Acute Renal Failure

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Acute Renal Failure

• Resident Lecture Series
• James Czarnecki, D.O.

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Background

• Defined as an abrupt or rapid decline in renal
  function.
• Evidence of Acute Renal Failure (ARF) is a rise
  in the serum blood urea nitrogen (BUN) or serum
  creatinine concentrations, with or without a
  decrease in urine output.
• The condition is often transient and completely
  reversible.

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Pathophysiology

• May occur in three clinical settings
• Adaptive response to severe volume depletion and
  hypotension (prerenal)
• Response to cytotoxic insults to the kidney
  (intrinsic)
• Obstruction to the passage of urine (postrenal)

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Frequency

• In the U.S.
• Approximately 1 of patients admitted to
  hospitals have ARF at the time of admission
• Incidence rate of ARF is 2-5 during
  hospitalization
• Approximately 95 of consultations with
  nephrologists are related to ARF

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Mortality / Morbidity

• Mortality rate estimates vary from 25 to 90
• Mortality rate is 40 to 50 in general care
  settings
• Mortality rate is 70 to 80 in intensive care
  settings

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Race

• There is no racial predilection for acute renal
  failure.

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History

• A detailed and accurate history is crucial to aid
  in diagnosing the type of acute renal failure and
  determining its subsequent treatment.
• Distinguishing ARF from chronic renal failure
  (CRF) is very important, although sometimes
  difficult.

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Chronic Renal Failure

• Differential symptoms to help diagnose CRF are
• Fatigue
• Weight loss
• Anorexia
• Nocturia
• Pruritus

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Comorbid Conditions

• Those who have the following are at higher risk
  for developing ARF
• Hypertension
• Congestive cardiac failure
• Diabetes
• Myeloma
• Chronic infection
• Myeloproliferative disorder

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History - Continued

• Urine output history can be useful because abrupt
  anuria suggests an acute obstruction, acute and
  severe glomerulonephritis, or an embolic event
  due to the renal artery occlusion.
• A gradually diminishing urine output may indicate
  a urethral stricture or bladder outlet
  obstruction due to prostate enlargement.

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Physical Exam

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Physical Exam

• Obtaining a careful thorough physical exam is
  extremely important when collecting evidence
  about the origination of acute renal failure.

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Physical Examination

• Note the following on physical exam
• Hypotension
• Volume contraction
• Congestive heart failure
• Nephrotoxic drug ingestion
• History of trauma or unaccustomed exertion

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Physical Examination - 2

• Blood loss or transfusions
• Evidence of connective tissue disorders
• Exposure to toxic substances such as ethyl
  alcohol or ethylene glycol
• Exposure to mercy vapors, lead, cadmium, or other
  heavy metals, which can be encountered in welders
  or miners

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Physical Exam - Skin

• Examination of the skin for petechiae, purpura,
  and ecchymosis provides clues to inflammatory and
  vascular causes of ARF
• Infectious diseases, thrombotic thrombocytopenic
  purpura, disseminated intravascular coagulation,
  and embolic phenomena can present with typical
  cutaneous changes

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Physical Exam - Eyes

• Evidence of uveitis may indicate interstitial
  nephritis and necrotizing vasculitis.
• Ocular palsy may indicate ethylene glycol
  poisoning or necrotizing vasculitis.
• Findings suggestive of severe hypertension,
  atheroembolic disease, and endocarditis may be
  observed after a careful examination of the eyes.

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Physical Exam - CV

• Most important part of the physical exam is
  assessment of cardiovascular and volume status.
• Exam must include pulse rate and blood pressure
  recordings, close inspection of jugular venous
  pulse, and assessment for presence of peripheral
  edema.

