Kidney Function Flashcards by Marlo Roque

Pair of bean-shaped organs located retroperitoneally on either side of the spinal column

Kidneys

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T/F: Each kidney contains 1-1.5 million nephrons with a total of 2-3 million nephrons

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Outer layer

Renal Cortex

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Inner layer

Renal Medulla

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The functional unit of each kidney

Nephrons

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What is the main function of nephrons

Filter blood to produce urine

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Enumerate the 5 basic parts of the kidney

Glomerulus
Proximal Convoluted Tubule
Loop of henle
Distal Convoluted Tubule
Collecting duct

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Glomerulus aka

Bowman’s capsule/Catch basin

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Facilitates non-selective filtration

Glomerulus

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Glomerulus

Plasma are filtered:

○ <70,000 daltons: filtered
○ >70,000 daltons: not filtered

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Tubular reabsorption (those filtered will be absorbed again)

Proximal Convoluted Tubule

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Enumerate what the proximal convoluted tubule reabsorbs

water, sodium, chloride, bicarbonate, glucose, amino acids, proteins, urea and uric acid

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How many percent are water, sodium and chloride are filtered and reabsorbed?

70%

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How many percent are water, sodium and chloride are excreted?

30%

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___% of glucose (renal threshold:
_________ mg/dL)

100%
160-180 mg/dL

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98% - 100% of ________ will be reabsorbed

uric acid

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_____ urea such as amino acids, vitamins and proteins (almost all are reabsorbed as they are essential)

40%

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Maintains the hyperosmolality of the renal medulla

Loop of henle

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Final site for urine concentration or dilution

Collecting duct

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Enumerate the functions of Kidneys

I. Main function is urine formation
II. Maintenance of blood volume and electrolyte imbalance
III. Maintenance of acid-base balance
IV. Endocrine function

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which functions of kidney is to release waste products

I. Main function is urine formation

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Which function of the kidneys is for the osmolality (amount of solute dissolved in the blood)

II. Maintenance of blood volume and electrolyte imbalance

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II. Maintenance of blood volume and electrolyte imbalance

90% of it is ____ (major)

Sodium

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T/F: ↑ Sodium = hyperosmolality = release of ADH / Vasopressin = reserves H2O or initiate thirst

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T/F: ↓ Sodium = hypoosmolality = prevent production of ADH = promotes urination and release of aldosterone(as sodium reabsorption and potassium secretion)

Which kidney function is responsible for maintaining blood pH

III. Maintenance of acid-base balance

Which kidney function promotes reabsorption and excretion of Bicarbonate

III. Maintenance of acid-base balance

○ ________: alkaline ○ ________: acidity

Excretion Secretion

Plasma contains 20-35 mg/dL of NPN compounds

NON-PROTEIN NITROGENOUS COMPOUNDS (NPN)

Enumerate the NPN compounds

○ Urea (45%) ○ Amino acid (20%) ○ Uric acid (20%) ○ Creatinine (5%) ○ Creatine (1-2%) ○ Ammonia (0.2%)

Ammonia percent

0.2%

Produced by the catabolism of amino acids and by bacterial metabolism in the intestine

Ammonia

Neurotoxin

Ammonia

T/F: Amino acids → Ammonia (can produce glutamate and cause coma) → Urea (Krebs Henseleit Cycle)

AMMONIA Most exist as _________ normal blood pH

ammonium ion (NH4+)

AMMONIA Used for diagnosis

hepatic failure Inherited deficiencies of urea cycle enzymes Reye’s syndrome

In hepatic failure, liver is the site of _______

urea cycle

acute metabolic disorder in the liver that is most common in children and associated with viral infection and aspirin medications

Reye's syndrome

AMMONIA Reference value

19-60 ug/dL (11-35 mmol/L)

How many percent UREA NITROGEN (BLOOD) – BUN

45%

most abundant NPN (freely filtered by the kidneys)

Urea

Major end product of protein and amino acid catabolism

UREA NITROGEN (BLOOD) – BUN

Approximately 80% of the nitrogen excreted

UREA NITROGEN (BLOOD) – BUN

First metabolite to increase in kidney disease

UREA NITROGEN (BLOOD) – BUN

UREA NITROGEN (BLOOD) – BUN ○ _______ excreted through Kidney/urine ○ _______ excreted through GIT/skin

>90% <10%

UREA NITROGEN (BLOOD) – BUN Reference value

8-23 mg/dL

Normal Bun:Creatinine Ratio:

10-20:1 mg/dL

Assays for urea were based on measurement of nitrogen content

UREA NITROGEN (BLOOD) – BUN

T/F: Urea: freely filtered but 60%% are reabsorbed by the PCT

F; 40%

Enmurate when UREA NITROGEN (BLOOD) – BUN is decreased

Low protein dietary intake, liver disease, severe vomiting or diarrhea, increase protein synthesis

UREA NITROGEN (BLOOD) – BUN Concentration is determined by:

○ Renal function - freely filtered ○ Dietary intake ○ Protein catabolism rate = ↑ urea

T/F: Urea = complete structure

True

Urea nitrogen = how many nitrogen of the urea?

