Renal Flashcards
UREA NITROGEN
-Major nitrogen-containing metabolic product of protein catabolism
-Primarily synthesized by hepatocytes
-Freely filtered by glomeruli, reabsorbed (amount varies) by tubules
Urea is synthesized mostly in the ___ as a by-product of the deamination of amino acids
Liver
*Urea is filtered by the glomeruli
The urea nitrogen level is greatly influenced by diet
BUN is not a sensitive indicator of renal dysfunction because ____
renal function must be reduced by more than 50% to result in a rise of BUN
CREATININE
-Derived from muscle creatine (1-2% of total muscle mass per day)
-Amount excreted daily is fairly constant and independent of urinary volume
-Average men excrete 1.5 g/d into the urine; women less; athletes more
-Patients with hepatic disease, muscular dystrophy, paraplegia and poliomyelitis may excrete less creatinine due to decreased production (PMPL = less)
Reference Range for serum creatinine
M: 0.67 - 1.17 mg/dL
F: 0.51 – 0.95 mg/dL
CR CL EQUATION
Reference Range:
male = 117 +/- 20 mL/min; female = 95 +/- 20 mL/min
Cockroft and Gault Equation
Urine osmolality is a measure of ___
the concentrating power of the kidney
*urine specific gravity is usually directly proportional to osmolality
Recurring values of _____ indicate isosthenuria (fixed specific gravity)
1.010 (1.008 - 1.012)
*this finding suggests loss of tubular concentrating and diluting ability and is frequently a prelude to anuria
Normal BUN/CR Ratio
~12-20
BUN production is dependent on available protein and liver function. In addition, the ratio is affected by the specificity of the creatinine method.
-increased protein intake increases the ratio
-decreased liver function lowers the ratio
-less specific methods give higher creatinine values
INCREASED BUN/CR RATIO =
-blood in GI tract
-muscle wasting disease
-severe tissue trauma
-dehydration, decreased cardiac output, or shock (= prerenal azotemia)
-renal disease (early acute glomerulonephritis, malignant nephrosclerosis, or postrenal obstruction)
MD GTR
DECREASED BUN/CR RATIO
-chronic glomerulonephritis with protein deficiency
-severe hepatic insufficiency
-starvation
-decreased urea reabsorption (overhydration and rapid hydration)
-hemodialysis
-acute tubular necrosis
im GUSHHN
Prerenal Azotemia
is caused by a decrease in renal blood flow, e.g. due to decreased cardiac output
BUN HIGH, CREAT NORMAL
Renal Azotemia
results from damage to the kidney
Postrenal Azotemia
is due to obstruction of urine flow, e.g. by prostatic hypertrophy or tumor
Selectivity Ratio Equation
IgG cl / Alb cl
-High <0.15 (minimal change)
-Poor >0.30
ACUTE GLOMERULONEPHRITIS LABS
-Elevated BUN, Cr (>1.17)
-Elevated uric acid (7+, 5.7+)
-BUN/CR > 20
-Decreased CrCl/GFR
-High K (5.1+)
-Acidosis (under 7.35)
-Hematuria (red smoky urine)
-Red cell casts (blood casts)
-Proteinuria
CHRONIC GLOMERULONEPHRITIS LABS
-Elevated BUN, Cr, uric acid
-Low Na < 136, Ca <8.5
-High K > 5.1, Phos > 4.5
-BUN/CR < 10
-Elevated Alk Phos > 129
-Proteinuria
-Isosthenuria (1.008-1.012 fixed sp gr)
-Cylindruria (tubular casts in urine)
-Anemia
*only one that affects Na/Ca, alk phos, has isosthenuria, LOW BUN/CR ratio
NEPHROSIS (NEPHROTIC SYNDROME) LABS
-Proteinuria > 3.5 g/day
-Hypoalbuminemia (1-2.5, < 3.2)
-Hyperlipidemia (increase in TG > 170, chol > 200, lipo)
-Edema generally present
-Excretion of red and white cells is common
-BUN/CR ~12 (normal), GFR normal
*NORMAL BUN/CR compared to others, only one that affects lipid panel, has edema, and hypoalbumin
PATCE
ACUTE PYELONEPHRITIS LABS
-Pyuria (pus in urine)
-Microhematuria
-White cell casts
-Bacteriuria
-Leukocytosis
*only one with pus in urine and bacteriuria
Hyaline Casts
all renal diseases associated with benign essential hypertension, and nephrotic syndrome
WBC Casts
associated with diseases with leukocytic exudation and interstitial inflammation.
example: pyelonephritis
Red Cell Casts
-acute glomerulonephritis
-lupus nephritis
-goodpasture’s syndrome
-subacute bacterial endocarditis (SBE)
GASL
Renal Epithelial Casts
associated with exposure to nephrotoxic agents and exposure to some viruses
Waxy Casts
severe chronic renal disease and amyloidosis
Fatty Casts
nephrotic syndrome, diabetes mellitus, and damaged renal tubular epithelial cells
