Urinalysis

CLBT 2200: CLT Certification Review

Unit 2: Complete Urinalysis Review

Urine Composition

• Urea

  • Urea & other organic chemicals dissolved in water.

  • Definition: A metabolic waste product produced in the liver from the breakdown of protein and amino acids.

  • Accounts for nearly half of the dissolved solids in urine.

Organic vs Inorganic Substances

• Organic Substances:

  • Uric Acid

  • Creatinine

  • Definition: Waste product from muscle metabolism.

• Inorganic Substances:

  • Chloride (major)

  • Sodium

  • Potassium

  • Traces of other inorganic materials.

  • Diet influences the amount; specific established values are not defined.

Urine Composition - Other Substances

• Other components in urine include:

  • Hormones

  • Vitamins

  • Medications

  • Formed Elements Which May Indicate Disease States:

  • Casts

  • Crystals

  • Mucus

Urine Volume

• Urine Volume is contingent upon:

  • The amount of water secreted by the kidney, influenced by the state of body hydration.

• Factors influencing urine volume include:

  • Fluid intake

  • Fluid loss from non-renal sources

  • Variations of ADH (Antidiuretic Hormone)

  • The necessity to excrete increased amounts of solids (e.g., glucose, salts).

Urine Volume - Normal Values

• Normal Urine Output:

  • Ranges from 600 to 2000 ml/day with an average of 1500 ml.

  • Oliguria: Scanty urine output (< 600 ml).

  • Anuria: No urine output (< 200 ml).

  • Nocturia: Increased urine production at night.

  • Polyuria: Excessive urine output (> 2000 ml).

  • Diabetes Mellitus: Urine appears dilute but possesses a high specific gravity.

  • Diabetes Insipidus: Urine appears dilute with a low specific gravity.

Urine Specimens

• Specimen Types & Purposes:

  • Random: Collected anytime for routine UA (Urinalysis).

  • First Morning: Upon waking; most concentrated; used for routine UA and pregnancy testing.

  • Fasting: Collection after voiding upon waking; used for routine UA and diabetes screening.

  • 2 hr Post Prandial: Collected 2 hours after eating; used to screen for diabetes.

  • Glucose Tolerance: Series of samples (fasting, ½ hr, 1 hr, 2 hr, and 3 hr) to diagnose diabetes.

  • 1 hr Gestational Tolerance: Fasting urine and 1 hr after glucose ingestion to test for diabetes during pregnancy.

  • Timed Urines: Collected over specified periods for quantitative analyses of hormones, electrolytes, and other analytes.

  • Catheterized: Sterile collection from bladder for cytology or routine UA.

  • Mid-stream: Collected mid-flow during voiding; for UA and culture.

  • Clean-catch: After cleansing the urethral opening; for UA and culture.

  • Suprapubic: Needle aspiration of bladder urine primarily for cytology.

  • Pediatric: Device used for collection from young children; for UA and culture.

  • Sterile: Containers primarily for urine culture; can be used for UA.

Specimen Collection - Labeling

• Proper Labeling Required:

  • Patient's name

  • Date and time of collection

  • Additional information per facility protocol (hospital number, age, location, physician's name, Social Security Number).

  • The label must be attached to the container, not the lid.

Specimen Handling

• Integrity of Specimen:

  • Must be tested within two hours or preserved.

• Preservation Methods:

  • Refrigeration: Most routine method, does not interfere with chemical testing.

  • Chemical preservatives.

Urine Specimen Preservation

• Preservative Types & Uses:

  • Thymol: Preserves sediment; interferes with protein & glucose.

  • Formalin: Preserves sediment for cytology; not for routine UA.

  • Toluene: Preserves biochemical analytes; used in routine UA.

  • Sodium Fluoride (NaF): Preserves glucose for drug screens.

  • Boric Acid: Anti-bacterial; preserves proteins, formed elements, does not interfere with routine UA.

  • HCl: Anti-bacterial; not for routine UA (destroys formed elements).

Changes in Urine Analytes

• Changes that can occur in urine samples include:

  • pH increases due to bacterial conversion of urea to ammonia.

  • Glucose levels decrease as bacteria use it.

  • Ketones may evaporate if not covered.

  • Bilirubin may decrease with light exposure.

  • Urobilinogen is oxidized by bacteria, causing loss.

