KIDNEY FUNCTION TEST Flashcards by V S

This is responsible for the reabsorption of:
Sodium
Chloride
Bicarbonate and other ions
Glucose
Amino acids
Proteins
Urea and
Uric Acid

Proximal Convoluted Tubule

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Renal Function Panel:

Glucose
BUN
Creatinine
Sodium
Potassium
Chloride
Phosphorus
Calcoum
Albumin
CO2

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Elimination of Waste products
Maintenance of blood volume
Maintenance of electrolyte balance
Maintenance of acid-base balance
Endocrine function (EPO secretion)

Functions of the Kidneys

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Measure of clearance of normal molecules that are not bound to protein and are freely filtered by the glomeruli neither reabsorbed nor secreted by the tubules

Glomerular Filtration Rate

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GFR is considered the best ___

Overall indicator of level of Kidney function

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Removal of substance from plasma into urine over a fixed time
Expressed in mL/minute

Clearance

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Plasma concentration is _____ to clearance

Inversely proportional

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Formula for Clearance:

(Urine/Plasma) x (Volume/1440) x (1.73/A)

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Reference Method

Inulin Clearance

Not routinely done

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Reference Method

Inulin Clearance

Not routinely done

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Reference Value of Inulin Clearance

Male = 127 mL/min
Female = 118 mL/min

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Provides an estimate of the amount of plasma that must flowed through the kidney glomeruli per minute
Excellent measure of renal function

Creatinine Clearance

Creatinine is freely filtered by the glomeruli but not reabsorbed

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Provides an estimate of the amount of plasma that must flowed through the kidney glomeruli per minute
Excellent measure of renal function

Creatinine Clearance

Creatinine is freely filtered by the glomeruli but not reabsorbed

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Reference Value of Creatinine Clearance

Male: 85-125 mL/min
Female: 75-112 mL/min

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High Cardiac Output
Pregnancy
Burns
CO poisoning

Increased Creatinine Clearance

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Impaired Kidney Function
Shock, Dehydration
Hemorrhage
Congestive Heart Failure

Decreased Creatinine Clearance

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Can demonstrate progression of renal disease or response to therapy
Not give reliable estimates of the GFR since it is freely filtered by the glomeruli but variably reabsorbed by the tubules

Urea Clearance

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Volume depletion decreases Urea Clearance by both:

Reduced Filtration
Increased Reabsorption

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Produced at a constant rate by all nucleated cells
Freely filtered at glomerulus, not secreted by the renal tubules but reabsorbed

Cystatin C

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Increases more rapidly than creatinine in the early stages of GFR impairment

Cystatin C

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Reference Value of Cystatin C

Adult: 0.5-1.9 mg/L
(>65 yo): 0.9-3.4 mg/L

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Low molecular weight glycoprotein
Functions as Prostaglandin D Synthase
Isolated primarily from CSF; Freely filtered at Glomerulus, then reabsorbed completely and catabolized by the proximal tubule

Beta Trace Protein

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Major end product of Protein and Amino Acid Catabolism
Synthesized in Liver from CO2 and Ammonia from deamination of AA
Glomerulus: Freely filtered
PCT: Substantially reabsorbed
**First Metabolite to Elevate in Kidney Disease

Easily removed by Dialysis

Blood Urea Nitrogen

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Reference Value of BUN

8-23 mg/dL

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BUN:Creatinine Ratio

10:1 20:1

End Product: Yellow Diazine Derivative

Diacetyl Monoxime Method | Chemical Method ## Footnote BUN

End Product: NH3 + CO2

Hydrolysis of Urea by Urease | Enzymatic Method (Indirect) ## Footnote BUN

End: Glutamate + NAD + H2O

Coupled Urease or Glutamate Dehydrogenase Method | UV Enzymatic Method ## Footnote BUN

End: Glutamate + NAD + H2O

Coupled Urease or Glutamate Dehydrogenase Method | UV Enzymatic Method ## Footnote BUN

Reference Method for BUN

Isotope Dilution Mass Spectrometry (IDMS)