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Physical Exam CV - 2

• Accurate daily records of fluid intake and urine
  output
• Daily measurements of patient weight
• Blood pressure recordings can be important
  diagnostic tools
• Severe hypertension with renal failure suggests
  renovascular disease, glomerulonephritis,
  vasculitis, or atheroembolic disease

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Physical Exam - Abdomen

• Abdominal examination findings can be very useful
  to help detect obstruction at the bladder outlet
  as the cause of renal failure, which may be due
  to cancer or an enlarged prostate
• The presence of an epigastric bruit suggests
  renal vascular hypertension

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Causes of Acute Renal Failure

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Causes - Prerenal

• Hypotension may be causing compromised renal
  perfusion
• CHF is implicated as an etiological factor for
  compromised kidney perfusion
• Hypovolemia from either renal loss or extrarenal
  loss may be present
• Patients may have intense vasoconstriction due to
  hypercalcemia, prostaglandin inhibition

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Causes - Intrinsic

• Can be grouped into the following factors
• Vascular
• Interstitial
• Glomerular

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Causes - Vascular

• Vascular causes include
• Vasculitis involving the small vessels
• Scleroderma
• Atheroembolic renal disease
• Malignant hypertension
• Thrombotic angiopathy

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Causes - Interstitial

• Usually results from a reaction to a specific
  drug or a group of drugs
• Most common ones implicated include penicillins,
  NSAIDs, diuretics, cimetidine, and allopurinal

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Causes - Glomerular

• Major factor is glomerulonephritis
• Others include lupus nephritis and hepatitis

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Causes - Postrenal

• Most common cause is secondary to bladder outlet
  obstruction due to prostatic hypertrophy.
• Obstruction must be distal to the bladder or
  bilateral to cause ARF unless only a single
  kidney is functioning properly.
• Renal ultrasound is a quick and noninvasive study
  that can help detect obstruction.

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Laboratory Studies

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Labs BUN / Cr

• Although increased levels of BUN and creatinine
  are hallmarks of renal failure, the rates of
  increase are also important
• BUN showing an increase larger than that of
  creatinine suggest prerenal ischemia

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Labs - CBC

• Tests are helpful, make sure to obtain peripheral
  smear as well
• Peripheral smear may show schistocytes which
  would show conditions such as hemolytic uremic
  syndrome or thrombotic thrombocytopenic purpura

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Labs - Urinalysis

• Remains the most important test in the initial
  evaluation of ARF
• Findings of granular muddy-brown casts are
  suggestive of tubular necrosis
• Reddish brown urine would show acute glomerular
  nephritis or the presence of myoglobin or
  hemoglobin

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Labs Urinalysis - 2

• RBC casts are pathognomonic for glomerular
  disease.
• Dysmorphic RBCs support a glomerular cause such
  as lupus nephritis.
• WBC casts may denote pyelonephritis or acute
  interstitial nephritis.
• Eosinophils suggest urinary tract infections,
  glomerulonephritis, actual embolic disease, or
  drug-induced interstitial nephritis.

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Histology

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Intratubular Cast Formation
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Intratubular Obstruction
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Imaging

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Imaging - Ultrasound

• Renal ultrasonography is useful for evaluating
  obstruction of the urinary collecting system.
• Ultrasound is also useful for detecting intrinsic
  renal disease, which enhances renal echogenicity.
• Ultrasound also aids in performing a renal
  biopsy, if needed to help diagnose ARF.

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Imaging - Doppler

• Useful for detecting presence and nature of renal
  blood flow.
• Quite useful in the diagnosis of thromboembolic
  or renovascular disease.

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Imaging Angiography

• Very helpful in the diagnosis of renal vascular
  disease, including renal artery stenosis, renal
  atheroembolic disease, atherosclerosis with
  aortorenal occlusion, and in certain cases,
  necrotizing vasculitis.

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Procedures - Biopsy

• Very useful in the diagnosis of intrarenal causes
  of ARF.
• In as many as 40 of cases, renal biopsy results
  reveal an unexpected diagnosis.

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Medical Care of Acute Renal Failure

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Medical Care

• Aggressive treatment should begin at the earliest
  indication of renal dysfunction.
• Remember a large proportion of the renal mass is
  damaged before any biochemical evidence is
  appreciated.
• Relationship between the GFR and serum creatinine
  level is exponential, not linear.

