Wednesday, April 18, 2012

Chronic Kidney Disease

GFR total = GFR single nephron  x  total # of nephrons

How to measure?
creatinine clearance is overestimate since creatinine is secreted (10%)
CKD EPI equation  kidney.org

Creatine clearance noisy (see graph)

Chronic kidney disease
  • kidney disease > 3 months
  • with or without decreased GFR
    • pathological abnl
    • abnl blood, urine
    • abnl imaging
  • GFR < 60 ml/min/1.73 m2
  • Identification
    • GFR
    • albuminuria
  • Prevalence = 23 million (1 in 8 people)
  • Progession CKD
    • intact nephron hypothesis
      • remaining nephrons increase their GFR
      • glomerular hypertrophy results
      • glomerular hypertension results in proteinuria - treat with ACE inhibitors (dilation of efferent arterioles)
    • trade off hypothesis
    •  
  • Stages of CKD
    • stage 1 - GFR >90
    • stage 2 - GFR 60-89
    • stage 3 - GFR 30-59
    • stage 4 - GFR 15-29 -  all patients should be referred for transplant
    • stage 5 - GFR  < 15 - need renal replacement therapy
  • Risk factors for CKD
    • African Americans (3.8 x)
    • Zuni Indians (highest rate in world)
    • age (GFR declines 1 ml/min/year starting at age 45)
    • etc.
  • Screening for CKD
    • proteinuria
  • Complications of CKD
    • anemia - decreased EPO production
      • keep Hb at 10-11 g/dL
      • treat with Fe
      • use EPO stimulating agents only if Hb < 10g/dL (increased risk of stroke if ESA used with Hb>11 g/dL
    • Secondary hyperparathyroidism (trade off hypothesis)
      • hypocalcemia - decreased Vit. D -stimulate PTH
        • treat with activated Vit. D.  
        • inhibiter of CaSR, decreases PTH secretion ($5000 per month)
      • hyperphosphatemia 
    • malnutrition
      • low albumin in plasma = increased mortality risk
      • goal albumin > 3.5-4 g/dL
    • hyperkalemia
      • goal keep K < 5 mEq/L
    • acidosis
      • goal keep HCO3- > 20-22mEq/dL
    • uremia
      • abnl water/electrolytes
      • cardiovascular
      • GI
      • blood
      • neuro
      • endocrine
  • Treatment
    • Renal replacement therapy -
      • hemodialysis
        • av fistula allows high flows in vein for dialysis
        • countercurrent exchange - diffusion & ultrafiltration (hydrostatic pressure removes excess fluid - also lose some wanted solutes)
      • peritoneal dialysis 
        • glucose containing solution (hyperosmotic) infused into peritoneal cavity
        • osmotic attraction for plasma to lose water and solutes
        • fluid then drained
    • transplantation - lowers mortality 
      • deceased donor
        • 6 year waiting list in NM (longest for type O)
        • greatest success with HLA identical sibling donor (Human Leukocyte Antigen)
      • living related & unrelated
        • tested for eligibility
        • recipient treated with immune suppressants 
All the normal homeostatic mechanisms of the kidney are impaired in CKD 

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