WCE 2019: Stone Prevention: Is it Possible?

Abu Dhabi, United Arab Emirates (UroToday.com) Dr. John Denstedt overviews strategies of stone prevention. The prevalence and incidence of stone disease has been rising worldwide in recent decades. In children, the prevalence of urolithiasis has increased 7-fold in the past 10 years. The direct cost of stones in the United States among employed individuals is estimated to be $4.5 billion dollars. Stone prevention is key in lowering cost of care; increased efforts towards stone prevention to curtail the recent increase in urolithiasis prevalence is needed.

The initial evaluation of a stone-forming patient includes labs, imaging, and stone analysis. Imaging can quantify stone burden and determine the number of stones and whether nephrocalcinosis is present. Urinalysis can determine pH, and a urine culture should be done if an infection is suspected. Stone analysis impacts the importance of the 24-hour urine collection. A metabolic workup is recommended, and is offered to about 8% of stone-forming patients.

Strategies specific to the various types of stones were outlined. Calcium stones are often linked to a high sodium diet. Increased sodium in the diet leads to more calcium in the urinary tract and hypocitraturia, which raises the risk of calcium stones. For this reason, a low sodium diet (goal: 2300 mg or less) is recommended in patients with calcium stones such as calcium oxalate or calcium phosphate. Other recommendations include hydration, with a fluid intake goal of creating 2.5L urine per day. It is important to emphasize to patients that cutting back on calcium in their diet is not advised, as this increases the risk of calcium oxalate stones. If the patient is hypercalciuric and non-responsive to dietary modification, thiazide therapy is recommended. If the patient is hypocitraturic and non-responsive to dietary modification, potassium citrate is recommended.

Management of other types of stones for prevention was also discussed. Increased fluid intake with a goal of creating 2.5L urine applies to all types of stones. Uric acid stones are primarily a pH problem, as low pH facilitates formation. The hallmark of prevention of uric acid stones is to reduce purine-rich foods and a high alkaline diet to increase urinary pH. Struvite stones are usually related to an underlying metabolic problem. In struvite stone-forming patients, treatment of the metabolic disorder is key in preventing recurrence. A pharmacologic therapy that may be useful is acetohydroxamic acid.  For cysteine stones, increased volume, low sodium diet, and alkalinized urine to pH>7 is recommended. Drug-induced stones have 2 main mechanisms: a poorly soluble drug metabolite that induces stone formation, or the drug alters urine pH to facilitate stone formation.

Overall, urolithiasis is increasing in prevalence, emphasizing the need for effective stone prevention strategies. Thorough workup followed by patient-specific dietary modifications and pharmacologic therapy are recommended to prevent stone recurrence.

Presented by: John Denstedt, MD, MD, FRCSC, FACS, FCAHS, Richard Ivey Professor, Treasurer, Endourological Society, Managing Editor, Journal of Endourology, Member, Board of Directors, American Urological Association, Western University

Written by: Rajiv Karani, Associate Research Fellow, Department of Urology, University of California, at the 37th World Congress of Endourology (WCE) – October 29th-November 2nd, Abu Dhabi, United Arab Emirates