Question
What is the pathology of edema in nephrotic syndrome
| A. |
Reduced plasma protein
|
| B. |
Sodium and water retention
|
| C. |
Increased venous pressure
|
| D. |
Hyperlipidemia
|
Show Answer
|
Correct Answer » A
Explanation
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|
The fundamental mechanism is loss of albumin in urine, causing ↓ plasma oncotic pressure.
This ↓ oncotic pressure leads to fluid shifting from the intravascular space to interstitial space, causing edema.
This process is known as the underfill theory, the classical and most accepted exam answer.
Explanation of Other Options:
– Option B: Sodium & water retention aids edema but is a *secondary mechanism*.
– Option C: ↑ venous pressure occurs in heart failure, not nephrotic syndrome.
– Option D: Hyperlipidemia is present but does not cause edema.
Important Clarification (Conceptual Insight):
Two mechanisms cause edema in nephrotic syndrome:
– Underfill theory: Hypoalbuminemia → edema (primary event)
– Overfill theory: Primary renal sodium retention
Despite this, MCQs commonly accept hypoalbuminemia as the primary cause.
Edema in Nephrotic Syndrome
Primary mechanism:
– Albumin loss → ↓ oncotic pressure → fluid shifts to interstitium
Secondary mechanism:
– RAAS activation → sodium & water retention