Also known as blood urea nitrogen, serum urea nitrogen or urine urea nitrogen

Urea nitrogen

T/F: Blood urea nitrogen is the correct term to use

F; Urea nitrogen

T/F UREA NITROGEN (BLOOD) – BUN is easily removed by dialysis

Enumerate the Clinical Application of UREA NITROGEN (BLOOD) – BUN

● Evaluate renal function ● To assess hydration status ● To determine nitrogen balance ● To aid in diagnosis of renal disease ● To verify adequacy of dialysis

Enumerate the Clinical Application of UREA NITROGEN (BLOOD) – BUN

● Evaluate renal function ● To assess hydration status ● To determine nitrogen balance ● To aid in diagnosis of renal disease ● To verify adequacy of dialysis

Almost all are excreted in the urine (always present in urine)

Creatinine

CREATININE Synthesized primarily by the liver from ______, _______ and _________

arginine, glycine and methionine

Creatinine is synthesized In the tissues / liver and converted to ________

creatine-phosphate

Creatine to creatinine by ___________ (dehydration)

dephosphorylation

Partially secreted by the proximal tubules via the organic cation transport pathway

Creatinine

Measure the completeness of 24 hour urine collection (urine creatinine)

Creatinine

CREATININE ○ COMPLETE: _______ ○ INC: _______

>0.8 g/day <0.8 g/day

Creatinine Always filtered by _______

Glomerulus

T/F: Creatinine is released into circulation at stable rate proportional to muscle mass

Creatinine Plasma creatinine concentration is a function of:

○ relative muscle mass, ○ rate of creatine turnover ○ and renal function

Index of overall renal function

Creatinine

Creatinine Reference value for male

0.9 - 1.3 mg/dL

Creatinine Reference value for female

0.6-1.1 mg/dL

Creatinine Reference value for Child

0.3-0.7 mg/dL

Elevated Creatinine is found is abnormal _________

renal function

Enumerate Measurement of creatinine concentration is used to determine:

○ sufficiency of kidney function ○ severity of kidney damage ○ monitor the progression of kidney disease

functional or structural abnormalities or markers of kidney damage (seen in blood, urine, tissue test, imaging studies) present for less than three months

Acute Kidney Injury (AKI)

Acute Kidney Injury (AKI) Kidney markers:

NPN and other metabolic wastes

Retention of the metabolic wastes

Acute Kidney Injury (AKI)

CREATINE Elevated in plasma and urine in:

Muscular dystrophy, hyperthyroidism, trauma

T/F: Elevation of creatine in plasma and urine is common because it is freely excreted

F; rare

From the muscle

Creatine

Immediate precursor of creatinine

Creatine

Plasma creatine levels usually normal, but urinary is elevated

Creatine

Elevated concentration of NPN in the blood

Azotemia

What are the NPNs elevated in the blood during azotemia?

Urea and Creatinine

Syndrome associated with high urea in plasma with renal failure

Uremia / Uremic Syndrome

AZOTEMIA Causes of urea plasma elevations are:

○ Prerenal ○ Renal ○ Postrenal

Pre-Renal Azotemia Causes: Anything that produces a decrease in functional blood volume, include:

○ Congestive heart failure ○ Shock ○ Hemorrhage ○ Dehydration

High protein diet or increased catabolism: _________________________

(Fever, major illness, stress)

State the process involving Prerenal Azotemia

Reduced Renal Blood Flow (most common) ↓ Less blood delivered to the kidney ↓ Less urea is filtered

“True Renal Disease”

Renal Azotemia

Renal azotemia Causes:

○ Acute/chronic renal disease ○ Glomerulonephritis ○ Tubular necrosis

Renal azotemia Enumerate the lab results considered

BUN Creatinine BUA Anemia Electrolyte imbalance

Renal azotemia lab results BUN = ___ (_________)

↑ abrupt increase

Renal azotemia lab results Creatinine – ___ (________;_______)

↑ slow increase: 20 mg/dL

Renal azotemia lab results BUA - ___ (by: ________)

↑ 12 mg/dL

Renal azotemia lab results Anemia = _________

low RBC production

Renal azotemia Complications

○ Coma ○ Neuropsychiatric changes

State the process involving Renal Azotemia

Damaged Kidneys ↓ Poor Excretion ↓ Increased Urea

Usually the result of urinary Tract Obstruction (In the ureter, urinary bladder, etc.)

