The document discusses renal function tests which evaluate how well the kidneys are functioning. There are three main groups of renal function tests: urine and blood analysis, assessment of renal clearance, and additional specialized tests. Renal function tests are useful for early detection of kidney damage, monitoring disease progression and treatment effectiveness, and predicting when renal replacement therapy may be needed. Common tests include analysis of urine volume, appearance, constituents, and sediment as well as blood tests of urea and creatinine levels. Clearance tests measure the glomerular filtration rate using markers like inulin, creatinine, or iohexol.

1. RENAL FUNCTION
TESTS
By
doctoroid

2. 1) Excretory – primary :by urine formation
2) Regulation of volume & electrolyte
composition of ECF
3) Regulation of acid-base balance
4) Endocrine function – produce & secrete:
erythropoietin, renin, calcitriol(1,25-
DHCC)
5) Site of neoglucogenesis – not primary: in
starvations- esp. from glutamine

3.  collective term for a variety of individual tests
and procedures that can be done to evaluate
how well the kidneys are functioning.
 Primarily reflects two basic mechs.– Glomerular
ultrafiltration & Tubular reabsorption/secretion
 Practically, divided into 3 groups –
1) Analysis of urine & blood
2) Specific assessment of renal clearance
3) Additional special Tests

4.  Early detection of possible renal damage &
assessment of its severity
 Measure progression of the renal
impairment & efficacy of corrective therapy
 Predict when renal replacement therapy
may be necessary
 Monitor safe & effective use of drugs, which
are principally eliminated through urine.

5.  A) PHYSICAL :
1)Volume > 800-2500 ml/dintake~2.5 L/d
 Polyuria >2.5L Chronic GN
 Anuria ,Oliguria
2) Appearance > clear
 Turbid (alkalinity d/t prolonged standing l/t
ppt of Ca/Mg-phosphates,↑phosphate ,
presence of pus d/t UTI)

6. 3) Colour> straw/amber-yellow urochrome
 Brownish yellow (jaundice)
 Dark (alkaptonuria)
 Reddish brown (RBC/Hb/Mb-uria,Porphyria etc.)
4) Odour> mild aromatic  volatile org. acids
 Unpleasant ammoniacal (prolonged standing)
 Acidotic fruity (DKA)

7. 5) Sp. Gravivity & Osmolality >
 1.003 to 1.030 & 50-1200 mOsm/kg (depends
on state of hydration of the body)
 Early morning urine sample(=after overnight
fast)if SG>1.018 & Osm>600 ≡Normal
 SG is simplest to measure but unreliable(in
presence of HMW substances) for evaluating
renal concentrating ability.
 SG  decreased,increased & fixed(1.010=CRF)

8. 1) Reaction > mild acidic  pH avg.6 (=4.5-
7.5)
 normal short PP alkaline tide
 Protein rich diet  acidic
 Vegetable rich diet  alkaline also in type II
DTA, UTI by urease producing organisms,
Acetazolamide therapy, alkali ingestion.

9. 2) For abnormal urinary constituents :
I) Proteins >
 Normal upto 150 mg/d—routinely undetected
 Proteinuria  albumin predominates
 By– a) heat & acetic acid test
b) Sulphosalicylic acid test
c) Esbach’s albuminometer

10. II) Reducing Sugars >
 Normally absent – glucose/fructose/galactose
 When renal threshold is exceeded
 By Benedict’s Test
III) Blood >
 Normally does not appear
 By Benzidine Test

11. IV) Ketone Bodies >
 Normally not present
 By- Rothera’s Test & Gerhardt’s test.
V) Bile salts >
 Only in early phases of obstructive
jaundice
 By- Hay’s test & Petenkoffer’s test

12. VI) Urobilinogen > N ~1 - 3.5 mg/d
 ↑ in persistent fevers, hepatobiliary diseases,
haemolytic jaundice
 By- Ehrlich’s test & Schlesinger’s test
VII) Bile-pigments >
 Bilirubinuria=↑conj.Bilirubin  hep/post-hep jaun
 By- Modified Fouchet’s Test

13. Imp findings in the urinary sediment includes---
I) Casts >> proteinaceous plugs
 Formation favoured by sluggish flow
 Various shapes c/t tubules in which
formed cellular or non-cellular
 Types  Hyaline, RBC, WBC, Granular,
Broad waxy etc.

14. II) Crystals >>
 Ca-oxalate/phosphate, Triple phosphate--
common
 May be normally found  risk of stone in future
 Urate or Cysteine crystals  pathologic
III) Cells >>
 RBCs, WBCs, pus cells, Sq.epithelial, Tubular
epithelial cells

15.  Strip impregnated with reagents for the
substances in question within a urine sample.
 By comparing the colour-change(in the paper-
squares)with the standardized colour-charts.
 Modern dipsticks with multiplied zones:
 Can detect/measure: Protein, hemoglobin,
glucose, urobilinogen, ketones, leukocytes,
specific gravity, and pH
 A promising tool everywhere at the level of
primary care!!!

