12 - Kidney Stones

Question 1

What are the demographic of who kidney stones?

Answer 1

• Men > women (2:1)
• White more commonly affected
• Peak incidence in middle age
• Substantial regional variations.

Recurrence rates exceed 50% in 5 yrs

Question 2

Where can kidney stones form? What are they called in these locations?

Answer 2

Nephrolithiasis/urolithiasis: stone forming diseases related to drugs.

Nephrocalcinosis: medullary sponge kidney, interstitial crystallization/randall’s plaque. Depisition within the kidney. Crystal nephropathy.

Bladder stones: retention of stone material within the bladder, associated with bladder dysfunction

Question 3

What are the different compositions of kidney stones? What is the most common types?

Answer 3

Calcium oxalate and calcium phosphate are the most common types.

Can also be: urate, struvate, or cysteine.

Question 4

What are key factors involved in the pathogenesis of kidney stones?

Answer 4

• Urinary supersaturation: concentration of substances high and volume of urine is low so you form crystals.
• Crystal retention at the renal papilla
• Associated risk factors

Know that supersaturation alone is insufficient to cause stone disease.

Question 5

How frequent are calcium stones? What precipitates them?

Answer 5

80% of stones are calcium.

Calcium oxalate: not dependent on urine pH but low urine pH favors uric acid crytal formation which serves as a nidus

Calcium phosphate: increase pH precipitates them

Question 6

What are conditions that cause calcium stones?

Answer 6

Hypercalciuria (increased PTH, excessive VitD, idiopathic)

Hypercalcemia (cancer, increased PTH, vitD excess)

Hyperoxaluria (vitC excess, ethylene glycol)

Taking too much vitamin C is a risk factor because vitamin C crystallizes as oxalate.

Question 7

How common are struvite sontes? What precipitates them?

Answer 7

15% of stones.

Increase pH precipitates them.

Question 8

What can be seen with struvite stones?

Answer 8

Urease positive organisms

Staghorn caliculi (refer to branched stones that fill all or part of the renal pelvis)

UTI

Envelope crystals

Question 9

How common are uric acid stones? What can precipitate them?

Answer 9

5% of stones, but increasing from an increase in cancer therapy and an increase in metabolic syndrome.

Precipitated by low pH

Question 10

What are characteristics of uric acid stones?

Answer 10

• Radiolucent
• Associted with metabolic syndrome
• Hyperuricemia
• Increased cell turnover

Question 11

How common are cystine stones? What precipitates them?

Answer 11

1% of stones are cystine; caused by hereditary disease.

Low pH precipitates them.

Question 12

What are characteristics of cystine stones?

Answer 12

Cystinuria

Hexagonal crystals

Question 13

What are risk factors for kidney stones?

Answer 13

Previous renal disease

Short gut/IBD, hyperparathyroidism, hypercalcemia, gout, HIV

Family Hx

Social Hx (dehydration)

Diet risk factors: low fluid, high salt, high protein, low calcium, high oxalate (spinach, beets, rhubarbm nuts, beans, chocolate, soy products)

Question 14

What drug causes stones?

Answer 14

Ethylene glycol

Question 15

What are drugs that can form stones?

Answer 15

Indinavir

Acyclovir

Triamterene

Sulfamethoxazole

Guaifenesin/Guaoiacol

Question 16

What are genetic diseases that cause stones?

Answer 16

Cystinuria - L-cystine

Primary hyperoxalosis - calcium oxalate

Dent disease - calcium oxalate or phosphate stones

Familial hypomagnesium with hypercalcemia and nephrocalcinosis (FHHNC) - calcium crystals

Adenosine phosphoribosyltransferase (APRT) deficiency

Distal renal tubular acidosis - calcium phosphate

Question 17

What is primary hyperoxalosis/hyperoxaluria?

Answer 17

Rare genetic disorder of liver enzymes leading to excessive endogenous oxalate synthesis.

Caused by 3 known gene defects (all recessive inheritance): PH1, (80%), PH2 (10%), and PH3 (10%).

Question 18

The highest oxalate excretion levels are seen in what?

Answer 18

Hereditary hyperoxaluria.

Then in enteric or diet related oxaluria.

Question 19

What is the presentation of kidney stones?

Answer 19

• Renal colic (radiation to abd, groin)
• Hematuria
• Fever, chills
• Nausea, vomiting
• Urinary frequency, dysuria
• Mild-moderate CVA tenderness
• Elevated serum creatinine
• Elevated WBCs

Question 20

How would you diagnose a kidney stone?

Answer 20

CT scan

Ultrasound

KUB: kidney and bladder Xray for surveillance

Question 21

What would you do for a laboratory analysis of kidney stones?

Answer 21

Serum studies

24 hr urine studies

Question 22

How do you treat acute (active) kidney stones?

Answer 22

• Pain control and fluids.
• Medical expulsive therapy (alpha-bllockers, steroids, Ca-blockers)
• Dissolution therapy (uric acid)
• Extra-corporeal shock wave lithotripsy
• Ureteroscopy if too big to pass: stone basketing/lithotripsy (laser)

Question 23

How would you treat chronic uric acid kidney stones?

Answer 23

• Dilution
• Low protein/high fruit diet to prevent urine acidity and keep urine alkaline
• Alkalinize urine
• Xanthine oxidase inhibitors: allopurinol, febuxostate

Question 24

How would you treat chronic struvite kidney stones?

Answer 24

• Dilution
• Sterilize urine: eliminate urea splitting bacteria
• Remove residual stone material
• Adjuvant therapies

Question 25

How would you treat chronic calcium kidney stones?

Answer 25

• Dilution
• Maintain normal calcium intake
• Reduce urine calcium excretion by limiting Na and protein in diet (add thiazide diuretics)
• Reduce urine pxalate by adding calcium and/or limiting oxalate in diet
• Increase urine citrate by reducing protein and increasing fruit in diet.

Question 26

Risk of calcium kidney stokes increase with a _____ calcium diet.

Answer 26

LOW!