Nephrolithiasis

Question 1

What is Nephrolithiasis?

Answer 1

Precipitation of urinary solute as a stone.

Question 2

What are risk factors for Nephrolithiasis?

Answer 2

1. High concentration of solute in the urinary filtrate

2. Low urine volume

Question 3

What is the classic presentation for Nephrolithiasis?

Answer 3

Presents as (1) Colicky pain with (2) hematuria and (3) unilateral flank tenderness.

Question 4

How long does it usually take a stone to pass? What happens if the stone remains lodged?

Answer 4

• Stone is usually passed within hours

- If not, surgical intervention may be required

Question 5

What is the most common type of Nephrolithiasis?

Answer 5

Calcium oxalate and/or calcium phosphate

Question 6

What is the most common cause of Calcium oxalate/Calcium phosphate Nephrolithiasis?

Answer 6

Idiopathic hypercalciuria

Question 7

What do you have to exclude (what could be the cause of) with Calcium oxalate/Calcium phosphate stones?

Answer 7

Hypercalcemia and its related causes

Question 8

What disease is associated with Calcium oxalate stones?

Answer 8

Crohn disease

Question 9

How does Crohn disease form calcium oxalate stones?

Answer 9

Small bowel damage –> Inc. resorption of oxalate –> Binds to calcium –> Forms Calcium oxalate stone

Question 10

How do you treat calcium oxalate/calcium phosphate stones?

Answer 10

Hydrochlorothiazide (Ca2+ sparing diuretic)

Question 11

What is the second most common type of Nephrolithiasis?

Answer 11

Ammonium magnesium phosphate

Question 12

What is the most common cause of an ammonium magnesium phosphate stone?

Answer 12

Infection with Urease-positive organisms

Question 13

What are urease-positive organisms?

Answer 13

• Proteus vulgaris

- Klebsiella

Question 14

What leads to the formation of a stone with urease-positive organisms?

Answer 14

Alkaline urine leads to formation of stone

Question 15

What does an ammonium magnesium phosphate stone classically result in?

Answer 15

Staghorn calculi in renal calyces –> acts as deposition site for UTIs

Question 16

How do you treat ammonium magnesium phosphate stones?

Answer 16

Surgical removal of stone (due to size) and eradication of pathogen (to prevent recurrence).

Question 17

What is the third most common form of Nephrolithiasis? What percentage of all Nephrolithiasis does it represent?

Answer 17

Uric acid

5%

Question 18

What do uric acid stones look like?

Answer 18

Radiolucent (as opposed to other types of stones which are radiopaque)

Question 19

What are risk factors for uric acid stones?

Answer 19

• Hot, arid climates
• Low urine volume
• Acidic pH

Question 20

What is the most common stone seen in patients with gout?

Answer 20

Uric acid stone

Question 21

What increases one’s risk for a uric acid stone?

Answer 21

Hyperuricemia (e.g. leukemia or myeloproliferative disorders)

Question 22

How do you treat uric acid Nephrolithiasis?

Answer 22

-Hydration
-Alkalinization of urine (potassium bicarbonate)
[Allopurinol is also administered in patients with gout]

Question 23

What is a rare cause of Nephrolithiasis?

Answer 23

Cystine

Question 24

What populations are Cystine Nephrolithiasis commonly seen in?

Answer 24

Children!

Question 25

What cause are Cystine stones associated with?

Answer 25

Cystinuria (a genetic defect of tubules that results in decreased reabsorption of cysteine)
–> then cystine piles up in the filtrate and this increases the risk for a kidney stone

Question 26

What might cystinuria of nephrolithiasis cause?

Answer 26

It may form Staghorn calculi

Question 27

How do you treat Cystine Nephrolithiasis?

Answer 27

• Hydration

- Alkalinization of urine