ACUTE RENAL FAILURE

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ACUTE RENAL FAILURE

• Pirouz Daeihagh, M.D.
• Internal medicine/Nephrology
• Wake Forest University
• School of Medicine

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Background

• Common in Hospitalized patients
• Associated with high Morbidity and Mortality
• Often Multifactorial
• Identifiable risk factors.

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Acute Renal Failure

• Sudden decrease in function (hours-days)
• Often multifactorial
• Pre-renal and intrinsic renal causes 70
• oliguric UOP lt 400 ml
• Non-oliguric (up to 65)
• Associated with high mortality and morbidity

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Acute Renal Failure Diagnosis

• Laboratory Evaluation
• Scr, More reliable marker of GFR
• Falsely elevated with Septra, Cimetidine
• small change reflects large change in GFR
• BUN, generally follows Scr increase
• Elevation may be independent of GFR
• Steroids, GIB, Catabolic state, hypovolemia
• BUN/Cr helpful in classifying cause of ARF
• ratiogt 201 suggests prerenal cause
• ratio 10-151 suggests intrinsic renal cause

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Acute Renal Failure Diagnosis (contd)

• Urinalysis
• Unremarkable in pre and post renal causes
• Differentiates ATN vs. AIN. vs. AGN
• Muddy brown casts in ATN
• WBC casts in AIN
• Hansel stain for Eosinophils

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Acute Renal Failure Diagnosis (contd)

• Urinary Indices
• FE Na (U/P) Na X (P/U)CrX 100
• FENa lt 1 C/W Pre-renal state
• May be low in selected intrinsic cause
• Contrast nephropathy
• Acute GN
• Myoglobin induced ATN
• FENagt 1 C/W intrinsic cause of ARF

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Prerenal Azotemia

• Nearly as common as ATN (think of as early part
  of the disease spectrum)
• Diagnose by history and physical exam
• N/V, Diarrhea, Diuretic use,...
• low FENa (lt1)
• high BUN/creat ratio, normal urinary sediment
• Treat by correction of predisposing factors

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Acute Renal Failure Etiologies

• Acute Tubular Necrosis
• Most common cause of intrinsic cause of ARF
• Often multifactorial
• Non-oliguria carries better prognosis
• Ischemic ATN
• Hypotension, sepsis, prolonged pre-renal state
• Nephrotoxic ATN
• Contrast, Antibiotics, Heme proteins

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Acute Tubular Necrosis (ATN) -- 2

• Diagnose by history, ? FENa (gt2)
• sediment with coarse granular casts, RTE cells
• Treatment is supportive care.
• Maintenance of euvolemia (with judicious use of
  diuretics, IVF, as necessary)
• Avoidance of hypotension
• Avoidance of nephrotoxic medications (including
  NSAIDs and ACE-I) when possible
• Dialysis, if necessary
• 80 will recover, if initial insult can be
  reversed.

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Contrast nephropathy

• 12-24 hours post exposure, peaks in 3-5 days
• Non-oliguric, FE Na lt1 !!
• RX/Prevention 1/2 NS 1 cc/kg/hr 12 hours
  pre/post
• Mucomyst 600 BID pre/post (4 doses)
• Risk Factors CRF, Hypovolemia.

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Rhabdomyolytic ARF

• Diagnose with ? serum CPK (usu. gt 10,000), urine
  dipstick () for blood, without RBCs on
  microscopy, pigmented granular casts
• Common after trauma (crush injuries), seizures,
  burns, limb ischemia occasionally after IABP or
  cardiopulmonary bypass
• Treatment is largely supportive care.
• Alkalinization of urine .

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Acute Glomerulonephritis

• Rare in the hospitalized patient
• Most common types acute post-infectious GN,
  crescentic RPGN
• Diagnose by history, hematuria, RBC casts,
  proteinuria (usually non-nephrotic range), low
  serum complement in post-infectious GN), RPGN
  often associated with anti-GBM or ANCA
• Usually will need to perform renal biopsy

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Acute Glomerulonephritis (2)

• If diagnosis is post-infectious, disease is
  usually self-limited, and supportive care is
  usually all that is necessary.
• For RPGN, may need immunosuppressive therapy with
  steroids Cytoxan, plasmapheresis (if assoc.
  with anti-GBM)

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Atheroembolic ARF

• Associated with emboli of fragments of
  atherosclerotic plaque from aorta and other large
  arteries
• Diagnose by history, physical findings (evidence
  of other embolic phenomena--CVA, ischemic digits,
  blue toe syndrome, etc), low serum C3 and C4,
  peripheral eosinophilia, eosinophiluria, rarely
  WBC casts
• Commonly occur after intravascular procedures or
  cannulation (cardiac cath, CABG, AAA repair, etc.)

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Acute Interstitial Nephritis

• Usually drug induced
• methicillin, rifampin, NSAIDS
• Develops 3-7 days after exposure
• Fever, Rash , and eosinophilia common
• U/A reveals WBC, WBC casts, Hansel stain
• Often resolves spontaneously
• Steroids may be beneficial ( if Scrgt2.5 mg/dl)

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Acute Renal Failure Etiologies

• Post-Renal
• Bladder outlet obstruction
• BPH, intrapelvic pathology
• Crystalluria
• Acyclovir, Indanivir, Uric Acid
• Papillary tip necrosis
• DM with pyelonephritis
• Analgesic abuse
• Sickle cell disease

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Prevention

• What works?
• Maintenance of euvolemia
• Avoidance of nephrotoxins when possible
• NSAIDs, aminoglycoside, Amphotericin, IV contrast
• BP control--avoidance of excessive hypo- or
  hypertension

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Prevention

• What doesnt work?
• Empiric use of
• Diuretics (i.e., Furosemide, Mannitol)
• Dopamine (or Dopamine agonists such as
  Fenoldopam)
• Calcium-channel blockers

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Acute Renal Failure Treatment

• Water and sodium restriction
• Protein restriction
• Potassium and phosphate restriction
• Adjust medication dosages
• Avoidance of further insults
• BP support
• Nephrotoxins

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Hyperkalemia

• Highly Arrhythmogenic
• Usually with progressive EKG changes
• Peaked T waves ---gt Widened QRS--gt Sinus wave
• Kgt 5.5 meq/L needs evaluation/intervention
• Usually in setting of Decrease GFR but
• medication also a common cause
• ACEI
• NSAIDS
• Septra, Heparin

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Dialysis Indications

• Refractory hyperkalemia
• Metabolic acidosis
• Volume overload
• Mental status changes

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