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NBME 22 Answers

nbme22/Block 2/Question#42

A 75-year-old woman has taken 12 over-the-counter ...

Plasma renin activity

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I think the increase in plasma renin activity with NSAIDs has to do with inhibition of efferent artery dilation by prostaglandins (PGE2), since that's what NSAIDs do by inhibiting COX. This decreased renal blood flow leads to RAAS activation to conserve water and ultimately renin increases.

htballer55  Afferent artery dilation* +4  
link981  There is decreased afferent renal artery dilation (less blood flow) leads to increased renin release from the juxtaglomerular cells (located near the afferent artery) to try to increase blood flow. I got it wrong but after reviewing saw my idiotic mistake. +1  

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submitted by lilamk(5),

I am so confused! The only logic I could come up w is that NSAIDs decrease dilation of afferent arteriole so this more constricted arteriole is interpreted as decreased blood flow and Renin increases? My issue w this is that when I google it and search UW for this renin affect nothing comes up only article I could find actually contradicts it and says renin would DECREASE from NSAIDs leading to the hyperkalemia we sometimes see ...

Any thoughts would be helpful! Thanks geniuses.

generic_login  I used that reasoning to pick C, but in looking it up now it seems like you are right ... There appear to be a bunch of mistakes on this test, and it’s not giving me a lot of confidence for the real thing. +  
mee48  I think it is because NSAIDs inhibit the local prostaglandin (PGE2) in afferent arteriole —-> less AA dilation —-> stimulation renin release. I think my reasoning came from sketchy pharm nsaid video but I can’t 100% remember +  
keycompany  NSAIDs constrict the afferent arteriole. ​ A. GFR would decrease due to decreased renal blood flow. B. Renal Blood flow would decrease. C. Renin would increase due to renal hypoperfusion. D & E. PGE2 and TXA would decrease (by MOA of NSAIDs). +1  
fallot4logy  UW says that Nsaids is one o +  
fallot4logy  UW says that Nsaids is one of the 5 drug categories that is able to cause hyperkalemia.Specificly ,Nsaids lower PG andrenin secretion .PGE2 stimulates JG cells to secrete renin...(how can i delete my previous unfinished message,lol?) +  

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submitted by privwill(4),

Step by Step:

  1. NSAIDs block prostaglandins which normally dilate the afferent arteriole
  2. Constriction = decreased blood flow to glomerulus (decreased GFR; decreased RPF)
  3. Decreased blood flow leads to activation of RAAS system
  4. Activation of RAAS leads to increased renin

Why not the other ones:

A. GFR will be decreased due to constriction of the afferent
B. Renal blood flow will be decreased due to vasoconstriciton of the afferent
D & E. Production blocked by NSAID so wouldn't even be around