Post-Renal Azotemia

Post-Renal Azotemia Urea level is higher than creatinine due to _________ of ____ into the circulation

back diffusion urea

Post-Renal Azotemia Causes:

nephrolithiasis, renal calculi, cancer/tumors of genitourinary tract, severe infection

Chemical name of Uric Acid

2,6,8-trihydroxypurine (aka BUA)

It is the major product of purine (adenine and guanine in DNA) catabolism

Uric Acid

It is the final breakdown of nucleic acids catabolism in humans

Uric Acid

Uric Acid is formed from_______ by the action of ________ in the __________

xanthine xanthine oxidase liver and intestine

Uric acid is transported to kidney and filtered (___)

70%

Uric Acid Remaining 30% by _____ (degraded by bacterial enzymes)

GIT

Source of nucleic acids (Ingestion and endogenous dead cells)

Uric Acid

Uric acid is measured to: Asses ______ of purine metabolism

Inherited disorders

Uric acid is measured to: Confirm diagnosis and monitor treatment of _____

gout

Uric acid is measured to: To assist in the diagnosis of ________

renal calculi

Uric acid is measured to: To prevent __________________ during chemotherapeutic treatment

Uric acid nephropathy

Uric acid is measured to: To detect _______________

Kindey dysfunction

Uric Acid Present in plasma as __________ (95%)

monosodium urate

Uric acid ● At plasma pH → relatively soluble/insoluble

insoluble

Uric acid If prolonged = uric acid crystals will deposit in the joints causing ______

gout

Uric Acid If pH of nephrons: _____ (acidic) = uric acid precipitates making crystals causing __________/_______________

<5.7 renal calculi / kidney stones

Uric Acid Reference value male:

3.5-7.2 mg/dL

Uric Acid Reference value female:

2.6-6.0 mg/dL

Uric Acid Reference value child

2.0-5.5 mg/dL

Condition called when there is ↑ uric acid

Hyperuricemia

Most common hyperuricemia

Gout

Gout ● Crystals are differentiated by the________

birefringent

○ GOUT (+) = with ___________ ○ PSEUDOGOUT (-) = _____ (_____________________________)

monosodium urate CPPD (Calcium pyrophosphate dihydrate crystal deposition)

Primarily in men and first diagnosed between 3rd and 5th decade of life

Gout

Pain & inflammation of joints by precipitation of sodium urates in tissues

Gout

Gout Uric acid is greater than _______

6.0 mg/dL

Increased risk of renal calculi/nephrolithiasis

Gout

hyperuricemia due to overproduction of uric acid (25- 30%)

Gout

INCREASED NUCLEAR METABOLISM - _________

Chemotheraphy

● causes elevated levels of uric acid because filtration and secretion are hindered

CHRONIC RENAL DISEASE

CHRONIC RENAL DISEASE BUA: ______

>10 mg/dL

● Inborn error of purine metabolism

LESCH NYHAN SYNDROME

It is deficiency of hypoxanthine-guanine phosphoribosyltransferase (involved in the uric cycle)

LESCH NYHAN SYNDROME

Other causes of hyperuricemia

1. Secondary to glycogen storage disease 2. Toxemia of pregnancy and lactic acidosis 3. Increased dietary intake 4. Ethanol consumption

Enumerate the causes of Hypouricemia

● Fanconi’s syndrome ● Wilson’s disease ● Hodgkin’s disease ● Overtreatment with allopurinol ● Chemotherapy (6-mercaptopurine, azathioprine) ● Alzheimer’s disease ● Parkinson’s disease

○ Filtered by the kidneys but not reabsorbed by the PCT

● Fanconi’s syndrome

Fanconi's syndrome ○ Resulting to low uric acid as _________ are not reabsorbed

98%-100%

uric acid not reabsorbed, excreted in urine

Fanconi's syndrome

○ Xanthine oxidase (gout)