  • Nitrites increase due to bacteria reducing nitrates in the sample.

  • Bacterial Growth: Reproduction in room temperature within 2 hours leads to sample degradation.

  • Turbidity due to bacterial overgrowth or precipitation of crystals as the sample cools.

  • Loss of RBC/casts occurs in diluted, alkaline urine.

  • Color Changes: Loss of color with loss of bilirubin.

Physical Examination of Urine

• Provides preliminary information about:

  • Inborn errors of metabolism

  • Glomerular bleeding

  • Urinary tract infection.

• Key characteristics to assess:

  • Color

  • Clarity

  • Specific Gravity

Macro Examination of Urine

• Parameters to Assess:

  • Color: Normal is pale yellow to dark yellow (ura-chrome).

  • Clarity: Clear with small amounts of white foam is expected.

  • Odor: Slightly aromatic.

  • Volume (24 hrs): Normal range is 600-2000 ml; average 1200-1500 ml/24 hrs.

  • pH: Ranges from 4-8.

  • Specific Gravity (Random Urine): Ranges from 1.003-1.030; (24 hr urine: 1.015-1.025).

  • Taste: Normally slightly salty.

Urine Color Variability

• Normal urine color ranges from colorless to black; influenced by metabolic changes.

• Terms used to describe colors include:

  • Colorless

  • Straw

  • Light yellow or pale yellow

  • Yellow

  • Dark yellow

  • Amber

• Straw color may signify polyuria.

Normal Urine Color

• Presence of Urochrome:

  • The yellow color estimate the hydration state.

• Other pigments in smaller quantities:

  • Uroerythrin: Pink pigment, causes pink brick dust appearance; precipitates in refrigerated urines.

  • Urobilin: Orange-brown color due to oxidation of urinary constituents; imparts color to non-fresh urine.

Abnormal Urine Color: Dark Yellow/Amber/Orange

• Causes of Dark Yellow/Amber/Orange:

  • Concentration or presence of bilirubin (indicating Hepatitis).

  • Yellow-green color due to photo-oxidation of bilirubin.

  • Presence of yellow foam when shaken indicates bilirubin.

  • Large amounts of white foam may indicate protein.

Specific Causes for Dark Yellow/Amber/Orange Color

• Urobilinogen: Oxidation causes yellow-orange urine.

• Drugs for UTI: Can produce colors that obscure natural urine color and interfere with tests.

  • Phenazopyridium (Pyridium): Causes yellow foam when shaken, may confuse with bilirubin.

  • Azo-gantrisin: Causes orange color due to Pyridium; may coat dipstick.

Red/Pink/Brown - Blood

• Myoglobin (Myoglobinuria): An oxygen-carrying pigment, presenting with red and clear urine.

• Differentiation between:

  • Hemoglobinuria: Presence of hemoglobin, examine plasma color: pink to red = hemoglobinuria; not red = myoglobinuria.

Hematuria vs. Hemoglobinuria

• Hematuria: Intact RBCs in urine; RBC sediment after centrifugation.

• Hemoglobinuria: Presence of hemoglobin in urine; No RBC sediment after centrifugation.

Urine Color Changes: Non-Pathological Causes

• Porphyrins: Associated with the oxidation of porphobilinogen, causing a port wine color.

• Non-pathogenic factors include:

  • Menstrual contamination

  • Highly pigmented foods (e.g., beets in alkaline urine, blackberries in acidic urine)

  • Medications (e.g., rifampin).

Brown/Black Urine Color

• Urines turning brown or black may require additional testing if blood tests are negative.

• Possible Causes:

  • Melanoma: Indicates malignancy.

  • Homogentistic Acid: Indicates an inborn error of metabolism.

  • Medications: May lead to melanuria.

Pathogenic Causes of Blue/Green Urine

• Causes include:

  • Bacterial infections

  • Medications such as Methocarbamol and Indican.

Urine Color Associations

• Colorless: Indicates polyuria.

• Amber: May indicate increased bilirubin (jaundice).

• Orange: Associated with Pyridium.

• Yellow-green: Associated with Biliverdin.

• Blue-green: Associated with Pseudomonas, methylene blue, or dyes.

• Pink-Red/Cloudy: Indicates blood (presence of RBCs);

• Pink-Red/Clear: Indicates hemolysis, either from hemoglobin or myoglobin.

• Brown-black: Old blood or melanin, indicating intravascular hemolysis.

