renal function tests - a deep insight by rxvichu!

RENAL FUNCTION TESTS- A DEEP INSIGHT PRESENTED TO : SEBIHA MAM, AND MY CLASS PRESENTED BY : VISHNU.R.NAIR,4TH YEAR PHARM.D,NATIONAL COLLEGE OF PHARMACY(NCP)

DEFINITION :“Tests, that include INTERPRETATION of LABORATORY TESTS, used in the ASSESSMENT of KIDNEY FUNCTION; in order to diagnose possible renal diseases”…………………

NEED FOR RENAL FUNCTION TESTS :RFTs are needed to :1. ASSESS FUNCTIONAL CAPACITY of KIDNEY2. DETECT(in early stages), possible RENAL IMPAIRMENT3. ASSESS SEVERITY & PROGRESSION of IMPAIRMENT 4. MONITOR RESPONSE to TREATMENT5. MONITOR SAFE & EFFECTIVE USE of DRUGS, that are excreted in

urine……………………….

WHEN SHOULD RFTS BE ASSESSED ? RFTs should be assessed in the following conditions:1. Older age 11. Obstruction to lower urinary

tract2. Family history of CKD 12. Drug toxicity……………….3. Decreased renal mass4. Reduced birth weight5. DM6. HTN7. Autoimmune diseases8. Systemic infections9. UTI10. Nephrolithiasis

MAJOR DIVISIONS OF THIS PPT :A. TESTS, USED TO ASSESS KIDNEY FUNCTIONB. URINALYSISC. CHEMICAL ANALYSIS(SEMIQUANTITATIVE TESTS)

A. TESTS, USED TO ASSESS KIDNEY FUNCTION :Classified into:I. EXOGENOUS MARKERS:Includes :- Inulin clearance - Iodothalamate & Cr-EDTA clearanceII. ENDOGENOUS MARKERS :Includes:- Cystatin C- Serum creatinine- Urea(BUN)- BUN: Scr ratio- Creatinine clearance

EXOGENOUS MARKERS:1. INULIN CLEARANCE:- NORMAL RANGE : a.127 mL/min/meter square(male)b. 118 mL/min/meter square(female)- Inulin is a FRUCTOSE POLYSACCHARIDE- Regarded as GOLD STANDARD for measuring GFR in ADULTS & OLDER CHILDREN

- This is restricted/ practical application is limited due to 1 reason :a. Requires special analytical methods, and thus, is COSTLY

II. IODOTHALAMATE & Cr-EDTA CLEARANCE:- NORMAL RANGE : a. 127 ml/min/meter square(males)b. 118 ml/min/meter square (females)- I-IODOTHALAMATE is a RADIOACTIVE MARKER- Marker injected intravenously take multiple blood samples, along with urine samples, to check its CLEARANCE

- Highly COSTLY thus sometimes replaced by Cr-EDTA………………….

ENDOGENOUS MARKERS :1. CYSTATIN C :- CYSTATIN C is a PROTEASE INHIBITOR- Mainly produced by NUCLEATED CELLS- Serum CYSTATIN concentration is INVERSELY PROPORTIONAL to GFR

Thus, changes in CYSTATIN C concentration is an INDIRECT INDICATIVE of GFR ……………….

2. SERUM CREATININE (SCr):- NORMAL VALUES:a. For ADULTS : 0.7-1.5 mg/dlb. For YOUNG CHILDREN : 0.2-0.7 mg/dl- CREATININE is a NON-PROTEIN, NITROGENOUS COMPONENT(BIOCHEMICAL) of BLOOD

- CREATINE Synthesized in LIVER Diffuses into bloodstream taken up by MUSCLE CELLS Stored in the form of CREATINE PHOSPHATE Helps in ATP REGENERATION Used to transform CHEMICAL ENERGY to MUSCLE ACTION

- CREATININE is produced in MUSCLE- It is a SPONTANEOUS DECOMPOSITION PRODUCT of CREATINE & CREATINE PHOSPHATE

- CREATININE Neither REABSORBED nor SECRETED by NEPHRONS Thus, GFR is responsible for SCr levels

- Since CREATININE is derived from MUSCLE TISSUE Serum levels vary, depending on the MUSCLE MASS of the individual.

HIGH LEVELS OF SCr FOUND IN:

LOW LEVELS OF SCr FOUND IN:

AMINOGLYCOSIDE USAGE REDUCED MUSCLE MASS (as in amputees)

DIABETIC NEPHROPATHY MUSCULAR DYSTROPHY

URINARY TRACT OBSTRUCTION

MYASTHENIA GRAVIS

GLOMERULONEPHRITIS

PYELONEPHRITIS

3. UREA (BUN):- NORMAL VALUE : 8-20 mg/dl- BUN refers to CONCENTRATION of NITROGEN (as UREA) in serum- BY-PRODUCT of PROTEIN CATABOLISM, produced by LIVER- FILTERED by GLOMERULUS- BUN is INVERSELY PROPORTIONAL to GFR- BUN is affected by :a. AMOUNT OF PROTEIN IN DIETb. HEPATIC FUNCTION- Used to assess:a. Hydrationb. Renal functionc. Protein tolerance, etc.

