Acute kidney injury

Definition—for practical clinical purposes, acute kidney injury (AKI) is defined as a significant decline in renal excretory function occurring over hours or days, detected by either a fall in urinary output or a rise in the serum concentration of creatinine. Oliguria—defined (arbitrarily) as a urinary volume of less than 400 ml/day—is usually present, but not always. Clinical approach: diagnosis—all patients admitted to hospital with acute illness, but particularly older people and those with pre-existing chronic kidney disease, should be considered at risk of developing AKI. The most common precipitant is volume depletion. Serum creatinine and electrolytes should be measured on admission in all acutely ill patients, and repeated daily or on alternate days in those who remain so. Assessment—after treatment of life-threatening complications, the initial assessment of a patient who appears to have AKI must answer three questions: (1) is the kidney injury really acute? (2) Is urinary obstruction a possibility? And (3) is there a renal inflammatory cause? General aspects of management—the immediate management of a patient with renal impairment is directed towards three goals: (1) recognition and treatment of any life-threatening complications of AKI, (2) prompt diagnosis and treatment of hypovolaemia, and (3) specific treatment of the underlying condition—if this persists untreated then renal function will not improve. Specific causes of acute kidney injury—there are many possible causes of AKI, but in any given clinical context few of these are likely to require consideration. By far the most frequent are prerenal failure and acute tubular necrosis, which together account for 80 to 90% of cases of AKI seen by physicians.