Among many patients, AKI is mild and is manifested only by a transient increase in the serum creatinine or fall in urine output. However, AKI can cause life-threatening complications, even among those with relatively less severe disease. In addition, the serum creatinine will not accurately reflect the glomerular filtration rate (GFR) in patients who are not in steady state. Thus, among patients who have just developed AKI and in whom the serum creatinine is actively increasing, the estimated GFR (eGFR), based upon the serum creatinine, will overestimate the actual GFR. Conversely, among patients who are recovering from ARF, the eGFR may underestimate the actual GFR [15–20].

All patients who present with AR must be carefully evaluated both for reversible causes, such as hypotension, volume depletion, or obstruction, and for the presence of complications such as hyperkalemia and volume overload. The initial evaluation of the patient with ARF is directed at determining the cause and identifying the complications that may require immediate attention [21–29].

The major complications of ARF include volume overload, hyperkalemia, metabolic acidosis, hypocalcemia, and hyperphosphatemia. With severe forms, mental status changes may be present. Hyperuricemia and hypermagnesemia may also occur. The initial assessment therefore should include the careful evaluation of volume status and measurement of serum electrolytes, particularly potassium and bicarbonate, and serum phosphate, calcium, and albumin. We also check serum uric acid, magnesium, and a complete blood count.