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1. OSMOREGULATION
URINE DILUTION
& CONCETRATION
Mohammed Abdel Gawad
Nephrology Specialist
Kidney & Urology Center (KUC) - Alexandria
drgawad@gmail.com
DNG Meeting – Mansoura – 20 June 2014
Nephrology – Back to Basics Series
Physiology Concepts

2. It is the number of particles - osmoles (mmol)
contained in 1 liter of water.
(it is the concentration by number)
Osmolality (mmol/L)
2

3. normally ranges between 285 and 295 mmol/L
Calculated Osmolality
3

4. Osmolar Gap
4

5. Specific gravity is the mass of one milliliter of solution in grams.
This gives an indication of both the number and weight of the particles in the urine.
Osmolality vs Specific Gravity
5

6. M.Gawad www.nephrotubecne.com
Goce Spasovski et al, Nephrol Dial Transplant (2014) 29 (Suppl. 2): ii1–ii39
Normally: ICF Osmolality = ECF Osmolality
Intracellular Extracellular
Effect of Plasma Osmolality Changes on
Cell Size

7. Intracellular Extracellular
Intracellular
swelling &
edema
H2O
M.Gawad www.nephrotubecne.com
Goce Spasovski et al, Nephrol Dial Transplant (2014) 29 (Suppl. 2): ii1–ii39
Effect of Plasma Osmolality Changes on
Cell Size
Consequences of Low Plasma Osmolality

8. Intracellular Extracellular
Intracellular
Shrinkage
M.Gawad www.nephrotubecne.com
Goce Spasovski et al, Nephrol Dial Transplant (2014) 29 (Suppl. 2): ii1–ii39
Effect of Plasma Osmolality Changes on
Cell Size
Consequences of High Plasma Osmolality
H2O

9. 9
Effect of Plasma Osmolality Changes on
Cell Size

10. A change in plasma osmolality of only 1% is detectable by the
hypothalamus
10
Plasma Osmolality Monitoring
General Concept

11. Mechanism of Changes in Plasma Osmolality
General Concept
11

12. Mechanism of Changes in Plasma Osmolality
General Concept
12

13. 13
How Body Adjust Plasma Osmolality?
General Concept

14. 14
How Body Adjust Plasma Osmolality?
General Concept

15. 15
How Body Adjust Plasma Hypo-Osmolality?
(1) Suppress Thirst

16. 16
How Body Adjust Plasma Hypo-Osmolality?
(2) Suppress ADH Secretion

17. 17
How Body Adjust Plasma Hyper-Osmolality?
(1) Stimulate Thirst
Thirst (causing the ingestion of water) is the most
effective defense against increases in osmolality.
This defense is so effective that, with ready
access to water, alert people cannot develop
significant increases in osmolality

18. 18
How Body Adjust Plasma Hyper-Osmolality?
(2) Stimulate ADH Secretion

19. Anti Diuretic Hormone (ADH)
19

20. ADH – Stimulation
20
• Arthur C. Guyton, John E. Hall. TEXTBOOK OF MEDICAL PHYSIOLOGY. 11th Edition, 2006.
• Sarah Faub el, Jo el Topf.The Fluid, Electrolyte and Acid-Base Companion. Chapter 4, 1999.

21. ADH – Stimulation
21

22. ADH
Formation, Storage & Release
22

23. ADH
Formation, Storage & Release
23

24. 24
ADH
Formation, Storage & Release
Osmoreceptors
in the hypothalamus

25. 25
ADH - Action
Formation of concentrated urine
Facultative water reabsorption

26. 26
ADH - Action
Formation of concentrated urine
Facultative water reabsorption

27. 27
ADH - Action
Formation of concentrated urine
Facultative water reabsorption

28. 28
ADH - Action
For completed action of ADH, we need
Concentrated Medullary Interstitium

29. 29
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic

30. 30
Loop of Henle
(Countercurrent
Multiplier)
Vasa Recta
(Countercurrent
Exchange Mechanism)
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic

31. 31
65%
8-10%
25%
Basics - Tubular Na Handling
Concentrated Medullary Interstitium

32. 32
65% by osmosis
(obligatory
reabsorption)
15-20%
by osmosis
(obligatory
reabsorption)
15%
Under effect of
ADH
(Facultative
reabsorption)
Basics - Tubular Water Handling
Concentrated Medullary Interstitium

33. 33
Loop of Henle
(Countercurrent
Multiplier)
Vasa Recta
(Countercurrent
Exchange Mechanism)
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic

34. 34
Loop of Henle
(Countercurrent
Multiplier)
Vasa Recta
(Countercurrent
Exchange Mechanism)
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic
To form a hyperosmolar
medullary interstitium

35. Loop of Henle: Countercurrent
Multiplication
35

36. Loop of Henle: Countercurrent
Multiplication
36

37. 37
Loop of Henle
(Countercurrent
Multiplier)
Vasa Recta
(Countercurrent
Exchange Mechanism)
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic

38. 38
Loop of Henle
(Countercurrent
Multiplier)
Vasa Recta
(Countercurrent
Exchange Mechanism)
Concentrated Medullary Interstitium
The renal medullary interstitium surrounding
the collecting ducts is normally hyperosmotic
To preserve the
hyperosmolar medullary
interstitium

39. 39
Vasa Recta: Countercurrent
Exchange

40. Vasa Recta: Countercurrent
Exchange
40

41. 41
ADH - Action
Formation of concentrated urine
Urea Reabsorption

42. 42
ADH - Action
Formation of concentrated urine
Urea Reabsorption

43. Mohammed Abdel Gawad
Thank You