Diabetes: How Does the Presence of Glucose in the Nephrons Result in the High Volume of Urine Output?
Saturday, September 27th, 2008 at
12:05 pm
Dave H asked:
Why does diabetes result in high volume of urine output?
Why does diabetes result in high volume of urine output?
I understand that with diabetes, the proximal tube/loop of henle/etc cannot get rid of all the excess glucose that is pumped through the nephrons, resulting in sugary urine. BUT, I don’t understand how the presence of glucose would increase the VOLUME of urine. Can someone explain?
I’m guessing it has something to do with osmosis but I can’t put my finger on it.
Paige, please don’t spam my thread ^_^
Tagged with: Excess Glucose • High Volume • Urine Output
Filed under: Diabetes
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Yeah I think so too.
Glucose acts as an osmotic diuretic. In diabetes, the maximum resorption capacity of the kidneys are exceeded, and glucose is spilled into the urine. The osmolarity of the filtrate is increased and water remains in the filtrate to maintain osmotic water balance. That increased water in the infiltrate means increased urine volume.
In the case you mentioned, glucose acts as an osmotic agent. As the glucose molecules pass through the nephron, it carries water because it acts as an osmotic load. Furthermore, since diabetes also injures the glomerular membrane in other ways such as causing proteins to spill into the urine, the proteins act as an osmotic load too, causing further diuresis.
The simple answer is that you want to get rid of the darn sugar in the blood. As the sugar goes into the urine, via the kidney, the water will follow to keep the solution isotonic.