Alternative names: Acute kidney injury (AKI)
·Acute renal failure
is an abrupt deterioration of renal function
·It develops within
hours or days
·It is a serious
condition which can lead to death
·The condition can be
classified into three groups according to the underlying causative mechanisms
treating the underlying cause of ARF
What is acute renal failure (ARF)?
This is when an abrupt deterioration of
renal function develops within hours or days. It is a very serious condition
with a high mortality and must be prevented in patients at risk.
Acute renal failure often develops in patients that are in
hospital for other conditions, like surgery, major burns or due to a motor
Urine production slows or stops and waste products and
excess water build up. Blood levels of urea and creatinine rise rapidly and
these waste products are the diagnostic indicators of ARF. The disturbance of
fluid and electrolyte balance, especially elevated potassium, is potentially
ARF affects the functioning of the whole body including the
heart, brain, lungs and digestive system. The current tendency is to dialyse
patients with acute renal failure early in order to save lives and prevent
Dialysis involves using a sophisticated filter connected to
a machine, to temporarily take over the function of the failed kidneys.
The dialysis procedure also simplifies a patient’s fluid and
electrolyte management and enables better nutritional support.
This condition is classified into three
groups according to the underlying causative mechanisms. It influences the
management plan and treatment given for AKI.
bloodflow to the kidneys: (pre-renal ARF)
A severe drop in blood pressure or
blood volume can lead to ARF. Both cause a reduction in the perfusion or
bloodflow to the kidney. This accounts for >50% of cases of AKI.
Decreased blood pressure can occur particularly
after motor vehicle accidents, during major surgery or as result of a heart
attack or serious infection in the blood.
A reduction in blood flow can occur
with massive bleeding and cause renal failure in this way. Dehydration caused
by vomiting and diarrhoea is the commonest cause of prerenal ARF in children
who suffer from gastroenteritis.
Pre-renal ARF may also occur in burn
victims. Blood clots to the kidney can also interrupt the normal bloodflow to
the kidneys, but are rare. This form of AKI results in acute tubular necrosis
2. Direct kidney injury
When the kidney cells or its filtering
units are damaged, it may be due to a direct renal injury e.g. acute or
malignant hypertension, severe glomerulonephritis or toxins such as NSAIs or
mushrooms. About 30 to 40% of AKI fall in this category.
3. Blockage of the urine
Obstruction of the urine flow from the
kidney or within the kidney can also lead to ARF and accounts for about 6% of
cases. The blockage can be caused by kidney stones, mass lesions like a tumour
or an enlarged prostate.
Doing a rectal or vaginal examination
can reveal tumours of the reproductive organs and prostate. It is very
important to exclude obstruction as a cause of renal failure because the
treatment is considerably different.
Special investigations like sonar of
the kidney or pyelogram are used to
determine the diagnosis. Pyelogram
is an X-ray of the kidney taken after giving a contrast agent or “dye”.
the disease progresses
ARF is a serious condition and its
complications can lead to death. It may resolve in time and sometimes within
days. Recovery also depends on the underlying cause and the treatment given.
Mortality is highest in surgical patients and the leading causes of death are
infection, bleeding of the digestive tract and fluid/electrolyte disturbances.
Children tend to have a better chance of regaining their kidney function than
adults. Who is at risk?
ARF must be prevented in high-risk
patients. This includes those with chronic diseases that can affect the kidneys
like diabetes, hypertension and heart disease. Heart attack can lead to cardiogenic shock and must be treated early. Pregnant patients who
suffer from eclampsia, a hypertensive
condition, have a high risk for kidney damage.
Patients with major injuries due to accidents require
optimal treatment to maintain blood flow to the kidneys and should be
Some drugs are nephrotoxic
(poisonous to the kidney), and therefore damaging to the kidneys. This includes
certain antibiotics called aminoglycosides,
anti-inflammatory drugs and the contrast media used in specific X-ray tests of
the urinary tract.
and signs of AKI with renal failure
In patients who develop ATN, other
features of disease or illness are often present: the patient may have
dehydration, may be receiving treatment for infection or has been involved in
In patients who develop glomerulonephritis,
there is often acute onset of facial swelling and the presence of “coke”
coloured urine. Urine production may slow down or stop completely in rare cases.
·The excess fluid
leads to elevated blood pressure and fluid build up in the lungs.
·This leads to
shortness of breath, especially when lying down.
·Distended neck veins
and a fast or irregular heartbeat can be present.
·Depending on the
cause of the renal failure, dehydration may be present and must be looked for
and corrected promptly.
The toxic effects of the waste products on brain function
can cause nausea, vomiting and tiredness. Patients lose their appetite and acid
buildup in the blood leads to deep breathing and headaches. If untreated, the
fluid and waste overload can lead to heart failure, altered brain functioning
like lethargy, seizures and coma.
The chemical balance of the blood is derailed and high
levels of electrolytes like potassium can be very dangerous and lead to
abnormal heart rhythm. The heart may become inflamed from the toxins
(pericarditis). This is a serious complication and can be treated by dialysis.
Muscle cramps and confusion are often found.
Dialysis can be life saving when serious chemical
abnormalities, fluid overload, congestive heart failure or severe hypertension
Diagnosis of ARF
Patients who develop ARF are often in
hospital for another condition that puts them at risk for the condition. This
includes major surgery, heart attack, crush injury and severe burns. Urine and
blood tests are done and the volume of urine produced is monitored. An abrupt
rise in the blood levels of urea and creatinine characterises ARF.
Urine production may be slowed down,
but patients often continue to pass more than one litre of urine per day.
Sophisticated urine and blood tests are done to determine the renal function.
It is important to determine if the patient might have
underlying chronic kidney failure that can slowly progress for years, without
causing symptoms. In this case, acute deterioration of the chronic condition
can be difficult to differentiate from ARF. Small scarred kidneys on sonar or
special X-ray of the kidneys, suggest the disease is of a chronic nature.
Taking a thorough history, careful physical examination,
urine and special tests will help the doctors establish whether the cause is
pre-renal, renal or post-renal.
Obstruction of the urine flow is an important post-renal
cause and should be excluded because the management is different from the other
forms of ARF. Dehydration is a common cause of pre-renal ARF and correcting the
patient’s fluid balance is a priority.
first principle of the treatment of ARF is to identify any potentially
reversible causes. Therefore, dehydration should be corrected, offending drugs
discontinued, obstruction relieved and infection treated.
Further treatment is tailored according to the underlying
cause of the ARF and the fluid and electrolyte disturbances.
Patients with ARF are monitored closely. This includes
charting the volume of urine produced and other clinical indicators, and doing
regular blood tests.
Treatment may include intravenous fluids in dehydrated
patients or restriction of fluids if overloaded. Blood levels of electrolytes
are corrected and medication to decrease potassium may be necessary. High blood
pressure is treated if necessary. A diet low in protein and high in
carbohydrates is generally recommended.
Tests to identify and manage the complications of ARF may
also be done, for example, chest X-rays to exclude heart failure.
tendency is to dialyse patients with ARF early to prevent complications. Only a minority of patients with ARF are left with permanent
residual kidney damage.
revised by Professor A M Meyers, MBBCh, FCP (SA), Cert Nephrology (SA), FRCP (London), Donald
Gordon Medical Centre, Klerksdorp Hospital, and National Kidney Foundation of
South Africa, March 2015.
Originally written by Dr K. Coetzee, reviewed by Dr R.Moosa, head of the Renal Unit,TygerbergAcademic Hospital 2008.