9/18- Urinalysis Flashcards
Equipment to examine urine? Basic pros/cons
Dipstick
- Rapid (2 min)
- Cheap and cost-effective
- No training required
- “Screening test”
Microscopy
- Automated or manual
- “Specific” findings can prompt additional testing
What characteristics are analyzed on dipstick examination?
- Color: fluid balance, diet, medicines, and diseases
- Clarity: normally clear. Bacteria, blood, sperm, crystals, or mucus can make urine look cloudy
- Odor: some diseases cause a change in the odor of urine; UTI > foul odor; diabetes or starvation > sweet/fruity odor
- Taste: even ancient physicians tasted urine, ie diabetes mellitus
What is leukocyte esterase?
- Detects esterase
Released by WBCs
- Usually suggests infection
- Should trigger urine culture
What is nitrite? What does it indicate in the urine?
Bacteria that cause a urinary tract infection (UTI) release an enzyme that changes urinary nitrates to nitrites
- Sensitivity and specificity high if both LE and nitrite are positive
- Some bacteria do no not produce nitrite
- If positive result, order urine culture
What does proteinuria indicate?
- Causes
- What does dipstick detect
Causes:
- Glomerular disease
- Tubular dysfunction
- Overflow proteinuria (increased quantity of serum protein)
Dipstick test detects:
- Albumin
- NOT Globulins or Bence-Jones proteins; may be missed!
Urine protein lab values for microalbumin of >30 mg/day correspond to a detection level within the “trace” to “1+” range of a urine dipstick
What does the sulfosalicylic acid test for in the urine?
- More sensitive precipitation test
- Can detect: albumin, globulins, and Bence-Jones protein at low concentrations (fills in gaps of proteinuria on dipstick)
How can you quantify proteinuria?
- What assumptions are involved?
Gold standard = 24 hr urine collection (difficult to perform accurately)
Alternative = protein/Cr ratio
- Urine protein = 100 mg/dL
- Urine creatinine = 20 mg/dL
- Ratio = 5 or 5g protein in 24 hr period
2 assumptions:
- Creatinine production and rate of proteinuria are constant throughout the day, including at the time of PCR determination
- Creatinine production is ~ 1g/day (not always true)
What is normal pH of the urine?
May range from 4.5 - 8.0
What may cause high urine pH?
- Renal tubular acidosis
- Kidney failure
- Stomach pumping (gastric suction)
- Urinary tract infection
- Vomiting
What may cause low urine pH?
- Diabetic ketoacidosis
- Diarrhea
- Metabolic acidosis
- Starvation
What is the normal specific gravity of urine?
What is high/what does this indicate?
- Specific gravity (density of urine/water) ranges from 1.002 - 1.035
- Glomerular filtrate SG = 1.007 - 1.010
Specific gravity > 1.035 indicates:
- Contamination
- Glucosuria, or
- Radiodye
If you see + blood (pigment) but no red cells, what should you think of?
Myoglobin
What are ketones? What do they indicate in the urine?
Ketones: acetone, aceotacetic acid, beta-hydroxybutyric acid
Results from:
- Diabetic ketosis (not well controlled)
- Proximal tubular dysfunction (MM, heavy metal toxicity…)
- Form of calorie deprivation (starvation)
What does bilirubinuria indicate?
- Hemolysis
- Liver/gallbladder disease
What is the process of microscopic analysis?
- Urine (usually 10-15 ml) is centrifuged in a test tube at relatively low speed (about 2-3,000 rpm) for 5-10 minutes
- The supernatant is decanted. The sediment is first examined under low power to identify most crystals, casts, squamous cells, and other large objects.
- The numbers of casts seen are usually reported as number of each type found per low power field (LPF)
What are the 4Cs of urine analysis?
- Cells
- Crystals
- Casts
- Crap
What are casts? Where are the formed/what are they made of?
- Urinary casts are formed in the lumen of the tubule.
- The renal tubules secrete a mucoprotein called Tamm-Horsefall protein which forms the glycoprotein matrix of the casts
What are hyaline casts?
- Characteristics
- Clinically
Characteristics
- Pale
- Colorless transparent
- Homogeneous
- Slightly refractile
Clinically:
- Normal
- Volume depletion
- CKD
What are RBC casts?
- Characteristics
- Clinically?
Characteristics
- May contain only a few RBCs in protein matrix
- May be many cells packed close together with no visible matrix RBC casts come from glomerulus!! Can’t be produced from bladder, ureter, etc.
Clinically:
- Glomerulonephritis
- Any condition that damages the glomerulus, tubules, or renal caps
What are WBC casts?
- Characteristics
- Clinically?
