What is the preferred approach between anatomical (resection following liver anatomy) and non-anatomical (resection not following liver anatomy) liver resection for patients with colorectal liver metastases (colorectal cancer that has spread to the liver)?

Non-Anatomical vs Anatomical Liver Resection for Colorectal Liver Metastases

Non-anatomical (parenchymal-sparing) resection should be the preferred approach for colorectal liver metastases, as it achieves equivalent oncologic outcomes to anatomical resection while preserving more functional liver parenchyma and reducing operative morbidity. 1

Primary Recommendation

The fundamental goal of liver resection is to remove all macroscopic disease with clear (R0) margins while preserving sufficient functioning liver volume—approximately one-third of standard liver volume or a minimum of two segments 2. The type of resection (anatomical vs non-anatomical) does not impact patient outcomes when this goal is achieved 3.

Evidence Supporting Non-Anatomical Resection

Wedge resections are not inferior to anatomical resections in terms of tumor clearance, pattern of recurrence, or survival 3. The most recent high-quality evidence from 2025 analyzing 145 patients over 23 years demonstrated:

• No difference in disease-free survival or overall survival between anatomical (n=62) and non-anatomical (n=83) resection groups 1
• No difference in positive resection margin rates between groups 1
• No difference in postoperative complication rates (19.6% anatomical vs 19.1% non-anatomical) 1
• Significantly higher intraoperative transfusion rates with anatomical resection (56.5% vs 12.0%) 1
• One surgery-related death occurred only in the anatomical group 1

When to Consider Each Approach

Non-Anatomical Resection is Preferred For:

• Metastases smaller than 2 cm located on the liver surface 4
• Multiple peripheral foci, including when both liver lobes are affected 4
• Bilobar disease where parenchymal preservation is critical 1
• Patients requiring maximal preservation of functional liver remnant 1

Anatomical Resection May Be Considered For:

• Tumorous foci larger than 2 cm located marginally between individual segments of a single lobe 4
• Multiple tumorous foci affecting a single liver lobe 4
• Cases where anatomical boundaries facilitate achieving clear margins 4

Critical Surgical Principles

Blood loss is an independent predictor of mortality and compromises long-term outcome after hepatectomy 3. The higher transfusion rates associated with anatomical resection (56.5% vs 12.0%) represent a significant disadvantage 1.

The ability to achieve clear margins (R0 resection) should be determined by the regional hepatobiliary unit 2. While one older study suggested anatomical resection lowers rates of histologically non-radical (R1) resections 4, the most recent evidence shows no difference in positive margin rates between approaches 1.

Common Pitfalls to Avoid

• Do not assume anatomical resection is inherently superior: The oncologic principle is complete tumor removal with negative margins, not adherence to anatomical planes 1
• Do not sacrifice excessive parenchyma unnecessarily: Preserving liver volume is critical for postoperative function and potential future re-resection 1
• Do not perform biopsy of hepatic lesions without discussion with the regional hepatobiliary unit, as this may cause extrahepatic dissemination and reduce long-term survival 2

Operative Morbidity Considerations

Operative morbidity and mortality following liver resection relate to hepatic failure, which is a function of the extent of resection 2. Anatomical resections have higher operative morbidity and mortality rates compared to non-anatomical limited resections 5. Other complications include hemorrhage, bile leak, intra-abdominal sepsis, and cardiopulmonary dysfunction 2.

Margin Requirements

Duration of survival is shortened by inadequate or involved resection margins 2. While historical data suggested margins >1 cm were associated with better survival (45% vs 23% five-year survival) 2, more recent evidence indicates that lesser margins may be acceptable as long as the tumor pseudocapsule is resected during dissection 2.

Algorithmic Approach to Decision-Making

1. Assess resectability: Can all macroscopic disease be removed with clear margins while leaving adequate liver remnant? 2
2. Evaluate tumor characteristics: Size, number, location, and distribution 1, 4
3. Default to non-anatomical resection for parenchymal preservation unless specific anatomical considerations mandate otherwise 1
4. Consider combination approaches: Resection plus ablation for bilobar disease 2, 6
5. Ensure decision-making by specialized hepatobiliary unit 2