Inclusion criteria:  Major subject (≥18 years old) Subject hospitalized in an intensive care unit, Strasbourg, Nancy or Reims hospitals, for severe COVID-19 between February 1, 2020 and July 31, 2020. Having presented acute renal failure KDIGO 2 (assessed on a doubling of serum creatinine compared to the patient's reference values) or 3 (serum creatinine greater than 3 times the patient's reference, or anuria, or any recourse to extra-purification renal) Having left hospital alive after initial treatment for COVID-19 Subject not having expressed his opposition, after information, to the reuse of his data for the purposes of this research.  Exclusion criteria:  Subject having expressed opposition to participating in the study Subject under guardianship or guardianship Subject under safeguard of justice