Urinalysis: Huch Flashcards
1
Q
What are some of the key dichotomies when assessing kidney disease?
A
- Prerenal, intrinsic renal, or post renal
- Acute or chronic in onset
- Glomerular versus tubular etiology
- Inflammatory or noninflammatory process
- Associated with systemic disease or not
2
Q
Describe the optimal urinalysis technique.
A
- Obtain fresh sample (analysis within 60 minutes) clean catch midstream collection
- Centrifugation to produce supernatant and urinary pellet supernatants for chemical analysis (urinary “dipstick”) and electrolyte assessment
- Sediment for light microscopy
3
Q
How is specific gravity different from osmolality? What things can throw off specific gravity?
A
- Specific gravity determined by # AND weight of solutes in solution
- Osmolality determined ONLY by the # of solutes in solution
- Specific gravity not a marker of concentration when there are abnormal #’s of heavy solutes in urine
1. Glycosuria -> can throw off readings
2. Post-contrast media -> can cause astronomically high urinary specific gravity readings
4
Q
How does specific gravity correlate to osmolality?
A
- 1.002 (max dilute) = 50/100 mOsm/kg
- 1.010 (isosthenuria) = 300 mOsm/kg
- 1.030 (max conc) = 1200 mOsm/kg
5
Q
What is normal urine pH? How might it change if you have a UTI?
A
- Normal range: 5.0-6.5 (meat-eating)
- Metabolic acidosis: <5.3
- UTI with urea splitting bacteria (e.g., proteus sp, E.coli): >7.5-8
- Reflection of dietary intake and state of acid-base system systemically
6
Q
When might you see glucose in the urine?
A
- Negative in normal urine
-
Hyperglycemia INC filtered load > reabsorptive capacity of proximal tubule, resulting in glycosuria
1. Normally seen with diabetics whose blood sugar is not in good control - Glycosuria in presence of normal blood glucose (renal glycosuria) = proximal tubular dysfunction -> FANCONI (associated with multiple myeloma and heavy metals)
7
Q
When might you see ketones in the urine?
A
- Negative in normal urine
- Present during fasting, DKA, and AKA (alcoholic ketoacidosis)
- Increased plasma ketoanions lead to filtered load exceeding proximal tubular reabsorptive capacity, resulting in ketonuria
- Dipstick specific for acetone and acetoacetate
8
Q
What kind of bilirubin may appear in the urine? Why?
A
- Assessment tool for abnormal hepatobiliary function
1. Conjugated (direct) bilirubin is water soluble
1. Unconjugated (indirect) bilirubin is NOT water soluble (not present in urine) - Elevated levels of plasma conjugated bilirubin lead to urinary excretion
- Urobilinogen (metabolic byproduct of bilirubin metabolism) is also excreted in the urine
- Feature of urinary dipstick
- Associated w/hyperbilirubinemia, liver disease, but really not that useful in terms of diagnosis (she said she doesn’t really pay much attention to this one)
9
Q
When might there be nitrite in the urine?
A
- Absent in normal urine
- Nitrate is excreted in urine
- Positive nitrite suggests UTI with nitrate-reducing bacteria (gram negative)
- Gram negative bacteria are the most common uropathogens
10
Q
When might leukocyte esterase be in the urine?
A
- Dipstick detects the neutrophil specific enzyme, leukocyte esterase
- Negative in normal urine
- Positive, when there are increased numbers of neutrophils in the urine; e. g., UTI’s
- WBC’s
- Think of infections if positive, or inflammatory renal disease like Lupus
11
Q
What are the different forms of urine protein measurement?
A
- Normal excretion: <150 mg/day
- Tamm-Horsfall protein, low molecular weight proteins secreted by tubular cells, micro-amounts of albumin
- Urinary dipstick is a semi-quantitative estimate of protein excretion (scale of trace to 3+)
- Quantitative proteinuria is measured in 24 hr collections (gm/24 hr)
- Ratio of urine protein over creatinine (both measured as mg/dl, so unit-less) in a “spot” urine sample is reliable estimate of quantitative proteinuria (ratio of 5 = ~5 gm/24 hr; 0.15 = normal excretion)
12
Q
What suggests glomerular proteinuria?
A
- Negative in normal urine
- More heavy proteinuria suggests INC permeability for protein in glomerular capillary wall -> some disease process has caused breakdown in barrier, allowing proteins to pass from blood to urinary space
- Most abundant protein albumin -> dipstick specific
-
Sulfosalicylic acid test detects all protein (also graded on 3+, 4+ scale based on cloudiness, and whether precipitates come out)
1. 3+ and 4+ suggests nephrotic range proteinuria (3.5g per 24 hrs. is nephrotic range)
13
Q
What type of proteinuria reflects tubular damage?
A
- Low molecular proteins are filtered and normally reabsorbed by pinocytosis in the proximal tubule
- Failure to reabsorb these proteins reflects proximal tubular dysfunction
14
Q
What is overflow proteinuria?
A
- Excess production of low molecular weight proteins
- INC filtered load exceeds reabsorptive capacity of proximal tubule
1. EX: light chain proteinuria; multiple myeloma -
Negative dipstick for albumin, but (+) sulfosalicylic acid test -> precipitating light chains and Ig’s (Bence-Jones proteins)
1. MM: plasma cell dyscrasia w/excessive production of in-tact Ig’s or light chains, then filtered by glomerulus and end up in the urine
15
Q
What are some additional UA components?
