## **Core Concept**
Glomerulonephritis is a group of kidney diseases characterized by inflammation of the glomeruli, which are crucial for filtering waste and excess fluids from the blood. The condition can lead to various complications, including edema (swelling), due to the kidneys' reduced ability to filter and manage fluid balance.

## **Why the Correct Answer is Right**
The correct answer, **C. Loss of albumin through urine**, explains that in glomerulonephritis, the inflammation damages the glomeruli, compromising their filtration barrier. This damage allows albumin, a protein that is usually retained in the blood vessels, to leak into the urine. Albumin helps keep fluid in your blood vessels so it doesn’t leak into other tissues. When albumin levels in the blood decrease (a condition known as hypoalbuminemia), fluid can leak out of blood vessels into the interstitial space, causing edema. This mechanism is a direct consequence of the nephrotic syndrome, which can be a manifestation of severe glomerulonephritis.

## **Why Each Wrong Option is Incorrect**
- **Option A: Increased sodium and water retention** is a consequence of nephritic syndrome, which can also present with edema but through a different mechanism. In nephritic syndrome, there's an acute reduction in kidney function leading to fluid overload and hypertension, not primarily due to loss of albumin.
- **Option B: Lymphatic obstruction** is not directly related to the pathophysiology of glomerulonephritis. While lymphatic obstruction can cause localized edema, it is not a primary cause of edema in the context of glomerulonephritis.
- **Option D: Increased capillary hydrostatic pressure** can contribute to edema in conditions like heart failure but is not the primary cause of edema in glomerulonephritis.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the nephrotic syndrome, characterized by heavy proteinuria (>3.5 g/1.73 m^2/24 hr), hypoalbuminemia, hyperlipidemia, and edema, can be a complication of glomerulonephritis. The loss of albumin through the urine is a hallmark, leading to edema.

## **Correct Answer: C. Loss of albumin through urine**