Amy Yau Profile picture
Dec 9, 2020 17 tweets 9 min read Read on X
🤔🔬Why are kidney stones so interesting?
Because the 🔑tubules > glomeruli

Disagree if you like, but it’s true.

A short thread on some mechanisms associated with calcium stones...

#nephtwitter #FOAMed #MedEd #uronephrology #kidneystone #nephrolith Image
Which is a risk factor for calcium oxalate stones?
Correct!

Risk factors for calcium oxalate stones classically include 📌hypercalciuria and 📌hyperoxaluria along with 💧low urine volume.

#Hypercalciuria can stem from a LOT of different causes and clinical settings. The most common in adults is idiopathic. Image
There is debate about whether hyperuricosuria can serve as a nidus for CaOx stones.

pubmed.ncbi.nlm.nih.gov/18059457/

Hypocitraturia and high urine pH (>7.0) tend to be stronger risk factors for CaP stones (we’ll discuss that later!)

Photo courtesy of @porische ImageImage
What is the link between hypercalciuria and salt (🧂NaCl) intake?
Right! ⬆️More NaCl --> ⬆️ Urine Calcium

❓How does this happen?!
💡The kidney has the answer.

In the proximal tubule, 🦴Ca reabsorption is linked with 🧂Na reabsorption.

With more 🧂Na reabsorption, 💧H2O follows paracellularly and “drags” 🦴Ca along with it. #solventdrag Image
In the DCT, ⬆️increased 🧂Na delivery reduces the stimulus for Na/Ca exchange on the basolateral membrane

This results in ⬇️less Ca influx via TRVP5 channel.

🌟If you understand this, you understand why normal saline is effective in hypercalcemia.

pubmed.ncbi.nlm.nih.gov/27009338/ Image
Now, what is the link between hypercalciuria and 🍋acidosis?
Essentially besides leaching Ca from 🦴bones, acidosis 🖇️uncouples Na reabs from Ca reabs in the DCT.

In acidosis,
📌PT: Na and Ca reabs linked
📌DCT: ⬇️LESS Ca influx due to inhibition of TRPV5 and reduced TRPV5 mRNA due to H+

🌟Net effect: ⬆️more UrCa

pubmed.ncbi.nlm.nih.gov/27468975/ Image
In the work up of hypercalciuria in calcium stone formers, it is important to consider 🧬monogenetic causes (esp in pediatrics)

pubmed.ncbi.nlm.nih.gov/15689405/
pubmed.ncbi.nlm.nih.gov/18446382/
pubmed.ncbi.nlm.nih.gov/18836558/ Image
When the initial screen and/or work up are negative, we’re stuck with 🤷‍♀️idiopathic hypercalciuria.
❓You may ask, should you counsel patients to reduce Ca intake to reduce risk of Ca stones and hypercalciuria?!
Correct, you should not.

Calcium intake has been found to reduce risk of stone formation likely by binding intestinal oxalate and reducing oxalate absorption.

pubmed.ncbi.nlm.nih.gov/8441427/ Image
But, (a) #PUSHing fluid💧 increases urine volume (ie lower the concentration of urinary calcium and reduce the relative supersaturation)

Coffee, tea, wine, beer, high citrate juices seem ok.👌


pubmed.ncbi.nlm.nih.gov/23676355/
Encourage low salt diet (UrNa goal < 80-100 mEq per day) and consider thiazide diuretics.

pubmed.ncbi.nlm.nih.gov/20042524/ Image
Hope that helps the next time you have a calcium stone former with hypercalciuria.

Suggestions/comments are always welcome! #uronephrology #kidneystone #nephrolith

Next up?
Lol I just realized answers A and B are the same. Why didn't anyone say anything?!!! #babybrain

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More from @amyaimei

Dec 2
💊 Hydralazine (Hz) was first introduced to the market in 1951.

The first case of Hz autoimmunity was in 1953, and the first series of Hz induced ANCA vasculitis overlapping with lupus was in 1984!

But, who is really at high risk and what are the outcomes? #nephsky #nephtwitter
🤔 Determining if Hz is the cause of glomerulonephritis can be challenging. But there may be a few clues.

