Nephrolithiasis

Question 1

calcium stones

Answer 1

80% of stones, made of calcium oxalate and calcium phosphate

• hypercalciuria, higher salt in diet, high non-dairy animal protein diet, high sucrose in diet, hyperPTH, hypercalciuric hypocalemia
• hyperoxaluria: increased intake of high oxalate foods like spinach and decreased oral intake of Ca2+
• hypocitraturia: citric acid decreases stone formation
• high urine pH (RTA type I)
• low urine volume

Question 2

uric acid stones

Answer 2

5-10% (urea = breakdown product of DNA)

1) hyperuricemia/uria: gout, polycythemia vera (large dna breakdown), tumor lysis syndrome
2) low urine pH: obesity, DMII, high non-dairy animal protein intake

Question 3

struvite stones

Answer 3

Magnesium/ammonium/phosphate stones (10-15%)

• reacent infection w/ urease producing bacter (Proteus or klebsiella)

Question 4

Cystine stones

Answer 4

less than 1%

• cystinuria (autosomal dominant disorder)

Question 5

clinical manifestations of stones?

Answer 5

Asymptomatic during formation

Renal colic when stone moves through and/or obstructs one of the ureters

Micro- or macro-hematuria

Sometimes associated with UTI
- Fever/leukocytosis/pyuria/sepsis

Question 6

Renal colic

Answer 6

hollow organ spasm, resulting in short and intense waves of pain

Sudden
Acute
Severe
Non-remitting with positional changes
Abdominal or back pain
Unilateral

Question 7

ddx?

Answer 7

based on clinical presentation
urine: RBC, WBC, crystals
Leukocytosis, ARF

Imaging:

Plain film: May show Calcium stones
IVP—used less frequently now
CT-renal protocol—gold standard
US—may show intrarenal stones and/or hydronephrosis. Not sensitive for ureteral stones

Question 8

medical therapy for acute attacks?

Answer 8

Pain control
Nausea control

Propulsive therapy

• Calcium channel blockers
• Alfa-blockers

Question 9

surgical therapy?

Answer 9

1. Ureteroscopy with stone removal and stent placement
2. Percutaneous nephrostomy: insertion of tube into kidney to drain urine and wait for stone to be removed
3. ECWL (lithotripsy) - US waves to break up large waves

Question 10

Dietary modifications to prevent calcium stones?

Answer 10

• increase fluid intake

Adequate dietary Calcium intake

• From food, not from supplements
• Not too much, not too little
• Likely binds oxalate and prevents its absorption

Restriction of nondairy animal protein (e.g., meat, chicken, seafood)

Avoidance of spinach (the highest oxalate-containing food).

Reducing sodium intake to less than 3g/day

• It will decrease concurrent urinary excretion of calcium
• Decreasing sucrose intake, which may increase urinary calcium excretion

Increasing potassium-rich foods.

Question 11

uric acid stone prevention

Answer 11

Increasing urine pH by:

• Reducing the intake of animal proteins
• Increasing the intake of alkali-rich foods (fruits and vegetables)
• Oral bicarbonate

Question 12

Meds for tx of calcium stones?

Answer 12

thiazides: drops all the lytes down except for calcium

- results in increased calcium reabsorption and decreases urine calcium

Question 13

allopurinol

Answer 13

decreases uric acid in the serum and urine

• used to treat uric stones

Question 14

magnesium

Answer 14

forms soluble complexes w/ oxalate in the bowel or urine

- used to treat calcium oxalate stones