|
Snapshot
  • A 54-year-old man is admitted to the cardiac care unit after coronary angiography and revascularization secondary to unstable agina. Approximately 1 week after the procedure he is found to have a "bluish" discoloration of the first and second digits of the foot. Laboratory testing is significant for an elevated serum creatinine. A urinalysis is benign. (Renal atheroemboli)
Introduction
  • Clinical definition
    • acute reduction in glomerular filtration rate (GFR)
      • recall that GFR represents the sum of the filtration rates of nephrons
        • therefore, GFR reflects functioning renal mass
  • Epidemiology
    • risk factors
      • hypertension
      • chronic kidney disease
      • dehydration and volume depletion
      • diabetes
      • chronic liver or lung disease
  • Etiology
    • prerenal causes
      • decreased renal perfusion (e.g., hemorrhage, congestive heart failure, and diuretic use)
    • intrarenal causes
      • acute tubular necrosis
        • ischemia and toxic causes
      • interstitial nephritis
      • glomerulonephritis
      • vasculitis
      • hemolytic uremic syndrome
      • cholesterol emboli
    • postrenal causes 
      • urinary flow obstruction (e.g., benign prostatic hyperplasia and nephrolithiasis)
      • post-operative secondary to bladder manipulation and anesthesia
        • bladder scans should be performed followed by urinary catheterization
  • Pathogenesis
    • based upcome etiology (look at etiology)
  • Prognosis
    • lower rates of recovery in patients > 65 years of age
    • increased risk of end-stage renal disease, chronic kidney disease, and mortality
Presentation
  • Symptoms
    • may be asymptomatic
    • oliguria
    • anuria
    • polyuria
    • confusion
  • Physical exam
    • hypertension
    • edema
    • decreased urine output
Imaging
  • Renal ultrasound
    • indication
      • initial imaging study for assessing acute kidney injury
        • can assess for renal size and hydronephrosis
        • to assess for postrenal obstruction
Studies
  • Labs
    • increase in serum creatinine by ≥ 0.3 mg/dL within 48 hours
    • blood urea nitrogen (BUN):creatinine ratio
    • urinalysis
      • dipstick
        • to assess for protein, glucose, leukocyte esterase, hemoglobin and myoglobin, and specific gravity
      • microscopy
        • for example
          • red dysmorphic cells suggests a glomerular etiology (e.g., glomerulonephritis)
          • muddy brown casts suggests tubular necrosis
          • white blood cell casts suggest pyelonephritis or acute interstitial nephritis
    • fractional excretion of Na+ (FeNa+)
      • if patient is on diuretics use FeUrea
    • urine osmolality and Na+
 
Studies To Assess For Prerenal, Intrarenal, and Postrenal Acute Kidney Injury (AKI)
Studies
Prerenal AKI Intrarenal AKI
Postrenal AKI
Urine osmolality (mOsm/kg)
  • > 500
  • < 350
  • < 350
FeNa+
  • < 1%
  • > 2%
  • < 1% in mild cases
  • > 2% in severe cases
Urine Na+ (mEq/L)
  • < 20
  • > 40
  • > 40
Serum BUN/Cr
  • > 20:1
  • < 15:1
  • Variable
 
Differential
  • Acute gastrointestinal bleeding
  • Rhabdomyolysis
  • Medication-induced impairment of creatinine secretion
    • cimetidine
    • trimethoprim
    • pyrimethamine
Treatment
  • Treatment is dependent on the etiology of AKI and its consequences
    • for example
      • a patient who is hyperkalemic and not responding to medical treatment should be dialyzed
      • a patient with a history of excessive fluid loss (e.g., diarrhea and vomiting) should be given intravenous fluid
Complications
  • Hyperkalemia
  • Metabolic acidosis 
  • Uremic encephalopathy and platelet dysfunction
  • Anemia
  • Chronic kidney disease
 

Please rate topic.

Average 4.0 of 2 Ratings

Questions (3)
EVIDENCE & REFERENCES (4)
POSTS (1)
Topic COMMENTS (18)
Private Note