A
- Measurement of urinary electrolytes: sodium, potassium, chloride
- Urinary osmolality (assessment of water handling) measured in supernatant
- Urinary creatinine and urine urea nitrogen: nutritional assessment, pt protein intake
- Urinary calcium, phosphorus, uric acid (kidney stones -> nephrolithiasis)
16
Q
What is the significance of the urinary anion gap?
A
- Assess hyperchloremic metabolic acidosis: to see if GI source w/diarrhea and lots of bicarbonate losses OR urinary source with inability to secrete acid (urinary acidosis)
1. If Na + K – Cl is (-), you can be sure cause is GI loss b/c kidney excreting as much NH4 as possible into urine; if (+), more suggestive of renal tubular acidosis -> have to have Na excretion >20, and urine pH neutral or lower to assure all filtered bicarbonate reabsorbed (limited use, but interesting)
19
Q
What do you see here?
A
- RBC’s
- Larger cell: WBC
20
Q
What do you see here?
A
- Crenated red blood cells
- Look kind of battered -> more a loss of cell volume by the red cells due to being in more concentrated supernatant (water sucked out)
21
Q
What are these? When might you see them?
A
- WBC’s: granular cytoplasm, irregular nucleus, glitter cells
- Normal urine: 0-4/hpf
- Bigger than RBC, but smaller than epithelial cell
- Seen with: UTI (more commonly), pyelonephritis, allergic interstitial nephritis, intense glomerulonephritis (like you would see in Lupus)
- In fresh urine with active infection, you can sometimes see IC movement that shines
22
Q
What do you see here?
A
- WBC’s: Larger than red cells, granular
- Large cell in the center is probably a renal tubular epithelial cell -> resemble a hard-boiled egg cut in half (white equivalent to cytoplasm) with fairly large nucleus (nucleus about the size of white cell)
- Hyphae (bands) of yeast in clumps scattered around this slide
23
Q
What do you see here?
A
- Squamous epi cells: large, plate-like cell with abundant cytoplasm, and a very small nucleus
- Line lower tract, urethra
- Can be predominant if there is a lot of vaginal contamination of urinary sample
- Don’t really indicate anything regarding renal status of the patient
24
Q
What do you see here?
A
- Renal tubular epi cells: likely to be found in patient with acute tubular necrosis (one of the hallmarks)
25
Q
What is this?
A
- Hyaline cast
- Only normal cast in the urine; very difficult to see
- Pale, found in normal person in states of volume depletion (i.e., ran a marathon and did not drink enough fluids)
- Ghost cells: density similar to surrounding fluid
- Protein: Tamm-Horsfall protein that is excreted by tubular cells, and forms matrix of all casts
27
Q
What are these?
A
- Waxy casts: acellular casts -> pathologic, large, very dense in appearance
- White line outlining casts is present when looking into microscope
- Aka, renal failure casts b/c found in CKD
- Have been present in tubules for long time (often with plaques in sides) -> sharp, broken off ends
- If you see these, you can be assured their renal function is not acute, but more chronic in nature
28
Q
What is this?
A
- Renal tubular epi cell: look for this when looking for evidence of acute tubular necrosis
29
Q
What do you see here?
A
- Uric acid crystals - rhombic: precipitate out in acidic urine
- May or may not provide clues of other disease processes
- Can be found in normal urine that has been allowed to sit, or has been put in fridge
- Variety of shapes and sizes
30
Q
What are these?
A
- Calcium oxalate crystals: envelope associated with nephrolithiasis (calcium oxalate being the most common type of stone)
31
Q
What are these?
A
- Triple phosphate crystals: resemble coffin lids (associated with infection)
32
Q
What are these?
A
- Cystine crystals: always pathologic; not a good thing to have (inherited disease usually diagnosed in pediatrics)
- Shape: flat, thick
- Associated with very dense nephrolithiasis
33
Q
What is this?
A
Hyaline cast
34
Q
What is this?
A
- Waxy cast
- Note the white border around the cast (this seems to be the only way to distinguish these from hyaline casts)
35
Q
What is this?
A
- Hyaline cast
- Difficult to separate out from the background
- Very ghost-like, and not pathologic
- Can provide clues of pre-renal causes of acute kidney injury
37
Q
What do you see here?
A
- Fatty casts: little areas with groupings of four bright, white lights on the right (Maltese casts)
- See these with nephrotic syndrome: heavy proteinuria, low albumin, elevated cholesterol
38
Q
What are these?
A
- Fatty casts
- Left: un-polarized
- Maltese crosses again on right
39
Q
What is this?
A
- Granular cast
- Bright white line, cracks on sides
- Sharp, broken appearing edges
- Not really pathopneumonic for anything, but not normal
- Breakdown of cellular debris as it passes through tubules (can’t differentiate what types of products these originated from)
- Starch granules (artifact)
40
Q
What is this?
A
- RBC cast
- Pathopneumonic for glomerulonephritis
41
Q
What is this?
A
- WBC cast
- Free red and white cells in the periphery allow you to compare size, shape, and texture to the cells within the cast -> helps identify what type of cell the cast is made of (b/c details often obscured)
- White cells you can distinguish in the cast
42
Q
What do you see here?
A
- Granular cast
- RBC’s, squamous epithelial cell (top right)
- Perhaps renal tubular epithelial cell at bottom of slide below the black arrow
