RENAL FUNCTION TEST is the best condition to get a call from you and
- 1. RENAL FUNCTION TEST DR.REVATHY.S ASSISTANT PROFESSOR DEPARTMENT OF BIOCHEMISTRY
- 2. Kidney Function Tests (RFT)
- 3. Nephron
- 4. Glomerular Function ▫ Glomeruli acts as filter ▫ The blood plasma is filtered through the capillaries of the glomerulus into the capsule Ultrafiltrate is free of cells and protein ▫ About 1200 ml of blood (650 ml plasma) passes through the kidneys, every minute. ▫ About 120-125 ml is filtered per minute by the kidneys & this is referred to as glomerular filtration rate (GFR).
- 5. • With a normal GFR (120-125 ml/min), the glomerular filtrate formed in an adult is about 180 litres/day, out of which only 1.5 litres is excreted as urine. • More than 99% of the glomerular filtrate is reabsorbed by the kidneys.
- 6. Functions of the tubule
- 7. Functions of the Tubules • In the proximal convoluted tubules, about 70% water, Na+ and Cl– as well as 100% glucose, amino acids • Urea, phosphate and calcium are partially absorbed.
- 8. PCT Reabsorption Secretion Na Cl HCO3 Glucose Aminoacids Uric acid water Hydrogen Acids & bases Ammonia
- 9. Loop of Henle • Its main function is to reabsorb water and sodium chloride from the filtrate. – Na – Cl – Ca – Mg
- 10. Distal convoluted tubule • responsible for the regulation of potassium, sodium, calcium, and pH • reabsorption – Na – Cl – Water • Secretion – 𝐻+ – K – Ammonia – Uric acid
- 11. Formation of urine • Glomerular filtration • Tubular secretion • Tubular reabsorption
- 12. Functions of kidney • Excretion- urea, creatinine,drugs,uric acid, toxins, acids and bases • Excretion of sodium, potassium, hydrogen ions • Maintain water balance • Activation of vitamin D • Production of erythropoietin • Filtration • Reabsorption
- 15. Acute kidney injury (AKI) • sudden episode of kidney failure or kidney damage that happens within a few hours or a few days. • due to renal tubular cell injury. • It is characterized by rapid rise of serum creatinine • low urine output
- 17. Signs and symptoms • Decreased urine output • Fluid retention, causing swelling in your legs, ankles or feet • Drowsiness • Shortness of breath • Fatigue • Nausea
- 18. Chronic kidney disease (CKD) • progressive loss in kidney function over a period of months or years. • GFR < 60 mL/min for 3 months or more with or without kidney damage.
- 19. Grading of chronic kidney disease state grade GFR ml/min/1.73sq m Minimal damage 1 >90 Mild damage 2 60 – 89 Moderate damage 3 30 – 59 Severe damage 4 15 – 29 End stage 5 < 15
- 20. Clinical features • weight loss and poor appetite • oedema • shortness of breath • tiredness • blood in urine • NOCTURIA • difficulty sleeping (insomnia) • itchy skin • muscle cramps • feeling sick • headaches
- 21. Azotemia • abnormally high levels of nitrogen-containing compounds (such as urea, creatinine, various body waste compounds) in the blood. • It is largely related to dysfunctional filtering of blood by the kidneys. • It can lead to uremia if not controlled.
- 22. Uremic syndrome • It is the terminal manifestation of renal failure. • It occurs when urea and other waste products build up in the body because the kidneys are unable to eliminate them. • A group of toxins contribute to this situation. • Increased urea lead to carbamoylation of proteins. • Increased uric acid causes uremic pericarditis. • Excess polyols is the basis of peripheral neuropathy. .
- 23. Assessment of the extent of renal damage Monitoring the progression of renal damage Monitoring and adjusting the dose of renal toxic drugs Renal Function Tests –required for……
- 24. Renal blood flow GFR Renal glomeruli function Renal tubular function Urinary output RFTs give information regarding…….
- 25. Classification of KFT SCREEN FOR KIDNEY DISEASE • Complete urine analysis • Plasma urea and creatinine. • Plasma electrolytes ASSESS RENAL FUNCTION Glomerular Function GFR Clearance tests Glomerular permeability Proteinuria Tubular Function Secretion tests Concentration and dilution tests Renal acidification
- 26. Common test to asses kidney function
- 27. Non-protein Nitrogen (NPN) • These include urea, creatinine and uric acid. The major route of excretion of these compounds is urine. • creatinine estimation is the most specific and sensitive index of renal function.
