The presence of large quantities of un-reabsorbed solutes in the renal tubule causes an increase in urine volume is called:
**Core Concept**
The presence of large quantities of un-reabsorbed solutes in the renal tubule leads to an increase in urine volume due to osmotic diuresis. This occurs when the kidneys are unable to reabsorb water from the tubules in response to the presence of solutes, resulting in a dilute urine.
**Why the Correct Answer is Right**
Osmotic diuresis is a mechanism by which the kidneys increase urine production in response to the presence of un-reabsorbed solutes. This can occur due to various reasons such as glucose excess in diabetes mellitus, mannitol administration, or other solutes that are not reabsorbed by the renal tubules. The presence of these solutes prevents the reabsorption of water, resulting in a dilute urine and increased urine volume.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not accurately describe the mechanism of increased urine volume due to un-reabsorbed solutes.
* **Option B:** This option is incorrect as it refers to a different mechanism of increased urine volume, which is not related to the presence of un-reabsorbed solutes.
* **Option C:** This option is incorrect as it refers to a different condition that can cause increased urine volume, but it is not related to the presence of un-reabsorbed solutes.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that osmotic diuresis can occur in various conditions, including diabetes mellitus, mannitol administration, and other solutes that are not reabsorbed by the renal tubules. This can lead to an increased urine volume and may require adjustments in fluid management and electrolyte balance.
**Correct Answer: C. Osmotic Diuresis**