Week 1-5 Overview of Urinalysis and Body Fluids

Specimen collection

Pre-analytical

Reagent Performance

Analytical

Result Performing

Post-analytical

Organic constituents of urine

Urea, Creatinine, uric acid

Inorganic constituents of urine

Chloride, Sodium, Potassium

Normal range of daily output of urine

Average: 1200-1500ml/day; Reference Range: 600-2000ml/day

Oliguria

Less than 600ml urine/day

Nocturia

Increased urine output at night

Polyuria

Increased urine output (over 2000ml/day)

Polydipsia

Increased thirst/water intake

Diabetes Mellitus

Decreased/defect in insulin production; Increased glucose in urine, high specific gravity

Diabetes Insipidus

Decrease in antidiuretic hormone; low specific gravity

Changes in urine specimen at room temperature for more than 2 hours

Color: modified/darkened; Clarity: Decreased; Odor: increases ammonia smell; pH: increased; Glucose: decreased; Ketones: decreased; Bilirubin: decreased; Urobilinogen: decreased; Nitrate: increased; RBCs, WBCs, and casts: decreased; Bacteria: increased; Trichomonas: decreased

Best preservation method for urine specimen

Refrigeration

Reasons a laboratory would reject a urine specimen

Specimen in unlabeled containers, non-matching labels and requisition form, specimens contaminated with toilet paper or feces, containers with contaminated exteriors

Methods for preserving urines

Refrigeration, Urine collection kits, Light gray and gray C&S tubes, Yellow UA plus tube; The ideal preservative is bactericidal, inhibits urease, and preserves the formed elements in the sediment (like casts, crystals, and cells)

Random urine specimen

Routine testing

First morning urine specimen

Routine testing, pregnancy testing, orthostatic proteins (prostatic issues)

24-hour urine specimen

Quantitative chemical tests

Catheterized urine specimen

Bacterial culture, or drugs of abuse on adolescents who are unwilling or unconscious

Midstream urine specimen

Routine testing, bacterial cultures

Suprapubic aspiration urine specimen

Bacterial cultures, cytology

Three and four glass collections urine specimen

Prostatic infections

Methods for determining whether a questionable fluid is urine

Creatinine and Urea test; specific gravity must be above 1.005 or it is not urine

Functions of the kidneys

Excretory, Regulatory, Synthetic

Functional unit of the kidney

Nephron

Cortical nephrons

85% are cortical nephrons, responsible for removal of waste products and reabsorption of nutrients, they are located in the renal cortex

Juxtamedullary nephrons

15% are juxtamedullary, located at the loops of Henle, and are responsible for the concentration of urine

Urinary filtrate flow

1. Bowman's capsule 2. Proximal convoluted tubule 3. Descending loop of Henle 4. Ascending loop of Henle 5. Distal convoluted tubule 6. Collecting duct 7. Renal Calyces 8. Ureter 9. Bladder 10. Urethra

Causes of glomerular filtering action

Hydrostatic pressure; Shield of negativity; Oncotic pressure caused by proteins

Hydrostatic pressure

Pressure exerted by a fluid at equilibrium due to the force of gravity.

Shield of negativity

Anything small enough to pass through, but has a negative charge will be repelled back and not passed through into the urine.

Glomerulus

Located in the bowman capsule and function is to filter the blood.

Normal glomerular filtration rate

120 mL/min.

Renin-angiotensin-aldosterone system

Responds to changes in the pressure and sodium content of blood, causing vasoconstriction of Efferent vessels, increased PCT sodium reabsorption, increased DST sodium reabsorption, and increased collecting duct water resorption to increase blood pressure and sodium.

Active transport

Requires a carrier protein.

Passive transport

Moves molecules according to a concentration gradient or electrical potential.

Maximal reabsorptive capacity

Tm is the ability for a solute by renal tubules.

Plasma renal threshold for glucose

160-180 mg/dL.

Antidiuretic hormone

Increased ADH causes more concentrated urine, with a high specific gravity; decreased ADH causes less concentrated urine, with a lower specific gravity.

Tubular secretion

Buffering capacity of blood depends on bicarbonate which is 100% reabsorbed in PCT; excess hydrogen ions depend on secretion to be excreted.

Creatinine clearance test

Creatinine is a product of muscle metabolism; range: 120 mL/min.

Formula for glomerular filtration rate using creatinine clearance

C= (UV)/P; C= creatinine clearance rate; U= Urine creatinine; V = urine volume/minute (divide volume/24 hours by 1440); P = plasma creatinine.

Estimated glomerular filtration rate results

Below 60 indicates renal disease/dysfunction.

Osmolarity

Measures the ratio of solutes in a solution.

Normal urine color

Urochrome is responsible for the normal pale yellow/straw color urine.

Urine colors and causes

Pale Yellow, yellow, darker yellow: normal caused by urochrome; Amber: dehydration, bilirubin; Orange: AZO dyes- Phenazopyridine/pyridium; Red/pink: RBCs, beets, Rifampin, rhabdomyolysis, transfusion reaction, porphyrin; Green: pseudomonas infections, asparagus; Blue/Green: Bacterial infections, medications; Brown/Black: Alkaptonuria, melanin, fava beans.