- BUN is INCREASED in the following conditions:PRE-RENAL CAUSES INTRA-RENAL CAUSES POST-RENAL CAUSES

DEHYDRATION NEPHROTOXIC DRUGS URETER OBSTRUCTION

SHOCK DM BLADDER NECK OBSTRUCTION

SEVERE HEART FAILURE

GLOMERULONEPHRITISPYELONEPHRITIS

TUBULAR NECROSIS

- BUN levels are decreased in :a. Malnourishmentb. Liver damage(due to inhibition of liver’s ability to SYNTHESIZE

UREA)……………

4. BUN:SCr RATIO:- BUN:SCr ratio is mainly used to assess KIDNEY FUNCTION(especially in ARF)

- In ARF volume depletion occurs increases levels of BUN & SCr- If BUN:SCr ratio > 20:1 suggests PRE-RENAL CAUSES of RENAL IMPAIRMENT

- If BUN:SCr ratio is in between 10:1 – 20:1 suggests INTRINSIC KIDNEY DAMAGE……………………….

5. CREATININE CLEARANCE (CrCl):- Refers to the amount of CREATININE excreted through URINE- Calculated by THREE EQUATIONS:A. BASIC EQUATION :- CrCl = [(UCr * V) / (SCr * T)] * (1.73/BSA), wherea. CrCl = Creatinine clearance (in mL/min)b. UCr = Urine creatinine concentration (in mg/dl)c. V = Volume of urine produced, during the COLLECTION INTERVAL (in

mL)d. SCr = Serum creatinine concentration ( in mg/dL)e. T = Time of collection interval (in minutes)f. BSA : Body surface area (in metre square)

- BSA is calculated by MOSTELLER EQUATION:

BSA = [square root of ( height (in cm) * weight (in kg) ) ] / 3600………….

B. COCKCROFT- GAULT EQUATION:- Here, CrCl is estimated, based on the following patient details:a. Age b. Weight c. SCr

concentration- There are 2 equations:

I. CrCl = {[(140-age) * weight (in kg) ] / [72 * SCr ] } * 0.85 (if female)

II.CrCl = {[ (140-age) * weight(in kg) ]/ [72 * SCr] } * 0.85 (if female) * [1.73 meter square / BSA]

C. FOR PEDIATRIC PATIENTS:- The NATIONAL KIDNEY FOUNDATION KIDNEY DISEASE OUTCOME QUALITY INITIATIVE( NKF-KDOQI) GUIDELINES, suggest use of either SCHWARTZ / COUNAHAN- BARRATT EQUATIONS to estimate kidney function, in patients>12 years of age

- SCHWARTZ FORMULA:CrCl = k * [(height, in cm) / SCr]For infants < 1 year of age k = 0.45For children and adolescent females k = 0.55For adolescent males k = 0.7- COUNAHAN- BARRATT FORMULA:GFR ( in ml/min/1.73 metre sq.) = 0.43 * [(height) / SCr)]………………..

STAGES OF CKD :There are 5 stages of CKD, based on KDOQI guidelines:STAGE OF CKD GFR VALUE(in

ml/min/1.73 m sq.)INTERPRETATION

1 >90 Normal/slight kidney damage, normal GFR

2 60-89 Slightly diminished GFR, Kidney damage

3 30-59 Moderately reduced GFR, Kidney damage

4 15-29 Significantly reduced GFR, Kidney damage

5 <15 Kidney failure, requires immediate dialysis

B. URINALYSIS :- Defined as “Clinical tool, that is used to evaluate various RENAL & NON- RENAL PROBLEMS(Endocrine, metabolic & genetic), using URINE SAMPLE TESTING”.- Classified into:I. MACROSCOPIC ANALYSISII. MICROSCOPIC ANALYSIS

I. MACROSCOPIC ANALYSIS :- Focusses on GENERAL APPEARANCE & COLOUR of URINE - Colour of urine varies, based on the solute concentration inside it- Colour of urine is derived from 2 pigments:a. UROCHROMEb. UROBILIN- Fresh normal urine is neither CLOUDY nor HAZY- TURBIDITY may occur if large amounts of RBCs/ WBCs are there- FOAMING may be due to presence of PROTEIN/ BILE ACIDS………………

COLOUR SIGNIFIES PRESENCE OF

POSSIBLE CAUSES

RED- ORANGE HEMOGLOBIN, RBCs, MYOGLOBIN

Electric shock, malaria, kidney stones, drugs (rifampin, doxorubicin)

BLUE- GREEN BILIVERDIN, BACTERIA, etc

Pseudomonas/ Proteus infection in UTI, drugs (amitriptyline, triamterene)

BROWN- BLACK MYOGLOBIN, BILE PIGMENTS, PORPHYRINS, etc

Electric shock, liver disease, hemolysis, porphyria, drugs (metronidazole, NTU, etc)

II. MICROSCOPIC ANALYSIS:- Mainly used to check the presence of FORMED ELEMENTS, like :a. CELLSb. CRYSTALSc. CASTS…………………..

