SM 216 Kidney Stones

Question 1

How common are kidney stones?

Answer 1

Effect 1 in 10 people

Question 2

Who gets kidney stones more often?

Answer 2

Men > Women, Asians and Caucasians, Stone Belt in the US

Question 3

How does climate effect Kidney Stones?

Answer 3

Hot and dry climates promote water loss which facilitates kidney stone formation

Question 4

What is supersaturation?

Answer 4

Supersaturation describes the process of crystal formation after the concentration of a substance improves the solubility threshold in solution, leading to precipitation out of solution and crystal formation

Question 5

What is a stone nidus?

Answer 5

A stone nidus is a solid particle that facilitates crystal formation of other particles

Question 6

What are the main determinants of solubility, and which ones are physiologically relevant?

Answer 6

Concentration of ion/compound, pH, and temperature

Temperature cannot be varied, so concentration’s of ions and pH are the physiologically relevant determinants

Question 7

How does urinary pH effect the relative solubility of molecules?

Answer 7

High urinary pH increases the solubility of some molecules and decreases the solubility of others

Question 8

Does high or low solubility of a substance facilitate stone formation?

Answer 8

Low solubility facilitates stone formation

Question 9

Which solutes have a higher solubility at high urinary pH?

Answer 9

Cysteine and Uric acid, which are more likely to form stones at lower pH

Question 10

Which solutes have a lower solubility at high urinary pH?

Answer 10

Ammonium Urate and Phosphate

Question 11

Which molecules are more likely to form stones at low urinary pH?

Answer 11

Uric acid and Cysteine, because they have higher solubility at high pH

Question 12

Which molecules are more likely to form stones at high urinary pH?

Answer 12

Ammonium Urate and Phosphate, because they have lower solubility at high pH

Question 13

Which stones look like “square envelopes”?

Answer 13

Calcium oxalate

Question 14

What is the most common type of kidney stone?

Answer 14

Calcium oxalate

Question 15

What is the second most common type of kidney stone?

Answer 15

Calcium phosphate

Question 16

What are the risk factors for calcium stones?

Answer 16

Hypercalciuria, Hyperoxaluria

Question 17

What is the main risk factor for calcium stone?

Answer 17

Hypercalciuria

Question 18

What can cause hypercalciuria?

Answer 18

Hypercalcemia (high serum Ca leads to high urine Ca)
Due to: hyperparathyroidism, malignancy, Vit D toxicity

May be idiopathic

Question 19

Where can hyperoxaluria come from?

Answer 19

Dietary intake of high-oxalate food, Vit C intake, and low calcium intake

Question 20

Why is Crohn’s disease a risk for hyperoxaluria?

Answer 20

Malabsorption in GI tract leads to increased oxalate reabsorption

Question 21

How does low Calcium intake lead to hyperoxaluria?

Answer 21

Ca normally binds oxalate leading to less systemic absorption, so low calcium lowers oxalate sequestration and leads to more absorption, causing hyperoxaluria

Question 22

What kind of stone appears as “coffin lids”?

Answer 22

Struvite stones (infection stones)

Question 23

What makes up Struvite stones?

Answer 23

Magnesium ammonium phosphate

Question 24

What are the risk factors for Struvite stones?

Answer 24

Alkalization of urine due to urease producing bacteria, which lowers the solubility of urinary phosphate-cation (Mg/Ca/NH4) complexes

Question 25

Which bacteria is associated with Struvite stones?

Answer 25

Proteus spp

Question 26

What are Staghorn calculi?

Answer 26

Very large Struvite stones that include more than one renal calyx, often due to Proteus spp

Question 27

What type of stones show up as diamonds or rhomboids?

Answer 27

Uric acid stones appear as diamond or rhomboid stones

Question 28

Which type of stones do now show up on X-Ray?

Answer 28

Uric Acid stones

Question 29

What pH promotes Uric acid stones?

Answer 29

Acidic urine, which lowers the solubility of uric acid

Question 30

What pH promotes Struvate stones?

