Acute renal failure

Acute renal Acute renal failurefailureDr. H. N. SarkerDr. H. N. Sarker

MBBS, FCPS, MACP(USA)MBBS, FCPS, MACP(USA)Associate professorAssociate professor

medicinemedicine

IntroductionIntroduction

Acute renal failure (ARF) refers to a Acute renal failure (ARF) refers to a sudden and usually reversible loss of sudden and usually reversible loss of renal function, which develops over renal function, which develops over a period of days or weeks and is a period of days or weeks and is usually accompanied by a reduction usually accompanied by a reduction in urine volume. in urine volume.


Acute renal failureAcute renal failure ( (ARF) ARF) is a is a rapid loss of renal function due to rapid loss of renal function due to damage to the kidneys, resulting in damage to the kidneys, resulting in retention of nitrogenous (urea and retention of nitrogenous (urea and creatinine) and non-nitrogenous creatinine) and non-nitrogenous waste products that are normally waste products that are normally excreted by the kidney. excreted by the kidney.


Depending on the severity and duration of Depending on the severity and duration of the renal dysfunction, this accumulation is the renal dysfunction, this accumulation is accompanied by metabolic disturbances, accompanied by metabolic disturbances, such as metabolic acidosis (acidification of such as metabolic acidosis (acidification of the blood) and hyperkalaemia (elevated the blood) and hyperkalaemia (elevated potassium levels), changes in body fluid potassium levels), changes in body fluid balance, and effects on many other organ balance, and effects on many other organ systems.systems.


It can be characterised by oliguria or It can be characterised by oliguria or anuria (decrease or cessation of anuria (decrease or cessation of urine production), although urine production), although non-non-oliguric oliguric ARF may occur. It is a life- may occur. It is a life-threatening medical emergency threatening medical emergency

CausesCauses

Acute renal failure is usually Acute renal failure is usually categorised (as in the flowchart categorised (as in the flowchart below) according to pre-renal, below) according to pre-renal, intrinsic and post-renal causes.intrinsic and post-renal causes.

Pre-renal Pre-renal Intrinsic Intrinsic

Post-renal Post-renal

Pre-renalPre-renal (causes in the (causes in the blood supply): blood supply):

hypovolemia (decreased blood volume), hypovolemia (decreased blood volume), usually from shock or dehydration and usually from shock or dehydration and fluid loss or excessive diuretics use.fluid loss or excessive diuretics use.

Heart failure.Heart failure. hepatorenal syndrome in which renal hepatorenal syndrome in which renal

perfusion is compromised in liver failureperfusion is compromised in liver failure vascular problems, such as atheroembolic vascular problems, such as atheroembolic

disease and renal vein thrombosis (which disease and renal vein thrombosis (which can occur as a complication of the can occur as a complication of the nephrotic syndrome)nephrotic syndrome)

Pre-renalPre-renal

infection usually sepsis, systemic infection usually sepsis, systemic inflammation due to infectioninflammation due to infection

severe burnssevere burns sequestration due to pericarditis and sequestration due to pericarditis and

pancreatitispancreatitis hypotension due to antihypertensives hypotension due to antihypertensives

and vasodilatorsand vasodilators

IntrinsicIntrinsic (damage to the (damage to the kidney itself) kidney itself)

Toxins or medication (e.g. some Toxins or medication (e.g. some NSAIDs, aminoglycoside antibiotics) NSAIDs, aminoglycoside antibiotics)

Sepsis Sepsis Rhabdomyolysis (breakdown of Rhabdomyolysis (breakdown of

muscle tissue) muscle tissue) Haemolysis (breakdown of red Haemolysis (breakdown of red

blood cells) blood cells)

Post-renalPost-renal (obstructive (obstructive causes in the urinary tract )causes in the urinary tract )

benign prostatic hypertrophy or benign prostatic hypertrophy or prostate cancer.prostate cancer.

kidney stones.kidney stones. due to abdominal malignancy (e.g. due to abdominal malignancy (e.g.

ovarian cancer, colorectal cancerovarian cancer, colorectal cancer

REVERSIBLE PRE-RENAL REVERSIBLE PRE-RENAL ACUTE RENAL FAILUREACUTE RENAL FAILURE

Haemodynamic disturbances can Haemodynamic disturbances can initially produce acute renal initially produce acute renal dysfunction that has the potential to be dysfunction that has the potential to be rapidly reversed, prompt recognition rapidly reversed, prompt recognition and treatment are important.and treatment are important.

