Thread by @nefron1310

Medullary Sponge Kidney

It's out there if you just know what you are looking for

Take a journey with me to find out more 👇

@NSMCInternship @ASPNeph @IPNA_PedNeph #tweetorial #Nephtwitter #medtwitter

17 yr woman with a long standing history of recurrent UTI’s. Normal kidney function and electrolytes. US showed normal sized kidneys with bilateral nephrocalcinosis with medullary cysts.
What is your top differential?

Before we get to the answer, first what is on your differential for nephrocalcinosis?
Depends on your serum calcium level, right?
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Several conditions can cause cysts in the kidney.
⚡️ But when you see cysts and nephrocalcinosis, think MSK
⚡️Location of the cyst whether cortical or medullary helps to differentiate MSK from other cystic kidney diseases

The top of my differential would be MSK!
👇

Let's talk about medullary sponge kidney also called Lenarduzzi-Cacchi-Ricci syndrome
⚡️ Mostly sporadic, 5% AD inheritance
⚡️ Typically adult onset, 1/5000 incidence
⚡️ F>M
academic.oup.com/ndt/article/28…
sciencedirect.com/science/articl…

Is it sporadic or developmental?

👉 GDNF-RET

🔶Disruption in GDN/RET gene associated with pre-calyceal dilation, proximal tubular defects, repolarisation of DCT cells
🔶Not all MSK cases have GDNF variants
🔶 5% familial, majority sporadic

cjasn.asnjournals.org/content/5/7/12…

What causes kidney stones in MSK?

largest risk factors
1⃣ Urinary stasis
2⃣ Hypocitraturia

pubmed.ncbi.nlm.nih.gov/11382681/

What is the gold standard for the diagnosis of MSK?

IV pyelography (IVP) remains the gold standard

🔥Pathognomonic sign 🔥

“bouquet of flowers💐” or "paint brush appearance🖌️" due to collection of contrast in dilated papillary ducts

Why is MSK under-diagnosed now?
♦️ IVP is obsolete now, particularly for kidney stones
♦️ We might be missing the diagnosis of MSK as IVP is very sensitive test for detecting dilated ducts seen in MSK
♦️ It is replaced by multi-detector CT scan which is less sensitive

What other imaging modality can you use?
🔥CT urography offers visualization of stones in early phase and medullary cysts in delayed phase

karger.com/Article/FullTe…

Lets talk about management goals next
✍🏾Rx hypercalciuria, prevent kidney stones
✍🏾Potassium citrate prevents stone formation and helps with dissolution.
✍🏾Thiazide diuretics to Rx hypercalciuria
✍🏾Urologic intervention for recurrent obstructing stones

cjasn.asnjournals.org/content/5/9/16…

What is the long term outcome with MSK?
It is generally benign, some patients can develop-
●Recurrent pyelonephritis with scarring
●Struvite stones
●Secondary hyperparathyroidism
●⬇️ bone mineral density
●Infrequently progresses to kidney failure

Last poll to recap🔢

Why do we not see many Medullary Sponge Kidney these days?

✅All of the above

In summary,
💐Cysts and kidney stones, think MSK
💐Sporadic gene mutations may be assoc with MSK
💐CT urography can be done when there is strong clinical suspicion

Goodbye Y'all for now! Stay Safe!
Many Thanks to @NSMCInternship @amyaimei @drM_Sudha @nephro_Sparks @swastithinks and all my mentors and fellow interns on Tetrapod #NSMC2021