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Urinalysis and Body
Urinalysis and Body Fluids
| Question | Answer |
|---|---|
| Renal Physiology: Nephron | • Major functional unit if the kidney • Approximately 1 million per kidney • Composed of glomerulus and renal tubules |
| Renal Physiology: Glomerulus | • Coil of capillary vessels • Non-selective filter f plasma substances of <70,000 MW • Water, glucose, electrolytes, amino acids, urea, uric acid, creatinine, and ammonia comprise the glomerular filtrate • Filters 120 ml/min or 1/5th of renal plasma |
| Proximal tubule function | • Reabsorbs water, sodium chloride, bicarbonate, potassium, calcium, amino acids, phosphates, protein, and glucose • Glucose-threshold substances, reabsorbs at 160-180mg/dl or less • Secretes- sulfates, glucuronides, hydrogen ions and drugs |
| Loop of Henle descending | • Reabsorbs water • No solutes reabsorbed |
| Loop of Henle ascending | • Reabsorbs solutes (sodium, chloride, calcium, magnesium) • No water reabsorbed |
| Distal and collecting tubules | • Reabsorbs sodium • Secretes potassium, ammonia, and hydrogen ions • Potassium ions exchanged for sodium ions |
| Normal urine volume | 1200-1500ml/day |
| Polyuria | • >2500ml/day • Disease/causes: diabetes insipidus, diabetes mellitus, diuretics, caffeine, alcohol, excessive water intake |
| Oliguria | • <400ml/day • Disease/causes: dehydration, vomiting, diarrhea, burns, perspiration |
| Anuria | • Complete cessation • Disease/causes: kidney damage, decrease blood flow to kidneys |
| Nocturia | Increase volume at night |
| Urine composition | • Urea (non-protein nitrogen) • Other organic solids (non-protein nitrogens) • Inorganic solids • Water |
| Urine composition: urea (non-protein nitrogen) | • Metabolic waste product produced in liver from breakdown of protein • ½ total urinary dissolved organic solids |
| Urine composition: other organic solids (non-protein nitrogens) | • Uric acid • Creatinine |
| Urine composition: inorganic solids | • Chloride-primary constituent • Na+ • K+ |
| Hormones: Aldosterone | • Source: Adrenal Cortex • Action: increases rate of sodium reabsorption |
| Hormones: Ariginine Vasopressin (AVP) (previously called Antidiuretic Hormone ADH) | • Source: Posterior Pituitary Gland • Action: reabsorption of water from distal tubules • Deficiency- diabetes insipidus |
| Hormones :Erythropoietin | • Source: Kidney • Action: simulates production of erythrocytes |
| Collection methods: random | • Most common specimen type • Easiest to collect • Useful for routine screen tests |
| Collection methods: first morning | • First voided specimen upon waking • Ideal screening specimen (most concentrated) |
| Collection methods: midstream clean catch | • Clean external genital area • First and last stream of urine voided; midstream collected |
| Collection methods: catheterization | • Insertion of catheter directly into bladder via urethra • Avoids external contamination- may introduce infection |
| Collection methods: pediatric | • Sterile plastic collection bag placed over genital area with adhesive • Bag checked ever 15mins • Many sources of contamination |
| Collection methods: suprapubic aspiration | • Insert needle through suprapubic abdominal area directly into bladder • Avoids external contamination- may introduce infections • Optimum specimen for bacterial culture; invasive procedure |
| 24 hour urine | • Collected over 24 hour period • First specimen discarded while all others collected • Used for quantitative urine studies • Completeness of collection monitored by creatinine levels (should be >1.0 mg/dl) |
| Analysis | Analyze within 1 hour of voiding (NOT 1 hour after received in lab) |
| Effects of prolonged sitting of specimens at room temperature: increase | • Increase: nitrite (bacterial growth), pH (urea converted to ammonia), turbidity (bacterial growth, red or white cells, or amorphous) |
| Effects of prolonged sitting of specimens at room temperature: decrease | • Decrease: glucose (glycolysis due to bacteria and yeast), ketones (volatization- exposure to air), bilirubin (exposure to light), urobilinogen (oxidized to urobilin), cells and cast (lysis) |
| Refrigeration urine specimen | • Preservation method of choice (up to 24 hours) • May result in precipitation of amorphous crystals • After removal from fridge let sample return to room temp before testing (approximately 15mins) |
| Physical Examination: odor | • Not evaluated but may provide clue to constituents • Associations Fruity- ketones Ammonia- old urine “Mousy”- phenylketonuria (PKU) Maple syrup- Maple Syrup disease (branched chain aminoaciduria) |
| Physical Examination: clarity | • Normal urine is clear • Any of the urinary elements (cells, cast, crystals), or bacteria may make urine cloudy |
| Physical Examination: color | • Normal urine is a pale yellow (straw) to yellow color • Urochrome gives urine its normal color |
| Physical Examination: color as a clue | • Red: hgb, RBC’s, myoglobin, porphyrin, uroerythrin • Port wine: porphyrin • Red-brown: hgb, RBC’s, myoglobin • Yellow-brown/Amber-yellow-green: bilirubin, biliverdin • Yellow-orange: bilirubin, urobilin, pyridium (drug) • Bright yellow: vita C |
| Physical Examination: color as a clue part 2 | • Dark yellow: concentrated specimen, bilirubin, urobilin • Brown-black: methemoglobin (oxidized RBC’s) Homogentisic Acid (Alkaptonuria), melanin • Blue: indicant (Tryptophane Metabolic Disorder) • Green/Blue-green: old urine, Pseudomonas |
| pH | • Normal urine is slightly acid (6.0), random (4.5-8.0) Postprandial sample (2hrs after eating), urine may be alkaline (alkaline tide) |
| pH at room temp or warmer for some time it may become | Alkaline |
