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Nephron
Basic structural unit of kidney
Urethra (Female)
3-4 cm
Urethra (Male)
20 cm
Urine formation (order)
Glomerulus Bowman's capsule PCT Loop of Henle DCT CD
PCT
65% of reabsorption
ADH
Regulate H2O reabsorption in DCT and CD
Urine composition
95-97% H2O, 3-5% solids, 60g TS in 24 hrs
Organic solids in urine
35g: Urea (major)
Inorganic solids in urine
25g: Cl (#1) > Na+ > K+
Glomerular Filtration
Clearance tests evaluate glomerular filtration
Creatinine clearance
Formula: Cc = U x V x 1.73 / P x A
Normal creatinine clearance values (Male)
107-139 mL/min
Normal creatinine clearance values (Female)
87-107 mL/min
Tubular Reabsorption
1st function to be affected in renal disease
Concentration tests
Evaluate tubular reabsorption
Fishberg test
Patient is deprived of fluid for 24hrs then measure urine SG (SG ≥ 1.026)
Mosenthal test
Compare day and night urine in terms of volume and SG
Specific Gravity
Influenced by # and density of particles in a solution
Osmolarity
Influenced by # of particles in a solution
Freezing point depression principle
- 1 Osm or 1000 mOsm/kg of H2O will lower the FP of H2O (0'C) by 1.86'C
Example calculation for Osm
Determine Osm in mOsm/kg: Temp. = -0.90'C, Solution: 1000 mOsm/kg = _ _x____ -1.86'C -0.90'C, x = 484 mOsm/kg
PAH test
p-aminohippuric acid
PSP test
Phensulfonphthalein test, obsolete, results are hard to interpret
Methods of Collection
Midstream/Catheterized, Urine culture, Suprapubic aspiration, Anaerobic urine culture
3 glass technique
For detection of prostatic infection: 1st portion of voided urine, Middle portion of voided urine: Serves as control for kidney and bladder infection, If (+), result for #3 is considered invalid
Prostatic infection
1 < 3 (10x)
Chain of custody
Step by step documentation of handling and testing of legal specimen
Required amount for drug specimen collection
30-45 mL
Temperature for urine specimen
32.5-35.7'C (within 4 mins)
Blueing agent
Used in toilet bowl to prevent adulteration
Types of Urine Specimen
Occasional/Single/Random, Routine, Qualitative UA, 24 hr, 12 hr, 4 hr, 1st morning, Fasting/2nd morning
Addis count
Measure of formed elements in the urine using hemacytometer
Nitrite determination
1st morning/4 hr; NO3 to NO2 indicates (+) UTI
Ideal specimen for routine UA
Most concentrated and most acidic = preservation of cells and casts
Changes in Unpreserved Urine
Decreased clarity, bacterial multiplication, glucose, ketones, bilirubin, urobilinogen; Increased pH, urea, bacteria, odor, nitrite
Contamination vs True infection
Contamination: Increased Bacteria; True infection: Increased Bacteria and WBCs
Preservation methods for urine
Refrigeration (2-8'C), Formalin, Boric acid, Sodium fluoride
Physical Examination of Urine
Volume NV: 24 hr = 600-1200 mL; Night: Day ratio = 1:2 to 1:3
Polyuria
Increased urine volume; Diabetes Mellitus: increased volume, increased SG; Diabetes Insipidus: increased volume, decreased SG
Oliguria
Decreased urine volume due to calculus/kidney tumors or dehydration
Anuria
Complete cessation of urine flow
Nocturia
>500mL with SG <1.018
Urine color
Indicates degree of hydration; should correlate with urine SG
Urine pigments
1. Urochrome: Major pigment (yellow); 2. Uroerythrin: Pink pigment
Urochrome
Production is directly proportional to metabolic rate; increased in thyrotoxicosis, fever, starvation
Uroerythrin
May deposit in amorphous urates and uric acid crystals
Urobilin
Dark yellow/orange; imparts an orange-brown color to a urine which is not fresh.
Bilirubin
Oxidized to Biliverdin.
Normal Urine Color
Colorless to deep yellow.
Abnormal Urine Color
Red/red brown (most common), colorless/pale yellow, amber, orange, yellow-green, green, blue-green.
Amber Urine
Indicates bilirubin presence (yellow foam).
Orange Urine
Caused by Pyridium (treatment for UTI); presents as yellow/orange foam, orange and viscous.
Yellow-green Urine
Indicates the presence of certain pigments.
Green Urine
Associated with Pseudomonas aeruginosa.
