Proteinuria Directed Study

Question 1

What is the normal for urine protein excretion?

Answer 1

1. normal protein excretion is <150 mg/24 hrs (usually 40-80 mg/24 hrs)
   
   1. protein excretion can increase on standing, exercise, fever, and in children and adolescent
2. Proteinuria is in excess of 3000 mg/24 hrs.
   
   1. nephrotic range
   2. if this is accom
   3. 4. pained by hypoalbuminemia, edema, hyperlipidemia, and lipiduria = nephrotic syndrome

Question 2

what is the amount of protein present to be considered proteinuria?

Answer 2

Proteinuria in excess of 3000 mg/24 hrs is referred to as nephrotic range proteinuria

if this is accompained by hypoalbuminemia, edema, hyperlipidemia, and lipiduria = nephrotic syndrome

Question 3

What are plasma proteins?

what are non-plasma proteins?

Answer 3

proteins that include, but not limited to, albumin, immunoglobulins, and light chains

non-plasma proteins are mainly Tamms-Horsfall protein

Question 4

what is the most consistant marker of glomerular pathology?

Answer 4

Albumin levels in the urine is the most consistant marker of glomerular pathology.

Albumin is the predominant protein filtered by the glomuerulus but is mostly reabsorbed and degraded by the renal tubules through endocytosis.

Question 5

What levels of urine albumin are considered abnormal?

What is microalbuminuria?

what is the creatanine ratio?

Answer 5

Abnormal levels of urine albumin are above 30 mg/day

microalbuminuria refers to an albumin excretion of 30-300 mg/day

an albumin level of 30-300 mg/day equates to a creatinine ratio >30 mg/g

Question 6

reagent strips

draw backs?

what can give a false negative?

a false positive?

Answer 6

changes color at albumin levels between 20-300 mg/dL. They canot detect microalbuminuria

the downside to these strips are insensitive to other urinary proteins such as globulins so they can underestimate urine protein levels when nonalbumin proteins are present.

dilute urine gives a false negative

strongly alkaline urine can give a false positive.

Question 7

What is microalbuminuria known to be an early indicator of?

Answer 7

microalbuminuria is known to be an early indicator of diabetic nephropathy.

Question 8

What is an abnormal protein-to-creatinine ratio?

when are the most consistant results for a urine specimine obtained?

Answer 8

an abnormal protein-to-creatinine ratio is >0.2 mg/dL protein per 1.0 mg/dL creatinine

The most consistant results are obtained from the first voided urine in the morning

Question 9

What three factors determine the amount of protein in the urine?

Answer 9

The amount of protein in the urine is a function of three factors:

1) amount of protein presented to the glomerulus (filtered load)
2) permeability of the glomerular capillary wall
3) the efficiency of proximal tubular reabsorption

Question 10

Where are the three places in the glomerulus that abnormal proteinuria can originate?

Answer 10

Abnormal proteinuria can originate from

1) glomerular pathology
2) tubular pathology
3) overflow of an abnormal protein
4) postrenal

Question 11

Glomerular proteinuria

causes:

Answer 11

Glomerular proteinuria arises when excess protein crossses the glomerular basement membrane and overwhelms the capacity for tubular reabsorption

Question 12

What charge does the GBM have? How does this impact filtration?

Answer 12

The GBM is negative charge due to heparin sulfate in the glomerular endothelial wall. This prevents similarly charged proteins, such as albumin, from passing across.

Therefore, glomerular pathology that impairs the ability of the GBM to maintain charge results in proteinuria.

Question 13

if the proteinuria is mainly comprised of albumin what type of damage has/has not occurred?

as more injury occurs, what happens to the composition of the proteinuria?

Answer 13

if the proteinuria is mainly comprised of albumin, overt glomerular injury is absent (selective proteinuria).

as more damage to the GBM occurs (proliferative glomerulonephritis or focal glomerulosclerosis) the composition of the proteinuria is made of more larger proteins including immunoglobulins.

Question 14

Nephrotic proteinuria:

Answer 14

nephrotic proteinuria implies proteinuria of glomerular origin of suffiecient severity to cause the clinical nephrotic syndrome with hypoalbuminemia, hyperlipidemia, edema, and lipiduria.

this proteinuria is >3000 mg/24hrs

Question 15

Tubular proteinuria

Answer 15

Tubular proteinuria results from a failure to absorb proteins normally filtered or secreted by the renal tubules due to tubular pathology.

Question 16

what is the composition of urine in tubular proteinuria?

Answer 16

the compsition of urine indicitive of tubular proteinuria:

albumin

alpha and beta globins (alpha-microglobulin and beta-microglobulin)

proteinuria is in the range of 200-2000 mg/24hrs

Question 17

what appears in the urine in hemolytic anemia?

Answer 17

in hemolytic anemia free hemoglobin not bound to haptoglobin appears in the urine

Question 18

myoglobinuria is a sign of what?

Answer 18

increased levels of myoglobin in the plasma result in myoglobinuria is a sign of rhabdomyolysis

Question 19

is there a correlation between severity of disease and amount of protein in the urine?

if so, what type of proteinuria is demonstrated by this correlation?

Answer 19

Yes, the more severe the disease, the greater the amount of proteinuria.

This corelation occurs mostly in overflow proteinuria

Question 20

if the proteinuria is relatively low concentration and contains some secreted IgA, what type of disease does this suggest?

what is likely to accompany these findings?

how do we detect it?

Answer 20

a relatively low concentration of proteinuria with IgA is suggestive of a postrenal proteinuria secondary to disease in the urinary tract.

nonglomerular hematuria is likely to accompany postrenal proteinuria and is best detectd on urine electrophoresis