1. Chronic Renal Disease 2. Stress 3. Burns 4. High Protein Diet 5. Dehydration

Increased BUN

1. Poor Nutrition 2. Hepatic Disease 3. Impaired Absorption (Celiac Dse) 4. Pregnancy

Decreased BUN

End Product of Muscle Metabolism derived from creatine Partially secreted by PCT via organic cation transport pathway Not reused in body's metabolism, solely as a waste product Commonly used to monitor renal function; index of overall renal function

Creatinine

Measure of the completeness of 24-hour urine collection Used to evaluate fetal kidney maturity

Creatinine

Reference Value of Creatinine

Male: 0.9-1.3 mg/dL Female: 0.6-1.1 mg/dL

Patients taking this antibiotics may have falsely increased result in Jaffe reaction:

Cephalosporin

A Red-Orange tautomer of creatinine picrate is formed when creatinine is mixed with alkaline picrate reagent

Direct Jaffe Method

False Increased Direct Jaffe

Ascorbate Glucose Uric Acid A-Keto acids

False decreased Direct Jaffe

Bilirubin Hemoglobin

A Sensitive but nonspecific method Phosphomolybdenum blue

Folin-Wu Method | Creatinine

A Sensitive but nonspecific method Phosphomolybdenum blue

Folin-Wu Method | Creatinine

Sensitive and Specific Method Uses Adsorbents to remove interferences

Lloyd or Fuller's Earth Method

Adsorbent of Lloyd's reagent

Sodium Aluminum Silicate

Adsorbent of Fuller's Earth Reagent

Aluminum Mg Silicate

Jaffe Reagent (Alkaline Picrate)

Saturated Picric Acid 10% NaOH

Requires Automated Equipment for precision Popular, inexpensive, rapid and easy to perform Serum is mixed with alkaline picrate and the rate of change in absorbance is measured between 2 points

Kinetic Jaffe Method

Used to eliminate nonspecificity of the Jaffe Reaction Specific than Jaffe test

Enzymatic Method Creatinine

Requires large volume of pre-incubated sample; not widely used End: Lactate + NAD

Creatinine Aminohydrolase-CK Method

Has the potential to replace Jaffe method Without interference from acetoacetate or cephalosportins End: Benzoquinonemine dye (Red)

Creatinase-Hydrogen Peroxide Method

Enzymes: 1. Creatinine Aminohydrolase/Creatininase 2. Creatine Kinase 3. Pyruvate Kinase 4. Lactate Dehydrogenase

Creatinine Aminohydrolase - CK Method

Enzymes: 1. Creatininase/ Creatinine aminohydrolase 2. Creatinase 3. Sarcosine Oxidase 4. Peroxidase

Creatinase- Hydrogen Peroxide Method

Reference Method for Creatinine

Isotope Dilution Mass Spectroscopy | Like in BUN

1. Impaired Renal Function 2. Chronic Nephritis 3. Congestive Heart Failure

Increased Serum Creatinine

1. Decreased Muscle Mass 2. Advanced and Severe Liver Disease 3. Pregnancy 4. Inadequate Dietary Protein

Decreased Serum Creatinine

Major product of Purine Catabolism Freely filtered, partially reabsorbed and secreted in renal tubules

Blood Uric Acid

Reference Value of BUA

Male: 3.5-7.2 mg/dL Femal: 2.6-6.0 mg/dL

Disease found primarily in males and first diagnosed between 3rd and 5th decade of lide Pain and inflammation of the joints Presence of **birefrinent crystals in synovial fluid** Persons with this disease are highly susceptible to Nephrolithiasis

Gout | Hyperuricemia

Seen in leukemia, lymphoma, multiple myeloma or polycythemia, hemolytic and megaloblastic anemia

Increased nuclear metabolism

Due to decreased GFR and tubular secretion

Chronic Renal Disease

Deficiency of Hypoxanthine-Guanine Phosphoribosyl Transferase (HGPRT)

