What is the best imaging modality for diagnosing a suspected biloma in an adult patient with a history of liver disease or recent abdominal surgery, and how should a triphasic CT (Computed Tomography) scan be utilized in this case?

Triphasic CT Scan for Biloma Detection

Abdominal triphasic CT is the recommended first-line diagnostic imaging investigation to detect intra-abdominal fluid collections including bilomas and ductal dilation in patients with suspected bile duct injury or biliary complications. 1

What is a Triphasic CT Scan?

A triphasic CT scan is a multiphase contrast-enhanced CT protocol that acquires images during three distinct phases of contrast enhancement:

• Arterial phase: Images obtained during peak arterial enhancement, typically 25-35 seconds after contrast injection 2
• Portal venous phase: Images obtained during peak portal venous enhancement, typically 60-70 seconds after contrast injection 2
• Delayed phase: Images obtained after equilibration of contrast, typically 3-5 minutes after injection 3

Technical specifications for optimal biloma detection include:

• Slice thickness of 2.5-5 mm for adequate lesion detection 2, 3
• Proper contrast bolus timing is critical for effective imaging 2
• IV contrast administration is essential; unenhanced images add no diagnostic value for biliary complications 2

Clinical Context for Triphasic CT in Biloma Diagnosis

Triphasic CT achieves 95.5% diagnostic accuracy compared to standard single-phase IV contrast CT, which has only 74-95% accuracy. 2

Key clinical scenarios where triphasic CT is indicated for suspected biloma:

• Post-cholecystectomy complications: Patients not rapidly recovering after laparoscopic cholecystectomy with alarm symptoms including fever, abdominal pain, distention, jaundice, nausea and vomiting 1
• Bile duct injury (BDI): Detection of intra-abdominal fluid collections and ductal dilation in suspected BDI 1
• Post-abdominal trauma: Evaluation of biliary tract injury and associated biloma following blunt or penetrating abdominal trauma 4, 5
• Complications of acute cholecystitis: When biloma, intraabdominal abscess, bile duct injury, hepatic injury, or retained stones are suspected 1

Diagnostic Capabilities and Limitations

What triphasic CT can detect:

• Intra-abdominal and intrahepatic fluid collections (bilomas appear as hypodense collections) 1, 4, 5
• Biliary ductal dilation 1
• Complications including abscess formation, hepatic injury, and small bowel injury 1
• Location and extent of fluid collections with intraparenchymal and subcapsular extension 4

Critical limitation: Triphasic CT cannot definitively demonstrate the exact location of bile duct injury or the site of bile leak. 4, 5

When to Complement Triphasic CT with Additional Imaging

If triphasic CT detects a fluid collection but cannot localize the bile leak source, proceed with:

• Contrast-enhanced MRCP (CE-MRCP): Provides exact visualization, localization and classification of bile duct injury, essential for planning tailored treatment 1
• ERCP (Endoscopic Retrograde Cholangiopancreatography): Both diagnostic and therapeutic, can demonstrate the exact location and extent of bile leak and allow endobiliary stent placement 4, 6, 5
• Hepatobiliary scintigraphy (HIDA scan): Can confirm extrahepatic biliary leakage into the peritoneum when other imaging is equivocal 6

Timing of Imaging

For suspected bile duct injury with negative or non-specific initial CT findings:

• Repeat CT scan within 12-24 hours from initial injury should be considered in hemodynamically stable patients with high clinical suspicion, elevated amylase/lipase, or persistent abdominal pain 1
• Serial clinical examination is an important part of follow-up after biliary trauma 1

Common Pitfalls to Avoid

Do not order CT without contrast alone - it has minimal diagnostic value for biloma characterization and will miss the majority of biliary complications 2

Do not order CT with and without contrast - the unenhanced phase adds no diagnostic value for biliary complications and doubles radiation exposure 2

Do not rely on single-phase contrast CT - if using CT for biloma evaluation, always obtain multiphase (triphasic) imaging for optimal diagnostic accuracy 2

Do not assume CT alone is sufficient - while triphasic CT detects fluid collections, it often fails to demonstrate the exact bile leak location, requiring complementary CE-MRCP or ERCP for definitive diagnosis and treatment planning 1, 4