Answer 30

Basic urine, which lowers the solubility of phosphate

Question 31

What are the risk factors of Uric acid stones?

Answer 31

Hyperuricosuria, low urinary pH

Question 32

What causes hyperuricosuria?

Answer 32

Dietary intake of purines and animal protein | High cell-turnover states which release uric acid

Question 33

What are high cell turn-over states?

Answer 33

Hemolysis, tumor-lysis syndrome = rapidly dying cells release uric acid

Question 34

What type of stones appear "hexagonal"?

Answer 34

Cysteine stones are hexagonal

Question 35

What causes cysteine stones?

Answer 35

Cysteine stones are secondary to inherited disorders of metabolism, because patients can't reabsorb Cysteine, raising concentration in the urine

Question 36

What is the treatment for Cysteine stones?

Answer 36

Cysteine is insoluble at low pH, so treatment is alkalinizing the urine

Question 37

What are general risk factors for stone formation?

Answer 37

Low urine volume High Na diet Hypocitraturia High protein diet

Question 38

Does low or high urine volume favor stone formation?

Answer 38

Low urine volume - raises the conc. of solutes which increase the probability of stone formation

Question 39

How does high Na favor stone formation?

Answer 39

High Na diets result in high urinary Ca due to Na/Ca reabsorption in the PCT

Question 40

How does hypocitraturia favor stone formation?

Answer 40

Citrate normally chelates ions and prevents stone formation with phosphate

Question 41

How does a high protein diet favor stone formation?

Answer 41

High protein diets increase the acid load, which results in bone resorption since bone is a major buffer, raising calcium levels in serum and urine, favoring stones formation

Question 42

What unexpected organ is a major buffer source?

Answer 42

The bone, at the cost of raising serum and urinary calcium

Question 43

How does urinary flow effect stone formation?

Answer 43

High flow = less stone formation | Low flow = more stone formation

Question 44

How do bacteria effect stone formation?

Answer 44

``` Sterile = less stone formation Infected = more stone formation ```

Question 45

How does fluid intake effect stone formation?

Answer 45

High fluid intake correlates with lower risk of stone formation, especially above 2L/day

Question 46

What is renal colic?

Answer 46

Renal colic is the acute presentation of kidney stones

Question 47

How do kidney stones present?

Answer 47

Flank pain radiating to the groin Extremely painful No comfortable position Hematuria

Question 48

Do kidney stones cause hematuria?

Answer 48

Yes, both gross and microscopic

Question 49

How are kidney stones differentiated from peritonitis?

Answer 49

Kidney stones do not have a position of comfort, while peritonitis does

Question 50

How painful are kidney stones?

Answer 50

Kidney stones are on par with childbirth

Question 51

What is the recommended way to diagnose kidney stones?

Answer 51

Non-contrast CT abdominal scan Uric acid stones don't show up on X Ray

Question 52

What is the major determinant of whether or not a kidney stone will pass?

Answer 52

Stone size is the major determinant; stones < 5mm will likely pass on their own

Question 53

Why might a kidney stone be treated instead of being allowed to pass?

Answer 53

Too large > 5mm Pain control Concurrent urinary/kidney infection or injury

Question 54

What intervention can treat large kidney stones?

Answer 54

Extracorporeal shock-wave lithotripsy

Question 55

What factor predisposes recurrent kidney stones?

Answer 55

Having a kidney stone predisposes another kidney stone

Question 56

How are kidney stones managed long term?

Answer 56

24 hour urine collections for calcium, oxalate, sodium, uric acid, citrate, phosphate, pH to identify major risk factors for medical intervention

Question 57

What are potential medical interventions for kidney stones?

Answer 57

Reduce hypercalciuria Increase urinary pH and citrate Assess medication list and address risk

Question 58

How can hypercalciuria be treated?

Answer 58

Thiazide diuretics - stimulate calcium reabsorption at the DCT

Question 59

What can increase urinary pH and citrate?

Answer 59

Potassium citrate supplementation - as part of kidney stone treatment