These topics are considered separately These topics are considered separately

from established acute renal failure. from established acute renal failure.

Pathogenesis Pathogenesis The kidney can regulate its own The kidney can regulate its own

blood flow and GFR over a wide blood flow and GFR over a wide range of perfusion pressures.range of perfusion pressures.

When the perfusion pressure falls-When the perfusion pressure falls-as in hypovolaemia, shock, heart as in hypovolaemia, shock, heart failure or narrowing of the renal failure or narrowing of the renal arteries-the resistance vessels in the arteries-the resistance vessels in the kidney dilate to facilitate flow. kidney dilate to facilitate flow.

Vasodilator prostaglandins are Vasodilator prostaglandins are important, and this mechanism is important, and this mechanism is markedly impaired by NSAIDs . markedly impaired by NSAIDs .

PathogenesisPathogenesis

If autoregulation of blood flow fails, the If autoregulation of blood flow fails, the GFR can still be maintained by selective GFR can still be maintained by selective constriction of the post-glomerular constriction of the post-glomerular (efferent) arteriole. (efferent) arteriole.

This is mediated through the release of This is mediated through the release of renin and generation of angiotensin II, renin and generation of angiotensin II, which preferentially constricts this which preferentially constricts this vessel. vessel.

ACE inhibitors interfere with this ACE inhibitors interfere with this response . response .


More severe or prolonged under-More severe or prolonged under-perfusion of the kidneys may lead to perfusion of the kidneys may lead to failure of these compensatory failure of these compensatory mechanisms and hence an acute mechanisms and hence an acute decline in GFR. decline in GFR.

The renal tubules are intact and The renal tubules are intact and become hyperfunctional; that is, become hyperfunctional; that is, tubular reabsorption of sodium and tubular reabsorption of sodium and water is increased. water is increased.


This leads to the formation of a low This leads to the formation of a low volume of urine which is volume of urine which is concentrated (osmolality > 600 concentrated (osmolality > 600 mOsm/kg) but low in sodium (< 20 mOsm/kg) but low in sodium (< 20 mmol/l). mmol/l).

Clinical assessment Clinical assessment

The clinical picture is often dominated by The clinical picture is often dominated by the underlying condition (e.g. septic the underlying condition (e.g. septic shock, trauma,diarrhoea) shock, trauma,diarrhoea)

There may be marked hypotension and There may be marked hypotension and signs of poor peripheral perfusion, such signs of poor peripheral perfusion, such as delayed capillary return.as delayed capillary return.

Clinical assessmentClinical assessment

Postural hypotension (a fall in blood Postural hypotension (a fall in blood pressure > 20/10 mmHg from lying pressure > 20/10 mmHg from lying to standing) is a valuable sign of to standing) is a valuable sign of early hypovolaemia. early hypovolaemia.

Metabolic acidosis and Metabolic acidosis and hyperkalaemia are often present. hyperkalaemia are often present.

Management Management

Establish and correct the underlying Establish and correct the underlying cause of the ARF.cause of the ARF.

If hypovolaemia is present, restore blood If hypovolaemia is present, restore blood volume as rapidly as possible (with blood, volume as rapidly as possible (with blood, plasma or isotonic saline (0.9%), plasma or isotonic saline (0.9%), depending on what has been lost).depending on what has been lost).

ManagementManagement

Optimise systemic haemodynamics. Optimise systemic haemodynamics. Monitoring of the central venous Monitoring of the central venous pressure or pulmonary wedge pressure or pulmonary wedge pressure as an adjunct to clinical pressure as an adjunct to clinical examination may aid in determining examination may aid in determining the rate of administration of fluid. the rate of administration of fluid.