Transfusion reaction urine

Clear red urine with red plasma.

Rhabdomyolysis urine

Clear red urine with clear plasma.

White urine foam

Indicates albumin/renal issues.

Yellow urine foam

Indicates bilirubin/hepatic issues.

Urine clarity classifications

Clear: no visual particulates, transparent; Hazy: few particulates, easy to see through; Cloudy: many particulates, blurry when looking through; Turbid: can't be seen through; Milky: may be particulate, clots, or very high WBCs.

Cloudy urine causes

Pathologic vs non-pathologic causes.

Non pathogenic

Vaginal creams, talcum powder, mucus, squamous epithelial cells, crystals (resemble pink brick dust presence of uroerythrin), amorphous phosphates, carbonates, urates with alkaline pH, amorphous urates with acidic pH, allowed to stand or refrigerated turbidity, semen or fecal contamination, radiographic contrast media.

Pathogenic

RBCs, WBCs, bacteria, yeast, Trichomonads, lymph fluid, abnormal crystals, lipids, non-squamous epithelial cells, clear urine not always normal.

Isothenuric

SG at 1.01.

Hyposthenuric

SG below 1.01.

Hypersthenuric

SG above 1.01.

Specific Gravity (SG)

Measures the kidneys ability to concentrate and or dilute urine.

Urine Refractometry

Measures specific gravity urine the velocity of light in air to the velocity of light in solution.

Aromatic urine odor

Normal.

Foul, ammonia-like urine odor

Bacterial decomposition, UTI.

Fruity, sweet urine odor

Ketones (diabetes mellitus, starvation, vomiting).

Maple Syrup urine odor

Maple syrup urine disease.

Mousy urine odor

Phenylketonuria.

Rancid urine odor

Tyrosinemia.

Sweaty feet urine odor

Isovaleric acidemia.

Cabbage/hops urine odor

Methionine malabsorption.

Bleach urine odor

Contamination.

Reasons for measuring urinary pH

Diagnosis of respiratory or metabolic acidosis or alkalosis, renal calculi formation (stones), treatment of UTIs, ID of crystals, defects in tubular secretion and reabsorption function.

pH testing by reagent strip

Double Indicator system; bromothymol blue.

Acidic urine pH

Orange-Red.

Basic urine pH

Blue.

Pre renal proteinuria

Proteins originate from location above the kidney in urine creation flow. Ex: Increase in light chain proteins (Bence Jones proteins) from Multiple myeloma.

Renal proteinuria

Proteins originate from the kidneys.

Glomerular proteinuria

Glomerulus basement membrane damage.

Irreversible damage causes for glomerular proteinuria

Amyloid material, toxic exposure, lupus, streptococcal glomerulonephritis.

Reversible causes for glomerular proteinuria

Strenuous exercise, dehydration, hypertension, pre-eclampsia.

Microalbuminuria

Not detected on dipstick.

Orthostatic (postural) proteinuria

Increased protein excreted when in vertical position.

Tubular proteinuria

When albumin can no longer be absorbed (has reached renal threshold, active transport will no longer occur). Associated with toxic substance and heavy metal exposure, severe viral infections, Fanconi's syndrome (a type of anemia).

Post renal proteinuria

Protein added as it passes through the lower urinary tract.

Causes of post renal proteinuria

Bacterial and fungal infections, inflammatory conditions, menstrual contamination, trauma/injury, kidney stones (cause inflammation, sloughing).

Protein error of indicators

Indicators will change color when exposed to protein at a constant pH.

Sources of interference in protein testing

Using tetrabromophenol blue buffered to pH of 3, sensitive to extreme pH changes: highly alkaline urine will cause False +.

Renal threshold of glucose

160-180mg/dL.

Glucose in urine

If this limit is reached it can no longer be reabsorbed and will spill into urine.

Increased plasma glucose causes

Diabetes will surpass the threshold.

Non-diabetic causes of glucose in urine

Pancreatitis, thyroid issues, Cushing's syndrome, hormones.

Glucose oxidase method

Double sequential enzyme reaction

False positive causes in glucose testing

False + caused by contamination with peroxide, bleach, or other strong oxidizers

False negative causes in glucose testing

False = caused by presence of reducing substances like ascorbic acid and salicylates

Ketone bodies in urine

Acetone- 2%, Acetoacetic acid- 20%, Beta-hydroxybutyrate- 78% (this one is not detected by dipstick)

Causes of ketonuria

Causes of ketonuria: diabetes mellitus, increased loss of carbohydrates from vomiting, starvation and malabsorption, keto diet.

Sodium nitroprusside reaction

Acetoacetic acid + sodium nitroprusside -> turns purple

Sensitivity of sodium nitroprusside reaction

Sensitive to 5mg/dL

False positive causes in ketone testing

False + from pigmented urine, medications with sulfhydryl groups, levodopa

False negative causes in ketone testing

False = from old or improperly preserved specimens

Hematuria

Presence of intact RBCs, will show red/cloudy urine; related to disorders of renal or genitourinary origin (or menstrual contamination)

Hemoglobinuria

Presence of destructed RBCs, will show red/clear urine; related to disorders where the amount of free hemoglobin present exceeds haptoglobin content (haptoglobin can no longer recycle it)