Objective: The aim of this study was to assess the impact of postoperative hypophosphatemia on liver regeneration after major liver surgery in the scenario of Associating Liver Partition with Portal vein ligation for Staged hepatectomy (ALPPS) and living liver donation (LLD).

Background: Hypophosphatemia has been described to reflect the metabolic demands of regenerating hepatocytes. Both ALPPS and LLD are characterized by an exceptionally strong liver regeneration and may be of particular interest in the context of posthepatectomy hypophosphatemia.

Methods: Serum phosphate changes within the first 7 postoperative days after ALPPS (n=61) and LLD (n=54) were prospectively assessed and correlated with standardized volumetry after 1 week. In a translational approach, postoperative phosphate changes were investigated in mice and in vitro .

Results: After ALPPS stage 1 and LLD, serum phosphate levels significantly dropped from a preoperative median of 1.08 mmol/L [interquartile range (IQR) 0.92-1.23] and 1.07 mmol/L (IQR 0.91-1.21) to a postoperative median nadir of 0.68 and 0.52 mmol/L, respectively. A pronounced phosphate drop correlated well with increased liver hypertrophy ( P <0.001). Patients with a low drop of phosphate showed a higher incidence of posthepatectomy liver failure after ALPPS (7% vs 31%, P =0.041). Like in humans, phosphate drop correlated significantly with degree of hypertrophy in murine ALPPS and hepatectomy models ( P <0.001). Blocking phosphate transporter (Slc20a1) inhibited cellular phosphate uptake and hepatocyte proliferation in vitro.

Conclusion: Phosphate drop after hepatectomy is a direct surrogate marker for liver hypertrophy. Perioperative implementation of serum phosphate analysis has the potential to detect patients with insufficient regenerative capacity at an early stage.