VA MTC 5/16/22: Stones Galore!

Today’s VA morning report was all about nephrolithiasis! We discussed a case of a young woman with recurrent nephrolithiasis, whose stones were a combination of calcium phosphate and calcium oxalate. Our residents worked together to compile the chart above with the crystal shapes, risk factors, underlying conditions and lab findings associated with the most common types of kidney stones. Dr. Beben, our expert nephrologist, also gave his valuable insight.

When seeing recurrent nephrolithiasis in the clinic, on the wards, or on the boards, it is important to remember:

  • Pay attention to the urine pH! This can be a helpful clue to the type of stone.
  • 24-hour urine collection, collected at least 1 month after an acute episode of nephrolithiasis, UTI, or urologic procedure, can also help to identify underlying problems such as hypercalciuria, hypocitraturia, hyperoxaluria, hyperuricosuria, and cystinuria.
  • Citrate is an important inhibitor of calcium crystallization in the urine. Therefore hypocitraturia can predispose patients to calcium stone formation.
  • Increasing fluid intake to a goal OUP of >2.5 L is an important recommendation regardless of the type of stone!
  • Other useful dietary changes, depending on the type of stone, include:
    • Low dietary sodium (Remember: calcium follows sodium and water!)
    • Low oxalate diet
    • Limit animal protein
  • *Limiting dietary calcium is NOT recommended
  • Some of the most common pharmacologic interventions may include:
    • Potassium citrate or potassium bicarbonate (helps with most types of stones by various mechanisms)
    • Thiazide diuretics (helps with calcium stones by decreasing urinary calcium)
    • Allopurinol (for uric acid stones)

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