Monday, April 21, 2014

Stone Disease: Minimizing Recurrence Through a Comprehensive Approach

The lifetime prevalence of kidney stones is estimated to be 10-15% in the United States.[1-2]  While kidney stones are more common in men, caucasians, and in warmer climates; the most common risk factor for a kidney stone is a prior stone.  After one episode, the risk of recurrence is 50% in the next 5-10 years.[3-5]

Brian Matlaga, MD, is the Director of Stone Disease at the Brady Urological Institute at Johns Hopkins,
"If you have one stone, you have a 50% lifetime recurrence risk, which is pretty high.  Patients with a stone have two problems: [the first is treating the stone, then] we need to figure out why the stone formed and how to lower those risk factors." 
For the majority of first-time stone formers, dietary and behavioral modifications are enough to reduce the risk of a second stone.  It is estimated that of patients with a first-time stone, 60% or greater are idiopathic stone formers (or stone formers without a particular cause).[6]  Therefore, making simple dietary modifications can help most people who form a stone, without subjecting them to a plethora of diagnostic tests.
These modifications include:

  1. hydration
  2. minimizing salt intake
  3. normal calcium in the diet
  4. low animal protein
     See the blog entry: Classic Manuscripts in Urology: Borghi, NEJM 2002 to learn more about dietary modifications in stone disease. 

However, other studies demonstrate that 50% of stone formers will have hypercalciuria or hyperuricosuria (elevated amounts of common components of kidney stones in the urine) and 20% of patients will have a systemic disease that contributes to stone formation.[7,8]  Therefore the decision to undergo a complete metabolic stone work-up should be based on an assessment and discussion of patient risk factors and evaluation of the obstructing kidney stone when it has been removed.

In general, a complete metabolic stone evaluation includes:

  • a thorough history and physical
  • medication review
  • blood work (basic metabolic panel, calcium , parathyroid hormone, uric acid)
  • stone analysis
  • 24-hour urinalysis (a patient may be required to do one or several repeat tests)

Patients at high-risk of stone recurrence (and therefore those that should undergo complete metabolic evaluation at the time of their first stone) include:

  • family history of stones
  • those with intestinal disease (particularly when causing chronic diarrheal states)
  • pathologic skeletal fractures/osteoporosis
  • urinary tract infection
  • gout
  • stones composed of: 
    • cystine
    • uric acid
    • struvite 
  • all children (children have a much higher risk of underlying systemic disease or metabolic derangement leading to recurrent stones)[9-13]

At the Brady Urological Institute, Dr. Matlaga helps coordinate a Comprehensive Stone Clinic, in which a patient can be seen, evaluated and managed by a urologist, nephrologist and nutritionist.  This "team approach" often helps determine who needs a complete metabolic evaluation and how often do patients need to be seen.  Using 24-hour urine tests, Dr. Matlaga and colleagues can "back-calculate" a patient's metabolic risk factors to see whether "it's too much calcium, too much oxalate or not enough inhibitors of stone formation, and then we can say,
"Your recurrence risk is now 50 percent; let's try and get it down to about 10% (the general population's risk)."
This works particularly well in the pediatric population where "[urologists] are used to taking care of complex surgical problems, we have a pediatric nephrologist who is used to taking care of complex medical problems, and the nutritionist manages the dietary issues."

If you, a loved one, or a patient has stone disease and would like to be evaluated by Dr. Matlaga and colleagues at Johns Hopkins, please call 410 955 6100 (adults) or 410-955-6108 (children).

Part of this blog was extracted from "A Comprehensive Approach to Stone Disease" in Johns Hopkins Urology News for Physicians, Spring 2014.

[1] Johnson CM, Wilson DM, O’Fallon WM,et al: Renal stone epidemiology: a 25-year study in Rochester, Minnesota. Kidney Int 1979; 16: 624-631
[2] Sierakowski R, Finlayson B, Landes R,et al: The frequency of urolithiasis in hospital discharge diagnoses in the United States. Invest Urol 1978; 15: 438-441
[3] Uribarri J, Oh MS, Carroll HJ,et al: The first kidney stone. Ann Intern Med 1989; 111: 1006-1009
[4] Ljunghall S, Danielson BG: A prospective study of renal stone recurrences. Br J Urol 1984; 56: 122-124
[5] Ljunghall S, Backman U: Calcium and magnesium metabolism during long-term treatment with thiazides. Scand J Urol Nephrol 1981; 15: 257-262
[6] Hosking DH, Erickson SB: The stone clinic effect in patients with idiopathic calcium urolithiasis. J Urol 1983; 130: 1115-1118
[7] Pak CY: Should patients with single renal stone occurrence undergo diagnostic evaluation?. J Urol 1982; 127: 855-858
[8] Strauss AL, Coe FL: Factors that predict relapse of calcium nephrolithiasis during treatment: a prospective study. Am J Med 1982; 72: 17-24
[9] Bartosh SM: Medical management of pediatric stone disease. Urol Clin North Am 2004; 31: 575-587x–xi
[10] Coward RJ, Peters CJ: Epidemiology of paediatric renal stone disease in the UK. Arch Dis Child 2003; 88: 962-965
[11] Pietrow PK, Pope JC: Clinical outcome of pediatric stone disease. J Urol 2002; 167: 670-673
[12] Polito C, Manna ALa: Clinical presentation and natural course of idiopathic hypercalciuria in children. Pediatr Nephrol 2000; 15: 211-214
[13] Tekin A, Tekgul S: Ureteropelvic junction obstruction and coexisting renal calculi in children: role of metabolic abnormalities. Urology 2001; 57: 542-545discussion 545–6

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