This presentation is focused for Undergraduate students (MBBS, BDS, B.Sc Nursing, BMLT students).

1. Renal Function Test
Dr. Apeksha Niraula
Assistant Professor
Department of Biochemistry
BPKIHS

2. Objectives
 General Anatomy
 Functions of Renal System
 Classification of renal function tests (Urine analysis,
blood, Glomerular function and Tubular function)
 Clinical Implications

3. Overview of General Anatomy
 Two bean shaped
 Both side of vertebrae
 Weight: 150 gm
 About 10 to 13 cm (4 to 5 inches) long
 Approximately 5 to 7.5 cm (2 to 3
inches) wide
 About 2 to 2.5 cm (1 inch) thick
 Size of fist
 Site: T11-L3

4. Functions of Kidney

5. Formation of
urine as the
waste product
Excretion of
NPN
substances
Regulation of
salt & water
balance
Regulation of
acid-base
balance
Production of
Hormones
Functions of
KIDNEY

6. Figure:
Countercurrent
multiplication
mechanism

7. Urine Analysis
 Normal color: Urochrome pigment : pale to amber
 Blue green: Riboflavin, pseudomonas infection etc
 Pink-orange-red: Hb, myoglobin, porphyrins
 Red-brown black: Hb, myoglobin, RBC, Homogentisic acid etc
 Specific gravity/osmolarity:
 Sp. Gr. :1.005-1.030
 Osmolarity (24hrs): 500-800 mOsm/kg of water
 Turbidity: Due to infection or fat particles

8.  Reagent impregnated cellulose strips
 Protein
 Albumin
 Hemoglobin
 Glucose
 pH
Reagent Strip Dipstick Test

9. Microscopic Examination
 Centrifugation of fresh sample
 Sediment observation under
microscope
 Erythrocyte
 Leukocyte
 Epithelial cells
 Casts ( composed of Tamm Horsfall
glycoprotein)
 Fat or pigmented particles
 Parasites or bacteria
 Crystals

10. Classification of Renal Function Tests
 Tests based on Glomerular filtration:
i. Urea clearance test.
ii. Endogenous creatinine clearance test.
iii. Inulin clearance.
iv. Cr51- EDTA clearance test.
 Tests to measure Renal Plasma Flow (RPF):
i. Para-amino hippurate test (PAH).
ii. Filtration fraction
 Tests based on tubular function:
i. Concentration and dilution tests.

11. Glomerular Function Measurement
 Plasma Urea
 Plasma Creatinine and clearance
 Calculated creatinine clearance (eGFR)
 Inulin clearance
 Isotopic technique for measuring GFR
 Cystatin C
 Plasma β2-microglobulin

12. Clearance Test
Clearance is that volume of blood or plasma from which a measured amount of
substance can be completely eliminated into the urine per unit of time.
C= UV / P
C= clearance
U= concentration of substance in urine ( in mg / 100 ml )
V= volume of urine in ml / min
P = concentration of substance in plasma/ blood
Clearance tests are
 Endogenous - Urea, Creatinine,
 Exogenous - Inulin , 51Cr-EDTA

14. Creatinine clearance
 At normal level of creatinine, this metabolite is filtered at the glomerulus but neither
secreted nor reabsorbed by the tubules. Hence, its clearance gives the GFR
 Convenient method for estimation of GFR since:
 Normal metabolite in the body
 Does not require the intravenous administration of any test material
 Estimation of creatinine is simple
 Procedure of test:
 An accurate 24 hr urine specimen is collected
 Collect a blood sample for serum creatinine determination
 Estimate the serum and urinary creatinine concentration
 Normal range: 95- 105 ml/ min

15. Serum Urea
 Plasma urea is widely ordered along with creatinine for measuring renal
function but has many disadvantages:
 Plasma concentration is dependent in part on its rate of formation
 Significant passive reabsorption from tubules
 Method of estimation
 Direct chemical : DAM in hot acidic medium
 Indirect Enzymatic method: Urease, Glutamate Dehydrogenase method

16. Cystatin-C
 Low mol. Wt. protein: 13.4 kDa, non glycated basic protein
 Cysteine protease inhibitor, found in surface of all nucleated cell
 Its plasma concentration appears to be far less dependent than that of
creatinine on weight, height, muscle mass, age or sex
 More sensitive index of mild renal impairment that is it increase in creatinine
blind range (GFR of 70-90mL/min/1.73m2)
 GFR estimation is far less variable
 Immunoassay technique available but expensive

