Kidney Stones - Wesson

Question 1

Sponge Kidney Disease typically features calcifications where?

Answer 1

calcifications along the corticomedullay junction and ‘painbrush-like’ appearance radiating outward from the calyces

Question 2

Where does nephrocalcinosis typically appear?

Answer 2

tubules and interstitial spaces

Question 3

What is the typical etiology kidney stone disease?

Answer 3

idiopathic

Question 4

What is the most common composition of a kidney stone?

Answer 4

Calcium-oxalate or Calcium-phosphate

Question 5

kidney stones often show distinct layers - what does this suggest?

Answer 5

This suggests that stones may form/grow due to some (not fully understood) cyclic process

Stones are generally made up of an aggregate - that is, it isn’t a continual or ‘epitaxial’ process of continous organized deposition

Question 6

What is the approximate lifetime prevalence of kidney stones in the US?

Who is at greater risk? (i.e. gender, race, age)

Answer 6

5-15% (annual incidence 1:1000)

men > women (2:1)

whites > other races

peak incidence in middle age

**also: substantial regional variation (diet?)

Question 7

Name a few (4, bolded) drugs that can form stones

Answer 7

• indinavir
• acyclovir
• triamterene
• sulfamethoxazole

Question 8

What is the etiology of cystinuria?

What is its approximate prevalence in the population?

Answer 8

A genetic defect in PCT amino acid transport (cysteine, arginine, lysine, ornithine), preventing reabsorption of these amino acids in the PCT

fairly rare - 1:10000

Question 9

Name the two genetic defects (and inheritance pattern) seen in cystinuria

Answer 9

• Type A: SLC 3A1. Recessive. Defective PCT S3 transporter
• Type B: SLC 7A9. Incompletely dominant. Defective PCT S1 transporter

Type AB: combination of type A and type B

Type B is more prevalant (47%) than Type A (38%)

Question 10

Describe primary hyperoxalosis/hyperoxaluria

Answer 10

Rare genetic liver enzyme disorder leading to excessive endogenous oxalate synthesis

Question 11

What are the key genetic defects (and inheritance pattern) seen in primary hyperoxalosis/hyperoxaluria?

Answer 11

All recessive inheritance

• PH1 (80%) - AGXT defect. Increased oxalate and glycolate.
• PH2 (10%) - GRHPR defect. Increased urine glycerate and oxalate.
• PH3 (10%) - HOGA1 defect. Increased urine oxalate

Question 12

Why are calcium oxalate crystals so prevalent (what mechanism makes them form so easily)?

Answer 12

Very low Ksp (~4e-8) -> low solubility -> crystals precipitate from solution even at relatively low concentrations

**Note: data has shown a relationship between oxalate excretion and increased risk of stones, but supersaturation alone is not sufficient to cause stone formation

Question 13

Name (5) general risk factors for formation of kidney stones

Answer 13

1. Previous renal disease (stones, PCKD, RTA, MSK, ESRD, transplant)
2. Other past medical issues (IBD/short-gut, hyperparathyroidism, hypercalcemia, gout, HIV)
3. Family history (multiple family members affected)
4. Social history (dehydration)
5. Diet (low fluids, high salt, high protein, low calcium, high oxalate)

Question 14

Does decreased dietary calcium increase or decrease risk of stone formation?

Answer 14

increased risk

Question 15

Name some common clinical presentations of kidney stones

Answer 15

• Renal colic
• hematuria
• fever, chills
• nausea, vomiting
• dysuria
• passed stones (there can be multiples)

Question 16

Name some common physical exam findings seen with kidney stones

Answer 16

• distress (often pacing around room)
• CVA/abdominal tenderness
• fever
• hematuria
• elevated WBCs
• elevated serum creatinine
• positive findings on imaging studies

Question 17

What is the gold-standard imaging methodology for identifying kidney stones?

What else might be used (though less effectively)?

Answer 17

CT Scan

ultrasound

IVP and KUB are old methods, mostly fallen out of favor

Question 18

What major type of kidney stone is radiolucent (i.e. won’t be picked up with x-ray imaging)?

Answer 18

uric acid stones

Question 19

Name the crystal type based on appearance:

1. round/amorphous
2. square/rectangular tetrahedal
3. lemon-shaped
4. rectangular-euhedral

Question 20

Describe the acute treatment of kidney stones

Answer 20

• noninvasive - pain control, fluids, expulsive or dissolution therapy
• extra-corporeal shock wave therapy (ESWL)
• Ureteroscopy -> lithotripsy or stone basketing
• Percutaneous surgical removal

Question 21

Describe the treatment strategy for chronic cystine stones

Answer 21

• dilution of urine
• alkalinization of urine
• cystine-binding drugs -> penicillamine, tiopronin, captopril

Question 22

Describe the treatment strategy for chronic uric acid stones

Answer 22

• dilution of urine
• low-protein/high-fruit diet
• alkalinize urine (increases solubility of urate)
• xanthine oxidase inhibitors (allopurinol, febuxostat)

Question 23

Describe the treatment strategy for chronic struvite stones

Answer 23

• Dilution
• Sterilize urine (eliminate urea-splitting bacteria)
• surgical removal of residual stone material
• adjunctive therapies: urease inhibitors (acetohydroxamic acid), chemolysis (hemiacidirin)

Question 24

Describe the treatment strategy for chronic calcium stones

Answer 24

• dilution
• maintenence of calcium intake
• reduce urine calcium excretion (sodium restriction and thiazide diuretics)
• reduce urine oxalate excretion (diet oxalate restriction, add pyridoxine)
• increase urine citrate (diet: decrease protein and increase fruit, add citrate or bicarb supplements)