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Kft Kft Presentation Transcript

  • KIDNEY FUNCTION TEST DR.RITTU CHANDEL M.D. BIOCHEMISTRY (2ND YEAR) GRANT GOVT MEDICAL COLLEGE, MUMBAI 21-08-2013
  • ANATOMY
  • PHYSIOLOGY
  • Glomerular filtration
  • GFR (120 – 130 ml/min/1.73 m2 • Rate of filtration affected by – state of blood vessels concentration of plasma proteins Volume of glomerular filtrate depends on – number of functioning glomeruli effective glomerular filtration pressure Volume reduced in extra renal conditions
  • Tubular function • Tubular epithelial cells are highly specialized tissue – able to reabsorb selectively some substances and secrete others • 170 l -------filtered • 1.5 l --------excreted • Nearly 99 % reabsorbed • Renal threshold – plasma level above which compound is excreted in urine substance Threshold value glucose 180 mg/dl lactate 60 mg/dl bicarbonate 28 mEq/l calcium 10 mg/dl
  • FUNCTIONS 1. Maintenance of homeostasis 2. Excretion of metabolic waste products 3. Retention of substance vital to body 4. Hormonal function a.Erythropoietin b.Calcitriol c.renin
  • Preliminary investigation • History – oliguria, polyuria, nocturia, ratio of frequency of urination in day time and night time, appearance of oedema • Physical examination • Urine analysis • Biochemical parameters – increase in three nitrogenous constituents of blood ( uric acid, urea, creatinine ) others
  • Renal function tests 1. • • • • • 2. • • 3. • • 4. On glomerular filtration Urea clearance test Endogenous creatinine clearance test Inulin clearance test Cr51 - EDTA clearance test Tests on glomerular permeability Measure renal plasma flow PAH test Filtration fraction Tubular function Concentration and dilution tests 15 min – PSP excretion test Miscellaneous test
  • clearance • Substance S -----stable concentration in plasma • Physiologically inert, freely filtered at glomerulus, neither secreted, reabsorbed, non toxic, not affected by dietary intake • Amount of S entering kidney = amount of S leaving it • Filtered S = excreted S s • GFR x Ps = Us x V • GFR = Us x V • Ps
  • Clearance • Volume of blood or plasma which contains the amount of substance which is excreted in the urine in 1 min Clearance = U X V P U ---- concentration of substance in urine V----- volume of urine ( ml/minute) P-----concentration of substance in plasma
  • substance filtered reabsorbed secreted Amount excreted /minute in relation to amount filtered Glucose Yes Yes, completely ( 180 gm/dl) TmG = 350 mg/mt No Not excreted normally Urea yes yes no less Creatinine Yes no no Very close PAH, phenol red, diodrast Yes No Yes More than that filtered Inulin, mannitol, yes thiosulphate No no GFR = clearance
  • UREA clearance tests • Maximum clearance ( urine volume > or = 2 ml/min) Clearance = U X V P = 1000 x 2.1 28 = 75 ml/ min Standard clearance (urine volume < 2ml /min) Clearance = U X √v P = 54 ml/ min
  • Expression of result as % = result of clearance is expressed as % of normal maximum or normal standard urea clearance depending on urinary output Relation with body surface area Cm x 1.73 BS Cs x √1.73 BS
  • • Procedure Break fast 1 hr Empt y bladd er Urine and blood collec tion 1 hr Urine collection Interpretation : Urea clearance ≥ 70% ----------average normal function 40 – 70 % ------mild impairment ≤ 20 % ----------severe impairment lunch
  • disease Urea clearance Chronic nephritis Falls progressively Reaches value half or less of normal before blood urea concentration begins to rise Terminal uremia About 5 % of normal Nephrotic syndrome Normal until onset of renal insufficiency Benign hypertension Normal clearance usually maintained indefinitely
  • Blood urea • Normal – 20 – 40 mg/dl • Serum concentration increases as age advances Increase in blood urea Pre - renal renal Post renal drugs Dehydration Severe vomiting Intestinal obstruction Diarrhea Diabetic coma 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 Decreased blood urea – late pregnancy, starvation, hepatic failure
  • Creatinine clearance test • 113 Da • Produced by muscle from creatine and creatine phosphate through non enzymatic dehydration process • 24 hr excretion of endogenous creatinine Ccr = U X V P Normal – 95 – 105 ml/min
  • • procedure 500 ml water given advantages disadvantages After 30 mins, bladder emptied and urine discarded After 60 mins, urine and blood sample collected • 1.Value close to GFR • 2.Long term monitoring • 1.Mild renal impairment ( creatinine blind area ) • 2.Moderate impairment (secretion component ) • 3.Severe impairment (extra renal excretion)
