Kidney Stones

Renal Stones

Nearly all Kidney (or Renal) Stones are preventable.

Classification of Disorders Causing Kidney Stones

1. Idiopathic (no known associated disease process)
2. Uric acid ("gout") related
3. Hyperoxaluria
4. Urinary track infection related (Struvite or Calcium phosphate Stone)
5. Hypocitraturia
6. Cystine stone
7. Magnesium deficiency
8. Hypercalcemia
9. Xanthine stones
10. 2,8-dihydroxyadenine stones
11. Kidney diseases

The comprehensive evaluation of a person who has had kidney stones consist of the following;
1. Historical health information
2. Urine Analysis (fasting)
2. Blood test
3. 24 hour urine collection and testing
4. Analysis of the kidney stone

Once a specific cause has been determined a specific preventive program can begun.

Historical health information;

Have you had any intestinal disease or surgery?

Have you had any urinary or bladder infections?

Do you have blood relatives with kidney stones?

Have you had Gout or is it in the family?

Do you have Sarcoidosis, calcium abnormalities or Parathyroid abnormalities?

A diet history especially regarding a high dietary protein intake, salt intake foods and dairy products.

What medication are you taking?

Blood test
1. Calcium
2. Phosphate
3. Creatinine
4. Uric Acid
5. Bicarbonate
6. Potassium
7. Magnesium
8. Sodium
7. Urea nitrogen
1. Calcium
2. Phosphate
3. Creatinine
4. Uric Acid
5. Bicarbonate
6. Potassium
7. Magnesium
8. Sodium
7. Urea nitrogen

24 hour urine

Two carefully collected 24 hour urines. On the persons normal diet and fluid intake.

Laboratory test preformed on the 24 hr urine;
1. Calcium
2. Uric acid
3. Creatinine
4. Oxalate
5. Cystine
6. Citrate
7. Urine volume

In addition a fasting urine pH should be measured on a different sample.

Analysis of the kidney stone

Types
Calcium oxalate containing stones -------------------------------------------49%
Calcium oxalate mixed with other calcium compounds -----------------------21%
Struvite stones(MgNH4PO4) -----------------------------------------------15%
Uric acid stones------------------------------------------------------------- 10%
Calcium monohydrogen phospate (brushite)---------------------------------- 2%
Cystine stones---------------------------------------------------------------- 1%
Calcium apatite etc.---------------------------------------------------------- 1%
Xanthine stones--------------------------------------------------------------<1%
2,8-dihydroxyadenine stone--------------------------------------------------<1%
Triamterene--------------------------------------------------------------------------------<1%
Oxypurinol-----------------------------------------------------------<1%
Tricalcium phosphate---------------------------------------------------------------------<1%
Protein--------------------------------------------------------------------------------------<1%

Diagnostic Approach

General preventive measures:
1. Avoid a high protein diet. For the average American this means cutting your beef, pork, lamb, fish and cheese consumption at least in half. Excess protein in the diet acidifies the urine and cause excess urinary calcium.
2. Drink enough water to cause a urine output of +2000cc (two quarts). Usually about 3 liters or quarts per day.
3. Avoid Colas. This is associated with a low urine pH which may cause the urine to form stones.
4. Avoid a high salt diet. Excess salt causes excess urinary calcium.

Specific Treatment Programs

1. Idiopathic (no known associated disease process).
See General preventive measures above.

2. Uric acid ("gout") related (may produce calcium oxatate or uric acid stones)
A low purine diet is indicated. Allopurinol will lower plasma uric acid and will usually prevent these stones. Sodium bicarbonate (usually about 1 to 1.5 mEq/kg/day) will raise the urine pH, making uric acid stone formation less likely. The goal is for the urine pH to be between 6 and 6.5.

