With this study, the investigators want to find out whether the use of a "lung machine" (extracorporeal membrane oxygenation (ECMO)) togethet with giving the lungs "rest" (by minimizing ventilary support) in people with severe pneumonia has an effect on how well the kidneys work.

The investigators will use information that was already collected while patients were staying in the intensive care unit. Patients do not need to do anything additional or undergo any additional procedures for this study.

Some people with severe pneumonia need to be admitted to the intensive care unit. In very serious cases, the lungs may work so poorly that breathing without help is no longer possible. These patients then receive support from a breathing machine (a ventilator). Sometimes even this support is not enough, and a special machine is needed to temporarily take over the function of the lungs. This machine is called a "lung machine" (also known as ECMO).

When a patient is connected to this lung machine, the patient's own lungs are exposed to as little pressure and stimulation as possible. This is called "lung rest" and gives the lungs time to heal.

In people who are very ill, such as those with severe pneumonia, other organs can also be affected. The kidneys, which are important for making urine and removing waste products from the body, may suddenly stop working as well as they should. This study will examine whether using the lung machine and lung rest affects how the kidneys work.

Inclusion Criteria:

• Age 18 years or older
• Admission to the Intensive Care Unit (ICU) of Ghent University Hospital
• Treatment with veno-venous extracorporeal membrane oxygenation (VV- ECMO)
• ICU admission between 1 January 2019 and 31 December 2023

Exclusion Criteria:

• Receipt of renal replacement therapy (RRT) prior to ICU admission
• Patients already receiving VV-ECMO at the time of admission to the ICU of Ghent University Hospital (i.e., patients referred from another hospital on VV-ECMO)
• Patients who received VV-ECMO immediately upon admission to the ICU of Ghent University Hospital

Adult patients admitted on the ICU of Ghent Univesity Hospital with acute respiratory distress who received support by veno-venous ECMO between 1 January 2019 and 31 December 2023

Data of individuals will not be shared according to General Data Protection Regulation (GDPR)