Acute Renal Failure

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Acute Renal Failure

• Deb Goldstein
• Argy Resident
• September, 2005

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Acute Renal Failure

• Rapid decline in the GFR over days to weeks.
• Cr increases by gt0.5 mg/dL
• GFR lt10mL/min, or lt25 of normal
• Acute Renal Insufficiency
• Deterioration over days-wks
• GFR 10-20 mL/min

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Definitions

• Anuria No UOP
• Oliguria UOPlt400-500 mL/d
• Azotemia Incr Cr, BUN
• May be prerenal, renal, postrenal
• Does not require any clinical findings
• Chronic Renal Insufficiency
• Deterioration over mos-yrs
• GFR 10-20 mL/min, or 20-50 of normal
• ESRD GFR lt5 of nl

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ARF Signs and Symptoms

• Hyperkalemia
• Nausea/Vomiting
• HTN
• Pulmonary edema
• Ascites
• Asterixis
• Encephalopathy

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Causes of ARF in hospitalized pts

• 45 ATN
• Ischemia, Nephrotoxins
• 21 Prerenal
• CHF, volume depletion, sepsis
• 10 Urinary obstruction
• 4 Glomerulonephritis or vasculitis
• 2 AIN
• 1 Atheroemboli

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ARF Focused History

• Nausea? Vomiting? Diarrhea?
• Hx of heart disease, liver disease, previous
  renal disease, kidney stones, BPH?
• Any recent illnesses?
• Any edema, change in
• urination?
• Any new medications?
• Any recent radiology studies?
• Rashes?

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Physical Exam

• Volume Status
• Mucus membranes, orthostatics
• Cardiovascular
• JVD, rubs
• Pulmonary
• Decreased breath sounds
• Rales
• Rash (Allergic interstitial nephritis)
• Large prostate
• Extremities (Skin turgor, Edema)

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W/U for ARF

• Chem 7
• Urine
• Urine electrolytes and Urine Cr to calculate FeNa
• Urine eosinophils
• Urine sediment casts, cells, protein
• Uosm
• Kidney U/S - r/o hydronephrosis

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FeNa (urine Na x plasma Cr)
(plasma Na x urine Cr)

• FeNa lt1
• 1. PRERENAL
• Urine Na lt 20. Functioning tubules reabsorb lots
  of filtered Na
• 2. ATN (unusual)
• Postischemic dz most of UOP comes from few
  normal nephrons, which handle Na appropriately
• ATN chronic prerenal dz (cirrhosis, CHF)
• 3. Glomerular or vascular injury
• Despite glomerular or vascular injury, pt may
  still have well-preserved tubular function and be
  able to concentrate Na

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More FeNa

• FeNa 1-2
• 1. Prerenal-sometimes
• 2. ATN-sometimes
• 3. AIN-higher FeNa due to tubular damage
• FeNa gt2
• ATN
• Damaged tubules can't reabsorb Na

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Calculating FeNa after pt has gotten Lasix...

• Caution with calculating FeNa if pt has gotten
  Loop Diuretics in past 24-48 h
• Loop diuretics cause natriuresis (incr urinary Na
  excretion) that raises U Na-even if pt is
  prerenal
• So if FeNagt1, you dont know if this is because
  pt is euvolemic or because Lasix increased the U
  Na
• So helpful if FeNa still lt1, but not if FeNa gt1
• 1. Fractional Excretion of Lithium (endogenous)
• 2. Fractional Excretion of Uric Acid
• 3. Fractional Excretion of Urea

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A 22yo male with sickle cell anemia and abdominal
pain who has been vomiting nonstop for 2 days.
BUN45, Cr2.2.

