Abstract: Two trials randomised in total 106 patients to piggy-back method (n = 53) versus conventional method with veno-venous bypass (n = 53). Both trials were at high risk of bias. There was no significant difference in post-operative mortality, primary graft non-function, vascular complications, renal failure, transfusion requirements, intensive therapy unit (ITU) stay, or hospital stay between the two groups. The warm ischaemic time was significantly shorter in the piggy-back method than the conventional method (MD -11.50 minutes; 95% CI -19.35 to -3.65; P < 0.01). The proportion of patients who developed chest complications were significantly higher in the the piggy-back method than the conventional method (75.8% versus 44.1%; P = 0.01). One trial randomised 80 patients to piggy-back with porto-caval bypass (n = 40) versus piggy-back without porto-caval bypass (n = 40). This trial was at high risk of bias. There was no significant difference in post-operative mortality, re-transplantation due to primary graft non-function, vascular complications, renal failure, or hospital stay between the two groups. Fewer patients required blood transfusion in the piggy-back with porto-caval bypass group (55%) than the piggy-back without porto-caval bypass group (75%) (P = 0.02). There was no significant difference in the mean amount of blood transfused between the groups (MD -1.00 unit; 95% CI -2.19 to 0.19; P = 0.10). The ITU stay was significantly shorter in the piggy-back with porto-caval bypass group (2.9 days) than the piggy-back without porto-caval bypass group (4.9 days; MD -2.00 days; 95% CI -3.82 to -0.18; P = 0.03). There were no trials comparing piggy-back method with conventional method without veno-venous bypass or different techniques of piggy-back method. There is currently no evidence to recommend or refute the use of piggy-back method of liver transplantation.

Plain-language summary: We systematically searched various medical databases to determine how the piggy-back method compares with the standard method of liver transplantation or with different piggy-back techniques. Two clinical trials randomised 106 patients to the piggy-back method (53 patients) versus the standard method (53 patients). Both trials were at high risk of systematic errors. There was no significant difference in post-operative death, primary graft non-function (the liver graft does not start functioning at all), complications related to the blood vessels, kidney failure, blood transfusion requirements, intensive therapy unit (ITU) stay, or hospital stay between the two groups. The proportion of patients who developed chest complications were significantly higher with the piggy-back method than with the conventional method (76% in piggy-back method versus 44% in conventional method; statistically significant). One trial randomised 80 patients to a variant of piggy-back (in which blood from the intestines is temporarily diverted; 40 patients) versus standard piggy-back method (in which blood from the intestines is blocked; 40 patients). This trial was at high risk of systematic error. There was no significant difference in post-operative death, re-transplantation due to primary graft non-function (liver graft does not start functioning at all), vascular complications, kidney failure, or hospital stay between the two groups. Significantly fewer patients required blood transfusion with the variant piggy-back method (55%) than with the standard piggy-back method (75%). The ITU stay was significantly shorter in the variant (2.9 days) than with the standard piggy-back method (4.9 days). There were no trials comparing piggy-back method and standard method of liver transplantation without diversion of venous blood or different techniques of piggy-back method. We conclude that there is currently no evidence to recommend or refute the use of piggy-back method of liver transplantation.