paganini
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I have another question on renal physiology, after seeing the previous answers to my questions in the forum I think that you really need to review this area.
A primary glomerular disease will tend to lower GFR by decreasing the surface area available for filtration. GFR will:
A. Be a good stimate of severity
B. Understimate severity
C. Overstimate severity
D. First decrease and later increase, therefore not reflecting the severity
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| paganini
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Ah, and please give an explanation, anyone can guess...
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| drhouse
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i think its B.
under estimate of severity
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| paganini
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As I said beore, you need to give an explanation. Otherwise you might be guessing.
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| ssrpk
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filtration across any membrane is based on starling's principle and in case of GFR its no different, however during the transit of blood flow through the glomerular capillaries, the equilibirum across the GBM occurs before the transit of blood flow b/w afferent and efferent arterioles completes, in other words the GFR is perfusion limited, partly because as the filtration occurs plasma oncotic pressure increase which will impede the filtration forces. Keeping this in view the severity of glomerular disease can not accurately correlated with the decrease in GFR.
answer is B.
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| paganini
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Interesting observation, however perfusion-limited is a concept for gas exchange not solutes or liquids that I don't think could be apply here.
The answer is B, but the correct explanation is that in a glomerular disease the fall in GFR will lead sequentially to decreased fluid delivery to the macula densa, activation of tubuloglomerular feedback, afferent arterilar dilation, and rise in intraglomerular pressure that will return GFR and macula densa flow toward normal. Thus, estimation of GFR will UNDERSTIMATE the severity of glomerular disease, since substantial damage can occur without any significant fall in GFR.
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| ssrpk
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yes ofcourse this perfusion limited concept in this case is more of an analogy here, but yeah its tubuloglomerular feedback which will conserve the GFR....gotta fire more neurons in my brain.
good work paganini, keep it up 
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