• A. ATN
• B. Glomerulo-nephritis
• C. Dehydration
• D. AIN from NSAIDs

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Prerenal ARF

• Hyaline casts can be seen in normal pts
• NOT an abnormal finding
• UA in prerenal ARF is normal
• Prerenal causes 21 of ARF in hosp. pts
• Reversible
• Prevent ATN with volume replacement
• Fluid boluses or continuous IVF
• Monitor Uop

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Prerenal causes

• Intravascular volume depletion
• Hemorrhage
• Vomiting, diarrhea
• Third spacing
• Diuretics
• Reduced Cardiac output
• Cardiogenic shock, CHF, tamponade, huge PE....
• Systemic vasodilation
• Sepsis
• Anaphylaxis, Antihypertensive drugs
• Renal vasoconstriction
• Hepatorenal syndrome

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Intrinsic ARF

1. Tubular (ATN)
2. Interstitial (AIN)
3. Glomerular (Glomerulonephritis)
4. Vascular

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You evaluate a 57yo man w/ oliguria and rapidly
increasing BUN, Cr.

1. ATN
2. Acute glomerulonephritis
3. Acute interstitial nephritis
4. Nephrotic Syndrome

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ATN

• Muddy brown granular casts (last slide)
• Renal tubular epithelial cell casts (below)

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More ATN

• Broad casts (form in dilated, damaged tubules)

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ATN Causes

• 1. Hypotension
• Relative low BP
• May occur immediately after low BP episode or up
  to 7 days later!
• 2. Post-op Ischemia
• Post-aortic clamping, post-CABG
• 3. Crystal precipitation
• 4. Myoglobinuria (Rhabdo)
• 5. Contrast Dye
• ARF usually 1-2 days after test
• 6. Aminoglycosides (10-26)

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ATNWhat to do

• Remove any offending agent
• IVF
• Try Lasix if euvolemic pt is not peeing
• Dialysis
• Most pts return to baseline Cr in 7-21 days

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ATN Prerenal
Cr increases at 0.3-0.5 /day increases slower than 0.3 /day
U Na, FeNa UNagt40 FeNa gt2 UNalt20 FeNalt1
UA epi cells, granular casts Normal
Response to volume Cr wont improve much Cr improves with IVF
BUN/Cr 10-151 gt201
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Which UA is most compatible w/contrast-induced
ATN?

1. Spec grav 1.012, 20-30 RBC, 15-20 WBC, Eos
2. Spec grav 1.010, 1-3 WBC, 5-10 renal tubular
   cells, many granular casts, occasional renal
   tubular cell casts, no eos
3. Spec grav 1.012, 5-10 RBC, 25-50 WBC, many bact,
   occasional fine granular casts, no eos
4. Spec grav 1.020, 10-20 RBC, 2-4 WBC, 1-3 RBC
   casts, no eos

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ATN

• B. Spec grav 1.010, 1-3 WBC, 5-10 renal tubular
  cells, many granular casts, occasional renal
  tubular cell casts, no eos
• Dilute urine failure to concentrate urine
• No RBC casts or WBC casts in ATN
• Eos classically in AIN or renal atheroemboli, but
  nonspecific

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56yo woman with previously normal renal function
now has BUN24, Cr 1.8. Which drug is
responsible?

1. Indinavir for her HIV
2. Gentamicin for her SBE
3. Motrin for her OA
4. Cyclosporin for her SLE

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WBC Casts

• Cells in the cast have nuclei
• (unlike RBC casts)
• Pathognomonic for Acute Interstitial Nephritis

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Acute Interstitial Nephritis

• 70 Drug hypersensitivity
• 30 Antibiotics PCNs (Methicillin),
  Cephalosporins, Cipro
• Sulfa drugs
• NSAIDs
• Allopurinol...
• 15 Infection
• Strep, Legionella, CMV, other bact/viruses
• 8 Idiopathic
• 6 Autoimmune Dz (Sarcoid, Tubulointerstitial
  nephritis/Uveitis)

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AIN from Drugs

• Renal damage is NOT dose-dependent
• May take wks after initial exposure to drug
• Up to 18 mos to get AIN from NSAIDS!
• But only 3-5 d to develop AIN after second
  exposure to drug
• Fever (27)
• Serum Eosinophilia (23)
• Maculopapular rash (15)
• Bland sediment or WBCs, RBCs, non-nephrotic
  proteinuria
• WBC Casts are pathognomonic!
• Urine eosinophils on Wrights or Hansels Stain
• Also see urine eos in RPGN, renal atheroemboli...