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Medical Care - 2

• Maintenance of volume homeostatis and correcting
  biochemical abnormalities remain the primary
  goals of treatment.
• All nephrotoxic agents should be avoided or used
  with extreme caution.
• Medications cleared by renal excretion should be
  avoided or doses adjusted.

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Medical Care - 3

• Corrected acidosis with bicarbonate
  administration is important.
• Current treatment of ARF is mainly supportive in
  nature.
• No therapeutic modalities to date have shown
  efficacy in treating the condition.

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Medical Care - 4

• Hyperkalemia should be treated by decreasing the
  intake of potassium, delaying the absorption of
  potassium, exchanging potassium across the gut
  lumen using potassium-binding resins, controlling
  intracellular shifts, and instituting dialysis.

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Medical Care - 5

• Correcting hematologic abnormalities warrants
  appropriate measures, including transfusions.

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Diet

• Dietary modulation is a very important facet of
  treatment.
• Diet and fluid restriction becomes crucial in the
  management of oliguric renal failure, wherein the
  kidneys do not excrete either toxins or fluid
  adequately.

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Pharmacologic Treatment of Acute Renal Failure

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Pharmacy

• Pharmacologic treatment of ARF has been attempted
  on an empiric basis, with varying success rates.
• Experimental therapies include growth factors,
  vasoactive peptides, adhesion molecules,
  endothelin inhibitors, and bioartificial kidneys.
  Aminophylline has also been used experimentally
  for prophylaxis against renal failure.

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Diuretics

• Although diuretics seem to have no effect on the
  outcome of established ARF, they are useful in
  fluid homeostasis and are used extensively.

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Vasodilators

• Dopamine in small doses causes selective
  dilatation of the renal vasculature, enhancing
  renal perfusion
• Dopamine also reduces sodium absorption, thereby
  decreasing the energy requirement of the damaged
  tubules. This enhances urine flow, which in turn
  helps prevent tubular cast obstruction

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Vasodilators - 2

• Most clinical studies have failed to establish
  this beneficial role of renal-dose dopamine
  infusion.

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Prognosis of Acute Renal Failure

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Prognosis

• Prognosis is directly related to the cause of
  renal failure, and to the duration of failure
  prior to therapeutic intervention.
• There are other prognostic factors to be included.

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Prognostic Factors

• Older age
• Multiorgan failure
• Oliguria
• Hypotension
• Vasopressor support
• Number of transfusions
• Noncavitary surgery

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Dialysis in Acute Renal Failure

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Dialysis

• Great controversy exists regarding the timing of
  dialysis.
• Dialysis may delay the recovery of patients with
  acute renal failure.

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Dialysis Indications

• Volume expansion that cannot be managed with
  diuretics.
• Hyperkalemia
• Correction of severe acid-base disturbances.
• Severe azotemia (BUN gt 100)
• Symptoms of uremic pericarditis, gastritis,
  seizures, or encephalopathy.

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Core Question Exam

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Question 1

• All of the following are causes of acute renal
  failure within the clinical setting, except
• Hypotension
• CHF
• Intense Vasoconstriction
• Red, swollen, inflamed joints
• Malignant Hypertension

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Question 1

• All of the following are causes of acute renal
  failure within the clinical setting, except
• Hypotension
• CHF
• Intense vasoconstriction
• Red, swollen, inflamed joints
• Malignant hypertension

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Question 2

• Factors which increase a patients risk for acute
  renal failure include all of the following
  except
• Hypertension
• Congestive heart failure
• Diabetes mellitus type II
• Myeloma
• Celiac Sprue

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Question 2

• Factors which increase a patients risk for acute
  renal failure include all of the following
  except
• Hypertension
• Congestive heart failure
• Diabetes mellitus type II
• Myeloma
• Celiac Sprue

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Question 3

• All of the following medications can play a role
  in acute renal failure except
• Penicillins
• NSAIDs
• Leflunomide
• Diuretics
• Cimetidine

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Question 3

• All of the following medications can play a role
  in acute renal failure except
• Penicillins
• NSAIDs
• Leflunomide
• Diuretics
• Cimetidine

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