How can I determine the future liver remnant (FLR) volume using contrast‑enhanced portal‑phase computed tomography (CT) volumetry and what percentage thresholds are required for safe hepatic resection in patients with normal versus diseased livers?

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Determining Future Liver Remnant Volume by CT Volumetry

Use contrast-enhanced portal-phase CT with dedicated volumetry software to calculate the future liver remnant (FLR) as a percentage of total liver volume minus tumor volume, requiring minimum thresholds of ≥20% for normal livers, ≥30-40% for chronic liver disease with Child-Pugh A cirrhosis, and up to 40% for severe steatosis or cholestasis. 1

Technical Approach to CT Volumetry

Obtain a contrast-enhanced portal-phase CT scan as the foundation for volumetric analysis, which provides optimal liver parenchymal enhancement and clear delineation of hepatic structures 1. The portal venous phase is critical because it maximizes the contrast between liver parenchyma and lesions while clearly defining vascular anatomy.

Calculation Method

  • Manually outline the liver parenchyma on each CT slice using dedicated volumetry software, excluding major vessels, tumor volumes, and the gallbladder 2, 3
  • Calculate total liver volume (TLV) by multiplying the outlined area on each slice by slice thickness and summing across all slices 2
  • Subtract all tumor volumes from the total liver volume to determine the functional liver volume 1
  • Outline the planned resection specimen based on the intended transection line to calculate resection volume 2, 3
  • Calculate FLR volume by subtracting the planned resection volume from the functional total liver volume 1
  • Express FLR as a percentage: FLR/TLV ratio = (FLR volume / functional total liver volume) × 100 1

Software Options

The 2025 EASL guidelines identify CT volumetry as a reliable predictor of post-hepatectomy remnant liver volume that is easily available 1. Multiple software platforms can be used:

  • Scanner-linked commercial software (e.g., Aquarius iNtuition) provides accurate measurements but requires radiologist support 2
  • Free open-source software (ImageJ, OsiriX) allows surgeons to perform volumetry independently with excellent accuracy (r² = 0.98 correlation with actual resection weights) 2, 3
  • 3D reconstruction software provides better correlation of future liver volume than conventional volumetry and is particularly useful for planning complex resections 1

Minimum Safe FLR Thresholds

Normal Liver Parenchyma

Require FLR ≥20% of total liver volume for patients with healthy, non-cirrhotic livers 1. This threshold is supported by multiple studies showing:

  • PHLF incidence of only 30% when FLR ≥20% versus 50% when FLR <20% in extended right hepatectomy 1
  • Significant increase in PHLF (34%) and death (11%) when FLR ≤20% compared to FLR 20-30% (10% PHLF, 3% death) 1

Chronic Liver Disease

Require FLR ≥30-40% for patients with chronic liver disease and Child-Pugh A cirrhosis 1. The specific threshold depends on disease severity:

  • 30-35% FLR for mild steatosis, cholestasis, and early Child-Pugh A cirrhosis 1
  • 40% FLR for severe steatosis and cholestasis 1
  • Consider resection of up to 50% liver volume only in highly selected cirrhotic patients without functional impairment or portal hypertension 1

Advanced Cirrhosis Contraindications

Child-Pugh B or C cirrhosis and clinically significant portal hypertension represent absolute contraindications to major resections (>2 segments), as even small resections can result in PHLF in these patients 1. The 2025 EASL guidelines provide strong consensus on this recommendation 1.

Critical Caveats and Pitfalls

Anatomic Variability

The right liver typically accounts for 65% of total volume but ranges from 49-82%, while the left liver accounts for 35% with a range of 17-49% 1. This substantial individual variation makes volumetric assessment mandatory rather than relying on anatomic assumptions about segment percentages.

Volume-Weight Correlation

Expect a volume-to-weight ratio of approximately 0.88 when correlating CT volumetry measurements with actual resection specimen weights 3. This discrepancy results from exsanguination of the liver after resection and should be factored into preoperative planning 3.

When FLR is Inadequate

For patients with FLR below recommended thresholds who are otherwise suitable surgical candidates, perform preoperative portal vein embolization (PVE) to induce hypertrophy in the future remnant 1, 4. PVE redirects portal blood flow toward the FLR, inducing hypertrophy over 4-8 weeks while the embolized portion undergoes atrophy 4.

Functional Assessment Beyond Volume

Consider supplementing CT volumetry with functional assessment when the extent of underlying parenchymal disease is unclear 1. Options include:

  • Preoperative biopsy (percutaneous or transjugular) of the FLR to predict PHLF likelihood 1
  • ICG-R15 testing to assess hepatic functional reserve 1
  • ALBI grade, FIB-4 score, or transient elastography combined with FLR volume for enhanced risk stratification 1

The 2025 EASL guidelines note that liver scintigraphy and MRI with hepatobiliary contrast agents may be more informative than CT volumetry alone for assessing functional liver reserve, though they require specialized equipment and expertise 1.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

4
Guideline

Optimizing Future Liver Remnant to Prevent Post-Hepatectomy Liver Failure

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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