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AIN Management

• Remove offending agent
• Most patients recover full kidney function in 1
  year
• Poor prognostic factors
• ARF gt 3 weeks
• Advanced age at onset

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You evaluate a 32yo woman with HTN, oliguria, and
rapidly increasing Cr, BUN. You spin her urine

1. ATN
2. Acute glomerulonephritis
3. Acute interstitial nephritis
4. Nephrotic Syndrome

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Acute Glomerulonephritis

• RBC casts cells have no nuclei
• Casts in urine think INTRINSIC renal dz
• If she has Lupus w/recent viral prodrome, think
  Rapidly Progressive Glomerulonephritis
• If she had a sore throat 10 days ago, think
  Postinfectious Proliferative Glomerulonephritis

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What are these?
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Glomerular Dz

• Hematuria (dysmorphic RBCs)
• RBC casts
• Lipiduria (increased glomerular permeability)
• Proteinuria (may be in nephrotic range)
• Fever, rash, arthralgias, pulmonary sx
• Elevated ESR, low complement levels

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Rapidly Progressive Glomerulonephritis

• Type 1 Anti-GBM dz
• Type 2 Immune complex
• IgA nephropathy
• Postinfectious glomerulonephritis
• Lupus nephritis
• Mixed cryoglobulinemia
• Type 3 Pauci-immune
• Necrotizing glomerulonephritis (often
  ANCA-positive, assoc. w/vasculitis)
• Can present with viral-like prodrome
• Myalgias, arthralgias, back pain, fever, malaise
• Kidney bx Extensive cellular crescents with or
  w/o immune complexes
• Can develop ESRD in days to weeks.
• Treat w/glucocorticoids cyclophosphamide.

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Postinfectious Proliferative Glomerulonephritis

• Usually after strep infxn of upper respiratory
  tract or skin 8-14 day latent period
• Can also occur in subacute bacterial
  endocarditis, visceral abscesses, osteomyelitis,
  bacterial sepsis
• Hematuria, HTN, edema, proteinuria
• Positive antistreptolysin O titer (90 upper
  respiratory and 50 skin)
• Treatment is supportive
• Screen family members with throat culture and
  treat with antibiotics if necessary

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A 19yo woman with Breast Cancer s/p chemo in the
ER has weakness, fever, rash. WBC15.4, Hct 24,
Cr 2.9, LDH 600, CK600. UA3 prot, 3blood, 20
RBC. What next test do you order? Whats her
likely dx?

1. Nephrotic Syn
2. Systemic Vasculitis
3. Acute Glomerulonephritis
4. Hemolytic-Uremic Syn
5. Rhabdomyolysis

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TTP

• Order blood smear to r/o TTP
• TTP associated with malignancy, chemo
• TTP may mimic Glomerulonephritis on UA (RBCs,
  WBCs)
• Thrombocytopenia, anemia not consistent with
  nephrotic or nephritic syndrome
• Need CK in the thousands to cause ARF

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Microvascular ARF

• TTP/HUS
• HELLP syndrome
• Platelets form thrombi and deposit in
  kidneys?Glomerular capillary occlusion or
  thrombosis
• Plasma exchange, steroids, Vincristine, IVIG,
  splenectomy....

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Macrovascular ARF

• Aortic Aneurysm
• Renal artery dissection or thrombosis
• Renal vein thrombus
• Atheroembolic disease
• New onset or accelerated HTN?
• Abdominal bruits, reduced femoral pulses?
• Vascular disease?
• Embolic source?