16.  There is no plasma constituent whose conc.
depends solely on the functionality of kidneys.
 Frequently used are 2 normal metabolic wastes
 Excreted by kidneys  accumulates in renal
dysfunction  ↑blood levels
I) Blood Urea Nitrogen >> 8-25 mg%
 begin to rise only after 50% renal damage
II) Plasma Creatinine >> 0.6 – 1.5 mg%
 More reliable as BUN is subjected to variations

17.  Vol. of plasma that is cleared of a substance in
unit time, by its’ urinary excretion ml/min
 Calculated as: C = UV/P
 Predominantly determine GFR: Relationship as
—
 Correlated more directly with the status of kidney
function  employed to assess GFR,RPF &
GFR = C No reabs, No
Secret
INULIN
GFR > C Much reabs, No Secret Gluc, AA, Na+, Cl-
GFR < C No reabs, Much Secret PAH, Diodrast

18.  Characteristics of an Ideal Marker :
 Constant rate of production (or for exogenous
marker can be delivered IV at a constant rate)
 Freely filterable at the glomerulus (minimal
protein binding)
 No tubular reabsorption/secretion
 No extrarenal elimination or metabolism
 Availability of an accurate & reliable assay
 For exogenous markers-- safe, convenient, readily
available, inexpensive & physiologically inert

19. Various markers used :
A) Exogenous >>
1) Inulin (gold standard but technically demanding)
2) Non-radiolabelled contrast media (e.g. Iohexol)
3) Radiolabelled compounds (e.g. 99m Tc-DTPA)
B) Endogenous >>
1) Creatinine (marginally overestimates—most widely
used in clinical practice)
2) Urea (one of the 1st
markers– not used at present)

20.  Approximation of bedside GFR with limited
accuracy by “Cockroft & Gault formula”
 Most widely used & best validated for adults
Ccr =(140-Age)x(Wt in Kg)/(Plasma
Creatinine x72)
 [Correction factor for females = 0.85]
 value to such formulas for GFR prediction is likely
to increase when an accurate plasma creatinine
assay is performed along with inhibition of
tubular secretion by cimetidine/probenecid.

21. Applying “Fick’s Principle” to
kidney :
Amount of a sub excreted by kidney in unit time(UV)
=RPF X renal A-V diff. in its plasma conc.(Pa - Pv)
 RPF(ml/min) =UV / (Pa - Pv)
 Criteria of the marker to be used
:
 Almost totally extracted from plasma with each
passage through kidney
 Not metabolised/stored/produced by kidney

22.  Use of PAH Clearance to measure
RPF/RBF:
 Cont. low dose PAH inf. plasma conc. Constant
 All PAH excreted in urinePv(PAH)=0eliminated
 ≡> RPF = UV/Pa(PAH) = Clearance of PAH(C-PAH)
 10% RPF perfuses non-excretory portionsERPF
 True RPF = ERPF/0.9
 RBF = true RPF / (1 – Haematocrit value)
 Normal ERPF = 600-650 ml/min/1.73 sq.mt BSA

23. A) TESTS FOR TUBULAR FUNCTIONS:
I) Urine Conc. Test >>
Early dinner  no food/fluid after 6 PMbladder
emptied @ 7AM  discarded specimens
collected @ 8 AM & 9AMatleast one should hv
SG >1.022 or Osm >850 mOsm/kg
II) Vasopressin test >>
No fluid after 6 PM s.c. ADH(5U)inj.@8PMurine
samples collected separately till 9AMatleast
one should SG>1.020 or Osm>800

24. III) Urine Dilution Test >>
Pt. completely empties bladder after overnight fast
drinks 1L waterhourly urine specimens
collected for next 4 hrsatleast 700ml will be
excreted & atleast one should hv SG <1.004
IV) Urine Acidification Test >>
Fasting from midnightcomplete bladder emptying
@morningOral Am.Cl.(0.1gm/kg) with 1L water
given hourly urine samples collected for next 6
hrs. atleast one should hv pH of 5.3 or less

25. V) Dye Excretion Test or PSP
Test>>
 Phenolsulphonphthalein(Phenol red)—
filtetred & secreted.
 600 ml water drink f/b IV 6mg PSPhourly
urine samples collected40-60% should be
excreted in 1st
hr. & another 20-25% should
excrete in 2nd
hr
 Excretion<50% over 2hrs. abnormal

26. VI) Other Sophisticated
Methods>>
 MICROPUNCTURE techniques
 MICROCRYOSCOPIC studies
 MICROELECTRODE studies
VII) Renal Biopsy >>
 Specimen subjected to LM,EM & IFM-studies
 ↑knowledge & better understanding of renal

27.  Plain radiograph of abdomen
 IVP
 USG, CT Scan, MRI Scan
 Radionuclide studies
 Strictly speaking, these are not considered to be
RFTs, but very useful in present day clinical
practice for structural & functional assessment of
kidneys.