• Milkiness or sediment: Phosphate crystals.

Determining Clarity/Appearance

• Clarity Definition: Refers to transparency or turbidity of the specimen.

• Assessment terms consistent with lab protocols may include:

  • Clear; Hazy; Cloudy; Turbid; Milky.

• Examining Clarity requires:

  • Ensuring specimen is well-mixed.

  • Using a clear container and good lighting for assessment.

Normal Clarity/Appearance

• Normal Clarity: Usually clear.

• Upon cooling or standing, precipitation of amorphous phosphates or carbonates may lead to transient white cloudiness in alkaline urine.

• Clear urine is not always indicative of normal results; abnormal chemical tests may necessitate microscopic examination.

Non-Pathogenic Causes of Turbidity

• Factors may include:

  • Squamous epithelial cells

  • Mucus

  • Semen

  • Talcum powder

  • Radiographic contrast media

  • Fecal contamination

  • Vaginal creams

• Refrigerated Specimens: Might show precipitation due to alkaline pH or acids with precipitated urates (pink brick dust).

Abnormal Causes of Turbidity

• Turbidity correlates with findings in microscopic exams and pathogenic causes such as:

  • RBCs & WBCs

  • Bacteria

  • Non-squamous epithelial cells

  • Yeast

  • Abnormal crystals

  • Lymph fluid or lipids.

Reporting Clarity

• Report clarity and appearance using:

  • Clear: 0

  • Hazy: 1+

  • Cloudy: 2+

  • Turbid: 3+

Specific Gravity Overview

• Normal Range: Generally between 1.003 and 1.035 (random samples).

• Abnormal Conditions:

  • Isosthenuria: Fixed SG at 1.010 indicating severe renal disease.

  • Hyposthenuria: Consistently <1.010; indicates diabetes insipidus or renal disease.

  • Hypersthenuria: Consistently >1.010; seen in glycosuria, heart failure, or excessive water loss.

Specific Gravity Correction Factors

• Correction Factors for Temperature:

  • For temperatures above 22°C: ADD 0.001 for every 3°C above.

  • For temperatures below 22°C: SUBTRACT 0.001 for every 3°C below.

• High levels of glucose or protein (>3+) require specific corrections.

Macro Examination - Odor

• Normal Odor: Faintly aromatic due to volatile acids.

• **Abnormal Odors: **

  • Ammonia indicates bacterial growth or old urine.

  • Fruity odor suggests acetone presence (diabetes).

  • Pungent odors may correlate with garlic or onions.

• Metabolic Disorders Impacting Odor:

  • Maple syrup: Maple syrup urine disease.

  • Mousy/musty: Phenyiketoneuria (PKU).

  • Cabbage: Associated with Methionine.

  • Sweaty feet: Indicates Isovaleric and glutaric acidosis.

Macro Examination – Odor Chart

• Odor Associations:

  • Ammonia: Indicates bacterial growth; UTI.

  • Putrid: Links to UTI.

  • Fruity: Indicates diabetes.

  • Fecal (H2S): Related to feces.

  • Maple Sugar: Represents maple syrup urine disease (MSUD).

  • Mousy: Suggests Phenylketonuria (PKU).

  • Mercaptan: Genetic trait.

  • Sulphur: Indicates cystinurias.

Chemical Examination of Urine

• Reagent Strips provide a simple, rapid way to perform significant chemical analyses.

• Tests on Strips Include:

  • pH

  • Bilirubin

  • Protein

  • Urobilinogen

  • Glucose

  • Nitrite

  • Ketones

  • Leukocytes

  • Blood

  • Specific Gravity.

Reagent Strip Technique

• Procedure:

  • Dip the reagent strip completely, but briefly, in a well-mixed urine sample.

  • Remove excess urine.

  • Reaction Reading is TIME CRITICAL. Wait specified duration for accurate results.

Immersing Strip in Urine for Routine UA

• Immersion Method:

  • Dip the strip into the urine without delay.

  • Remove the strip and drag against the container side to eliminate excess.

  • Hold horizontally to avoid cross-reaction between pads.

Reading Reagent Strip Reactions

• Color Reactions Comparison:

  • Compare colors with provided charts for interpretation.

  • Reactions graded as negative, 1+, 2+, 3+, 4+.