A. CELLS:- Usually, 1-2 cells may be found- Cells include:i. MICROORGANISMS:- Normal range : 0-trace- Presence of FUNGI, BACTERIA, SINGLE-CELL ORGANISMS, suggests UTI/ COLONIZATION……….

ii. RBCs:- Normal range : 1-3 / hpf- HAEMATURIA : “Abnormal renal excretion of RBCs”- Few RBCs are seen in the urine of a healthy woman/man, especially after FEVER, EXERTION, TRAUMA, etc

- Increased levels of RBC are seen in:a. GLOMERULONEPHRITISb. PYELONEPHRITISc. RENAL INFARCTIONd. TUMORSe. STONES……………iii. WBCs:- Normal range : 0-1/ hpf- Increased levels of WBCs are seen in:a. UTIb. GLOMERULONEPHRITISc. INTERSTITIAL NEPHRITIS…………………

iv. TUBULAR EPITHELIAL CELLS:- Normal range : 0-1/ hpf- Increased amounts of epithelial cells are found in:a. ACUTE TUBULAR NECROSISb. GLUMERULONEPHRITISc. INTERSTITIAL NEPHRITIS…………………….

B. CASTS:- CASTS are CYLINDRICAL SHAPED GLYCOPROTEINS- Formed in TUBULES- In some conditions Casts are released into urine This condition is known as CYLINDURIA

- Different types of casts include:i. HYALINE CASTSii. CELLULAR CASTSiii. GRANULAR CASTSiv. WAXY CASTSv. BROAD CASTS………………

i. HYALINE CASTS:- Difficult to observe under microscope- Seen in :• Concentrated urine• Diuretic usage………….ii. CELLULAR CASTS:- Cellular casts include RBC casts, WBC casts & EPITHELIAL CELL casts

CASTS TYPE POSSIBLE INDICATION/S

WBC Pyelonephritis, Acute interstitial nephritis

RBC Glomerulonephritis

EPITHELIAL CELL Glomerulonephritis

iii. GRANULAR & WAXY CASTS:- Older, degenerated forms of (i) and (ii)- Found in:• Acute tubular necrosis• Glomerulonephritis………………………….

C. CRYSTALS:- Presence of CRYSTALS in urine, depends on 3 factors:i. Urine PHii. Degree of saturation of urine, by the substance, that forms

crystalsiii. Presence of other substances in urine, that promote crystallizationCRYSTAL TYPE INDICATES

CYSTINE CYSTINURIA

STRUVITE (Magnesium ammonium phosphate)

STRUVITE STONES

CALCIUM OXALATE, CALCIUM PHOSPHATE & URIC ACID

STONES

C. CHEMICAL ANALYSIS (SEMIQUANTITATIVE TESTS):- Here, main focus is on BIOCHEMICAL ANALYSIS of urine, for the detection of PROTEIN, URINE PH, BILIRUBIN, BILE, etc…………………

A. PROTEIN:- NORMAL RANGE : 0- trace- Urinary proteins include:i. ALBUMINii. LMW SERUM GLOBULINS- Healthy individuals excrete 80-100 mg of protein/day- TERMINOLOGIES :TERM DEFINITION

PROTEINURIA Renal loss of proteinALBUMINURIA Abnormal renal excretion of albuminCLINICAL PROTEINURIA Loss of >500 mg/day of protein

through urineMICROALBUMINURIA Loss of 30-300 mg/day of albumin

TYPE OF PROTEINURIA

RENAL PROTEIN EXCRETION(in g/day)

FOUND IN

MILD <0.5 Lower UTI, Renal tubular damage

MODERATE 0.5-3 Diabetic nephropathy, pyelonephritis, Glomerulonephritis

SIGNIFICANT >3 Lupus nephritis, Glomerulonephritis, Diabetic nephropathy

B. pH:- NORMAL RANGE : 4.5-8.0- Urinary PH can be affected by various ACID-BASE DISORDERS- Urine PH can turn ACIDIC/ ALKALINE, depending on the following conditions:URINE PH NATURE CAUSES SUGGESTS

ALKALINE Hyperventilation Respiratory/ metabolic acidosis

Proteus splits urea to NH3

UTI

Drugs Thiazides, acetazolamide

ACIDIC Food Fruit juices, plumsDM, high fever KetoacidosisCellular hypoxia Metabolic acidosisDrugs NH4Cl, Methenamine