3. Hyperoxaluria
Calcium carbonate (Tums) will bind oxalate in the intestines thereby reducing the oxalate excretion in the urine. It may also reduce the acidity of the urine. Both these effects of calcium carbonate in combination with the "General preventive measures" are effective measures in stone prevention. One Tums (500mg) four time per day is the recommended dose. It should be taken with food or later in the day when food is in the intestinal track (i.e. when there is food containing oxalate to bind). If taken on an empty stomach it may have a reverse effect by raising the calcium level in the urine.
In crohn's disease or small intestinal resection Cholestyramine will bind the excess bile reducing the colonic absorption of oxalate.
Pyridoxine (Vitamin B 6) will reduce the urinary excretion of oxalate.
A dietary restriction of oxalate containing food is also helpful. High oxalate foods are, rhubarb, peanuts, chocolate, spinach, beets, strawberries, tomatoes and strongly brewed teas.

Some recommended foods that are low in oxalates and protein but rich in vitamins include brewer's yeast, soybeans, bananas , baked potatoes with skins, watermelon, avocados, and dried cereals (not wheat brain however).

4. Urinary track infection related (Struvite or Calcium phosphate Stone)
Identifing the bacteria is important and base the choice of antibiotic on the sensitivities. Prolong treatment is required especial if there are stones present.

5. Hypocitraturia ( Renal tubular acicdosis, idiopathic or hypokalemic related)
The goal in treatment is to reduce the acidity of the urine. Potassium citrate in a dose of 1 mEq/kg is a effective therapy and has been shown to reduce the incidents of new stones.

6. Cystine stone
1. Increase urine volume. It is needed, at the usual acidic pH, to dilute the cystine in the urine to 300mg/L. If the cystine excreted in the urine is 900mg per day then 3+liters of urine would need to be produced. This would require about 1 gallon of water/fluid ingestion per day. Unfortunately some with this disorder produce + 1000 mg /day making this dilution difficult to achieve.
2. Increase urine pH to +7.5 making cystine more soluable. Also difficult to ingest enough Sodium bicarbonate and/or potassium citrate..
3 Reduce salt intake
4. Protein restriction
5. Medications
    1. Tiopronin less toxic then Penicillamine.
    2. Penicillamine toxic but low nocturnal dose may be helpful.
    3. Captopril (50mg TID) only somewhat helpful.

7. Magnesium deficiency
Magnesium is a inhibitor of the formation of calcium oxalate crystals in the urine. In a study by Johansson and Backman U in the Journal of the American College of Nutrition a trial was done to determine the effect a magnesium therapy on preventing calium containing kidney stones. 55 patients with recurrent renal calcium stone disease without signs of magnesium deficiency (normal serum magnesium and urinary magnesium) from their "outpatient stone clinic" were treated for up to four years with 500 mg Mg2+, in the form of Mg(OH)2, daily. "The mean stone episode rate before therapy was 0.8 stones/year/patient. Forty-three recurrent renal calcium stone-formers without medical therapy served as controls. The urinary calcium excretion remained unchanged. The magnesium/calcium ratio in the urine increased and approached a value earlier found in healthy subjects without stone disease. Urinary citrate increased on therapy when analysed after three years of treatment. The mean stone episode rate decreased from 0.8 to 0.08 stones/year on treatment and 85% of the patients remained free of recurrence during follow-up, whereas 59% of the patients in the control group continued their stone formation. Side effects were few." They concluded that "magnesium treatment in renal calcium stone disease is effective with few side effects. No clinical signs of magnesium excess were observed." (1)

8. Hypercalcemia (hyperparathyroidism, Sarcoidosis or cancer related)
The specific disease should be treated if possible.

9. Xanthine stones
Xanthine is poorly soluble at any pH. Changing the pH of the urine is not benefical. A high fluid intake and a low purine diet is the only therapy.

10. 2,8-dihydroxyadenine stones
Similar to Xanthine stone treatment.

11. Renal Tubular Acidosis
Type 1 Renal Tubular Acidosis is manly treated with sodium bicarbonate. 100 to 200 mg/kg/day in divided dosages will reduce the occurrence of kidney stones. The serum HCO3 level can be normalized.

Type II Renal Tubular Acidosis is treated with potassium bicarbonate. A low serum potassium may develop if it is treated with sodium bicarbonate alone. The plasma HCO3 level cannot be normalized

12. Primary hypocitraturia
Potassium citrate in a dosage of about 1 mEq/kg. It may work (mainly) because it produces a alkali load. It also raise the urinary citrate excretion.