Medical Therapy of Nephrolithiasis

Question 1

What does the screening evaluation consistent of in a patient newly diagnosed with kidney or ureteral stones?

Answer 1

Guideline 1: A thorough history and physical examination, dietary history, close look at their medications, serum chemistries and UA (both macro and micro)/UC

Question 2

What are stone provoking medications and dietary supplements?

Answer 2

probenecid, some protease inhibitors, lipase inhibitors, triamterene, chemotherapy, vitamin C, vitamin D, calcium and carbonic anhydrase inhibitors such as topiramate, acetazolamide, and zonisamide

Question 3

What health conditions are associated with an increased risk of stones?

Answer 3

Increased risk of stones: obesity, hyperthyroidism, gout, renal tubular acidosis (RTA) type 1, diabetes mellitus type 2, bone disease, primary hyperparathyroidism

malabsorptive gastrointestinal states due to bowel resection, bariatric surgery or bowel or pancreatic disease

Question 4

When should you obtain serum intact parathyroid hormone (PTH)?

Answer 4

Guideline 2: when serum calcium is high or high normal.

Note: Measurement of vitamin D levels may additionally be helpful as low vitamin D levels may mask primary hyperparathyroidism, or contribute to secondary hyperparathyroidism

Question 5

What different stone analysis should clue you into different etiologies?

Answer 5

Guideline 3: Stone composition of uric acid, cystine or struvite implicates specific metabolic or genetic abnormalities

Calcium phosphate stone composition is more likely to be associated with certain medical conditions or medications, such as RTA Type 1, primary hyperparathyroidism, medullary sponge kidney and the use of carbonic anhydrase inhibitors.

Question 6

How do you access for stone burden?

Answer 6

Guideline 4: Clinicians should obtain and review available imaging studies to quantify stone burden

Question 7

Who should get additional metabolic testing (24H urine study)?

Answer 7

Guideline 5: recurrent stone formers, interested first time stone formers, pediatric stone formers

Also “high risk” stone formers: family history of stone disease, malabsorptive intestinal disease or resection, recurrent urinary tract infections, obesity or medical conditions predisposing to stones and solitary kidney persons

Question 8

What is “metabolic testing” for recurrent and high risk stone formers?

Answer 8

Guideline 6: one or two 24-hour urine collections obtained on a random diet and analyzed for total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium and creatinine

Question 9

Should you do a fast and oral calcium load test to distinguish among types of hypercalciuria

Answer 9

Guideline 7: NO

Question 10

What minimum urine output volume should be the target for all stone formers?

Answer 10

Guideline 8: At least at least 2.5 liters (85 oz) per day (note: this is urine output- intake needs to be higher in order to achieve this). This can be easily monitored on a 24 hour urine study.

Question 11

What dietary changes should you counsel patients with calcium stones and relatively high urinary calcium?

Answer 11

Guideline 9: limit sodium intake and consume 1,000-1,200 mg per day of dietary calcium- this is a normal amount of dietary calcium (not on supplements but also not shying away from calcium food)

Sodium increases urinary calcium excretion. The Panel supports a target of ≤100 mEq (2,300 mg) sodium intake daily. This goal is difficult to achieve.

Question 12

What dietary changes should you counsel patients with calcium oxalate stones and relatively high urinary oxalate to make?

Answer 12

Guideline 10: limit intake of oxalate-rich foods (and stop vitamin C supplements) and maintain normal calcium consumption (however, persons with enteric hyperoxyalate absorption such as gastric bypass should be counseled to increase their calcium intake with meals to absorb the oxalate and poop it out)

Question 13

What dietary changes should you counsel patients with calcium stones and relatively low urinary citrate to make?

Answer 13

Guideline 11: increase their intake of fruits and vegetables and limit non-dairy animal protein

Question 14

What dietary changes should you counsel patients with cystine stones to make?