  • Estimated GFR ( eGFR) • Cockcroft - Gault equation Ccr = (140 – age in yrs) x wt(kg) (0.85 in females) x Pcr 72 MDRD ( modification of diet in renal disease) eGFR = 186 x {creatinine} - 1.154 ( age ) – 0.203 x 0.742 88.4
  • Serum creatinine Normal = 0.7 – 1.5 mg/dl decrease increase Low muscle mass Females Malnutrition Thiazides vancomycin Old age Males Glomerulonephritis Pyelonephritis Renal failure Urinary obstruction CCF, dehydration, shock Amphotericin B Captopril Cephalosporin kanamycin
  • 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 Normal = 125 ml/min range = 100 – 150 ml/min Inulin clearance x 0.6 = maximum urea clearance
  • Cystatin C • • • • • • 122 amino acids, 13000 Da Inhibitor of cysteine proteinase Produced by all nucleated cells Production rate constant Not affected by muscle mass, sex, race High isoelectric point, which enable it to be more freely filtered • Sensitive changes in creatinine blind area • Extremely sensitive to minor changes in GFR • Measurment expensive and difficult
  • Substances used in clearance tests Endogenous substance – urea, creatinine, cystatin C, β – trace proteins, β - 2 – microglobulin, tryptophan glycoconjugate β - 2 – microglobulin Polypeptide, 11.6 kDa, 99 amino acid Component of MHC -1 In all nucleated cells Needed for production of CD-8 tryptophan glycoconjugate Mannopyranosyl – l – tryptophan (MPT) – produced in body by glycoconjugation of tryptophan Measured by HPLC
  • Clearance tests • • • • • • • • • • • Gold standard – inulin ( sinistrin) Silver standard – Cr51 - EDTA Tc99 - DTPA I125 – iothalamate iohexol Bronze standard – creatinine cystatin C Uncertain clinical use – creatinine clearance urea retinol binding protein α1 - microglobulin
  • 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 CKD = GFR < 60 ml/min/1.73 m2 for 3 months or more with or without kidney damage
  • 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 Others Nephron loss proteinuria Urogenic protreinuria Increase in low mol. Wt proteins • Overflow proteinuria Decrease in reabsorptive capacity • Tubular proteinuria
  • • 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
  • • Microalbuminuria/ minimal albuminuria/pauci albuminuria 30 – 300 mg/day in urine Earliest sign of renal damage – diabetes mellitus, hypertension Overflow proteinuria Hemoglobinuria (hemolytic anemia) Myoglobinuria ( crush injury) Multiple myeloma Hematuria –confirms glomerular damage, also earliest sign before decrease in GFR
  • 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. Β – d –glucosaminidase, lysozyme
  • 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
  • 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
  • Pathophysiology of tubular function Alteration in Tubular function ischemia Toxic substances Impairing transfer of substances across tubular cells
  • Concentration and dilution tests • Ability to concentrate and dilute urine dependent on: GFR RPF Tubular mass Healthy tubular cells Presence of ADH
  • • • • • Concentration tests/fluid deprivation tests ability of kidney to concentrate urine measurement of specific gravity of 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
  • 2. Lashmet and newburg concentration test Severe fluid intake restriction over a period of 38 hrs 3.With posterior pitutary extract s.c. inj of 10 pressor units of posterior pitutary extract (0.5 ml of vasopressin inj) Result – specific gravity - > or = 1.020 -----normal Failure to concentrate -----renal damage Advantages – CCF, DI
  • Water dilution or elimination test • Ability of kidney to eliminate water is tested by measuring urinary output after ingesting large volume of water Patient in supine position 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
  • Test of tubular excretion and reabsorption • Phenol sulphthalein (PSP) excretion test 94%----excreted, 6%----glomerular filtration 15 min PSP Test - reliable and sensitive Test 1 ml ( 6 mg) inj iv 30 -50 % excreted in 1st 15 mins <23% excreted in 1st 15 mins
  • Miscellaneous tests • Test of renal ability to excrete acid Give NH4Cl in gelatin coated capsule (0.1 mg/kg) Collect all urine samples in next 6 hrs. measure pH and NH3 content Empty bladder 1 hr later, urine discarded 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
  • • IVP • Radioactive scanning • Renal biopsy • Immunological tests 1. Anti GBM antibodies 2. ANCA 3. Pattern of complement in nephritis
  • 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
  • bibliography • • • • • • • • Satyanaryan Ranna shinde Vasudevan Kaplan Teitz Varley Pankaja naik THANK YOU