Chemistry Chapter 11

  1. BUN (Blood Urea Nitrogen)
    • Product of protein catabolism
    • Filtered by the glomerulus but also reabsorbed by renal tubules
    • Some is lost through the skin and the GI tract
  2. Plasma BUN is affected:
    • Renal function
    • Dietary protein
    • Protein catabolism
  3. What are the most important NPN's?
    • BUN (Blood Urea Nitrogen)
    • Creatinine
    • Uric acid
    • Ammonia
  4. Azotemia
    Elevated plasma BUN
  5. Disease correlations Prerenal increased BUN
    • (Not related to renal function)
    • Low Blood Pressure (CHF, Shock, hemorrhage, dehydration)
    • Decreased blood flow to kidney (No filtration)
    • Increased dietary protein
  6. Disease correlations Prerenal decreased BUN
    • (Not related to renal function)
    • Decreased dietary protein
    • Increased protein synthesis (Pregnant women, children)
  7. Renal causes of increased BUN
    • Renal disease with decreased glomerular filtration
    • -Glmerular nephritis
    • -Renal failure from Diabetes Mellitus
  8. Post renal causes of increased BUN
    • (Not related to renal function)
    • Obstruction of urine flow
    • -Kidney stones
    • -Bladder or prostate tumors
    • -UTIs
  9. Normal BUN/Creatinine ratio
    10 - 20 to 1
  10. Increased BUN     
    Normal Creatinine
    • Pre-renal increased BUN/Creat ratio
    • BUN is more susceptible to non-renal factors
  11. Increased BUN        
    Increased Creatinine
    • Post-renal increased ratio BUN/Creat ratio
    • Both BUN and Creat are elevated
  12. Decreased BUN    
    Normal Creatinine
    • Renal decreased BUN/Creat ratio
    • Low dietary protein or severe liver disease
  13. BUN analytical methods
    • Specimen: plasma or serum
    • To convert BUN to Urea: BUN x 2.14=Urea(mg/dl)
  14. Creatinine
    • Plasma creatine is a function of glomerular filtration
    • Unaffected by other factors
    • It's a very good test to evaluate renal function
  15. Creatinine disease correlations
    • Increased: decreased glomerular filtration (renal function)
    • Plasma creatinine is unaffected by diet
    • Very stable from day to day
  16. Jaffee Method
    • Creatinin analytical technique
    • Creatinine + Picrate Acid ---> Colored chromogen
    • Specimen: Plasma or serum
    • Elevated bilirubin and hemolysis causes falsely decreased results
    • Reference range: 0.5 - 1.5 mg/dl
  17. Uric Acid
    • Breakdown product of purines (nucleic acid/DNA)
    • Purines from cellular breakdown are converted to uric acid by the liver
    • Uric acid is filtered by the glomerulus
    • Elevated plasma uric acid promote formation of solid uric acid crystals in joints and urine
  18. Uric acid diseases
    • Increased plasma uric acid:
    • Gout
    • Leukemias and lymphomas (Increased DNA catabolism)
    • Megaloblastic anemias (Increased DNA catabolism)
    • Renal disease (but not very specific
Card Set
Chemistry Chapter 11
Non-Protein Nitrogen