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NBME 20 Answers

nbme20/Block 4/Question#28

A 78-year-old man dies of chronic congestive heart ...

Failure of the Na+–K+ pump

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submitted by xxabi(81),

Swelling of the cell (e.g., hydropic degeneration): tissue ischemia → decreased ATP production → decreased Na+/K+ ATPase and Ca2+pump activity → diffusion of Na+ and water into the cell → cellular swelling

endochondral1  can someone explain how to cross out the other choices> +1  
endochondral1  what is hydropic degneration and where do i learn about it? why is it not the loss of plasma membrane integrity? +  
shaeking  Endochondral1, I had the same question. I tried figuring it out and this is what I came up with. The CHF and congestion of the lungs is reducing the amount of oxygen getting to the renal cells. With hypoxia there is decreased aerobic resp in mitochondria with decreased ATP. Without ATPase Na builds up and water follows. As far as the loss of membrane integrity. I think it would cause cellular destruction not just hydropic changes. This is my best guess. +1  
charcot_bouchard  Membrane damage is irreversible stage of cellular injury. if membrane is damaged cell is dying & it will shrink. or totally destroyed by inflammation. they are specifically asking hydropic changes ie cellular swelling. which is the 1st sign of reversible cell injury due to failure of Na/K pump +  

 +1  upvote downvote
submitted by nwinkelmann(56),

This explains it really well with a picture:

Hydropic change = one of the early signs of cellular degeneration in response to injury that results in accumulation of water in the cell. Hypoxia/ischemia leads to decease in aerobic respiration in the mitochondria and decreased ATP production due to failure of the Na+/K+ ATPase leading to Na+ and water diffusion into the cell. Individual tubule cells appear swollen and "empty" with almost occluded lumen, glomerulus is hypercellular.