Médico cirujano

Seminar

Acute kidney injury
Rinaldo Bellomo, John A Kellum, Claudio Ronco

Acute kidney injury (formerly known as acute renal failure) is a syndrome characterised by the rapid loss of the
kidney’s excretory function and is typically diagnosed by the accumulation of end products of nitrogen metabolism
(urea and creatinine) or decreased urine output, or both. It is the clinicalmanifestation of several disorders that affect
the kidney acutely. Acute kidney injury is common in hospital patients and very common in critically ill patients. In
these patients, it is most often secondary to extrarenal events. How such events cause acute kidney injury is
controversial. No specific therapies have emerged that can attenuate acute kidney injury or expedite recovery; thus,
treatment issupportive. New diagnostic techniques (eg, renal biomarkers) might help with early diagnosis. Patients
are given renal replacement therapy if acute kidney injury is severe and biochemical or volume-related, or if uraemictoxaemia-related complications are of concern. If patients survive their illness and do not have premorbid chronic
kidney disease, they typically recover to dialysis independence.However, evidence suggests that patients who have
had acute kidney injury are at increased risk of subsequent chronic kidney disease.

Introduction
Acute kidney injury is the new consensus term for acute
renal failure.1 It refers to a clinical syndrome characterised
by a rapid (hours to days) decrease in renal excretory
function, with the accumulation of products of nitrogen
metabolism suchas creatinine and urea and other
clinically unmeasured waste products. Other common
clinical and laboratory manifestations include decreased
urine output (not always present), accumulation of
metabolic acids, and increased potassium and phosphate
concentrations.
The term acute kidney injury has replaced acute
renal failure to emphasise that a continuum of kidney
injury exists that beginslong before sufficient loss of
excretory kidney function can be measured with standard
laboratory tests. The term also suggests a continuum of
prognosis, with increasing mortality associated with even
small rises in serum creatinine, and additional increases
in mortality as creatinine concentration rises.

Epidemiology
The described notions have led to a consensus definition
of acute kidneyinjury by the Acute Dialysis Quality
Initiative. These RIFLE (risk, injury, failure, loss, end
stage) criteria (figure 1)1 have been broadly supported
with minor modifications by the Acute Kidney Injury
Network,2 and both definitions have now been validated
in thousands of patients3 and seem to work similarly to
each other. A new consensus definition merging the
RIFLE criteria and the AcuteKidney Injury Network
definition has emerged from the Kidney Disease:
Improving Global Outcomes (K-DIGO) group.3
Acute kidney injury is a common and important
diagnostic and therapeutic challenge for clinicians.4
Incidence varies between definitions and populations,
from more than 5000 cases per million people per year
for non-dialysis-requiring acute kidney injury, to
295 cases per millionpeople per year for dialysisrequiring disease.5 The disorder has a frequency of 1·9%
in hospital inpatients4 and is especially common in
critically ill patients, in whom the prevalence of acute

kidney injury is greater than 40% at admission to the
intensive-care unit if sepsis is present.6 Occurrence is
more than 36% on the day after admission to an
intensive-care unit,6 and prevalence isgreater than 60%
during intensive-care-unit admission.7
Some causes of acute kidney injury are particularly
prevalent in some geographical settings. For example,
cases associated with hypovolaemia secondary to
diarrhoea are frequent in developing countries, whereas
open heart surgery is a common cause in developed
countries. Furthermore, within a particular country,
specific disorders are...