Establishing the Minimum Future Liver Remnant Volume for Safe Hepatectomy

BACKGROUND: An adequate future liver remnant volume (FLRV%) reduces the risk of posthepatectomy liver failure (PHLF). This study evaluates (1) the association of FLRV% with grade 4/5 morbidity and (2) the safe FLRV% threshold for PHLF- and non-PHLF-related major morbidity. STUDY DESIGN: Patients undergoing major hepatectomy for malignancy from 2000 to 2020 were included. FLRV%, morbidity, and cause (PHLF- or non-PHLF-related) were determined; patients were stratified by normal livers (NLs) or impaired livers (ILs). The relationship between FLRV% and both all-cause and PHLF-related grade 4 or 5 morbidity was analyzed. The data were then randomly divided into training and testing cohorts to validate a safe FLRV% threshold. RESULTS: A total of 1,748 patients were included: 70% had metastatic liver cancer, and 42% underwent right hepatectomy. Median FLRV% was 42% (range 16% to 90%). Overall morbidity was 51%. Grade 4/5 morbidity was 3.2%: 28 (50%) PHLF-related, and of these, 26 (26 of 28; 92.9%) were fatal. There was a significant association between FLRV% and grade 4/5 PHLF-related morbidity. For every 10% increase in FLRV%, the odds of grade 4/5 PHLF-related morbidity decreased by nearly 40% after adjusting for age and functional liver status (odds ratio 0.61, 95% CI 0.45 to 0.84, p = 0.002). Conversely, there was no significant association between FLRV% and non-PHLF-related grade 4/5 morbidity (odds ratio 0.95, 95% CI 0.74 to 1.21, p = 0.65). FLRV% of ≥30% in NL and ≥50% in the IL group were established as safe minimum thresholds. CONCLUSIONS: There was a close correlation between grade 4/5 PHLF-related morbidity and FLRV%, but the safe limit of resection was dependent on the liver remnant quality (>30% NL, >50% IL). By contrast, 50% of all grade 4 and 5 morbidities was unrelated to PHLF and not influenced by FLRV%.