Wilson's disease

○ Enzyme for uric acid synthesis

Wilson's disease

○ Low uric acid

● Overtreatment with allopurinol

○ Inhibited by the uric acid synthesis

● Overtreatment with allopurinol

________ - xanthine oxidase is inhibited

Allopurinol

● Best overall indicator of the level of kidney function

Glomerular Filtration Rate (GFR)

● Clearance of substances that are not bound to protein

Glomerular Filtration Rate (GFR)

Glomerular Filtration Rate (GFR) ○ High MW = ________

not filtered

Glomerular Filtration Rate (GFR) ● _______ of glomerular filtrate is produced daily

150 liters

Glomerular Filtration Rate (GFR) ● _______ of glomerular filtrate is produced daily

150 liters

Glomerular Filtration Rate (GFR) GFR decreased by ____________ after age 20- 30

1.0 mL/minute/year

● Removal of the substance from plasma into urine over a fixed time.

Clearance

● It represents the volume of plasma that would contribute all the solute excreted.

Clearance

Clearance ● Plasma concentration is (directly/inversely) proportional to clearance

inversely

Specimen in clearance

○ 24 hour urine ○ Serum

Formula in clearance

(di ko malagay bahala k n)

Formula of clearance: o U – conc. of analyte (______) o P – conc. of analyte (______) ▪ What is measured o Volume – Urine volume in mL (___ hours) o Minutes – time required to collect urine (_____ minutes) o _____ – ave. body surface of adult individual (0.717 for pediatric) o A – _____ of patient (nomogram: height and weight are taken)

urine Plasma 24 1440 1.73 body surface

Enumerate the different methods in clearance

a. INULIN CLEARANCE TEST b. CREATININE CLEARANCE c. UREA CLEARANCE

● Reference method in clearance

a. INULIN CLEARANCE TEST

● Exogenous substance administered to the patient

a. INULIN CLEARANCE TEST

INULIN CLEARANCE TEST Priming dose:

2.5 mL of 10%

INULIN CLEARANCE TEST Continuous dose:

500mL of 1.5% inulin

● Not routinely done due to the necessity for continuous

a. INULIN CLEARANCE TEST

Alternatives to insulin:

○ Radioactive marker: 125I-iothalamate & 99mTc-DTPA ○ Iohexol and Chromium 51-labelled EDTA ○ Nonradiolabeled iothalamate

INULIN CLEARANCE TEST Reference value male

127 mL/min

INULIN CLEARANCE TEST Reference value female

118 mL/min

● Best alternative method to Inulin

b. CREATININE CLEARANCE

● Endogenous and all are still excreted

b. CREATININE CLEARANCE

T/F: Creatinine clearance is not affected by diet

CREATININE CLEARANCE o approx. _________ is excreted

1.2-1.5g/ day`

● Excellent measure of renal function

CREATININE CLEARANCE

● Measure of completeness of 24 hour urine (SERUM: collect within 24 hours)

CREATININE CLEARANCE

CREATININE CLEARANCE Major limitation:

accurate urine collection

CREATININE CLEARANCE Reference value for male:

85 - 125 mL/min

CREATININE CLEARANCE Reference value for female:

75 - 112 mL/min

Creatinine clearance formula:

(di ko malagay bhl k n)

Traditional formula

CREATININE CLEARANCE FORMULA:

CREATININE CLEARANCE FORMULA T/F: Affected by body surface area and correction for body mass should be included in the formula

● Commonly used in laboratory

COCKCROOFT-GAULT FORMULA

● Results are not corrected for body surface area

COCKCROOFT-GAULT FORMULA

Assumes that women will have a 15% lower creatinine clearance than men at the same level of serum creatinine

COCKCROOFT-GAULT FORMULA

● Accurate: does not involved body weight

MODIFICATION OF DIET IN RENAL DISEASE FORMULA (MDRD)

MODIFICATION OF DIET IN RENAL DISEASE FORMULA (MDRD) ● Multiply result by _______ if black

1.212

MODIFICATION OF DIET IN RENAL DISEASE FORMULA (MDRD) ● Multiply result by _____ if female

0.742

MODIFICATION OF DIET IN RENAL DISEASE FORMULA (MDRD) Variables: _________________

Age, serum, race, gender

● One of the first clearance tests

c. UREA CLEARANCE

UREA CLEARANCE ● It is not reliable as some variables are still reabsorbed (_____)

40%

● Demonstrate progression of renal disease or response to therapy

c. UREA CLEARANCE

● Low molecular weight protease inhibitor and produced at a constant rate by all nucleated cells.

