In liver transplantation, the main problem is the shortage of grafts due to the small pool of donors. In order to increase the number of donors, grafts are increasingly being taken from older donors, known as 'expanded criteria' donors, who have liver steatosis lesions. Currently, expanded criteria donors account for 75% of liver transplants, whereas in 2009 they accounted for less than 30% of liver transplants.

Steatosis and its progression Non-alcoholic steatohepatitis (NASH) is an emerging disease in industrialised countries due to obesity, and corresponds to the accumulation of intracytoplasmic triglycerides.

Steatosis is diagnosed when this fat content represents more than 5% of the total liver mass. There are two types of steatosis: microvesicular steatosis and macrovacuolar steatosis, defined by the presence of lipid droplets larger than the nucleus with a nucleus displaced to the periphery. Macrovacuolar steatosis is responsible for impaired liver function if it is present in ≥30% of hepatocytes. It is a factor in poor prognosis for liver transplants, with reduced graft and recipient survival and an increase in early graft dysfunction after liver transplantation. The quantification of hepatic steatosis is based on the pathological analysis of a liver biopsy, which is currently the gold standard.

This technique has disadvantages: it is an invasive method, requiring an experienced pathologist, and presents inter-individual variability in the assessment and quantification of steatosis.

It is therefore essential to develop new non-invasive diagnostic tools that can identify the presence of steatosis > 5% and ≥ 30%. Several non-invasive techniques for diagnosing steatosis have been studied: Fibroscan, CT scan, MRI, but none of those studied previously allow for the accurate quantification of hepatic steatosis, particularly macrovacuolar steatosis, with instant results.

Inclusion Criteria:

Liver grafts:

• Men or women aged 18 and over
• All donors accepted by the MA4FC procurement team, including brain-dead donors and Maastricht 3 donors, even if placed on a perfusion machine
• Donors whose families have received information about the study and have not expressed any opposition

Surgical specimens (hepatectomy):

• Men or women aged 18 years and older
• Subjects who have undergone surgery for any indication of hepatectomy
• Affiliated with social security,
• Having received information about the study and not having expressed opposition

Exclusion Criteria:

Liver grafts:

• Donors whose liver will be subject to a SPLIT procedure
• Donors for whom there is a medical-legal obstacle
• Donors whose family or loved ones oppose scientific sampling: The hospital coordination team will consult the national refusal register and question loved ones to determine whether the deceased would have opposed sampling. If the donor and/or family oppose scientific sampling, then sampling will not be performed.

Surgical specimens (hepatectomy):

• Subjects covered by Articles L1121-5 to 1121-8 of the Public Health Code (minors, adults under guardianship or curatorship, patients deprived of their liberty, pregnant or breastfeeding women),
• Subjects who do not understand the French language