Up to 30% of hospitalized
critically ill patients may have a rise in serum
creatinine concentration. In addition to history and physical examination, there is diagnostic value in assessing urinary
electrolytes, solute excretion, and urine flow in these patients. The correct interpretation of these urinary parameters can avoid unnecessary volume overload and
mechanical ventilation, risk factors for increased mortality in patients with rising serum
creatinine. The present article also discusses the role of arterial underfilling in causing prerenal
azotemia in the presence of an increase in total body
sodium and extracellular fluid expansion. As with extracellular fluid volume depletion, arterial underfilling secondary to impaired cardiac function or primary arterial vasodilation can delay or prevent recovery from ischemic or toxic acute tubular
necrosis. The present brief review discusses the various aspects of the correct interpretation of urinary
electrolytes, solute excretion, and urine flow in the setting of a rising serum
creatinine concentration.