  • Some results estimated semi-quantitatively (in mg/dL).

pH Reaction

• Definition of pH: Hydrogen ion concentration in urine.

• Operational Principle: Employs double pH indicators.

• Characteristics: Old urine may present a pH around 9 with ammonia odor.

• Consideration of Protein Pad Influence: The protein pad may affect the run-over pH results.

Chemical Test - Protein

• Significance: Most indicative of renal disease; if positive, casts should be sought.

• Sensitivity: The test is most sensitive to albumin.

• Reagent: Tetrabromphenol, following the protein error of indicators.

• False Positive Instances: Highly alkaline urine can yield inaccuracies, as can radiographic media.

• False Negatives: May occur in the presence of other proteins or very alkaline urine.

• Confirmatory Test: SSA (sulfosalicylic acid) detects all proteins.

Chemical Tests – Glucose

• Definition of Glucosuria: Detectable glucose present in urine.

• Renal Glucosuria: Normal blood glucose level with low tubular reabsorption.

• Enzymatic Assay: Specific for glucose, with sensitivity down to 100 mg/dL.

• False Negatives: May arise through interference from ascorbic acid.

• Copper Reduction Tests (Clinitest): Used for pediatric patients, notably detecting galactose or lactose.

Chemical Tests – Ketones

• Ketone Bodies Composition: Includes acetoacetic acid (20%), acetone (2%), and β-hydroxybutyric acid (78%).

• Clinical Significance: Commonly seen in diabetes, malnutrition, inadequate carbohydrate intake, or vomiting episodes.

• Reagent Utilized: Sodium nitroprusside (Acetest).

• False Negatives: Possible due to evaporation or bacterial degradation.

• False Positives: May occur in highly pigmented urines.

Chemical Tests – Blood

• Hematuria: Intact RBCs present; urine appears pink-brown and could be cloudy/smoky. Indicative of urinary tract diseases or exercise.

• Hemoglobinuria: Free hemoglobin; urine maintains similar color but remains clear. Associated with intravascular hemolysis or trauma.

• Myoglobinuria: Myoglobin presence; urine color matches but remains clear, often due to muscular trauma.

• Reagent Used: Tetramethylbenzidine. False positives may arise from bleach or microbial peroxidases.

Blood - Reading Results

• The test utilizes tetramethylbenzidine, with false positives potentially coming from bleach or microbial interference. It is crucial to distinguish between intact RBCs in hematuria vs. lysed RBCs in hemoglobinuria.

Chemical Test – Bilirubin

• Origin: Formed by macrophages from hemoglobin degradation.

• Metabolic Processing of Bilirubin: Iron reentering stores in the marrow; globin released into amino acid pool; biliverdin reduced to bilirubin.

• Transport in Blood: Bilirubin bound to albumin (unconjugated or indirect bilirubin).

Bilirubin Metabolism Overview

• Processes Involved Include:

  • Conversion of hemoglobin to iron and its cycles, storage, or usage.

  • Bile transport and eventual excretion routes of tributary transformation.

Bilirubin Test Details

• Reagent Used: Diazonium salts.

• Interferences: False negatives from ascorbic acid or light exposure; false positives from drug interaction.

• Confirmatory Test: Ictotest detects direct or conjugated bilirubin, essential for conditions such as hepatocellular disease or biliary obstruction.

Chemical Test – Urobilinogen

• Conjugated bilirubin is reduced by microbes in the intestine to urobilinogen.

• Normal Value Range: 0.2 - 1.0 Ehrlich units.

• No confirmatory tests exist.

• Increased levels indicate hemolytic reactions or liver disease, while decreased levels occur in biliary obstruction. False results can arise from drugs or light exposure.

Comparing Urinary Bilirubin and Urobilinogen in Jaundice

• Bile Duct Obstruction: Urine bilirubin +++, urobilinogen normal.

• Liver Damage: Urine bilirubin + or -, urobilinogen ++.

• Hemolytic Disease: Urine bilirubin negative, urobilinogen +++.

Chemical Test - Nitrite

• What It Measures: Bacterial ability to convert dietary nitrates to nitrites.

• Outcome: Positive tests suggest over 100,000 bac/mL, leading to bacterial presence in microscopic exams.

• False Negatives due to: Microbial enzyme deficiency, improper sample handling, or lack of dietary nitrates.

