USMLE Renal 5: Nephron Tubular Defects

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/ lymed Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day.
Follow along with First Aid, or with my notes which can be found here: www.dropbox.co...
This video is on tubular defects of the nephron! We went over the anatomy and the physiology (with some pharmacology thrown in), now it's finally time for some pathology. Tubular defects are either inherited defects or acquired defects in your nephron. It's separated into where it affects your nephron!
PCT: Fanconi syndrome is a generalized reabsorption defect in your proximal convoluted tubule. This can lead to acidosis due to decrease reabsorption of bicarbonate. Causes include hereditary, toxins, ischemia and drugs.
Loop of Henle / Thick ascending limb: Bartter syndrome, an autosomal recessive defect here affects the Na/K/Cl transporter and looks identical to loop diuretic use. This massive diuresis can lead to contraction alkalosis by inducing the RAAS pathway.
DCT: Gitelman syndrome is a defect in the Na/Cl channel in the distal convoluted tubule. Looks identical to thiazide diuretic use and can manifest itself as increased calcium reabsroption.
Collecting duct: Liddle syndrome is a GAIN of function of the ENAC channel. Recall this channel reabsorbs sodium at the expense of potassium and H+. Thus, it leads to hypertension, hypokalemia and alkalosis. This looks like hyperaldosteronism HOWEVER your labs will show decreased aldosterone due to negative feedback.
The last one is called Syndrome of Apparaent Mineralcorticoid Excess. This is due to a deficiency of 11B-hydroxysteroid dehydrogenase which leads to a buildup of cortisol which can act on our aldosterone receptor. It presents the same as Liddle syndrome even down to the labs. Know that licorice (liquorice) has a substance called glycyrrhetic acid that blocks this enzyme. Know this well!

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Much love, -Mike

[@lilahsanduby1424]

I don't know what it is about the way you explained it, but it was perfect for me to finally understand these syndromes instead of memorizing! Renal NBME in a few days. Thanks!

[@XxmoondustxX]

I know you said not to use uworld for a gauge on how well I will do, but your videos are making my scores much higher now. thank you so much :)

[@monye9963]

All of your videos are great, thanks 👍

[@ShanilR]

You sir are a legend

[@samg893]

THANK YOU SO MUCH !!!! The All Might to my Midoriya

[@azamatabdyraimov811]

thank u

[@CurlyGirlMD]

great video!!

[@sharmilasenthamizselvan1846]

Simply amaging👌

[@MafiaDiesel]

You failed to mention why bartter result in hypercalciuria and gitelman result in hypocalciuria

[@qny1286]

I thinktThe bartter and gielman look identical to that loop and thiazide diuretics, which have been mentioned in nephron parmacology.

[@shwetakalita]

i was hoping a little more details would be mentioned.

[@Michelle-rc2xv]

At least you can speak well. But wrong people have died of gitelman I have it. Gitelman is never explained enough. Tired of explaining GS to doctors and nurses