## **Core Concept**
Nephritic syndrome is characterized by inflammation of the glomeruli, leading to impaired renal function. The core concept here involves understanding the pathophysiological changes that occur in nephritic syndrome, particularly how they relate to fluid balance and edema formation.

## **Why the Correct Answer is Right**
The correct answer, . (or "increased capillary hydrostatic pressure due to sodium and water retention"), is right because in nephritic syndrome, the glomerular injury leads to a decrease in glomerular filtration rate (GFR). This decrease triggers the renin-angiotensin-aldosterone system (RAAS), resulting in sodium and water retention. The retained fluid increases blood volume, which in turn elevates capillary hydrostatic pressure. According to Starling forces, an increase in hydrostatic pressure favors fluid movement out of the capillaries into the interstitial space, causing edema.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is incorrect because nephritic syndrome is not primarily associated with significant loss of albumin through the urine (as seen in nephrotic syndrome), which would lead to decreased oncotic pressure and edema.
- **Option B:** is incorrect because, although lymphatic obstruction can cause edema, it is not a primary mechanism in nephritic syndrome.
- **Option C:** is incorrect because decreased capillary oncotic pressure is more characteristic of nephrotic syndrome, not nephritic syndrome.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the edema in nephritic syndrome is primarily due to sodium and water retention leading to increased hydrostatic pressure, distinguishing it from nephrotic syndrome where edema is mainly due to hypoalbuminemia.

## **Correct Answer: D. increased capillary hydrostatic pressure due to sodium and water retention**