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