Table 1.

Characteristics of included studies

Study	Country	Design	Sample size	Procedures	Operative diagnoses	Time of lactate measurement	Outcomes measured	Follow‐up
Watanabe et al (2007)	Japan	Retrospective cohort	151	Liver resections	—	Postoperative (Day 0)	Mortality; morbidity; length of stay; peak bilirubin	Duration of admission
Wiggans et al (2013)	United Kingdom	Retrospective cohort	488	Liver resections	Benign: 8.2% Primary malignancy: 20.7% Secondary malignancy: 71.1%	Postoperative (Day 0)	Mortality; renal dysfunction; peak bilirubin & prothrombin time; length of stay	90 d
Meguro et al (2014)	Japan	Prospective cohort	77	Liver resections	Benign: n.a. Primary malignancy: 63.6% Secondary malignancy: 36.3%	Intra‐operative (highest level)	Wound or intra‐abdominal infections	Duration of admission
Riediger et al (2014)	Germany	Prospective cohort	337	Open liver resections	Benign: 20.8% Primary malignancy: 32% Secondary malignancy: 45.7% Liver trauma: 1.5%	Pre‐operative (Day 0)	Mortality; morbidity; re‐operation	30 d
Pagano et al (2015)	Italy	Retrospective cohort	45	Extended hepatectomies	Benign: 8.9% Primary malignancy: 33.3% Secondary malignancy: 53.4% Liver trauma: 4.4%	Postoperative (Day 0 and Day 5)	Mortality; morbidity; length of stay	90 d
Vibert et al (2015)	France	Prospective cohort	519—TC 466—VC	Liver resections	Benign: 10.3% Primary malignancy: 42.2% Secondary malignancy: 45.2% Parasitosis: 2.1%	Postoperative (Day 0, 1‐4 h postoperative)	Comprehensive complication index; mortality; morbidity	90 d
Lemke et al (2017)	Canada	Retrospective cohort	490	Liver resection	Benign: 10.2% Primary malignancy: 12% Secondary malignancy: 73.4% NET: 4.3%	Postoperative (Day 0)	Mortality; morbidity; length of stay	90 d

Abbreviations: n.a., data not available; NET, neuroendocrine tumours; TC, training cohort; VC, validation cohort.