Transcript
URINE OSMOLARITY
PBL TUTOR(Group-IV)Dr.Rupesh Shrestha
PresenterLalit karki
Case correlation
• Sudhir,13 years boy presents with puffy face,haematuria,frothy urine and his urine amount has markedly decresed.
• He was primarily confirmed as the case of acute on chronic renal failure.
• Dr. Anish wanted to do urine for osmolarity and fractional excretion of sodium.
Introduction
• Urine osmolarity is the number of dissolved particles per unit of water in the urine.
• Urine concentration
• An index of the concentration of osmotically active particles,particularly chloride, sodium, urea, glucose and potassium in the urine.
• Minimum urine concentration:50 - 70 mOsm / L
• Maximum urine concentration :1200 - 1400 mOsm / L
Excreting a dilute urine
• Decrease water reabsorption
• Continue electrolyte reabsorption
Mechanism:•decreased ADH release and reduced water permeability in distal and collecting tubules
Excreting a concentrated urine
• Continue electrolyte reabsorption• Increase water reabsorption
Mechanism: • Increased ADH release which increases water
permeability in distal and collecting tubules• High osmolarity of renal medulla• Countercurrent flow of tubular fluid
Role of ADH
Counter current multiplier system
• High permeability of thin descending
limb to water.
• The active transport of Na and Cl out of thick ascending limb
• Inflow of tubular fluid from the proximal tubule with outflow into the distal tubule.
Vasa recta-counter current exchangers
• Supply medullary parts
• Prevents rapid dissipation of medullary hyperosmolarity
• On descending part Nacl and urea is reabsorbed.and water is secreted
• On ascending part NaCl and urea are secreted into the interstitium, while water is reabsorbed.
Urea concentrating medullary intestitium
• Contribution is about 40-50%
• 4 urea transporters (UT1-4)
• UT-A1 and UT-A3 is activated by presence of ADH
• Amount of urea in urine and medullary interstitium depends on filtration.
Concentrated urine
Concept of…
• Free Water Cleareance
To quantitate the gain or loss of water by excretion of a concentrated or dilute urine.
C(H2O)=V-(Uosm x V)/Posm
-ve for hypertonic urine
+ve for hypotonic urine• Osmotic diuresis
Presence of unreabsorbed solutes increase the urine volume.
• Relation of urine concentration to GFR
Decrease in GFR increase the urine concentration and vice-versa.
References
• Textbook of medical physiology, Guyton and Hall,12th edition
• Ganong’s Review of medical physiology,23rd edition
Group members:-Aliza Hamal-Anup Bhatta-Bijay Shrestha-Bikash Sapkota-Lalit Karki-Prabesh Raghubansi-Prayash Panthi-Suchana Sharma-Sujata Pandey-Sunder Chapagain
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