Lecture 5: Urinalysis Flashcards
What are the 3 components of a complete urinalysis?
- Gross assessment
- Macroscopic/Dipstick analysis
- Urine microscopy
What are the components of a gross assessment for urine? What do they mean?
- Color
Pink/Red/Brown = Blood, food, or medicine
Orange/Red = Phenazopyridine
Black = Hemoglobin, myoglobin, homogentisic acid
White = WBCs
Green/blue = Pseudomonas infection, urinary catheter - Clarity
Clear = normal
Turbid = abnormal (crystals, sperm, proteins, cells)
What are components of dipstick analysis?
Specific gravity
pH
Leukocytes
Nitrite
Protein
Glucose
Ketones
Blood
What is specific gravity?
Specific gravity is the density of urine:distilled water (vol urine = vol water)
What does urine specific gravity tell us about a patient?
Tells us about the kidney’s concentrating ability
What is the range of specific gravity and what does the numbers mean?
Range: 1.003 (v. dilute) - 1.035 (v. concentrated)
Low SG (<1.010) = Increased fluid intake, diuretics, diabetes
High SG (>1.030) = Dehydration, decreased renal perfusion, syndrome of inappropriate ADH (siADH)
Fixed SG (1.010) = Severe renal disease with inability to concentrate or dilute urine
What is normal urine pH?
pH 4.5-8
What does pH tell us about a patient? Give 2 examples for acidic urine and 4 examples for alkaline urine.
Acidic:
1. High protein diet
2. Metabolic/respiratory acidosis
Alkaline:
1. Vegetarian diet
2. Metabolic/respiratory alkalosis
3. Renal tubular acidosis
4. UTI
What is leukocyte esterase?
Enzyme found in neutrophils and macrophages
What does leukocyte esterase tell us if found in the urine?
A positive test indicates:
1. Inflammation
2. Infection - confirm with culture
3. Malignancy
4. Stones
5. Glomerulonephritis
False negatives might occur due to
1. High urine protein/glucose
2. Positive Vit C
What does nitrite tell us when found in the urine?
UTI
What are the causes of false negatives and positives when measuring nitrite in urine?
False positive:
1. Bacterial contamination
2. Delayed analysis
3. Improperly stored dipstick strips
False negative:
1. Low nitrate diet
2. Insufficient urine dwell time in bladder
3. Antibiotic use
4. Certain urine bacteria don’t form nitrite
What is the normal range for protein in the urine?
<150 mg/day
What kind of protein does the urine dipstick detect?
Albumin
Cannot detect monoclonal Ig light chains for MM
What does a positive protein result mean in urine dipstick analysis?
Glomerular proteinuria
What is the grading of protein for urine dipstick analysis?
1+ = 200-500 mg/day
2+ = 0.5-1.5 g/day
3+ = 2-5 g/day
4+ = >7g/day
What are some cons that come with testing protein for urine dipstick analysis?
- Dependent on urine concentration
- Not sensitive enough to detect moderately increased albuminemia
Why would glucose be present in the urine? (2)
- Filtered glucose load exceeds the reabsorptive capacity of the renal tubule
- Defect in reabsorption of filtered glucose (plasma glucose lvl < 10 mM)
What are some errors that can come with glucose urine dipstick analysis?
May be false -ve with high levels of Vitamin C
Is ketones present in the urine normally?
No
Where do ketones come from?
Fatty acid metabolism
What are the possible causes of a positive urine dipstick analysis for ketone? (IMPT)
- Diabetes
- Starvation
- Alcoholic ketoacidosis
How does the urine dipstick work in order to detect blood in the urine?
Dipstick detects peroxidase activity of RBC
What does a positive urine dipstick analysis for blood suggest?
Presence of:
1. Hemoglobin - intravascular hemolysis
2. Myoglobin - rhabdomyolysis
What is urine microscopy used for?
- Atypical samples
- Abnormal urine dipstick
What are the steps of urine microscopy?
- Centrifuge
- Throw supernatant
- Examine under microscope
What are the components found under urine microscopy?
