Organ rinsing © Charité | Nathanael Rashzok
Team uses “organ lavage” to determine whether rejected organs are transplantable
Berlin, October 15, 2025
In Germany, far fewer donor livers are available than are needed – a shortage that costs lives. A research team at the Charité – Universitätsmedizin Berlin now wants to shorten the waiting time for a liver transplant for many affected patients. To do this, they are identifying organs that are suitable for transplantation from those initially declared untransplantable. The key: machine perfusion, a kind of “well-being organ flushing” that allows donor livers to recover from transport and enables thorough quality control. If the study is successful, the number of available donor livers could increase significantly in the future.
The wait for a transplant is long. Sometimes too long: Up to a third of people who need a liver transplant become too ill for the procedure or die from their illness during the waiting period. “Unfortunately, the situation is getting worse because fewer and fewer organs are being donated,” says Prof. Nathanael Raschzok. He is a senior physician at the Charité’s Department of Surgery and is leading the recently launched ExTra study. “We want to use normothermic machine perfusion to provide donor livers that would otherwise have been discarded, thus reducing the waiting time for transplantation for people further down the waiting list.”
Why organ lavage is necessary
In normothermic machine perfusion, the organ is lavaged with a nutrient- and oxygen-rich blood substitute fluid – at body temperature. The body-temperature conditions are intended to give the tissue time to regenerate, as organs are typically cooled on ice after removal to minimize damage during the perfusion-free transfer. “Cooling is well suited for organs in top condition,” explains Nathanael Raschzok. “However, there are also less healthy but functional organs that do not survive refrigerated transport and storage on ice as well.”
This becomes noticeable as soon as the organs are warmed to body temperature and thus receive a better blood supply again – this is known as reperfusion injury. This occurs whenever a tissue’s blood supply is increased again after an interruption in its blood supply. During organ transplantation, the damage usually occurs within the recipient’s body and can lead to rejection reactions or even transplant failure. If the organs are not in optimal condition, the phenomenon is more significant than usual.
Organ lavage protects and creates time for strict quality control
With the help of machine perfusion, the reperfusion is brought forward and takes place outside the body. “By preparing the organs for transplantation for a few hours under ‘comfortable conditions’ after refrigerated transport, we give them time to recover, allowing harmful substances to be washed out in peace,” explains Nathanael Raschzok. “This makes the transplant less complicated and safer. We are also extending the time window in which the transplant must take place.”
The clinical team is using this time window to conduct a thorough quality assessment of donor livers that would previously have been classified as untransportable or unsuitable for transplantation. Since the organs are metabolically active during machine perfusion, it is possible to determine how well they produce bile or excrete lactate, for example. “We apply particularly strict criteria to this functional assessment,” emphasizes Nathanael Raschzok. “Initial studies have shown that livers that pass the quality test can be successfully transplanted.”
Goal: Reduce waiting times – and save lives
In the ExTra study, the tested organs deemed functional are offered to patients with a so-called Re-MELD sodium score of up to 21 points, i.e., whose liver disease necessitates a transplant but is not yet classified as high-urgency. Eighteen of the 19 university liver transplant centers in Germany will participate in the study; four centers have already begun work. The first “salvaged” donor liver has already been successfully transplanted at the Charité.
“We very much hope that with the ExTra study, we can increase the number of suitable donor livers and thus shorten the agonizing waiting time for those affected,” says Nathanael Raschzok. If this hope is confirmed, the technique could become the new standard in liver transplantation – and save many lives. In Germany, over a hundred donor livers suitable for organ lavage are selected each year. “We estimate that half of these organs would be transplantable, meaning that with this procedure, we could transplant an additional 50 or more livers per year in Germany,” emphasizes the study leader.
About the ExTra study
ExTra (Ex vivo liver machine perfusion for decreasing time to transplantation) is an open-label, prospectively randomized, multicenter study that includes patients aged 18 years and older with a Re-MELD sodium score ≤ 21 without eligibility for special points. Study participants are randomly assigned to either the control or intervention group. Patients in the control group will follow the regular organ allocation, while patients in the intervention group will also be offered salvaged organs that have undergone quality control using machine perfusion. The study is led by the Charité and is funded by the German Research Foundation (DFG) with approximately €1.8 million for an initial three years. The planned duration of the study is six years. In addition to the Charité, the transplant centers of the university hospitals in Aachen, Bonn, Essen, Frankfurt, Hamburg, Hanover, Heidelberg, Jena, Kiel, Leipzig, Magdeburg, Munich, Münster, Regensburg, Rostock, Tübingen, and Würzburg will participate in the study. The centers at the Charité, in Aachen, Hamburg, and Münster, have already started.