Renal func & dysfunc may 2016

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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