This document provides an overview of renal function and renal function tests. It discusses the key functions of the kidneys including electrolyte and water balance, acid-base balance, and excretion of waste products. It describes factors that regulate renal function such as autoregulation, neural and hormonal control. Causes of renal dysfunction including acute and chronic kidney disease are outlined. Consequences of impaired renal function like retention of waste products and end organ damage are summarized. Finally, the document categorizes and describes various renal function tests including clearance tests, urine analysis, imaging studies, and renal biopsy.

1. Renal function & dysfunction:
a summary
Dr. Madanmohan. MD, DSc, FIAY
Prof & Head, Dept. of Physiology
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2. Scheme of my talk
• Functions of kidneys
• Renal function in children
• Regulation of renal function
• Causes of renal dysfunction
• Consequences of impaired renal function
• Renal function tests:
classification
description 2

3. Function(s) of kidneys ?
functions are related to structure
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4. Functions of kidneys ?
Function related to structure
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5. 5

6. Juxtaglomerular apparatus
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7. Defence of milieu interieur and homeostasis:
1. Electrolyte and water balance
2. Acid–base balance:
pH: arterial plasma: 7.38–7.42, urine: 4.3–8.0
3. Excrete unwanted toxic substances
Metabolites: H+
, urea, u.acid, creatinine, bilirubin
Drugs: trimethoprim, amoxycillin, erythromycin
Heavy metals: Au, Pb, Li, Cd, Hg.
“Death due to renal failure”
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8. • GFR : 125 ml / min or 180 L/d
• Reabsorption (per day):
Fluid: 178.5 L
Glucose : 200 g; NaCl: 1kg
• Urine : 1.5 L / d
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9. Normal urine
• 1500 (800 – 2500) ml/d. <500 ml : oliguria
• SG: 1022 – 1030 (1003 – 1032)
• Normal constituents:
urea, uric acid, creatine, creatinine
• Abnormal constituents:
protein, glucose, ketone bodies, bilirubin, blood
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10. Non-excretory functions:
1. Regulation of BP: ECF volume,
renin-angiotensin
2. Endocrine function:
renin, erythropoietin, 1,25-DHC,
natriuretic hormone, PGs
3. Regulation of pH, H2O & electrolyte balance
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11. Renal function in children
• Infants: nephrons incompletely developed
• Less BP, RBF, GFR, reabsorption, secretion
• Inulin clearance : 25%
• Urine acidic, albumin often present
• Less responsive to hormones 11
Contd…

12. Renal function in children
Urine output:
• First 2 days: 20 ml
• 12th
day : 225 ml
• ~10 y: near adult values
• Narrow margin, especially in premature
• Diarrhea, vomiting, fever, hyperthermia:
cannot concentrate urine 12
…Contd

13. Regulation of renal function
• Autoregulation
• Neural and reflex regulation:
– Rich sympathetic innervation
– Exercise, shock: vasoconstriction
• Humoral regulation
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14. Humoral regulation
• ADH: water reabsorption
• Aldosterone: Na reabsorption in DCT
• PTH: Ca reabsorption & PO4 excretion
• Thyroxine: renotropic
• Glucocortocoids: for normal response to ADH
• PGs: modulate effect of other hormones
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15. Causes of renal dysfunction
1. Acute renal disease : infection, ischemia
2. Chronic renal disease :
chronic glomerulonephritis,
tuberculosis, obstruction, polycystic kidney
3. Acute on chronic  acute renal failure
4. Resection: 1 kidney compatible with life.
½ kidney ?
HT, DM  CKD
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16. Consequences of impaired renal function
1. Retention of waste products in blood:
H+
, K+
, urea, uric acid, creatine, creatinine
2. Abnormal constituents in urine: protein, cells, casts
3. Decreased ability to concentrate/dilute urine
4. End organ damage. Multi system dysfunction
5. Clinical features: edema/dehydration, increase BP,
anemia/polycythemia, decreased immunity 16

17. Renal failure
• Acute: H, K, urea (900 mg%).
Disturbed milieu interieur.
Death in 5–7 d.
• Chronic: loss of nephrons (>70%)
DM, HT, chronic infections,
polycystic kidney.
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21. Classification of RFTs
(battery of tests)
Direct measurement is difficult: clearance
Indirect estimation is simple: blood chemistry
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22. 1. Clearance techniques.
2. Measure maximum tubular transport:
TmG, TmPAH, TmPO4
3. Assessment of functional state:
i) dilution test
ii) concentration test
iii) acidification test
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Classification of RFTs
Contd…

23. 4. Blood constituents (biochemistry)
Plasma concentration is
inversely proportional to clearance
Waste products: urea, uric acid,
creatine, creatinine
Electrolytes : H+
, K+
, Na+
, Cl-
5. Urine: macroscopic, microscopic, chemical
inexpensive & useful
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Classification of RFTs
Contd…
…Contd

24. 6. Clinical examination
7. Biopsy
8. Experiments: animals
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…Contd

25. Clearance studies
• Definition
• GFR
• RPF
• Amount reabsorbed
• Amount secreted
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Filtered
Secreted
Reabsorbed

26. GFR by inulin clearance
• Amount in urine = amount filtered
Uin x V = Pin x GFR
GFR = Uin x V / Pin
= 120 ml / 1.7 m2
Curea : 75 ml Ccreatinine : ~150 ml
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27. RPF by PAH clearance
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PAH: filtered + secreted
UPAH x V / PPAH

28. Tubular secretion (PAH)
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Amount in urine = amount filtered + amount
secreted
Amount secreted = amount in urine - amount
filtered
UPAH X V - GFR X PPAH

29. Tubular reabsorption (glucose)
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Glucose: filtered & reabsorbed
Amount in urine = amount filtered – amount
reabsorbed
Amount reabsorb = amount filtered – amount in
urine

30. Dilution test
• Excretion of H2O load: hourly samples
• H2O: 2% of body wt in 20 – 30 min, ~ 7 AM
(70 kg x 20 ml = 1400 ml)
• Urine at 8, 9, 10 AM
• One sample SG <1003 ( N: 1022 – 1030 )
• Within 3-6 h, all the input should come out
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31. Concentration (Addis) test
• Dry meals for 18 h, no fluids from 8 PM to 8 AM
• SG: >1025, >700 mOsm/L
• Simple, but crude test
• Early detection of renal disease
• Contra-indications: hot weather, dehydration,
diuresis/polyurea (DM), adrenal insufficiency31

32. Acidification test
• NH3Cl : 0.1 g / kg orally
• Hourly urine samples for 8 h
• About 6 h : pH < 5.3
(normal pH : 4.3 – 8)
• > 8 pH : urinary infection
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33. Imaging
• Plain X ray
• Ultrasonogram
• CT, MRI
• IVP
• Retrograde pyelography
• Renal arteriography (angiography)
• Radiorenogram: 125
I 131
I - hippuran 33

34. Renal biopsy
• For exact histological details
• Contraindications:
i) one kidney
ii) bleeding tendency
iii) carcinomas
iv) renal cyst (large)
v) malignant hypertension
vi) perinephric abcess
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35. • Electrophysiological studies:
transtubular, transcellular potentials
• Stop / flow studies
• Micropuncture & microperfusion
• Microcryosopic studies
• Tissue slice experiments 35
Experimental studies

36. Thank you
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