Critically ill patients may require invasive Critically ill patients may require invasive haemodynamic monitoring to assess haemodynamic monitoring to assess cardiac output and systemic vascular cardiac output and systemic vascular resistance, and the use of inotropic drugs resistance, and the use of inotropic drugs to restore an effective blood pressure .to restore an effective blood pressure .


Correct metabolic acidosis.Correct metabolic acidosis. Restoration of blood volume will Restoration of blood volume will

correct acidosis by restoring kidney correct acidosis by restoring kidney function.function.

Isotonic sodium bicarbonate (e.g. Isotonic sodium bicarbonate (e.g. 500 ml of 1.26%) may be used. 500 ml of 1.26%) may be used.

ESTABLISHED ACUTE ESTABLISHED ACUTE RENAL FAILURE RENAL FAILURE

Established ARF may develop Established ARF may develop following severe or prolonged under-following severe or prolonged under-perfusion of the kidney (pre-renal perfusion of the kidney (pre-renal ARF). In such cases, the histological ARF). In such cases, the histological pattern of acute tubular necrosis is pattern of acute tubular necrosis is usually seen. usually seen.

'renal' and 'post-renal' causes 'renal' and 'post-renal' causes produce established ARFproduce established ARF

Features of established Features of established ARFARF

These reflect the causal condition, These reflect the causal condition, such as trauma, septicaemia or such as trauma, septicaemia or systemic disease, together with systemic disease, together with features of renal failure. features of renal failure.

'Uraemic' features -anorexia, nausea 'Uraemic' features -anorexia, nausea and vomiting followed by drowsiness, and vomiting followed by drowsiness, apathy, confusion, muscle-twitching, apathy, confusion, muscle-twitching, hiccoughs, fits and coma.hiccoughs, fits and coma.

Features of established Features of established of ARFof ARF

Alterations in urine volume Alterations in urine volume

Patients are usually oliguric (urine Patients are usually oliguric (urine volume < volume < 500 ml daily). 500 ml daily).

Anuria (complete absence of urine) Anuria (complete absence of urine) is rare and usually indicates acute is rare and usually indicates acute urinary tract obstruction or vascular urinary tract obstruction or vascular occlusion occlusion

Features established of Features established of ARFARF

In about 20% of cases, the urine In about 20% of cases, the urine volume is normal or increased (non-volume is normal or increased (non-oliguric ARF). oliguric ARF).

Disturbances of water, electrolyte Disturbances of water, electrolyte and acid-base balance and acid-base balance Hyperkalaemia is commonHyperkalaemia is common Metabolic acidosis . Metabolic acidosis .

Features established of Features established of ARFARF

Hypocalcaemia, due to reduced renal Hypocalcaemia, due to reduced renal production of 1,25-production of 1,25-dihydroxycholecalciferol, is common. dihydroxycholecalciferol, is common.

Respiratory rate -increased due to Respiratory rate -increased due to acidosis, pulmonary oedema or acidosis, pulmonary oedema or respiratory infection. respiratory infection.

Anaemia is common, due to excessive Anaemia is common, due to excessive blood loss, haemolysis or decreased blood loss, haemolysis or decreased erythropoiesis .erythropoiesis .

Diagnosis-Diagnosis-

Consensus criteria for the diagnosis Consensus criteria for the diagnosis of ARF are:of ARF are:

Risk: serum creatinine increased 1.5 Risk: serum creatinine increased 1.5 times OR urine production of <0.5 times OR urine production of <0.5 ml/kg/h body weight for 6 hoursml/kg/h body weight for 6 hours

Injury: creatinine 2.0 times OR urine Injury: creatinine 2.0 times OR urine production <0.5 ml/kg/h for 12 hproduction <0.5 ml/kg/h for 12 h

Diagnosis-Diagnosis- Failure: creatinine 3.0 times OR creatinine Failure: creatinine 3.0 times OR creatinine

>355 μmol/l (with a rise of >44) OR urine >355 μmol/l (with a rise of >44) OR urine output below 0.3 ml/kg/h for 24 houtput below 0.3 ml/kg/h for 24 h

