Acute kidney injury (AKI) is common in intensive care unit (ICU) patients and remains associated with a dismal prognosis. The diagnosis of AKI relies on functional criteria (oliguria and serum creatinine elevation), which carry several important limitations. Additionally, the investigators lack biomarker that may predict short term renal prognosis.

Doppler-based renal resistive index (RI) measurement is a rapid and noninvasive investigative tool that may hold promise for early AKI detection in ICU patients or in differentiating transient from persistent AKI in selected critically ill patients. Although several studies have suggested adequate performance in predicting short-term reversibility of AKI, most of these studies were performed in limited patient samples. Additionally, a recent study has identified discrepant results regarding its diagnostic performance.

The main objective of this large prospective multicentre study is to assess diagnostic performance of Doppler-based renal resistive index in diagnosing persistent AKI in critically ill patients requiring mechanical ventilation.

Inclusion Criteria:

• Sinus rhythm
• Use of conventional mechanical ventilation

Exclusion Criteria:

• Refusal: patient, family or trusted person to participate in the study
• Renal artery stenosis known
• Pregnant
• Severe Chronic Renal Failure (clearance < 30 ml.min-1)