| Acidic pH for urine maybe due to | • Metabolic or respiratory acidosis • High protein diet • Cranberry juice |
| Alkaline pH for urine maybe due to | • Vegetarian |
| Specific Gravity (SG) | • Offers the simplest way to check the concentration and dilution functions of the kidney tubules • Normal urine: 1.002-1.035 |
| The highest the kidney can concentrate of specific gravity | • 1.040 Higher values are due to either large amounts of glucose or radiographic dyes from renal x-ray procedures Reagent strip SG test not affected by radiographic dyes |
| Specific Gravity is directly proportional to color | • The higher the SP the deeper the color (Exception: a pale color urine with a high SG is probably due to glucose- urine is diluted due to loss of concentrating ability by diabetics) |
| Diabetes Mellitus | • Defect: decrease insulin • Polyuria (increase urination) • Polydipsia (thirsty) • Increase specific gravity • Increase glucose • Increase ketones |
| Diabetes Insipidus | • Defect: decrease ADH/AVP • Polyuria (increase urination) • Polydipsia (thirsty) • Decrease specific gravity • Neutral glucose • Neutral ketones |
| Chemical examination: Protein | • Principle-protein error of indicators pH of protein-testing portion is kept at 3.0 albumin in urine binds to dye binding shifts the dye’s spectrum so that it appears to change color from yellow to green • More sensitive to albumin than globulin |
| Chemical examination: Protein-interfering substances | Highly alkaline urine (false positive) |
| Proteinuria | • Best single indicator of renal abnormality (glomerular involvement) • Associated with multiple myeloma, orthostatic proteinuria (benign conditions resulting in proteinuria after standing) and strenuous exercise |
| Chemical examination: Protein | • Detected by sensitive albumin tests • Monitoring patients w/diabetes, hypertension, peripheral vascular disease • Enables patients with low levels albuminuria to begin treatment before kidney disease occurs |
| Chemical examination: Glucose- reagent strip part 1 | • Analyzed for diabetes Renal Threshold 160-180 mg/dl • Specific for glucose only • Principle- glucose oxidase (double sequential enzyme reaction) |
| Chemical examination: Glucose- reagent strip part2 | • Positive copper reduction test with negative strip=sugar (or other reducing substance) other than glucose • Negative copper reduction test with positive strip possible because strip is more sensitive than copper reduction method |
| Chemical examination: Glucose- reagent strip part 3 | • Interference by oxidizing agents (bleach or peroxide)- false positive |
| Chemical examination: Glucose- Clinitest | • For glucose and other reducing sugars • Principle- Benedict’s copper reduction test • CuSO4+NaOH+reducing substance=Cu2O |
| CuSO4+NaOH+reducing substance=Cu2O | • Sugars (and other reducing substances) reduce the cupric ion to the cuprous state in the presences of alkali and heat • Color of reaction ranges from blue-green to orange-red depending upon amount of sugar |
| Clinitest | • Screening test for galactosemia (rare congenital carbohydrate metabolic conditions in pediatric patients) • Galacotose, lactose, fructose, maltose, and pentose gives positive results |
| Clinitest | • Ascorbic acid (vitamin C) causes false negative results (but only in extremely high doses) |
| Clinitest- how to avoid pass through by | Use 2 drops method rather than 5 drop method to minimize “pass through” reactions (reaction goes from negative blue to positive orange and back to negative blue) |
| Chemical examination: Ketones part 1 | • Acetone, diacetic acid (acetoacetate) and beta-hydroxy-butyric acid- (end products of fat metabolism) • Principle (strip and tables)- sodium nitroprusside + ketone = purple color • Strip specific for diacetic acid |
| Chemical examination: Ketones part 2 | • Confirmation test (Acetest tablets) specific for diacetic acid & acetone • Interference by highly pigmented urine and levodopa metabolites cause a false positive result |
| Chemical examination: Ketones part 3 | • Uncontrolled diabetes mellitus, high protein diets, and GI disturbances give positive results |
| Chemical examination: Blood part 1 | • 2-step enzymatic procedure Peroxide on strip + blood =O2 O2 + color producer = color change |
| Chemical examination: Blood part 2 | • Bleach and other oxidizing agents can interfere- false positive results • Ascorbic acid (vitamin C)- false negative results (newer reagent strips are more resistant to this effect) • Hemoglobin and myoglobin have peroxidase activity |
| Chemical examination: Blood-positive results | • Associated w/systemic bleeding disorders, renal diseases, cystitis, calculi, and strenuous exercise • Associated with hemolytic anemias, incompatible transfusions, malaria, and strenuous exercise • Myoglobinuria associated with muscle destruction |
| Chemical examination: Bilirubin | • Diazo Reaction: diazonium salt + bilirubin = bluish purple color • Ictotest (tablet) more sensitive than reagent strip • False negative • Bilirubinuria associated with bile duct obstruction and liver damage (hepatitis and cirrhosis) |
| Chemical examination: Urobilinogen | • Normal: 1 mg/dl or less; 1 EU • Principle (strip)- Ehrlich’s reaction: Para-dimethylaminobenzaldehyde in acid buffer reacts with urobilinogen to produce a peach to pink color |
| Chemical examination: Urobilinogen-false negatives | Formalin (preservative) |
| Chemical examination: Urobilinogen-false positive | • Highly pigmented urine • Some medications |
| Chemical examination: | |
| Chemical examination: |
Created by:
evk2369
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