Characteristics:
- Refractile
- Exhibit granules
- Multilobed nuclei! (distinguishes them from RBC casts)
Clinically
- Signifies infection or inflammation within the nephron
- Pyelonephritis
- AIN
What are granular casts?
- Characteristics
- Clinically?
Characteristics:
- Result either from the breakdown of cellular casts or the inclusion of aggregates of plasma proteins (e.g., albumin) or immunoglobulin light chains
- Can be classified as fine or coarse
Clinically:
- Acute tubular necrosis
What are waxy casts?
- Characteristics
- Clinically?
Characteristics:
- Smooth homogeneous appearance
- Short, broad with blunt or broken ends
- Cracked or serrated edges
Clinically:
- Indicative of chronic kidney disease
What are fatty casts?
- Characteristics
- Clinically?
Characteristics:
- Formed by incorporated free fat droplets or oval fat bodies
- If cholesterol esters are present, associated with Maltese cross sign under polarized light
Clinically:
- Nephrotic syndrome
- Toxic renal poisoning
What are epithelial cell casts?
- Characteristics
- Clinically?
Characteristics:
- Formed by inclusion or adhesion of desquamated epithelial cells of the tubule lining.
- Cells can adhere in random order or in sheets and are distinguished by large, round nuclei and a lower amount of cytoplasm.
Clinically
- Tubular degeneration and necrosis
What do RBCs look like in urinalysis?
What does dysmorphia indicate?
Normal:
- No nuclei
- Pale or yellow apperance
Dysmorphic RBCs are suggestive of glomerular disease
- As RBC pass through the basement membrane, they are squeezed tightly and result in abnormal pathology
What do WBCs look like in urinalysis?
What does pyuria indicate?
Normal
- Typically neutrophils
- Larger than RBC
- Contain nucleus and cytoplasmic granules
Pyuria indicates inflammatory process somewhere along the urinary tract
What do renal tubular cells look like in urinalysis?
- Slightly larger than WBC
- Flat, cuboidal or columnar appearance
- One larger round nucleus
What do transitional epithelial cells look like in urinalysis?
- 2-4 times larger than leukocytes
- Round, pear-shaped, tail-like projections
- Large round nucleus
- Originate from renal pelvis, ureters, bladder or urethra
What do squamous epithelial cells look like in urinalysis?
- Large, flat, irregular-shaped cells
- Principally from the urethra and vagina
What do uric acid crystals look like in urinalysis?
- Many different shapes, diamond, rhombic prism or rosette
- Yellow or brown
- Very common
- Can be normal occurrence
- Associated with increased purine metabolism
What are amorphous urates? What do they look like in urine?
- Urate salts of sodium, potassium, magnesium, and calcium
- Usual form is non crystalline and amorphous. Appears as yellow red granules
What does calcium oxalate look like in urine? Caused by?
- Colorless, octahedral or envelope
- Ingestion of oxalate-rich foods: spinach, rhubarb, tomatoes, garlic, oranges, asparagus
- High intake of ascorbic acid
- Ethylene glycol poisoning
What does cystine look like in urine? Diagnostic for what?
- Colorless, refractile, hexagonal plates
Of diagnostic importance, for:
- Congenital cystinosis
- Cystinuria
What does leucine look like in urine? Diagnostic for what?
- Oily, highly refractile, yellow or brown spheroids and concentric striations
- Clinically significant for maple syrup urine disease, Oasthouse urine disease, severe liver disease
- Seen with tyrosine in liver disease
What does cholesterol look like in urine? Diagnostic for what?
- Large, flat, transparent
- Notched corners
- Excessive tissue breakdown
- Obstructed lymphatic flow
- Seen in nephritis and nephrotic conditions
What does triple phosphate look like in urine? Diagnostic for what?
- Colorless prisms, 3-6 sides, oblique ends
- Coffin lids
- Appear in alkaline urine
Associate with urea-splitting bacteria
- Proteus
- Pseudomonas
- Klebsiella
- Mycoplasma
What does calcium phosphate look like in urine? What is diagnostic for?
- Long thin, colorless needles
- One pointed end
- Arranged as rosettes or star
- Can be found in normal urines
Case)
- 45 yo male with depression and alcohol abuse, now recently unemployed, admitted to BTGH after being found by family members passed out on the floor
- Labs significant for metabolic acidosis. Urine sediment below
What is the cause of his presentation?
A. Acute ethanol ingestion
B. Ethylene glycol ingestion
C. Methanol ingestion
D. Acute gout
What is the cause of his presentation?
A. Acute ethanol ingestion
B. Ethylene glycol ingestion
C. Methanol ingestion
D. Acute gout
- Ethylene glycol as indicated by calcium oxalate crystals
Case)
- 44 yo with history of poorly controlled diabetes
- Complains of burning of urination for past week with foul smelling urine
What is the most likely bacterial species?
