A 42-year-old woman with nephrotic syndrome is given 40g albumin IV but shows minimal clinical improvement. The most appropriate physiological explanation for the refractoriness to albumin infusion is:
- A Albumin undergoes rapid hepatic catabolism before distributing
- B Albumin redistributes exclusively into the lymphatic compartment
- C Increased glomerular permeability allows infused albumin to be rapidly lost in urine, and low interstitial oncotic pressure gradient minimizes transcapillary effect ✓
- D Tubular reabsorption of albumin is saturated causing massive albuminuria
Explanation
In nephrotic syndrome, albumin is continuously lost in urine due to increased glomerular permeability; infused albumin is similarly filtered and excreted rapidly. Additionally, in nephrotic syndrome, the interstitial albumin concentration has also fallen (due to chronic protein loss), reducing the oncotic pressure gradient across capillaries. Per Starling forces, net fluid movement depends on the oncotic pressure difference between plasma and interstitium—when interstitial oncotic pressure is also low, the gradient driving fluid back into the intravascular space is less than expected. Tubular reabsorption of albumin occurs but is not the primary explanation for refractoriness.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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