**Core Concept**
Nephritic syndrome is characterized by inflammation of the glomeruli, leading to hematuria, proteinuria, and edema. The pathophysiology involves damage to the glomerular basement membrane, resulting in impaired glomerular filtration and fluid retention.

**Why the Correct Answer is Right**
The primary cause of edema in nephritic syndrome is hypoalbuminemia due to proteinuria, not because of increased sodium reabsorption or fluid overload as seen in nephrotic syndrome. The kidneys' inability to filter waste and excess fluids properly leads to fluid accumulation in the interstitial spaces, resulting in edema. The glomerular damage disrupts the normal balance between filtration and reabsorption, causing edema.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it may be a cause of edema in other conditions, such as heart failure or liver cirrhosis, but not specifically in nephritic syndrome.
**Option B:** This option is incorrect because it is a characteristic of nephrotic syndrome, not nephritic syndrome.
**Option C:** This option is incorrect because it is a possible complication of nephritic syndrome, but not a primary cause of edema.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between nephritic and nephrotic syndrome, as their pathophysiology and clinical presentations differ significantly. Nephritic syndrome is typically associated with hematuria, hypertension, and reduced kidney function, whereas nephrotic syndrome is characterized by massive proteinuria, hypoalbuminemia, and hyperlipidemia.

**Correct Answer: D.**