Kidney stones and Onconephrology

Question 1

Adult athletic male with kidney stones? cause?

Answer 1

High salt and high protein diet> Hypercalciuria and Hypocitrateuria

Question 2

What is the primary determinant of uric acid stones? How to prevent?

Answer 2

-Acidic urine, urine pH means not enough urine buffers>
urate converted to uric acid> precipitates
-Are they eating lot of protein> acid?
-Weight reduction if obese and alkalinize urine( K citrate)
-no Allopurinol right away
-urine has to be alkaline throughout. Even early morning drop in urine pH sufficent to form stones. Moving K citrate to bedtime, adding Diamox bedtime some tricks to alkaline urine round the clock

Question 3

Pathogenesis of Caphosphate stones in dRTA

Answer 3

• alkaline urine+ hypercalciuria+ hypocitraturia
• impaired urine acidification means HPO4 is not converted to H2PO4
• Calcium binds to phosphate
• Rx is challenging, K citrate very carefully because can increase urine pH and make things worse

Question 4

Tumor lysis syndrome, role of urine alkalinization?

Answer 4

fallen out of favor due to

• increased precipitation of Caphos stones
• usually those patients on Allopurinol and increased xanthine which also precipitates

Question 5

Where is VEGF produced and where are VEGF receptors?

Answer 5

Produced by podocytes and receptors are in glomerular endothelial cells, mesangium and peritubular cappilaries.

Question 6

What is the indication of hemodialysis in hypercalcemia?

Answer 6

Hypercalcemia, oliguria-anuria and severe renal failure. Do low calcium dialysis as opposed to Bisphonates

Question 7

Mechanisms of AKI in hypercalcemia?

Answer 7

• vasoconstriction of afferent arterioles
• salt wasting ( Ca sensing receptor on basolateral of TAL and shuts off ROMK and NKCC on apical)
• water wasting loss of medullary tonicity ( fails to insert aquaporins on collecting duct)
• nephrocalcinosis

Question 8

HTN, Hypokalemia and metabolic alkalosis in a patient of small cell lung cancer

Answer 8

Excess ACTH from tumor> increased production of cortisol from adrenal gland and moderately increased aldosterone
cortisol is excess and even 11 beta hydroxysteroid dehydrogenase can’t prevent much from conversion> excess mineralocorticoid activity

Question 9

What are the types of TMA in cancer chemotherapy?

Answer 9

1) Type I ( Gemcitabine/ Mitomycin): cumulative, slow, more permanent and irreversible, can’t rechallenge
2) Type II( VEGF inhibitors): can occur any time, not dose related, may be rechallenged

Question 10

Cystine stones, what to check in urine?

Answer 10

retinol binding protein (LMW protein) in urine

Question 11

Increased urine alkali and ammoniagenesis

Answer 11

taking k citrate for stones> alkali> decrease urine ammonium

Question 12

Calcium oxalate stones in Crohn or gastric bypass patients, what recs will you give?

Answer 12

low fat diet and calcium citrate

Question 13

Young patient with h/o kidney stones, bilateral nephrocalcinosis, imaging of choice?

Answer 13

-CT urogram for dx of Medullary sponge kidney