- 28. Serum creatinine decrease increase Low muscle mass Females Malnutrition Thiazides vancomycin Old age Males Glomerulonephritis Pyelonephritis Renal failure Urinary obstruction dehydration, shock Amphotericin B Captopril Normal = 0.7 – 1.4 mg/dl
- 29. 29 Creatinine analytical techniques • Jaffe’s Method ( the Classic technique ) Creatinine + Picrate Acid Colored chromogen Specimen : Plasma or serum Elevated bilirubin and hemolysis causes falsely decreased results Reference Values of Creatinine Adult males, 0.7 – 1.4 mg/dL Adult females, 0.6 – 1.3 mg/dL Children, 0.4 – 1.2 mg/dL
- 30. • Faster • More specific • Most widely used Implemented on various automated instruments. • JAFFE’S KINETIC ASSAY Kinetic analyses modes(Automated method)
- 31. • In this method Jaffe’s reaction principle is carried out at 30 degree centigrade by using special type of spectrophotometer or autoanalyser, equipped with a thermocuvette. • First reading is recorded at 20 sec. Most of the interfering non-creatinine chromogens react with alkaline picrate reagent and are recorded after 20 seconds. AUTOMATED METHOD
- 32. Blood urea • Normal – 15 – 40 mg/dl • Serum concentration increases as age advances Pre - renal renal Post renal drugs Dehydration Severe vomiting Diarrhea Severe burns Fever Severe infections Acute glomerulonephritis Nephrosis Malignant hypertension Chronic pyelonephritis Stones in urinary tract Enlarged prostate Tumors of bladder ACEI Acetaminophen Aminoglycosides Amphotericin B Diuretics NSAIDS Increase in blood urea Decreased blood urea – late pregnancy, starvation, hepatic failure
- 33. Estimation of urea • Estimation of urea is done by enzymatic method urease glutamate dehydrogenase. Enzymatic Berthelot Method is used for blood urea estimation. Principal: Urea + H2O Ammonia + CO2 Ammonia + Phenolic Chromogen + Hypochlorite Green Colored Complex whose absorbance is read at 570nm Urease
- 34. 34 BUN analytical methods • Specimen : Plasma or serum UREA 2 NH4 + + HCO3 - Urease NH4 + + 2-OXOGLUTARATE GLDH GLUTAMATE NADH NAD Measure the rate of decreased absorbance at 340 nm NADH absorbs … NAD does not absorb Reference range : 10 – 20 mg / dl To convert BUN to Urea : BUN x 2.14 = Urea ( mg / dl )
- 35. 35 • BUN / Creatinine Ratio – Normal BUN / Creatinine ratio is 10 – 20 to 1 – Creatinine is another NPN – Pre-renal increased BUN / Creat ratio – BUN is more susceptible to non-renal factors – Post-renal increased ratio BUN / Creat ratio – Both BUN and Creat are elevated – Renal decreased BUN / Creat ratio – Low dietary protein or severe liver disease Increased BUN Normal Creat Increased BUN Increased Creat Decreased BUN Normal Creat
- 36. 36 • URIC ACID – Breakdown product of purines ( nucleic acid / DNA ) – Purines from cellular breakdown are converted to uric acid by the liver – Uric acid is filtered by the glomerulus ( but 98 – 100 % reabsorbed ) – Elevated plasma uric acid can promote formation of solid uric acid crystals in joints and urine
- 37. 37 Uric acid analysis Uric acid + O2 + H2O Allantoin + CO2 Uricase Uric acid absorbs light @ 293 nm , Allantoin does not. The rate of decreased absorption is proportional to the uric acid concentration. Specimen : Plasma or serum + H2O2 Reference range : 3.5 - 7.2 mg/dl (males) 2.6 - 6.0 mg/dl (females) Let’s remember 3.0 - 7.0 mg/dl
- 38. Cystatin C • 120 aa • Cysteine-protease inhibitor • Produced at constant rate by all nucleated cells • Freely filtered at glomerulus • Reabsorbed/ catabolised in proximal tubule • Serum conc mainly determined by GFR • Proposed as improved GFR marker • Extremely sensitive to minor changes in GFR • Measurement expensive and difficult
- 40. Volume Normal- 1-2.5 L/day Oliguria- Urine Output < 400ml/day Seen in – Acute glomerulonephritis – Renal Failure Polyuria- Urine Output > 2.5 L/day Seen in – Increased water ingestion – Diabetes mellitus and insipidus. Anuria- Urine output < 100ml/day Seen in renal shut down
- 41. Appearance
- 42. • Odor: Normal urine has a faintly aromatic smell • Urine in diabetic ketoacidosis may have fruity odor due to acetone. • Color: Normal urine is straw colored (amber- yellow) due to the pigment, urochrome. Presence of bilirubin makes urine yellow in jaundiced patients.
