Tag: stone

FAQ: Understanding Kidney Stones (Part II)

In a previous post, I wrote about: What are kidney stones, how common are kidney stones, kidney stones composition and risk factors for kidney stones disease.

  • A first-time kidney stone (urolithiasis) former is at risk of having another episode?

Yes. First-time stone formers have a 50% risk for recurrence within the sub­sequent 10 years.

  • Which patients need metabolic evaluation (work-up)?

Those that are recurrent stone formers, who have a strong family history of stones, those with chronic diarrhea or with history of pathologic fractures, osteoporosis, urinary tract infection (UTI) with calculi, gout, solitary kidney, urological anatomic abnormalities, renal insufficiency or those with stones composed of struvite, uric acid or cystine.

  • What are the general conservative recommendations for all patients who have had kidney stones (urolithiasis)?

Consume enough fluids to produce at least 2 liters of urine per day. Soda beverages flavored with phosphoric acid may increase stone risk, whereas those with citric acid may decrease risk. Regarding diet, studies have shown a great advantage of a diet with reduced animal protein (meat) intake. Dietary sodium restriction. Have a diet high in fruits and vegetables. Calcium restriction INCREASES stone recurrence risk and calcium supplements should be taken with meals.

eat-less-salt-sodium

keep-calm-and-drink-more-water

Uric acid nephrolithiasis

Kidney stones (nephrolithiasis or urolithiasis) affect approximately 12% of men and 5% of women during their lifetime. Nearly half of all first time stone formers will have another stone episode within the next four years.

Stones can form when calcium, oxalate, uric acid or cystine are at high levels in the urine.

Uric acid stones represents 5 – 10% of all kidney stones. But they comprise 40% in areas with hot/arid climates where low urine volume and acid urine pH promote uric acid precipitation.
Prevalence:  In patients with gout without antihyperuricemic treatment is 20%. Hundreds-fold greater than healthy adults.

Risk factors: It primarily occurs in patients without abnormality in uric acid metabolism such as: relatively high serum uric acid levels, comparatively low urinary pH, and low fractional excretion of urate. Clinical gout. Hyperuricosuria, chronic diarrhea (bicarbonate loss and dehydration).  Diabetes, metabolic syndrome and overweight.

How it occurs?:  Two major factors contribute uric acid precipitation

  • a high concentration of uric acid in urine
  • acid urine pH

Diagnosis: Is suggested from the acute onset of flank pain, a positive non-contrast-enhanced CT scan, and history of a predisposing disease (gout, cancer, etc). Plain X-ray is not helpful because these stones are not radiopaque. Confirmation of the diagnosis is best made by chemical analysis of a stone that has been passed.

Treatment:

  • Maintenance of the urine output above 2 L/day to diminish the urine uric acid concentration
  • alkalinization of the urine (increase the urine pH) with potassium bicarbonate or potassium citrate (cytra-k; polycitra-k; urocit-k; citro-k) can be given and this regimen can both dissolve preexisting stones and prevent the formation of new ones.
  • Allopurinol (zyloprim; aloprim; atisuril)
  • Reduction in dietary purine intake (protein)
Image courtesy of: Urocit-K