Fluid overload is associated with adverse outcomes in patients with severe acute kidney injury. It remains unclear if fluid overload is merely a marker of disease severity or if organ congestion is a mediator of complications. Point-of-care ultrasound could be a modality used to assess organ congestion and its clinical implications. The objective of this study is to determine whether ultrasound markers of organ congestion are associated with major adverse kidney events in critically ill patients with severe acute kidney injury.

Background: Fluid overload is associated with adverse outcomes in patients with severe acute kidney injury. It remains unclear if fluid overload is merely a marker of disease severity or if organ congestion is a direct mediator of complications. Point-of-care ultrasound could be a modality used to assess organ congestion and its clinical implications.

Objective: To determine whether ultrasound markers of organ congestions are associated with major adverse kidney events and other adverse clinical outcomes.

Study design: A cohort of critically ill patients with a new onset of severe acute kidney injury will undergo repeated ultrasound assessments to detect the presence of the following markers:

• Portal flow pulsatility on pulse-wave Doppler
• Discontinuous intra-renal venous flow on pulse-wave Doppler
• Abnormal hepatic vein waveform on pulse wave Doppler
• Presence of pulmonary B-line artifacts on 2D lung ultrasound
• Presence of dilated and non-collapsible inferior vena cava on 2D ultrasound
• Presence of systolic right ventricular dysfunction
• Presence of systolic left ventricular dysfunction

Clinical outcomes will be collected for up to 90 days after recruitment.

Perspective: An approach targeting the resolution of organ congestion might improve the prognosis in patients with severe acute kidney injury. Identifying clinically relevant markers of organ congestion is a precursor to the design of future interventional trials investigating personalized fluid balance management.

Inclusion Criteria:

• Age ≥ 18 years
• Admitted to the ICU
• Women with serum creatinine ≥ 100 µmol/L and men with serum creatinine ≥ 130 µmol/L
• Severe acute kidney injury (AKI) defined either: A ≥ 2-fold increase in serum creatinine from a known pre-morbid baseline or during the current hospitalization OR achievement of a serum creatinine ≥ 354 µmol/L with evidence of a minimum increase of 27 µmol/L from pre-morbid baseline or during the current hospitalization OR Urine output < 6.0 mL/kg over the preceding 12 hours OR initiation of renal replacement therapy (RRT) for severe AKI initiated less than 72 hours before recruitment.

Exclusion Criteria:

• Lack of commitment to provide RRT as part of limitation of ongoing life support. (Operational definition: Critical care team has deemed the patient not to be eligible for escalation of life support, including the initiation of RRT, or substitute decision makers have declined offer of same.)
• Known pre-hospitalization advanced chronic kidney disease, defined by an estimated glomerular filtration rate < 20 mL/min/1.73 m2 in a patient who is not on chronic RRT. (Operational definition: The coordinator will review all documented serum creatinine values within 365 days prior to the date of admission for the current hospitalization. The value closest to the admission date will be considered as the "baseline" and will be used to calculate the corresponding estimated glomerular filtration rate using an online calculator. A value of < 20 mL/min/1.73 m2 derived from the CKD-EPI equation will be grounds for exclusion.

Critically ill adult patients with severe acute kidney injury