CYSTATIN C

● Presence will give problem to the reabsorption

CYSTATIN C

Why cystatin c's presence will give problem to the reabsorption?

○ As it should be 100% reabsorbed and sent back to the circulation

● THE ONLY KIDNEY FUNCTION TEST that is never measured in the urine

Cystatin C

● Indirect estimate of GFR

Cystatin C

Not affected by muscle mass, age, diet and gender

Cystatin C

_______ is freely filtered by the glomerulus but completely reabsorbed by the tubules

Cystatin C

Cystatin C Specimen:

Serum or Plasma

Cystatin C Increased (↓ GFR):

acute and chronic renal failure, diabetic nephropathy

Cystatin C Reference value of adults

0.5-1.0 mg/L

Cystatin C Reference value of >65 years old

0.9-3.4 mg/L

Cystatin C GFR is computed using ___________

Modified Cystatin C Equation:

● A low molecular weight glycoprotein

Beta Trace Protein

● Freely filtered by glomerulus and completely reabsorbed and catabolized by the PCT

Beta Trace Protein

● Belongs to the lipocalin protein family and functions as prostaglandin D synthase

Beta Trace Protein

● Isolated primarily from CSF

Beta Trace Protein

Beta Trace Protein Increased: ________

Renal disease

GFR FORMULA USING B TRACE PROTEIN

White formula Page formula

All should be in adequate amount

TEST FOR RENAL BLOOD FLOW

UREA NITROGEN METHODOLOGIES Sample:

Serum, plasma, urine

o PLASMA: should never be in _________

fluoride or citrate

Fluoride and Citrate: inhibits ______

urease

T/F: Refrigerate sample if delay in testing is expected

T/F: If sample is not refrigerated. ○ bacteria that are urease positive will be inhibited (PMCKEYS (genus)))

Assays for urea were based on measurement of ________, hence the name blood urea nitrogen.

nitrogen

Atomic mass of Nitrogen

14 g/mol

Molecular mass of urea

60 g/mol

Urea = ___ nitrogen atoms

2 nitrogen atoms (______ of the total weight of urea)

46.6%

Formula of Urea to BUN

Urea = BUN x 2.14

3 methods of Urea nitrogen methodologies

1. Chemical Method Diacetyl Monoxime (DAM) Method 2. Enzymatic Method 3. Isotope Dilution Mass Spectrometry (Reference Method)

Indicator dye and not specific

1. Chemical Method Diacetyl Monoxime (DAM) Method

Enumerate the types of enzymatic method in urea nitrogen methodologies

UREASE BERTHELOT METHOD UREASE GLUTAMATE DEHYDROGENASE METHOD (GLD)

Urea is from

Jack beans

In Urease Berthelot Method, ______ and ____ can be measured by different method to calculate the concentration of urea in the sample

Ammonia CO2

UREASE GLUTAMATE DEHYDROGENASE METHOD (GLD) ● Uses:

○ Coupled Enzymatic Method ○ UV Enzymatic Method

Reference method for Urea Nitrogen Methodologies

Isotope Dilution Mass Spectrometry

Creatinine methodologies Sample:

Serum, plasma, urine

CREATININE METHODOLOGIES Interferences

Hemolysis, Ictericia, Lipemia

4 methods for Creatinine Methodologies

1. Direct Jaffe Method (Chemical Method) 2. Kinetic Jaffe Method 3. Enzymatic Method 4. Isotope Dilution Mass Spectrometry

1. Direct Jaffe Method (Chemical Method) ● Principle: ________________

Folin Wu Method

1. Direct Jaffe Method (Chemical Method) End-product:

red-orange tautomer

Jaffe Reagent components

o Saturated picric acid o 10% NaOH

When jaffe reagent is mixed, it produces:

▪ Picramic acid ▪ Methyl guanidine

● Uses spectrophotometry

1. Direct Jaffe Method (Chemical Method)

1. Direct Jaffe Method (Chemical Method) Interferences: False Increase

▪ Creatinine-Like analytes: Uric acid, ascorbic acid, glucose, a-keto acids ▪ Medications: Cephalosporins, dopamine, Lidocaine

1. Direct Jaffe Method (Chemical Method) Interferences: False Decrease

Bilirubin, Hemoglobin

Types of Direct Jaffe Method

Folin Wu Method Lloyd or Fuller's earth method

Kidney Function Flashcards

(235 cards)