Osmotic Diuresis

Question 1

Does the concentration of Na+ change significantly while traveling through the proximal tubule?

Answer 1

No, not under normal conditions

Question 2

How cool is Omid on a scale of 1 to 10?

Answer 2

Infinity. He broke the scale.

Question 3

What is osmotic diuresis?

Answer 3

When poorly permeable substances are present in the plasma and pass into the glomerular filtrate.

Question 4

What are some poorly re-absorbable substances that are present in osmotic diuresis? (2)

Answer 4

Sucrose and Mannitol

Question 5

What is another illness that exhibits the symptoms of osmotic diuresis?

Answer 5

Diabetes Mellitus

Question 6

How is diabetes mellitus related to osmotic diuresis?

Answer 6

Blood glucose levels get really high and the tubules cannot reabsorb all of it. Glucose then acts as a diuretic because water follows solute.

Question 7

Does luminal osmolality change during osmotic diuresis? Why?

Answer 7

No, because as the concentration of Na+ in the tubule lumen falls and the concentration of poorly re-absorbable solutes (ex. mannitol) in the tubule lumen rises, the osmolality stays constant.

Question 8

What is one situation where osmotic diuresis can be a good manipulation to use in the clinic involving the brain?

Answer 8

Inducing osmotic diuresis in patients with high intracranial pressure due to high fluid volumes in the brain can be prescribed a poorly re-absorbable substance (ex. mannitol) and water can be drawn out of the brain into the urine, decreasing pressure in the brain.

Question 9

What are some ways intracranial pressure can rise in the brain? (5)

Answer 9

1. Expanding tumor
2. Abscess
3. Hematoma
4. Hemorrhage
5. Edema

Question 10

What is another benefit of inducing osmotic diuresis aside from reducing intracranial pressure?

Answer 10

Mannitol and other poorly re-absorbable substances help to reduce the risk of radiocontrast-induced acute renal failure in those patients that are injected with radioactive dyes.

Question 11

What are the 2 types of osmotic diuresis?

Answer 11

1. Solute diuresis

2. Water diuresis

Question 12

What is the difference between solute and water diuresis?

Answer 12

Solute diuresis is defined by larger than normal urine volume that is rich in solutes. Water diuresis has large urine volumes that is very dilute and unconcentrated in solutes.