Nephrolithiasis II

Question 1

Approach to renal colic/nephrolithiasis

nephrolithiasis can be broken down into two stone types: __ containing stones (90%) and _ __ stones (10%).

Calcium containing stones can be broken down into hard and soft types. The hard types are made of _ _, and soft stones are made of _.

Hard calcium sontes are often caused by 3 broad reasons: 1. incresaed solute due to ___ or __, 2. decreased solubility due to low __ ___ or ___, or an 3. anatomical problem like ___ ___ ___.

NON-calcium sontes (10% of stones) can me made of either ___ (in cysteinuria) or __ __ (due to high ___ intake or hyperuricosuria)

Answer 1

Approach to renal colic/nephrolithiasis

nephrolithiasis can be broken down into two stone types: Calcium containing stones (90%) and non calcium stones (10%).

Calcium containing stones can be broken down into hard and soft types. The hard types are made of calcium oxalate, and soft stones are made of struvite.

Hard calcium sontes are often caused by 3 broad reasons: 1. incresaed solute due to hypercalciuria or hyperoxaluria, 2. decreased solubility due to low urine volume or hypocirtraturia, or an 3. anatomical problem like medullar sponge kidney.

NON-calcium sontes (10% of stones) can me made of either cysteine (in cysteinuria) or uric acid (due to high protein intake or hyperuricosuria)

Question 2

rare causes of “renal colic” that should be rued out

Answer 2

1. clot
2. sloughed papilla
3. renal mass
4. ectopic pregnancy
5. aortic aneurysm

Question 3

scoring system for diagnosing nephrolithiasis

Answer 3

• Flank pain (1pt)
• Acute onset pain (1 point)
• hematuria (2 points)
• positive KUB (2 points)
• Likelihood of stones (4 points for 90%, 5 points for 96%, and 6 points for 98.5%)

Question 4

3 ways you can determine clues to the stone type

Answer 4

1. stone analysis – the deifnitive test
2. radiology
3. urine microscopy

Question 5

Type of calculus and typical composition

Answer 5

Typically these stones are composed of “struvite” AKA “triple phosphate” (Magnesium Ammonium Phosphate)

STAGHORN CALCULUS

Question 6

type of crystla

Answer 6

Calcium oxalate crystals

Question 7

type of crystal?

Answer 7

Brushite (CaHPO4) crystals

Question 8

Type of crystal?

Answer 8

Struvite (MgNH4 PO4) crystals

Question 9

Type of crystal

Answer 9

Uric acid crystal

Question 10

Type of crystal?

Answer 10

Cystine crystals

Question 11

Stones form because of conditions leading to ___

Answer 11

Stones form because of conditions leading to supersaturation

Question 12

Types of stones that form in the tubular lumen

Answer 12

struvite, uric acid, brushite, cysteine

NOT CA OXALATE USUALLY

Question 13

types of crystals that form in the kidney interstitium

Answer 13

Ca Oxalate

Question 14

In the LOH cells, Positive luminal charge facilitates paracellular __, ___ reabsorption

Answer 14

Positive luminal charge facilitates paracellular Ca, Mg reabsorption

Question 15

___ calculi made of ____ are associated with chronic infection of urine, particular by ___ and ___ containing urease

Answer 15

STRUVITE calculi made of MhNH4PO4 are associated with chronic infection of urine, particular by KLEBISELLA and PROTEUS containing urease

Question 16

___ ____ calculi is associated with gout and is very ___ sensitive

Answer 16

uric acid calculi. very pH sensitive, forms in acid urine

Question 17

T/F women are more likely to develop recurrent stones

Answer 17

false. men

Question 18

Management of first stone or asymptomatic stones

Answer 18

Investigation:

• stone analysis, serum creatinine, [Ca] and/or [urate] • Radiological follow-up @ 6 - 12months

Treatment: • High fluid intake (urine output >2 L/day) ↓ risk by ~ 50% @ 5
years (but not soda)
• Normal calcium intake (vs. low) ↓ risk by ~ 50% @ 5 years

Question 19

T/F during the treatment of your first stone, you should lower the amount of calcium in your diet to prevent it from growing larger or for recurring

Answer 19

false • Normal calcium intake (vs. low) ↓ risk by ~ 50% @ 5 years

Question 20

investigations of recurrent calcium oxalate stone formers

Answer 20

urine: look at volume, Ca2+, oxalate, sodium, cirate.

Question 21

Management of recurrent calcium oxalate stone formers:

1. Hypercalciuria
2. hyperoxaluria
3. hypocituria
4. no abnormality?
   - radiological follow up in ___ year if remains asymptomatic

Answer 21

1. Hypercalciuria: DO NOT REDUCE DIETARY CA2+. Limit Na+ intake. Thizide diuretics
2. hyperoxaluria: low oxalate diet
3. hypocituria: K+ citrate
4. no abnormality? decrease urinary ca2+ and increase urinary citrate?
   - radiological follow up in 1 year if remains asymptomatic

Question 23

80 – 90% of stones passed without intervention. What are the 5 Ps requiring referral to urology?

Answer 23

1. pyrexia (pyonephrosis)
2. post-renal failure
3. persistent symptoms
4. previous problems
5. pretty big stone >5 mm

Question 24

Question 25

most common stone in kids

Answer 25

cystine crystals

Question 26

why does crohns predispose someone to stone formation?

Answer 26

crohns disease; problematic ileum that is involved in bile salt and probiotic excretion. resection due to chrogns disease resutls in decresaed bile salt reabosrption. as a consequence, other positively charged ions will attract fatty acids, speciifically calcium. when they bind, there is less calcium to bind to oxalate. there is free oxalate in the gut, which then gets absorbed into the blood, and then gets into the urine.

therefore crohsn causes creation of calcium oxalate stones.This also explains why people with a low calcium diet arre at higher risk to developing calcium oxalate stones too.

Question 27

most common sites of stone formation

Answer 27

form in collecting tubules (proximal usually). anatomically, stones form at sites where theeyre more liekyl to achieve supersaturation; 1 in the tubular lumen of distal nephron, and 2. interstitium

Question 28

at the heart of the of a calcium stone is a bud of calcium called ___ plaque– typically develop just outside the basolateral membrane of the cells of the ___.

Answer 28

at the heart of the of a calcium stone is a bud of calcium called randal’s plaque– typically develop just outside the basolateral membrane of the cells of the LOH.

Question 30

why does LOH have a predisposition for stone formation? (recall randal plaque starting)

Answer 30

because it is a site of supersaturation. facilitated by excess Ca2+ and Mg2+ reabsorption.there is also little water in the interstitium, causing a higher likely hood of supersaturation