• Standing Conditions: Allowing urine stand without testing can further cause false results,

Chemical Test – Leukocyte Esterase

• What it Measures: Detects white blood cells (WBCs) in urine, whether intact or lysed.

• Clinical Significance: Increased levels indicate infections such as UTI, pyelonephritis, cystitis, etc.

• Sensitivity and Correlation: Correlates with microscopic estimation of WBCs, with high glucose or specific gravity leading to potential false negatives.

Chemical Analysis Principles

• Each analyte undergoes specific biochemical reactions that yield color changes or effects recorded via policy.

Microscopic Review of Urine

• Reporting Criteria for Low Power Field (LPF) and High Power Field (HPF) Assessments:

  • LPF: Reporting includes casts and normal/abnormal crystals along with squamous epithelial cell counts.

  • HPF: Focuses on RBCs, WBCs, renal tubular epithelial cells, bacteria, yeast, and sperm counts.

Cellular Elements - Normals

• Normal findings may include:

  • RBC (0-2/hpf)

  • WBC (0-5/hpf)

  • Normal Crystals (Hyaline and granular casts, few)

  • Bacteria and yeast (contaminants from skin)

  • Artifacts.

Cellular Elements - RBCs

• Normal count: 0-5/hpf; Bi-concave discs without nuclei. Ghost cells may appear in hypotonic or alkaline urine; crenated cells in more hypertonic fluid.

• Larger counts indicate potential renal or lower urinary diseases.

Cellular Elements - WBCs

• Normal count: 0-5/hpf; notable types include neutrophils and specific findings in infections/inflammation.

• Clumps termed glitter cells may signify higher infections or disease.

Cellular Elements – Epithelial Cells

• Types:

  • Squamous: Represent lower tract, not clinically significant.

  • Transitional: Line the tubules and bladder.

  • Renal tubular: May signify renal damage upon higher counts.

Cellular Elements – Oval Fat Bodies

• Definition: Epithelial cells that absorb lipids or exhibit degenerative changes; may indicate nephrotic syndrome.

• Detection methods:

  • Cholesterol polarized creates a Maltese Cross.

  • Triglycerides identify as red/orange globules with Sudan III or Oil Red O staining.

Casts – Formation

• Proteins such as Tamm Horsfeld mucoprotein create casts; types to normalize include hyaline and cellular forms.

• Normal Appearance: Fine granular casts present, release from tubular debris.

Casts - Types

• Types and Clinical Associations:

  • Hyaline: Non-refractile, 0-2/lpf normal.

  • Granular (both Fine & Coarse): Degenerative changes marked in pyelonephritis.

  • RBC Casts: Signify pathology; acute/chronic glomerulonephritis or renal damage.

Casts - WBC and Bacterial

• WBC Casts appear in pyelonephritis, renal epithelial suggest necrosis or rejection in transplants. Bacterial casts indicate acute pyelonephritis.

Casts – Fatty and Waxy

• Fatty Casts: Associated with nephrotic syndrome; may exhibit Maltese Cross appearance.

• Waxy Casts: Indicative of chronic renal disease.

Casts – Crystals & Pseudo

• Crystal Casts: Highlight crystal deposits within tubules, indicative of damage or obstruction.

• Pseudocasts: Not true casts;include aggregates or mucous strands, indicate varying conditions.

Normal Crystals - Acid pH

• Acidic pH Crystals (<7.0):

  • Amorphous urates

  • Calcium oxalate

  • Uric acid

  • Hippuric acid

Normal Crystals - Alkaline pH

• Alkaline pH Crystals (>7.0):

  • Amorphous phosphates

  • Triple phosphate (coffin lids)

  • Ammonium biurate (thorny apples)

Abnormal Crystals - 1

• Leucine, Tyrosine, Cystine: Associated with liver diseases; notably different in microscopic appearances.

Abnormal Crystals - 2

• Associated with medication interactions, including sulfa drugs and cholesterol metabolites.

Abnormal Crystals - 3

• Hemosiderin and trace radiographic dyes indicate hemolytic conditions and artifacts respectively.

Miscellaneous Items in Urine

• Bacteria: May indicate contamination or infection, consider WBC, nitrite, and esterase tests.

• Yeast: Indicative of infections or contaminants; includes features for identification like Candida albicans.

• Parasites: Such as Trichomonas vaginalis, require careful differentiation from WBCs in older urine specimens, marked by motility features.