluation including comprehensive laboratory testing and abdominal ultrasound, followed by CT imaging if necessary.

Initial Laboratory Evaluation

• Complete blood count (CBC): Look for neutrophilic leukocytosis >10 × 10⁹/L, which is common in liver abscess 1
• Liver function tests: Pay particular attention to elevated alkaline phosphatase, which is characteristic of liver abscess 1
• Inflammatory markers: Check ESR and CRP, which are typically elevated in infectious processes 1
• Blood cultures: Collect at least two sets (ideally 60 mL total) from different anatomical sites without time intervals between collections 2
  • If central venous catheter is present, obtain simultaneous peripheral and catheter cultures to calculate differential time to positivity 2

Imaging Studies

First-Line Imaging

• Abdominal ultrasound: Initial imaging of choice for suspected liver abscess with sensitivity of 85.8% 1
  • Particularly indicated in patients with fever, hepatomegaly, and abnormal liver function tests 2, 1
  • Can detect acalculous cholecystitis, liver abscesses, perforated bowel, and ascites 2

Second-Line Imaging

• CT scan with contrast: Indicated when:

  • Ultrasound is negative but clinical suspicion remains high
  • Further characterization of abscess is needed
  • Triple-phase contrast CT is recommended for optimal characterization 1
  • Essential for patients who have recently undergone thoracic, abdominal, or pelvic surgery 2

• Chest radiograph: Should be performed in all patients with fever during workup 2

  • A raised right hemi-diaphragm may suggest amoebic liver abscess 1

Additional Imaging Based on Clinical Context

• MRI: Alternative to CT scan when:

  • Need to distinguish between abscess and other cystic lesions
  • Evaluating biliary tree involvement
  • Patient has contraindications to CT 1

• 18F-FDG PET/CT: Consider when other diagnostic tests have failed to establish etiology 2

Specific Diagnostic Considerations

Pyogenic Liver Abscess

• Most common presentation includes fever (67-98%), right upper quadrant pain (72-95%), and hepatomegaly (43-93%) 1
• Evaluate for potential sources:
  • Biliary source (37% of cases): Check for biliary obstruction, bilioenteric anastomosis, or biliary stents 1
  • Portal source (16% of cases): Evaluate for intra-abdominal infection (diverticulitis, appendicitis) 1

Amoebic Liver Abscess

• Consider in patients with relevant travel or exposure history
• Perform indirect hemagglutination (IHA) testing, which has >90% sensitivity 1
• Typically responds well to metronidazole regardless of abscess size 1

Echinococcal Disease (Hydatid Cyst)

• Consider in patients from endemic regions (Middle East, Eastern Europe, North/East Africa, Central Asia) 2
• Presentation may include hepatomegaly, right upper quadrant pain, and fever (particularly if cysts leak) 2
• Diagnosis through serology and compatible ultrasound/CT appearances 2

Other Considerations

• Hepatic tuberculosis: Consider in patients with minimal constitutional symptoms and focal hepatic lesion 3
• Hepatic glycogenosis: In diabetic patients with hepatomegaly and abnormal liver tests 4
• Systemic calcium pyrophosphate deposition disease: Can present with back pain and fever 5

Management Algorithm

1. Initial assessment:

   • Laboratory tests (CBC, liver function tests, inflammatory markers, blood cultures)
   • Abdominal ultrasound
   • Chest radiograph

2. If ultrasound is positive for liver abscess:

   • For small pyogenic abscesses (<3-5 cm): Antibiotics alone or with needle aspiration
   • For larger pyogenic abscesses (>4-5 cm): Percutaneous catheter drainage plus antibiotics
   • For amebic abscesses: Metronidazole regardless of size 1

3. If ultrasound is negative but suspicion remains high:

   • Proceed to CT scan with contrast
   • Consider MRI if CT is contraindicated

4. If diagnosis remains unclear after initial imaging:

   • Consider 18F-FDG PET/CT 2
   • Evaluate for less common causes based on epidemiology and risk factors

Pitfalls and Caveats

• Liver abscess may present with non-specific symptoms; maintain high suspicion when fever, hepatomegaly, and back pain coexist
• Acalculous cholecystitis is an important but uncommon cause of fever in critically ill patients and is frequently unrecognized 2
• In endemic areas, positive serology for amoebic liver abscess should be interpreted cautiously as it may represent previous exposure rather than active disease 1
• Avoid routine use of abdominal ultrasound in patients with fever without abdominal signs/symptoms or liver function abnormalities 2
• Mortality is higher for abscesses associated with malignancy 1