17. Plasma β2-Microglobulin
 Mol wt. of 11.8 KDa is shed into plasma at constant rate
 Passes freely through the glomeruli
 Normally <2 mg/L in plasma
 Impaired renal function: upto 40 mg/L
 Direct relationship between plasma β2-microglobulin and GFR but its
measurement has not been widely adopted as an index of GFR for
methodological reasons

18. Exogenous Substances for GFR
 Inulin:
 Plant polysaccharide (fructose monomer)
 satisfies all criteria for estimation of GFR (Gold standard for estimation of GFR)
Disadvantages:
 Time consuming
 Poor specificity of analysis
 Chromium-EDTA
 Isotopic (simple)
 Time consuming

19. Test of Tubular Function
 Proximal tubular function
 Phosphate reabsorption test
 Detection of urinary amino acid
 Detection of glycosuria
 Distal tubular function
 Urinary concentration and dilution
 Urinary acidification

20. Urine concentration tests
 Restrict water intake for 14- 16 hours
 Collect three urine samples at 1-, 2- and 4 hours
 Measure specific gravity
 Normal tubular function - >1.025
 Decreased renal function = 1.020
 Severe renal impairment approaches < 1.010
 Normal finding does not rule out active kidney diseases
“Fluid deprivation may be contraindicated in heart diseases and early renal
failure”

21. Quantitative Assessment of Proteinuria
 Total protein measurement
 Albumin
 Bence Jones Proteinuria
 Myoglobinuria

23. Diabetic Nephropathy
 Diabetic nephropathy has been classically defined by the presence of
proteinuria>0.5 g/24 h or
 Clinically important indicator of deteriorating renal function in diabetic subjects so
regular screening of albumin loss a valuable in monitoring type 1 and type 2 DM
 ACR measures more accurately than random or timed albumin excretion
measurement

24. Acute renal failure / Acute Kidney Injury
 ARF is essentially characterized by a sudden decline in renal function, leading to
retention of nitrogenous and other waste products, disordered hydrogen ion
homoeostasis and disturbances of extracellular fluid volume and composition
 Potentially life threatening condition and, developing as it often does in patients
who are already severely ill
 In many cases of acute renal failure there is oliguria (urine flow rate: <15mL/hr)

25. Glomerular Diseases
 Suggested clinically by finding blood and protein in urine on urine reagent strip
testing
 Primary Glomerular Disease: IgA nephropathy, membranous nephropathy
 Nephrotic Syndrome: Heavy proteinuria (>3g/d), reduced serum albumin and
edema
 Acute nephritic syndrome: rapid onset of hematuria, proteinuria, reduced
GFR, sodium and water retention followed by hypertension and localized
peripheral edema
 Cause: group A alpha-hemolytic streptococcal infection of pharynx

26.  Several disease that results in:
 Injury and increase permeability of glomerular basement
membrane
 Abnormal findings
 Massive proteinuria (>3.5 gm/day)
 Hypoalbuminemia
 Generalized edema
 Other hallmarks. Hyperlipidemia and lipiduria
Nephrotic syndrome

27. Tubular Disease
 Renal Tubular Acidosis
 Inherited and acquired disorders affecting proximal and distal tubule
 Characterized by hyperchloremic, normal anion gap metabolic acidosis and urinary
bicarbonate or hydrogen ion excretion abnormality
 Distal RTA (type I): inability to secrete hydrogen ions in DCT in acidosis
 Proximal RTA ( type II): failure in bicarbonate reabsorption from PCT
 Selective Aldosterone Deficiency (type IV): Aldosterone deficiency or
resistance

29. Chronic Kidney Disease
 The National Kidney Foundation-Kidney Disease Outcomes Quality
Initiative (NKF-KDOQI) defines CKD is as abnormalities of kidney
structure or function, present for >3 months, with implications for
health

31. 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……

32. What to examine???
Renal function tests are divided into the following:
 Urine analysis
 Blood examination
 Glomerular Function Test
 Tubular Function Test

33.  Teitz textbook of Clinical Chemistry and Molecular Diagnostics; 5th
Edition
 Clinical Biochemistry Metabolic and Clinical Aspects; William J
Marshall, 3rd Edition
 Textbook of Biochemistry 8th edition; DM Vasudevan
 Clinical Chemistry 6th edition; Marshal
References

34. Thank You