- 43. Specific gravity • Depends on conc of solute • EMU is used Normal 1.015 -1.025 • Decreased in – Excess water intake – DI • Increased in perspiration, DM • Isothenuria -1.010 • Earliest manifestation of renal disease
- 44. Chemical Characteristics of Urine • Reaction to Litmus • The pH of urine varies from 5.5 to 7.5. • PROTEIN • The proteinuria is commonly assessed by the heat and acetic acid test • dipstick test. • Microalbuminuria is detected by radial immunodiffusion or immunoturidimetry methods.
- 45. Blood • Hematuria is seen in nephritis and postrenal hemor rhage. • Hemoglobinuria is due to abnormal amount of hemolysis. • Occultest tablets and Hemastix strips are available for rapid testing of blood in urine.
- 46. Reducing Sugars (Glycosuria) • Benedict’s test Ketone Bodies • acetoacetic acid, beta hydroxybutyric acid and acetone. • Ketonuria is seen in diabetes mellitus, starvation, persistent vomiting, and in alkalosis. • Rothera’s test. • ketostix strips are available for rapid test for ketone bodies
- 47. Bile Salts • Bile salts are present in urine during the early phase of obstructive jaundice • Hay’s test. Bile Pigments • Bilirubin appears in urine during obstructive jaundice
- 48. MARKERS OF GLOMERULAR FILTRATION RATE • GFR measured by clearance test. • GFR is also affected by age, sex, body size, protein intake and pregnancy. • Normal GFR for young adults is 120–130 mL/mt/1.73M2.
- 49. Clearance • Amount of plasma that is cleared off that particular substance in unit time and is expressed in ml/mt • Clearance = U X V P U ---- concentration of substance in urine V----- volume of urine ( ml/minute) P-----concentration of substance in plasma
- 50. Substance used for Clearance Tests • Exogenous markers inulin, 51Cr-labeled EDTA, 99Tec-labeled EDTA, etc. • These are not used in clinical practice. • Endogenous markers urea creatinine. • creatinine is the best
- 52. Creatinine clearance test Creatinine is an excretory product derived form creatine phosphate. This conversion is spontaneous and non- enzymatic. Creatinine is an ideal substance for clearance test: Since, it is already present in body fluids, it’s plasma concentration is steady throughout the day. Freely filtered and not reabsorbed.
- 53. No need for intravenous administration as it is produced endogenously. Ccr = U X V P Directly related to the GFR. Hence, its measurement is used to asses the renal glomerular function. Normal value : 90 – 120 ml/min ↓sed creatinine clearance indicates ↓se GFR.
- 54. • procedure 500 ml water given After 30 mins, bladder emptied and urine discarded After 60 mins, urine and blood sample collected • 1.Extrarenal factors will rarely interfere. • 2. Conversion of creatine phosphate to creatinine is spontaneous, non-enzymatic. • 3. As the production is continuous, the blood level will not fluctuate. • 4. It is not affected by diet or exercise advantages
- 55. UREA clearance tests • End product of protein metabolism • Less sensitive than creatinine clearance because: • Partially reabsorbed Increased by dietary protein • Urea clearance • Normal Value : 75ml/min
- 56. UREA clearance tests. • Procedure Break fast lunch 1 hr 1 hr Empt y bladd er Urine and blood collec tion Urine collection Interpretation : Urea clearance ≥ 70% ----------average normal function 40 – 70 % ------mild impairment ≤ 20 % ----------severe impairment
- 57. UREA clearance tests • Maximum clearance ( urine volume > or = 2 ml/min) Standard clearance (urine volume < 2ml /min) Clearance = U X V P = 1000 x 2.1 28 = 75 ml/ min Clearance = U X √v P = 54 ml/ min
- 58. UREA clearance tests disease Urea clearance Chronic nephritis Falls progressively Nephrotic syndrome Normal until onset of renal insufficiency Benign hypertension Normal clearance usually maintained indefinitely
- 59. Estimated GFR ( eGFR) • Estimating creatine clearance using s.creatine level • eGFR can be used for staging of patients with chronic kidney disease. • This would eliminate the need for timed urine collections. • A commonly used formula is Cockcroft-Gault equation. •
- 60. Estimated GFR ( eGFR) • Cockcroft - Gault equation Ccr = (140 – age in yrs) x wt(kg) (0.85 in females) x Pcr 72
- 61. Inulin clearance test • Inulin is a polysaccharide of fructose. • It is not metabolized by the body. • It is neither absorbed nor secreted by the tubules. Therefore, inulin clearance is a measure of GFR. • The value of GFR as measured by inulin clearance is 125 mL/min
- 62. Inulin clearance test • Ideal substance • Procedure: Overnight fast Light breakfast at 7:30 am 10 gm inulin in 100 ml saline inj i.v. at 10 ml/min at 8am Bladder emptied at 9am, urine discarded After 30 mins, urine and blood collected After 60 mins, urine and blood collected
- 63. Test for renal blood flow 1. Measurment of renal plasma flow PAH - filtered and secreted - removed completely during a single circulation of blood through the kidneys RPF = 574 ml/min
- 64. 2. Filtration fraction: Fraction of plasma passing through the kidney FF = Cin = GFR = 125 = 0.217 ( 21.7%) CPAH RPF 594 Normal range = 0.16 – 0.21 disease Filtration fraction Essential hypertension Normal in early period, as disease progresses ↓ RPF > ↓ GFR -------FF ↑ Malignant phase of hypertension ↑↑↑↑ FF glomerulonephritis Greater ↓ in GFR than RPF, ↓FF
- 65. Test for glomerular permeability The low molecular weight proteins are freely filtered albumin (mol wt 69 kD) is retained in the blood, but free hemoglobin (mol wt 67 kD) is filtered and excreted in urine. Normal protein excretion is less than 150 mg/24 hours(Tamm Horsfall glycoprotein) immunochemical methods.