Blue-green Urine
Caused by Clorets, methylene blue, or phenol.
Indican
Blue color associated with Hartnup disease or Blue diaper syndrome.
Cloudy/Smoky Red Urine
Indicates hematuria (intact RBCs).
Clear Red Urine
Indicates hemoglobin or myoglobin presence.
Brown/Black Urine
Indicates methemoglobin (acid urine) or homogentisic acid (alkaptonuria); urine darkens after a period of standing.
Cola-colored Urine
Caused by Levodopa (treatment for Parkinsonism).
Red to Brown Urine
Caused by Mepacrine/Atabrine (treatment for malaria, giardiasis).
Red to Brown Urine (Metronidazole)
Caused by Metronidazole/Flagyl (treatment for trichomoniasis, amoebiasis, giardiasis).
Bright Orange-red Urine
Caused by Phenazopyridine/pyridium (treatment for UTI).
Bright Yellow Urine
Indicates riboflavin (multivitamins) presence.
Nubecula
Faint cloud in urine after a period of standing; indicates WBCs, epithelial cells, and mucus.
Clarity of Urine
Clear: transparent, no visible particulates; hazy: few particulates; cloudy: many particulates; turbid: print cannot be seen.
Specific Gravity (SG)
Density of solution compared with density of similar volume of distilled H2O at a similar temperature; normal value is 1.003-1.035.
Isosthenuria
Specific gravity of 1.010 (glomerular filtrate).
Hyposthenuria
Specific gravity less than 1.010.
Hypersthenuria
Specific gravity greater than 1.010.
Urine Odor
Normal is aromatic/odorless; abnormal odors include ammoniacal (from urea), fruity/sweet (from DM), and others.
Harmonic Oscillation
A repetitive variation, typically in time, of some measure about a central value.
Densitometry
The measurement of the density of a substance, often used in medical diagnostics.
Frequency of soundwave
The rate at which a soundwave enters a solution, changing in proportion to the density (SG) of the solution.
pH Normal Range
The normal pH range for urine is 4.5-8.0.
1st morning urine pH
The pH of first morning urine is typically between 5.0-6.0.
pH 9.0
Indicates unpreserved urine.
Acid urine causes
Caused by DM (Ketone bodies), starvation (Ketone bodies), high protein diet, and cranberry juice (Tx: UTI).
Alkaline urine causes
Caused by after meal, vomiting, renal tubular acidosis, vegetarian diet.
Old specimen reaction
Urea reacts with Urease to produce NH3.
Double indicator system
Uses Methyl red and Bromthymol blue for pH measurement.
Normal protein value
Normal protein levels in urine are < 10 mg/dL or < 100 mg/24 hrs.
Pre-renal proteinuria
Occurs prior to reaching the kidney due to intravascular hemolysis, muscle injury, severe inflammation, or multiple myeloma.
Bence-Jones protein
Ig light chains that precipitate at 40-60°C and dissolve at 100°C, seen in multiple myeloma.
Renal proteinuria
Results from glomerular and tubular disorders, including diabetic nephropathy and Fanconi's syndrome.
Microalbuminuria
Proteinuria not detected by routine reagent strip.
Orthostatic proteinuria
Proteinuria occurring when standing due to pressure on renal veins.
Protein (Sorensen's) error
An error in protein measurement in urine due to indicator interference.
Cold precipitation test
A test that reacts equally to all types of protein, used to identify the presence of other proteins.
CSF protein testing
CSF protein is frequently tested using TCA (preferred) and SSA.
SSA Reactions (Protein)
A scale measuring turbidity in protein concentration from negative (< 6 mg/dL) to 4+ (> 400 mg/dL).
Glucose in urine
Most frequently tested in urine, indicating renal threshold of 160-180 mg/dL.
Fructose
A sugar found in fruits and honey syrup, elevated in certain conditions.
Galactose
Elevated in infants with enzyme deficiencies such as Galactosemia.
Lactose
Elevated during lactation or strict milk diets.
Hyperglycemia associated Glycosuria
Increased blood glucose leading to increased urine glucose, associated with conditions like DM and Cushing's syndrome.
Fanconi's syndrome
Defective tubular reabsorption of glucose and amino acids.
Double sequential enzyme reaction
A method involving glucose oxidase and peroxidase.
Chromogen
A substance that changes color in a chemical reaction, such as KI (Brown) and Tetramethylbenzidine (Blue).
Copper Reduction test (Clinitest)
A test that relies on the ability of glucose and other substances to reduce CuSO4 to Cu2O in the presence of alkali and heat.