**Question:** All the following are signs of overhydration except

A. Increased urine volume and frequency
B. Dry mucous membranes
C. Decreased urine concentration
D. Dark yellow urine

**Core Concept:** Overhydration refers to an excessive intake or retention of fluids, leading to an imbalance in electrolyte concentrations within the body fluids. This can result in various clinical manifestations, including those listed in options A, C, and D, which are all signs of overhydration due to increased water intake or retention.

**Why the Correct Answer is Right:** Option B, "Dry mucous membranes," is not a sign of overhydration. Dry mucous membranes (e.g., in the mouth) are typically associated with dehydration, not overhydration. Dehydration results in reduced blood volume and decreased perfusion to mucous membranes, causing them to become dry.

**Why Each Wrong Option is Incorrect:**

A. Increased urine volume and frequency: These signs indicate that the kidneys are attempting to eliminate excess fluid by producing more urine. Overhydration can lead to increased urine output as the kidneys try to conserve sodium and balance the extracellular fluid volume.

B. Decreased urine concentration: Overhydration causes a decrease in urine concentration due to increased water in the urine. This occurs because overhydration dilutes the solutes (such as sodium and urea) in the blood, leading to a reduced concentration of these substances in the urine.

C. Dark yellow urine: Dark yellow urine is a result of the presence of urochrome (a waste product of hemoglobin breakdown) and reduced fluid volume. In overhydration, the increased water content in urine dilutes the urochrome, leading to lighter-colored urine.

D. Dark yellow urine: This option aligns with the correct answer (C), as increased fluid volume due to overhydration dilutes the urochrome, resulting in lighter-colored urine.

**Clinical Pearl:** Monitoring urine color can be a useful tool for assessing hydration status. In medical practice, dark yellow urine indicates appropriate hydration, while lighter colors (e.g., straw-colored) suggest overhydration.