Lesch-Nyhan Syndrome

1. Fanconi Syndrome 2. Wilson's disease 3. Hodgkin's Disease

Hypouricemia

Principle: Redox reaction End: Tungsten blue + Allantoin + CO2

Chemical Method | BUA

Principle: Redox reaction End: Tungsten blue + Allantoin + CO2

Chemical Method | BUA

Enzymes for Chemical Method | BUA

1. Sodium Cyanide 2. Sodium Carbonate

Tests that uses Sodium Cyanide

Folin Newton Brown Benedict

Tests that uses Sodium Carbonate | Na2CO3, BUA

Archibald Henry Caraway

Incubation period after the addition of an alkali to inactivate non-uric acid reactants

Lagphase

Specific Method Uric Acid has UV absorbance peak at 293 nm The decrease in absorbance is proportional to the concentration of uric acid present in the sample

Uricase Method End: Allantoin (No absorption at 293 nm) + CO2 + H2O

Reference method for Uric Acid

Isotope Dilution Mass Spectrometry | Crea & BUN

Reference method for Uric Acid

Isotope Dilution Mass Spectrometry | Crea & BUN

Diminished glomerular filtration with normal renal function Decreased renal blood flow Cause: 1. Dehydration 2. Shock 3. CHF

Pre-Renal Azotemia

Damage within Kidneys so decreased GFR BUN; >100 mg/dL Crea: 20 mg/dL BUA: 12 mg/dL Cause: 1. Acute/Chronic Renal Disease 2. Glomerulonephritis

Renal Azotemia

Result of Urinary tract obstruction so decreased GFR Urea level is higher than creatinine due to back-diffusion of urea into the circulation Cause: 1. Renal Calculi (Nephrolithiasis) 2. Cancer or Tumors of Genitourinary Tract

Post-Renal Azotemia

Marked elevation in plasma urea and other nitrogen waste products, accompanied by acidemia & electrolyte imbalance (Inc K) Characterized by: 1. anemia (normocytic normochromic) 2. Uremic frost (dirty skin) 3. Generalized edema 4. Foul breath 5. Sweat is urine-like

Uremia

Uremia is responsible for changes in red cell shape such as:

Burr Cells/ Echinocytes Ellipsoidal cells

Reflects the function of the collecting tubules and the loops of Henle Assess the quantiy of solutes present in urine, which reflects ability of kidneys to produce a concentrated urine

Concentration Test

Three most prevalent solutes excreted:

1. Urea 2. Chloride 3. Sodium

Simplest test of renal concentrating ability Compares weight of fluid with that of distilled water

Specific Gravity

Reference Value of SG

1.005-1.030

Concentration in terms of total number of solute particles present/kg of solvent Affected only by the number of solutes present (More accurate than SG) Useful in assessing water deficit or excess

Osmolality

Urine osmolality is primarily due to:

Urea

Serum osmolality is primarily due to:

Sodium Chloride

Osmolality is determined by measuring a colligative property of sample such as:

1. Freezing point 2. Vapor Pressure 3. Osmotic Pressure and 4. Boiling Point

Increased Osmolality, Increased:

Osmotic Pressure Boiling Point

Increase Osmolality, Decreased:

Freezing Point Vapor Pressure

Reference Value of Osmolality

Serum: 275-295 mOsm/kg 24-hour: 300-900 mOsm/kg

Popular method in determining Osmolality Direct Method

Freezing Point Osmometry

Formula for Computing Serum Osmolality:

Serum Osm = 1.86Na + Gluc/18 + BUN/2.8

Normal ratio of Urine osmolality to Serum osmolality:

1:1

Loss of renal concentrating ability:

1.2:1

Diabetes Insipidus

< 1:1

Glomerular Disease & Presence of Increase solute in urinary filtrate

(> 1:1)

Hyperglycemia Uremia Anion Gap Acidosis

Serum Osmolality (>2.1-2.3)

Difference between measured and calculated plasma osmolality

Osmolal Gap

Sensitive indicator of Alcohol or Drug overdose, causing a large gap in Ethanol Intoxication

Osmolal Gap

Serum anion gap is increased in patients with:

Lactic Acidosis