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)
17
Q
RBC’s in urine
A
- Normal urine has 0-2 rbc/hpf and urine dipstick is negative for blood
- Most common cause of positive dipstick for blood is presence of rbc’s in urinary sediment
- Dipstick also sensitive to free hemoglobin and myoglobin, but urinary sediment will be negative for rbc’s; if elevated:
1. Free hemoglobin: hemolysis
2. Free myoglobin: rhabdomyolysis - Pellet (sediment) after urine centrifugation
- RBC’s in urine doesn’t necessarily mean its of renal origin; young women who are menstruating will invariably have RBC’s
18
Q
How can you distinguish renal vs. extra-renal origin of hematuria?
A
- Renal origin: dipstick positive, RBC’s in sediment, some dysmorphic, battered (having gone through glomerular barrier), RBC casts (pathopneumonic for renal origin and glomerulonephritis), absence of clots, often associated with proteinuria (if red cells getting through, protein will too)
-
Extra-renal origin: dipstick positive, RBC’s in sediment, normal shape, NO RBC casts, clots may be present, absence of heavy proteinuria
1. Plumbing: ureters, bladder, urethra
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
What is this?
- **_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
26
What are urinary casts?
- Represent precipitates of protein forming in lumen of tubules (collecting tubules)
- **_Tamm-Horsfall protein_**: produced by thick ascending limb of Henle cells, forms matrix of all casts
- Cylindrical shape with distinct margins
- _May contain cellular debris (granular cast) or cells (cellular cast)_
- Hyaline casts are the only normal cast
27
What are these?
- **_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
What is this?
- **_Renal tubular epi cell_**: look for this when looking for evidence of acute tubular necrosis
29
What do you see here?
- **_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
What are these?
- **_Calcium oxalate crystals_**: envelope associated with nephrolithiasis (calcium oxalate being the most common type of stone)
31
What are these?
- **_Triple phosphate crystals_**: resemble coffin lids (associated with infection)
32
What are these?
- **_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
What is this?
Hyaline cast
34
What is this?
- Waxy cast
- Note the white border around the cast (this seems to be the only way to distinguish these from hyaline casts)
35
What is this?
- 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_
36
When might you see lipid in the urine? What forms could it take?
- Absent in normal urine
- Associated with heavy proteinuria (nephrotic syndrome)
- Caused by presence of lipoproteins
- Maltese crosses, oval fat bodies, or fatty casts may be noted using polarized light
- _If you see this, you can be assured the patient has nephrotic syndrome_
37
What do you see here?
- **_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
What are these?
- **_Fatty casts_**
- Left: un-polarized
- Maltese crosses again on right
39
What is this?
- **_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
What is this?
- **_RBC cast_**
- Pathopneumonic for glomerulonephritis
41
What is this?
- **_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
What do you see here?
- **_Granular cast_**
- RBC’s, squamous epithelial cell (top right)
- Perhaps renal tubular epithelial cell at bottom of slide below the black arrow