- 66. Test for glomerular permeability • First sign of glomerular injury (before decrease in GFR) • Proteinuria • Normal protein excretion = <150 mg/24 hrs Glomerular damge • Glomerular proteinuria Increase in low mol. Wt proteins • Overflow proteinuria Decrease in reabsorptive capacity • Tubular proteinuria Others Nephron loss proteinuria Urogenic protreinuria
- 67. • Glomerular proteinuria Albuminuria ( early morning urine sample prefered) 300 mg/day Benign proteinuria 300 – 1000 mg/day Pathological proteinuria >1000 mg/day Glomerular proteinuria Large quantity of albumin nephrosis Small quantity of albumin Acute nephritis, pregnancy Measurment of albuminuria is helpful in monitoring kidney function and response to therapy in many forms of CKD
- 68. Microalbuminuria/ minimal albuminuria/pauci albuminuria • 30 – 300 mg/day in urine • Earliest sign of renal damage – diabetes mellitus, hypertension Overflow proteinuria • Small molecular weight proteins are ↑ in blood • Hemoglobinuria (hemolytic anemia) • Myoglobinuria ( crush injury) • Multiple myeloma • Detected by immunoprecipitation.
- 69. Tubular proteinuria Functional nephrons decrease, GFR decreases Remaining nephrons are overworked Tubular reabsorption impaired Low molecular wt. protein appear in urine Hence can be used as markers of tubular damage Eg. RBP,alpha 1 microglobulin.
- 70. Concentration tests • ability of kidney to concentrate urine • Simple, bedside procedure • Most sensitive means of detecting early impairment in renal function 1. Fishberg concentration test – Procedure: Meal at 7 pm------no fluid from 8 pm to 10 am. Urine specimen collected at 8, 9, 10 am Determine specific gravity Result: Specific gravity of any one specimen > 1.025----NORMAL < or = 1.020 ---impaired fixed at 1.010 ----severe
- 71. Water dilution or elimination test • Ability of kidney to eliminate water is tested by measuring urinary output after ingesting large volume of water Evening meal at 8 pm After 12 hrs i.e. 8 am first urine sample discarded After 8 am , 1200 ml given in half hr Bladder emptied at 9, 10, 11 ,12 Kidney function Urine voided in 4 hrs Specific gravity of at least 1 specimen normal >1000 ml (80%) Larger part excreted in first 2 hrs) < or = 1.003 impaired <1000 ml (80%) Doesn’t fall to 1.003 Fixed at 1.010 in severe renal damage Patient in supine position
- 72. Urinary Acidification • Test of renal ability to excrete acid Give NH4Cl in gelatin coated capsule (0.1 mg/kg) Empty bladder 1 hr later, urine discarded Collect all urine samples in next 6 hrs. measure pH and NH3 content Kidney function pH NH3 normal 5.3 30 -90 mEq/min Renal failure decreases decreases Renal tubular acidosis 5.7 - 7 decreases Contraindications : liver disease, acidosis
- 73. GLOMERULAR DYSFUNCTION TUBULAR DYSFUNCTION Increase in Se urea Urinary concentration decreases Increase in Se creatinine Dilution tests abnormal Inulin clearance decreases Uric acid excretion decreases Creatinine clearance decreases Blood uric acid increases Urea clearance decreases Acidification of urine decreases Urine volume decreases Aminoaciduria present Specific gravity increases Urine volume increases Se phosphate increases Specific gravity decreases Poteinuria present Se phosphate decreases
- 74. Novel biomarkers of tubular injury • neutrophil gelatinase associated lipocalin (NAGL) • kidney injury molecule-1 (KIM-1), • liver fatty acid binding protein (LFABP), • interleukin-18 (IL-18)
- 75. Thank you