- Casts
- Crystals
- Cells
- Organisms
What does it mean when you find yeast in urine using urine microscopy?
- Sample contamination
- Yeast infection
What does it mean when you find squamous epithelial cells in urine using urine microscopy?
Sample contamination
What does it mean when you find neutrophils and bacteria in urine using urine microscopy?
- Infection
- Interstitial nephritis
- Glomerulonephritis
- Stones
- Sample contamination
What does it mean when you find sperm in urine using urine microscopy?
- Normal for adult males
- Contamination for adult females
- Sexual abuse for children?
What does it mean when you find transitional epithelial cells in urine using urine microscopy?
- Normal
- Inflammatory/malignant disease of urinary tract
How are casts formed?
Formed from Tamm-Horsfall protein secreted by tubular cells and develop in the distal convoluted tubule/collecting ducts
What are urinary casts made out of?
- Matrix
Contains TAMM-HORSFALL MUCOPROTEINS produced by renal tubular cells in the thick ascending limb of the loop of Henle - Trapped elements embedded in matrix
This results in casts with different appearances
What are the different types of urinary casts?
Fatty casts
RBC casts
Hyaline casts
What do fatty casts indicate?
- Nephrotic syndrome
- Lipid storage diseases
What do RBC casts indicate?
- Glomerulonephritis
- Acute Interstitial nephritis
What do hyaline casts indicate?
- Normal
- Exercise
- Dehydration
- Fever
What are urinary crystals?
Common crystals that form when urine is supersaturated with chemical constituents
What are the factors affecting crystal formation?
- Concentration of constituents
- Hydration status
- Temperature
- pH
What are the 3 types of crystals?
- Common crystals
- Pathological crystals
- Drug crystals
What are common crystals made out of? What do they indicate?
- Uric acid
- Calcium oxalate - normal, ethylene glycol poisoning
- Triple phosphate crystals - Normal, UTI
What are pathological crystals made out of? What do they indicate?
- Cholesterol - nephrotic syndrome, lipid storage disorder
- Cystine - cystinuria
- Bilirubin crystals
What are significant findings of urine microscopy in respect to cells?
- > 3 RBCs / high power focus (HPF)
- > 5 WBCs / HPF
- > 2 renal tubular or transitional cells / HPF
What are significant findings of urine microscopy in respect to casts?
- > 3 hyaline or granular casts / low power focus (LPF)
- Any WBC, RBC, or epithelial cast
- Any fatty cast
What are significant findings of urine microscopy in respect to crystals?
- Any pathological crystal
- A lot of non-pathological crystals
What are significant findings of urine microscopy in respect to organisms?
- > 10 bacteria/HPF in a fresh sample
- Any fungus/parasite
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of acute glomerulonephritis?
Gross: Smoky/turbid
Macroscopic: Blood/protein
Microscopy: RBC casts, RBCs, WBC casts, renal tubular epithelial cell casts, WBCs (sometimes), epithelial cells (sometimes)
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of nephrotic syndrome?
Gross: Frothy
Macroscopic: +++ protein
Microscopic: Fatty casts, cholesterol crystals, oval fat bodies
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of acute tubular necrosis?
Gross: Non-specific
Macroscopic: Fixed SG, mild protein, maybe blood
Microscopic: Renal tubular epithelial cell casts, epithelial cells
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of diabetes mellitus?
Gross: Non-specific
Macroscopic: Glucose, ketones (diabetic ketoacidosis), proteins (diabetic nephropathy)
Microscopic: Non-specific
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of end-stage renal disease?
Gross: various
Macroscopic: Fixed SG, maybe blood and/or proteins
Microscopic: Broad casts
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of acute pyelonephritis?
Gross: Turbid
Macroscopic: Nitrite, leukocyte esterase, mild protein
Microscopic: WBC casts, WBCs, bacteria, epithelial cells (maybe)
What are the urine findings (gross assessment, macroscopic analysis, microscopic analysis) of lower UTI?
Gross: Turbid
Macroscopic analysis: Nitrite, leukocyte esterase, maybe blood
Microscopic analysis: WBCs, transitional epithelial cells, bacteria
NO CASTS
