Acute renal failure requiring renal replacement therapy (RRT) is a frequent complication in critically ill patients with high morbidity and mortality. Early prediction of who is going to need RRT is clinically useful in the intensive care unit (ICU). Patients' with diuretic resistant pulmonary edema, hyperkalemia/metabolic acidosis refractory to medical therapy and uremic complications (pericarditis, encephalopathy, bleeding) are candidates who need RRT as an earlier intervention with continuous haemofiltration, which might be beneficial to the patient and even prevent clinicians from implementing unnecessary, futile and perhaps injurious escalations in medical therapy (e.g., low-dose dopamine, mannitol boluses, further fluid loading, introduction of additional vasoactive drugs) to rescue kidneys that are beyond rescuing. Recent evidence also suggests that RRT may be useful as an immunomodulator and best initiated early in the course of the patient's illness with multiple system involvement.