Loss: persistent ARF or complete loss of Loss: persistent ARF or complete loss of kidney function for more than four weekskidney function for more than four weeks

End-stage Renal Disease: complete loss of End-stage Renal Disease: complete loss of kidney function for more than three kidney function for more than three monthsmonths


Routine investigation-Routine investigation-

urine for R/Eurine for R/E

Blood urea & electrolytesBlood urea & electrolytes

S. creatinineS. creatinine

ABGABG


Imaging-Imaging-

. Renal ultrasound: usually required . Renal ultrasound: usually required urgently to confirm/refute two equal-urgently to confirm/refute two equal-sized, unobstructed kidneyssized, unobstructed kidneys

Chest X-ray, X-ray KUBChest X-ray, X-ray KUB ECG: if > 40 years or there are risk ECG: if > 40 years or there are risk

factors for cardiac diseasefactors for cardiac disease


Microbiology Microbiology Blood culturesBlood cultures C-reactive protein (ESR is misleading in ARF)C-reactive protein (ESR is misleading in ARF) Mid-stream urineMid-stream urine Other cultures, e.g. wound, sputum, cathetersOther cultures, e.g. wound, sputum, catheters Hepatitis and HIV serology: urgent if dialysis Hepatitis and HIV serology: urgent if dialysis

is needed (isolation of dialysis machine if is needed (isolation of dialysis machine if positive)positive)

Management Management

Emergency resuscitation –Emergency resuscitation – Hyperkalaemia (a plasma K+ Hyperkalaemia (a plasma K+

concentration > 6 mmol/l) must be concentration > 6 mmol/l) must be treated immediately to prevent the treated immediately to prevent the development of life-threatening development of life-threatening cardiac arrhythmias. cardiac arrhythmias.

Circulating blood volume should be Circulating blood volume should be optimised to ensure adequate renal optimised to ensure adequate renal perfusion. perfusion.


Hypovolaemia must be treated as for Hypovolaemia must be treated as for reversible pre-renal ARF monitoring of reversible pre-renal ARF monitoring of central venous or pulmonary wedge central venous or pulmonary wedge pressure as required. pressure as required.

Patients with pulmonary oedema usually Patients with pulmonary oedema usually require dialysis to remove sodium and require dialysis to remove sodium and water. water.

Severe acidosis can be ameliorated with Severe acidosis can be ameliorated with isotonic sodium bicarbonate (e.g. 500 ml isotonic sodium bicarbonate (e.g. 500 ml of 1.26%) if volume status allows. of 1.26%) if volume status allows.


In an anuric or volume-overloaded In an anuric or volume-overloaded patient, renal replacement therapy may patient, renal replacement therapy may be required. be required.

Treatment of the underlying cause of the Treatment of the underlying cause of the ARF .ARF .

Fluid and electrolyte balance Fluid and electrolyte balance After initial resuscitation, daily fluid After initial resuscitation, daily fluid

intake should equal urine output, plus an intake should equal urine output, plus an additional 500 ml to cover insensible additional 500 ml to cover insensible losseslosses


Protein and energy intake Protein and energy intake

In patients in whom dialysis is In patients in whom dialysis is likely to be avoided, accumulation of likely to be avoided, accumulation of urea is slowed by dietary protein urea is slowed by dietary protein restriction (to about 40 g/day) restriction (to about 40 g/day)

Infection control. Infection control.

Renal replacement therapy Renal replacement therapy

Prognosis Prognosis

In uncomplicated ARF, such as that In uncomplicated ARF, such as that due to simple haemorrhage or drugs, due to simple haemorrhage or drugs, mortality is low even when renal mortality is low even when renal replacement therapy is required.replacement therapy is required.

In ARF associated with serious In ARF associated with serious infection and multiple organ failure, infection and multiple organ failure, mortality is 50-70%. mortality is 50-70%.

PrognosisPrognosis

Outcome is usually determined by Outcome is usually determined by the severity of the underlying the severity of the underlying disorder and other complications, disorder and other complications, rather than by renal failure itself.rather than by renal failure itself.

Acute renal failure

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