Differentiate between anuria and oliguria
Anuria:
LACK of urine output
< 50 mL/day
Oliguria:
Decreased urine output
< 400 mL/day
Define “casts”
Protein aggregates, outlined in shape of renal tubules, secreted into the urine
Define ISOSTHENURIA
Urine with a fixed specific gravity
Range: 1.008 - 1.012
What are popular screening tests for renal function?
Serum urea nitrogen
Serum creatinine **
*in elderly, these measurements may be less reliable, so CL tests = better measures of glomerular function
Why does the ratio of non-urea to urea nitrogen increase in hepatic failure?
The liver is unable to make urea and delaminates amino acids
What is SUN?
Serum urea nitrogen
Normal: 45%
Dz: ~80%
When is urea made?
Synthesized by liver mostly as by-product of amino acid deamination
What is the equation for creatinine clearance?
C(creat) =
U(creat)/S(creat) * V * 1.73/A
Where
V = urine flow
A = body surface area
Which are the most useful tubular function tests?
Renal concentrating power
Ability to produce acid urine
How do urine osmolality and urine specific gravity relate?
What factors give misleading results?
Directly proportional
Can give overestimates if significant:
+glycosuria
+proteinuria
What can recurring values of 1.010 mean?
Isothenuria (fixed specific gravity)
= loss of tubular concentrating and diluting ability
What factors is the SUN ratio dependent on?
Available protein
Liver function
Specificity of creatinine method
What factors increase the SUN ratio?
Increased urea synthesis:
+blood in GI tract
+decreased tubular flow as a result of: dehydration, decreased CO, or shock
+renal disease
What are 3 categories of azotemia?
Prerenal =
Dec. RBF (like from dec. CO)
Renal =
Kidney damage
Postrenal =
Obstruction of urine flow (tumor, prostatic hypertrophy)
What is acute glomerulonephritis?
Acute diffuse inflammatory changes in glomeruli with
Hematuria
RBC casts
Mild proteinuria
Often: HTN, edema, azotemia
What are serum chemistries for acute glomerulonephritis?
Elevated:
+SUN
+Creatinine
+Uric acid
SUN/creatinine >20
Dec. creatinine clearance
GFR decreased
Acidosis
Describe urinalysis for acute glomerulonephritis
Smoky urine
Red urine
Blood casts
Proteinuria
What does a selectivity ratio do?
Gives indication of nature of glomerular damage in proteinuria, if still selective between high and low MW proteins
What is the selectivity ratio equation?
Define range for high and poor selectivity
Selectivity ratio =
IgG clearance / albumin clearance
High <0.15 (minimal change)
Poor >0.30
Describe chronic glomerulonephritis
Slowly progressive glomerular disease
Diffuse sclerosis of glomeruli and loss of nephrons
Other clinical finding: anemia
What serum chemistry values are associated with chronic glomerulonephritis?
Uremia (elevated SUN, creatinine and uric acid)
Hypo: -natremia, -calcemia
Hyper: +kalemia, +phosphatemia
Dec. Cr CL
🍋Acidosis
Elevated alkaline phosphatases
SUN/creatinine <10
Dec. GFR
Describe urinalysis of chronic glomerulonephritis
Proteinuria
Episodic hematuria
Isothenuria
Cylindruria (tubular casts in urine)
Describe nephrosis (nephrotic syndrome)
Condition that follows prolonged increase in glomerular permeability for proteins
Describe the “triad” associated with nephrotic syndrome
Proteinuria >3.5 g/day
Hypoalbuminemia
Hyperlipidemia
Edema
Normal SUN/creatinine + GFR
