Outcome reporting for liver transplantation machine perfusion studies: a systematic review.

BACKGROUND

Studies examining machine perfusion (MP) in liver transplantation (LT) report variable post-transplant outcomes, making comparison difficult. Core outcome sets (COS) with standardized definitions and specified time points have been proposed to mitigate this variability. This study explores the quality of outcome reporting in studies with MP in LT.

METHODS

We conducted a systematic review examining outcome reporting within MP LT studies. PubMed, Embase and Ovid Medline were queried for studies examining perfusion techniques from January 1st 2018 to June 1st 2025. Articles that reported clinical outcomes after LT with current perfusion techniques, i.e., normothermic (NMP), hypothermic (HMP) and normothermic regional perfusion (NRP) with >10 cases were included. Risk of bias was assessed with Rob2 and Newcastle Ottawa scores. Median number of COS were reported by perfusion technique. The percentage of studies reporting each measured outcomes was recorded and classified by perfusion technique. The study was registered on PROSPERO (ID: CRD42024590000).

FINDINGS: 2789 records were screened, and 166 articles met inclusion criteria. HMP, including oxygen per-sufflation, was examined by 35 studies, NMP by 55 and NRP by 34 studies, respectively. Forty-two studies included a combination of perfusion techniques. The median number of COS measured was highest in studies examining HMP at 9.0 (IQR 6.0-11.0). NMP studies had the lowest median number of COS measured per article (5.0; IQR 3.0-9.5). Of the 13 COS metrics, patient and graft survival were the most frequently reported, at 88.4% and 87.1% followed by primary-non-function (72.3%), length of stay (68.4%) and non-anastomotic biliary strictures (61.3). Weighted and cumulative complications metrics, i.e., the Clavien-Dindo-Classification and Comprehensive Complication Index were poorly assessed (28.4% and 19.4%, respectively). Only 4 studies examined all 13 COS parameters (2.6%), and 24 reported >10 COS (15.5%). There was significant heterogeneity in outcome parameter definitions and time-points of assessment, especially amongst biliary complications.

INTERPRETATION: There is significant variability in post-transplant complications reporting by LT with MP studies. Uniform definitions and standardized guidelines are critical to allow rigorous comparison of different perfusion techniques and other future innovations.

FUNDING: None.