Stones

Question 1

Prevalence of kidney stones

Answer 1

11% men; 5.6% women (NEJM 2010)

Question 2

Racial distribution of kidney stones

Answer 2

white 3x black (NEJM 2010)

Question 3

Most common kidney stone composition

Answer 3

caclium oxalate with calcium phosphate

Question 4

Risk of recurrence after passage of first kidney stone

Answer 4

40% at 5 years; 75% at 20 years

Question 5

Chronic diseases associated with kidney stone formation

Answer 5

Chronic kidney disease; HTN

Question 6

What is urinary supersaturation

Answer 6

ratio of urinary calcium oxalate concentration to its solubility (or calcium phosphate or whatever). If supersaturation is below 1, crystals dissolve. If above 1, can form stones.
Calcium oxalate supersaturation is independent of urine pH
Calcium phosphate supersaturation increases s pH rises.
Calcium oxalate forms around calcium phosphate, which is why both can be treated with pH adjustment.

Question 7

Most common metabolic abnormality associated with kidney stone formation

Answer 7

Hypercalciuria- hereditary. Serum levels normal.

Question 8

DDX of recurrent calcium stones

Answer 8

Malabsorption (Caclium oxalate)
Sarcoid, gout, renal tubular acidosis; hyperthyroidism;
meds: topiramate, calcium, carbonic anhydrase inhibitor, vitamin D, alkali;
Diet

Question 9

Why doesn’t low calcium diet decrease risk of kidney stone recurrence

Answer 9

Calcium binds oxalate in the gut and hinders absorption. So oxalate more absorbed when low calcium.

Question 10

Workup of recurrent stones

Answer 10

Stone analysis
CT urogram (renal utz if concerned radiation)
Serum calcium, phosphate, Cr, Bicarb, Cl, K,(sarcoid, hyperparathyroid, RTA) UA with micro and urine cystine.
If planned to prophy: 24 hour urine collection (x 2)

Question 11

Indication to intervene Kidney stone

Answer 11

obstruction, infection, significant bleeding, persistant pain

Question 12

Size of ureteral stone requiring intervention

Answer 12

> 10mm
<5mm will generally pass
5-10 are variable. More distal are more likely to pass

Question 13

Meds to help pass ureteral stones

Answer 13

alpha adrenergic receptor blockers

calcium channel blockers

Question 14

Surgery options for ureteral stones

Answer 14

lithotripsy (shock wave vs ureteroscopy with laser)
Ureteroscopy better but more complications
ex-lap/LSC
percutaneous nephrolithotomy