questions 5

Acute Renal Failure

Topic updated on 02/01/17 1:28pm

Kidneys not perfused 
Kidneys parenchyma not functioning
Kidneys output obstructed
< 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

  • Defined as an abrupt decrease in renal function leading to
    • azotemia (elevated creatinine and BUN)
    • oliguria (<500mL / day)
    • metabolic alkalosis 
  • Acute Renal Failure is categorized into three types
  • 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
  • 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)

    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
  • See table above.
  • 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


Qbank (2 Questions)

(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

(M2.RL.4754) A 69-year-old male presents to the emergency department for sudden shortness of breath that came on while he was sleeping. He currently is short of breath, but denies any chest pain, arm pain, or jaw pain. The patient has a past medical history of hypertension, obesity, diabetes, and GERD. The patient states he has not filled his prescriptions for any of his medications in months and cannot remember what his medications are. An EKG is performed and is seen in Figure A. A chest radiograph is obtained and is seen in Figure B. Lab values at admission are below:

Na+: 139 mEq/L
K+: 4.0 mEq/L
Cl-: 100 mEq/L
HCO3-: 24 mEq/L
BUN: 22 mg/dL
Glucose: 72 mg/dL
Ca2+: 9.9 mg/dL
Mg2+: 1.5 mEq/L
Creatinine: 0.9 mg/dL

The patient is started on appropriate treatment and his symptoms resolve. He is recovering on the medicine floor. His laboratory values are ordered and are below:

Na+: 137 mEq/L
K+: 3.5 mEq/L
Cl-: 100 mEq/L
HCO3-: 26 mEq/L
BUN: 39 mg/dL
Glucose: 70 mg/dL
Ca2+: 9.7 mg/dL
Mg2+: 1.5 mEq/L
Creatinine: 1.5 mg/dL

The patient states that he has not urinated in the past 24 hours. Which of the following is the most likely cause of this patient's current presentation? Topic Review Topic
FIGURES: A   B        

1. Furosemide
2. Intrarenal kidney injury
3. Urinary tract obstruction
4. Chronic kidney disease
5. Cholesterol emboli

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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.
N Engl J Med. 2010 Aug 12;363(7):609-19. PMID: 20581422 (Link to Pubmed)
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