Table 193.1Extrarenal Factors Affecting BUN and sCr

Factor by mechanismBUNsCr
Increased substrate
 High protein intake→ or sl ↑
 Gastrointestinal bleeding
 Catabolic states (fever, steroids, burns, etc.)
 Rhabdomyolysis↑↑
Decreased substrate
 Malnutrition
 Starvation
Hypoperfusion
 Dehydration
 Congestive heart failure
 Shock
 Diminished blood volume (GI bleeding)
Urinary tract obstruction

Key: ↑ = increase, ↓ = decrease, → = no change.

From: Chapter 193, BUN and Creatinine

Cover of Clinical Methods
Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition.
Walker HK, Hall WD, Hurst JW, editors.
Boston: Butterworths; 1990.
Copyright © 1990, Butterworth Publishers, a division of Reed Publishing.

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