Nephrolithiasis

Question 1

What is the pain with a stone in the upper tract?

Answer 1

• flank pain

- upper anterior abdominal pain

Question 2

What is the pain with a stone in the lower tract?

Answer 2

• groin pain

- ipsilateral testicular/labial pain

Question 3

What is an atypical presentation of a stone?

Answer 3

• painless hematuria

- persistent UTI

Question 4

What is the most common type of stone? What are the two next common?

Answer 4

70-80%=calcium oxalate or calcium phosphate
10-15%=uric acid
10-15%=magnesium ammonium phosphate a.k.a struvite

Question 5

What are the steps for stone formation?

Answer 5

1. supersaturation
   - increased urinary ion excretion
   - decreased urine volume
2. nucleation
   - crystal growth and aggregation

Question 6

What are the promoters of crystallization?

Answer 6

1. hydrogen ions (low pH)
2. sodium
3. magnesium
4. uric acid

• sites of prior injury
• gravity dependent locations (lower pole calyx)

Question 7

What are inhibitors of crystallization?

Answer 7

1. high urine flow rates

2. citrates and other substances

Question 8

What are the states that lead to calcium stones?

Answer 8

1. HYPERCALCIURIA*
2. +/-hypercalcemia
3. chronic metabolic acidosis
4. low urine volume
5. hyperuricosuria
6. hyperoxaluria
7. hypocitraturia
8. high protein, low carb diet
   - mark acid load, decreased calcium balance

Question 9

What are causes of calcium stones?

Answer 9

1. idiopathic
2. hyperparathyroidism*
3. vitamin D excess
4. sarcoidosis (D production in granules)
5. glucocorticoid excess
6. RTAs (basic urine)
7. Hyperthyroidism
8. Malignant neoplasms
9. loop diuretics

Question 10

How do calcium and oxalate interact in the lumen of the GI tract, how does this affect how they interact in the kidney?

Answer 10

Lumen:
dietary calcium binds oxalate and impedes oxalate absorption
Kidney:
absorbed oxalate binds urinary calcium and can lead to stone formation

Question 11

What are factors that favor calcium stone formation?

Answer 11

1. high dietary oxalate
2. increased fractional oxalate absorption
   - low dietary calcium
   - IBD (via fat malabsorption)-dietary calcium binds to FFAs in small bowel
3. Increased endogenous oxalate production-genetic causes

Question 12

What causes uric acid stones?

Answer 12

ACIDIC URINE

1. chronic metabolic acidosis
2. low urinary pH

Question 13

What causes struvite stones?

Answer 13

Chronic upper respiratory tract infection with urease producing bacteria:

1. proteus species
2. haemophilus species
3. klebsiella species
4. ureaplasma urealyticum

• results in ammonia and persistently alkaline urine–> promotes struvite formation
• more common in women, chronic urinary obstruction (neurogenic bladder)

Question 14

What causes cystine stones?

Answer 14

Cystinuria: autosomal recessive condition

GI and renal transport disorder of four amino acids:

1. cystine
2. ornithine
3. arginine
4. lysine

-cystine insoluble in normally- acidic urine, so cystinuria in genetic disorders leads to stones

Question 15

What is the preferred method of detecting stones?

Answer 15

CT without contrast

Question 16

Do you need to retrieve the stone?

Answer 16

yes it is crucial

Question 17

How do you prevent future calcium stones?

Answer 17

• low sodium, low animal protein diet
• normal dietary calcium
• medication: thiazide diuretics–>decrease calcium excretion in urine

Question 18

How do you prevent future uric acid stones?

Answer 18

low purine, low animal protein diet

Medications:
1st line: 
-sodium bicarbonate, potassium citrate
-alkalinize urine, maintain ph>6.5 
2nd line:
allopurinol 
-decrease uric acid levels
-useful with hyperuricemia, marked hyperuricosuria
-also useful in patients that cannot maintain urine ph>6.5

Question 19

HOw do you prevent struvite stones?

Answer 19

eradicat infection with antibiotic therapy

• complete removal of all stones-including residual fragments, often requires intervention
• prevent future UTIs

Question 20

How do you prevent future cystine stones?

Answer 20

alkalinize urine
-sodium bicarbonate, potassium citrate

-D-penicillin, tiopronin (increase solubility)

Question 21

What does vitamin C do to oxalate?

Answer 21

facilitates urine oxalate excression

Question 22

WHat are foods high in purines?

Answer 22

meats
-offal, seafood, shellfish
alcohol

Question 23

What are foods high in oxalate?

Answer 23

black tea
chocolate
soymilk
nuts 
berries 
beans, spinach, okra
beets rhubarb
carrots
celery swiss chard
sweet potatoes

Question 24

If you have hyperuricosuria what should you do?

Answer 24

low purine, low animal protein diet

allopurinol therapy

Question 25

If you have hypocitraturia what should you do?

Answer 25

low animal protein diet increase fruits/veggies (high in citrate) citrate supplements (potassium citrate)