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Your 68yo male inpatient with baseline Cr1.2 had
negative cardiac cath 4 days ago, now Cr1.8 and
blanching rash.

• Renal Artery Stenosis
• Contrast-Induced Nephropathy
• C. Abdominal Aortic Aneurysm
• D. Cholesterol Atheroemboli

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Why do his toes look like this?
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Renal Atheroembolic Dz

• 1 of Cardiac caths atheromatous debris scraped
  from the aortic wall will embolize
• Retinal
• Cerebral
• Skin (Livedo Reticularis, Purple toes)
• Renal (ARF)
• Gut (Mesenteric ischemia)
• Unlike in Contrast-Induced Nephropathy, Cr will
  NOT improve with IVF
• Diagnosis of exclusion will NOT show up on MRI
  or Renal U/S WILL show up on renal bx
• Tx supportive

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Post-Renal ARF

• Urethral obstruction prostate, urethral
• stricture.
• Bladder calculi or neoplasms.
• Pelvic or retroperitoneal neoplams.
• Bilateral ureteral obstruction (neoplasm,
• calculi).
• Retroperitoneal fibrosis.

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Doc, your pt hasnt peed in 5 hrs....what do you
want to do?

• Examine pt Dry? Septic (vasodilated)?
• Flush foley (sediment can obstruct outflow)
• Check I/Os (has she been drinking?)
• Give IV BOLUS (250-500cc IVF), see if pt pees in
  next 30-60 min
• If she pees, then she was dry
• If she doesnt pee, then shes either REALLY dry
  or in renal failure
• Check UA, UCx, urine lytes
• Consider Renal U/S if reasonable

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Youre called to the ER to see...

• A 35yo woman with previously normal renal
  function now with BUN60, Cr3.5. Do you call
  the Renal fellow to dialyze this pt?
• What if her K5.9?
• What if her K7.8?

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Indications for acute dialysis

• AEIOU
• Acidosis (metabolic)
• Electrolytes (hyperkalemia)
• Ingestion of drugs/Ischemia
• Overload (fluid)
• Uremia

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• You admit this pt to telemetry and aggressively
  hydrate her.
• You recheck labs 6h later and BUN85, Cr4.2.
  Suddenly the pt starts to seize.
• Now what?

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UremiaSo what?

• General
• Fatigue, weakness
• Pruritis
• Mental status change
• Uremic encephalopathy
• Seizures
• Asterixis
• GI disturbance
• Anorexia, early satiety, N/V,
• Uremic Pericarditis
• Plt dysfunction/bleeding

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A pt with chronic lung disease has acute
pleuritic pain and desats to 92RA. You want to
r/o PE but her Cr1.4. Can you get a CT with IV
contrast?

• Send her for Stat CT with IV contrast
• Send her for Stat CT without IV contrast
• C. Just give her heparin
• Begin IV hydration
• Begin pre-procedure Mannitol
• Get a VQ scan instead

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Contrast-Induced Nephrotoxicity

• Cr increases by 25 or gt0.05 post-procedure
• Contrast causes renal vasoconstriction? renal
  hypoxia
• Iodine itself may be renally toxic
• If Crgt1.4, use pre-procedure prophylaxis

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Pre-Procedure Prophylaxis

• 1. IVF ( 0.9NS)
• 1-1.5 mg/kg/hour x12 hours prior to procedure and
  6-12 hours after
• 2. Mucomyst (N-acetylcysteine)
• Free radical scavenger prevents oxidative tissue
  damage
• 600mg po BID x 4 doses (2 before procedure, 2
  after)
• 3. Bicarbonate (JAMA 2004)
• Alkalinizing urine should reduce renal medullary
  damage
• D5W with 3 amps HCO3 bolus 3.5 mL/kg 1 hour
  preprocedure, then 1mL/kg/hour for 6 hours
  postprocedure
• 4. Possibly helpful? Fenoldopam, Dopamine
• 5. Not helpful! Diuretics, Mannitol