C. SPECIFIC GRAVITY:- NORMAL RANGE : 1.010-1.025- SPECIFIC GRAVITY is defined as “RATIO of WEIGHT of a given FLUID , to the WEIGHT of an EQUAL VOLUME of DISTILLED WATER”

- SODIUM, UREA, SULFATE & PHOSPHATE are major contributors of URINE SPECIFIC GRAVITY

LOW VALUES FOUND IN HIGH VALUES FOUND IN

Acute tubular necrosis Dehydration

Diabetes insipidus Fasting

Renal failure Proteinuria

Syndrome of inappropriate ADH secretion(SIADH)

D. UROBILINOGEN:- NORMAL RANGE: 0-1 Erlich Unit- UROBILINOGEN is formed by BACTERIAL CONVERSION of CONJUGATED BILIRUBIN in the INTESTINEHIGH VALUES ARE FOUND IN

LOW VALUES ARE FOUND IN

CIRRHOSIS DRUGS(Neomycin, Tetracycline, Chloramphenicol)

VIRAL HEPATITIS TOTAL BILIARY OBSTRUCTION

HEMOLYTIC ANEMIA

E. BILIRUBIN:- NORMAL RANGE: 0- BILIRUBINURIA is a condition, in which there is presence of BILIRUBIN in URINE, resulting in DARK YELLOW/ GREENISH-BROWN colored urine

- Observed in:i. Intrahepatic cholestasisii. Bile duct stones, tumors, etc…………………………….

F. BLOOD & HEMOGLOBIN:- NORMAL RANGE: 0- trace- Presence of blood/ hemoglobin in urine indicates:i. HAEMATURIAii. HEMOGLOBINURIA(In intravascular hemolysis)iii. MYOGLOBINURIA( In rhabdomyolysis)………………………

G. LEUKOCYTE ESTERASE:- NORMAL RANGE: 0- Trace- This test gives a SEMI-QUANTITATIVE ESTIMATION of PYURIA(Pus in urine), that suggests UTI……………………………

H. NITRITE:- NORMAL RANGE: None- Bacteria(E.Coli, Klebsiella, Proteus, Staphylococcus) reduce NITRATE to NITRITE Suggests UTI……………………….

I. GLUCOSE:- NORMAL RANGE: None- At glucose concentration >180 mg/dl capacity of PCT to reabsorb glucose exceeds thus, glucose is found in urine suggests DM, GLYCOSURIA, etc…………………..

J. KETONES:- NORMAL RANGE: 0- In patients, with KETONURIA + GLYCOSURIA Indicates TYPE I DM- KETONURIA is observed in:i. Pregnancyii. Starvationiii. Carbohydrate-free diets……………………….

K. URINARY ELECTROLYTES:Include the estimation of SODIUM, POTASSIUM, etcI. SODIUM:- NORMAL RANGE: Varies- Sodium conc. is used to ASSESS VOLUME STATUS of a patientLOW VALUES FOUND IN HIGH VALUES FOUND IN

Vomitting Diuretics

Diarrhea SIADH

Burns ARF/CRF

Cirrhosis Renal tract obstruction

Nephrotic syndrome Sodium chloride tablets

II. POTASSIUM:- NORMAL RANGE: Varies- Urine potassium levels are generally helpful , only in patients, with UNEXPLAINED HYPOKALEMIA

- Urine potassium levels between 0-10 mEq/L Suggests GI tract as a source for POTASSIUM LOSS

- Urine potassium levels > 10 mEq/L Suggests renal potassium lossLOW LEVELS ARE FOUND IN HIGH LEVELS ARE FOUND INAdrenal gland insufficiency HyperaldosteronismHypoaldosteronism Acute tubular necrosisDrugs (Beta-blockers, Li, NSAIDs) Metabolic acidosis

III. FE(Na) TEST:- Defined as PERCENT of SODIUM(FRACTION), that is FILTERED in the GLOMERULUS, that is eventually excreted in the urine

- Calculated by the following formula:a. FE(Na) = [(Urinary sodium) * Serum creatinine)]/ [(Serum

sodium) * (Urinary creatinine)]- If FE(Na) < 1% indicates PRE-RENAL AZOTEMIA- If FE(Na) > 2-3% indicates ACUTE TUBULAR NECROSIS…………………………..

BIBLIOGRAPHY/ REFERENCE:1. Thrombetta.P.D; Foote.T.Edward; “Chapter

7:THE KIDNEYS”; “Basic skills in Interpreting Laboratory Data by Mary Lee”; 4th edition; American Society of Health-System Pharmacists Inc. ; 2009; Pg: 161-176.

2. Normal lab values app.

THANK YOU