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Acute Renal Failure

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Topic updated on 01/15/17 8:26am

 
Prerenal
Prerenal
Renal
Postrenal
 
Kidneys not perfused
Kidneys parenchyma not functioning
Kidneys output obstructed
FeNa
< 1%
> 2%
> 4%
BUN / Creatinine
> 20
< 15
> 15
Urine Na
< 20
> 20
> 40
Urine Osmolarity
> 500
< 350
< 350
Causes 1. Volume depletion
2. Heart failure
3. Liver failure
4. Sepsis
5. Heat stroke (myoglobinuria)
6. Burns
7. Bilateral renal stenosis
8. Drugs (NSAIDS)
1. ATN (most common)
2. Renal ischemia
3. Nephrotoxin

Obstruction due to:
1. BPH

2. Tumors

3. Calculi

4. Recent surgery

 
Introduction
  • Defined as an abrupt decrease in renal function leading to
    • azotemia (elevated creatinine and BUN)
    • oliguria (<500mL / day)
  • Acute Renal Failure is categorized into three types
Presentation
  • Symptoms
    • anorexia
    • fatigue
    • mental status changes
    • nausea and vomiting
    • pruritus
    • shortness of breath
  • Physical exam
    • asterixis and myoclonus
    • pericardial or pleural rub
    • arrhythmias 
    • oliguria
    • peripheral edema
    • pulmonary rales
Evaluation
  • Always pass a urinary catheter to rule out obstruction  (post renal)
  • Renal ultrasound to rule-out upstream obstruction (stone)
  • Calculate FeNa = (UrineNa / Plasma Na) / (Urine Cr / Plasma Cr)

    Disease
    Microscopic Urine Analysis
    End Stage Renal Failure Waxy casts
    ATN muddy brown granular casts
    Pyelonephritis White Blood Cell (WBC) Casts
    Glomerulonephritis Red Blood Cell Casts (pathognomonic)
    Nephrotic Syndrome Double-refractile fat bodies
    Atheroembolic disease Urinary eosinophils 
    Allergic nephritis Urinary eosinophils
Differential
  • See table above.
Treatment
  • Fluid and electrolyte balance
  • Dialysis if indicated by
    • Acidosis
    • Electrolyte Abnormality (e.g. K > 6.5)
    • Ingestions
    • Overloaded fluid
    • Uremic Symptoms of pericarditis and encephalopathy
Prognosis, Prevention, and Complications
  • Prevention
    • contrast-induced nephropathy
      • good hydration before contrast administration
  • Complications
    • anemia due to failure of erythropoeitin production
    • renal osteodystrophy due to decreased activation of Vitamin D
    • hyperkalemia leading to cardiac arrest
    • Na and H2O excess leading to CHF and pulmonary edema


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Qbank (2 Questions)

TAG
(M2.RL.42) A 70-year-old man was diagnosed two days ago with a myocardial infarction and underwent percutaneous coronary intervention to reperfuse his left anterior descending artery. Two days later his creatinine is noted to be elevated (despite being normal the day before) and he complains of a "rash" on his foot (Figure A). Which of the following would most likely be found in laboratory studies? Topic Review Topic
FIGURES: A          

1. Hyponatremia
2. Hypokalemia
3. Granular urinary casts
4. Elevated white blood count in urine
5. Eosinophiluria

PREFERRED RESPONSE ▶
TAG
(M2.RL.72) A 75-year-old male presents to an otolaryngologist for evaluation of worsening hoarseness for the last several months. On laryngoscopic examination, he is noted to have a suspicious mass of the true vocal cord extending anteriorly to the anterior commissure. Suspecting laryngeal carcinoma he is sent for a CT of the neck with iodinated contrast as part of the staging evaluation. Several days later he presents to the emergency room with nausea, vomiting, and confusion. Upon serological exam he was noted to have a BUN of 42 mg/dL (normal range = 20-40) and creatinine of 3.1 mg/dL (normal range = 0.7-1.2). What could have prevented this patient's acute condition? Topic Review Topic

1. Preprocedural hydration with isotonic solution
2. Preprocedural administration of N-acetylcysteine
3. Preprocedural administration of ACE-inhibitors
4. Postprocedural dialysis
5. Postprocedural hydration with isotonic solution

PREFERRED RESPONSE ▶

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Cooper BA, Branley P, Bulfone L, Collins JF, Craig JC, Fraenkel MB, Harris A, Johnson DW, Kesselhut J, Li JJ, Luxton G, Pilmore A, Tiller DJ, Harris DC, Pollock CA; IDEAL Study.
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