A. E. Coli
B. Proteus
C. Enterococcus
D. Ebola
What is the most likely bacterial species?
A. E. Coli
B. Proteus
C. Enterococcus
D. Ebola
- Urease splitting organism
Case)
- 64 yo with history of HTN, CKD, alcohol abuse, who has recently had worsening pain in great toe. Urine sample below
What is the crystal seen?
A. Calcium oxalate crystal
B. Triple phosphate crystal
C. Cholesterol crystal
D. Uric acid crystal`
What is the crystal seen?
A. Calcium oxalate crystal
B. Triple phosphate crystal
C. Cholesterol crystal
D. Uric acid crystal`
- Amorphous, seen in gout
Case)
- 57 yo history of DM, HTN in SICU following motor vehicle accident
- He has been on ventilator and has been septic for several weeks
- The same foley urethral catheter in place for weeks….
What is seen on the urine sample?
A. Fat bodies
B. Yeast
C. Bacteria
D. Air Bubbles
What is seen on the urine sample?
A. Fat bodies
B. Yeast
C. Bacteria
D. Air Bubbles
- Budding organisms seen in pts with longstanding indwelling foley catheters
Case)
- 38 yo presents to clinic for routine physical.
- Urine sample collected below
The lab calls the doctors office and tells the nurse what?
A. The patient likely has renal failure
B. The patient has fungal infection
C. The patient needs to recollect the sample
D. The patient is pregnant
The lab calls the doctors office and tells the nurse what?
A. The patient likely has renal failure
B. The patient has fungal infection
C. The patient needs to recollect the sample
D. The patient is pregnant
- These are squamous cells (large epithelial cells)
Case)
- 21 yo presents to physician for routine care.
- Pt reports recent unprotected sexual intercourse
What is the next step?
A. Treat with penicillin G
B. Treat with ceftriaxone
C. Pregnancy test
D. Repeat urine analysis
What is the next step?
A. Treat with penicillin G
B. Treat with ceftriaxone
C. Pregnancy test
D. Repeat urine analysis
- What is seen is crap (no spirochete) from specimen cup or mcuoproteins (artifacts)
- Need to repeat the test
Case)
- 64 yo with history of poorly controlled diabetes presents with flank pain, fevers, chills.
What is the etiology of patient’s presentation?
A. Constipation
B. Cholecystitis
C. Pyelonephritis
D. Diverticulitis
What is the etiology of patient’s presentation?
A. Constipation
B. Cholecystitis
C. Pyelonephritis
D. Diverticulitis
- In the right clinical setting, WBC casts are suggestive of pyelonephritis
Case)
- 33 yo with newly diagnosed HTN presents complains dark urine for several weeks
- Urine sediment below.
What is the likely etiology of patient’s hematuria?
A. IgA nephropathy
B. Bladder cancer
C. Hemorrhagic cystitis
D. Urinary tract infection
E. Minimal change disease
What is the likely etiology of patient’s hematuria?
A. IgA nephropathy
B. Bladder cancer
C. Hemorrhagic cystitis
D. Urinary tract infection
E. Minimal change disease
- Nephritic syndrome
- RBC casts can only come from glomerulus…
Case)
- 23 yo medical student on his surgery rotation in the operating room retracting for 8 hours, tired, but asymptomatic
What does the patient do next?
A. Go to ER for stat intravenous normal saline
B. Drink plenty of water and eat a normal meal
C. High dose steroids
D. Consult with Dr. Raghavan for kidney biopsy
What does the patient do next?
A. Go to ER for stat intravenous normal saline
B. Drink plenty of water and eat a normal meal
C. High dose steroids
D. Consult with Dr. Raghavan for kidney biopsy
- If severe Sx of volume depletion, you can send to ER for IV fluids
Label the features of this picture
- Squamous epithelial cells
- Granular casts
- Leukocyte
Peripheral eosinophilia is typically associated with what?
Cholesterol embolization
In what conditions are serum complements commonly low?
Cholesterol embolization
Features of cholesterol embolization?
- Peripheral eosinophilia
- Low serum complements
Contrast can injure cells and cause what?
Acute tubular necrosis
How can you rule out post-renal causes (obstruction)?
Renal ultrasound, or
Uretheral catheter (foley) to empty the bladder (bypass the prostate) and determine if residual urine present
- If patient has > 100 ml of urine in bladder after voiding (“post-void”), there is some degree of obstruction
Obstruction may be anatomic (e.g. prostate) or functional (e.g. neurogenic bladder – seen in severe diabetic neuropathy)
Does this renal ultrasound show hydronephrosis (obstruction)?
No