Answer 14

Guideline 13: Oral intake of at least 4L of water a day and limit sodium and protein intake

Question 15

What dietary changes should you counsel patients with calcium or uric acid stones and relatively high urinary uric acid to make?

Answer 15

Guideline 12: limit intake of non-dairy animal protein (fish, seafood, poultry and red meats, “Anything with a face”)

Question 16

Who should you offer thiazide diuretics?

Answer 16

Guideline 14: high or relatively high urine calcium and recurrent calcium stones

Note: these are: hydrochlorothiazide (25mg orally, twice daily; 50mg orally, once daily), chlorthalidone (25mg orally, once daily), and indapamide (2.5mg orally, once daily)

check potassium and calcium while on this medication (BMP)- causes hypokalemia and glucose intolerance

Note- this only works if the patient also does sodium restriction

will cause hypercalcemia if a person has an undiagnosed hyperparathyroidism

Question 17

To whom should you offer potassium citrate?

Answer 17

Guideline 15: patients with recurrent calcium stones and low or relatively low urinary citrate

Check potassium- frequent abdominal side effects with hyperkalemia

Alternatives to increase urinary pH: sodium bicarbonate, sodium citrate

Question 18

To whom should you offer allopurinol?

Answer 18

Guideline 16: recurrent calcium oxalate stones who have hyperuricosuria and normal urinary calcium

NOT uric acid stones- remember, they need urinary alkalization with K citrate instead. In fact, guideline 19 says do not offer allopurinol routinely to uric acid stone formers

Causes elevated LFTs

Question 19

What pharmacotherapy should you offer a person with recurrent calcium stones in whom other metabolic abnormalities are absent or have been appropriately addressed and stone formation persists?

Answer 19

Guideline 17: Clinicians should offer thiazide diuretics and/or potassium citrate

Question 20

What pharmacotherapy should you try to give someone with uric acid and cystine stones to try to raise their urinary pH?

Answer 20

Guideline 18: potassium citrate

Question 21

To whom should you offer cystine-binding thiol drugs, such as alpha-mercaptopropionylglycine (tiopronin, Thiola)

Answer 21

Guideline 20: patients with cystine stones who are unresponsive to dietary modifications and urinary alkalinization, or have large recurrent stone burdens.

Side effects: Elevated LFTs, anemia and other myelosuppression

Question 22

To whom should you offer acetohydroxamic acid (AHA)?

Answer 22

Guideline 21: patients with residual or recurrent struvite stones only after surgical options have been exhausted. Remember this is like a last hope effort.

Side effects: anemia, phlebitis and hypercoagulable phenomena

Question 23

When should you get a 24H urine test after initiation of treatment to assess response to dietary and/or medical therapy?

Answer 23

Guideline 22: You should get a single 24H urine test within 6 months

Question 24

When should you consider getting a repeat stone analysis?

Answer 24

Guideline 25: When patients are not responding to treatment

Question 25

What are some pharmacotherapy adverse events that you should think about when monitoring people on these meds?

Answer 25

Guideline 24: obtain periodic testing to access for this:

Thiazides: hypokalemia and glucose intolerance
allopurinol and tiopronin may cause an elevation in liver enzymes
AHA and tiopronin may induce anemia and other hematologic abnormalities
potassium citrate may result in hyperkalemia

Question 26

What should you monitor patients with struvite stones for?

Answer 26

Guideline 26: reinfection with urease-producing organisms and utilize strategies to prevent such occurrences

Question 27

What are some urease producing bacteria?

Answer 27

Klebsiella, proteus, and pseudomonas

Question 28

What are some general medications that are stone-provoking?

Answer 28

Topiramate, acetazolamide, zonisamide (carbonic anhydrase inhibitor- causes RTA)

Triamterene (potassium sparing diuretic- causes medication crystals)

Vitamin C (coverts to oxalate)

Vitamin D and high levels of calcium (> 1200 mg/day)

Lipase inhibitors

Probenecid

chemotherapy (tumor lysis)

certain protease inhibitors (indinivir)- not able to see on CT