1. multiple autoantibodies and anti-histone
2. presence of VERY high ANCA titers
3. overlap with vasculitis and lupus on biopsy
🔎 Presence of autoantibodies are common.
💉Up to 50% on Hz have +ANA, and 27% have +antihistone. But, few will develop clinical sx.

In the Columbia series, Hz-V pts
-98% ANCA
-39% dual c/pANCA
-89% ANA
-98% antihistone

buff.ly/3ZiDAh4
buff.ly/4eQzQZT
Read 13 tweets
Jan 12, 2023
🧵Let's talk hypernatremia

So often we discuss the correction rate of hyponatremia, but what about hypernatremia? #medtwitter #nephtwitter #meded

🧐What is your correction rate for chronic hypernatremia?
Older guidelines recommend a correction of no more than 8-10 mEq/dL in 24 hours borrowed from pediatric literature

“Fast” correction is generally considered to be more than 12 mEq/dL per day

pubmed.ncbi.nlm.nih.gov/20412412/
There are some cases in which you may tolerate permissive hypernatremia, but the evidence behind its benefits we can discuss another day.

Ahem #neurocriticalcare looking at you….
Read 8 tweets
Sep 13, 2021
⁉️What is the difference between mineral and organic acidosis?
⁉️Why does one cause more hyperkalemia than the other?

Join me on this 🐇🕳️rabbit hole #tweetorial on metabolic acidosis and it's effect on potassium.

📊To start, which type of acidosis causes more hyperkalemia?
Metabolic acidosis is defined as a ⬇️low pH due to a ⬇️decrease in bicarbonate extracellularly

💎Mineral acids (aka inorganic acids) are “synthesized from earth minerals.”

🥬Organic acids are metabolized by the cell and occur naturally.
Both can have a 🩸high anion-gap...just depends on anion accumulated.

💎Mineral acids are often (not always) a hyperchloremic normal anion gap metabolic acidosis

Think of 🥬organic acidosis as high anion gap metabolic acidosis (though not always true)
Read 19 tweets
Feb 6, 2021
The 🎩baron of kidney stone prevention has been citrate supplementation.

📖Let’s quickly review hypocitraturia and its relationship to stones.

Where is most of your citrate reabsorbed?
Which condition is ❌NOT associated with hypocitraturia?
Before we get into the #tweetorialanswers, let’s establish that hypocitraturia is a risk factor.

Previous data show around 📊46-60% of stone formers have hypocitraturia.

In Ca stone formers, hypocitraturia is the 📊sole abnormality in 10%.

pubmed.ncbi.nlm.nih.gov/32715836/
Read 13 tweets
Jul 28, 2020
Which is your favorite hypertension syndrome #eponym?
So a short #VisualMnemonic quiz thread on some of the #HTNsyndromes I can never remember🤔 (list is not all inclusive)

Some are better than others.🤷‍♀️If nothing else, hope it's fun.🎉
#timetostudy #boardprep
A young man comes to you with high blood pressure since teen years.

K is high, Bicarb is low.

What is the mechanism of his HTN?
(MC = mineralocorticoid)
Read 10 tweets
Jun 2, 2020
Is being pregnant magical🌟?
I’m not so sure, but let’s give OB a Nephrology twist. 🍼🐣

#nephtwitter #obtwitter #endotwitter #reallythekidneysarethecoolest #medtwitter #tweetorial

Why do you gain weight when you are pregnant?
The average woman ⬆️gains a plasma volume of 1250 mL (an increase of 45-55%).

Significant lab values changes include
- Plasma Na ⬇️reduced by ~ 5 mmol/L
- Plasma osmolality ⬇️reduces by ~10 mOsm/kg
- Cr ⬇️decreases by 0.3 mg/dL due to increased GFR among other changes ImageImage
There is an entire milieu of hormone changes during pregnancy🤰. Some are natriuretic and some are anti-natriuretic.

Sources: Comprehensive Clinical Nephrology Chapter 42, pubmed.ncbi.nlm.nih.gov/22879432 ImageImage
Read 18 tweets

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