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ORLANDO -- Treatment tailored to individual patient and stone characteristics provides the basis for an American Urological Association clinical guideline on medical management of kidney stones.

Several compelling reasons make stone disease a good candidate for a clinical guideline, said guideline co-chair , of the University of Texas Southwestern Medical Center in Dallas.

"Kidney stones are a common problem, one with a high rate of recurrence," Pearle said of the guideline during the AUA meeting here. "Despite effective established treatment regimens for medical management, there is evidence of underutilization of management of patients for stones. Finally, there is a lack of uniformity in the treatment of patients with recurrent stone disease."

The AUA partnered with the and the to develop a clinical guideline to address the shortcomings of current approaches to medical management of kidney stones. The guideline covers four broad areas of clinical management: evaluation, diet, pharmacology therapy, and follow-up.

All patients with newly diagnosed kidney stones should have a thorough screening evaluation that considers dietary and medical history. The dietary history should focus on evidence of high or low calcium intake, low fluid intake, excessive consumption of animal protein, and limited intake of fruits and vegetables.

The medical history should include conditions that have known or suspected links to stone disease, including renal tubular acidosis, primary hyperparathyroidism, type 2 diabetes, gout, obesity, bowel disease or resection, and bariatric surgery.

Additionally, the initial evaluation should explore the patient's medication history, including drugs such as topiramate, zonisamide, acetazolamide, triamterene, probenecid, protease inhibitors, and vitamin C.

Serum chemistry can provide key diagnostic clues, Pearle continued. Abnormalities involving sodium, potassium, chloride, carbon dioxide, calcium, creatinine, and uric acid can contribute to stone formation. For example, elevated calcium and decreased phosphorus might indicate primary hyperparathyroidism.

Assessment of serum parathyroid hormone is optional but should be obtained whenever primary hyperparathyroidism is suspected, she added.

A stone analysis should be performed at least once if a stone is available.

"Knowledge of the stone composition can implicate certain underlying etiologies, such as low urine pH in patients with uric acid stones," said Pearle.

A metabolic evaluation should be performed for patients with recurrent stone formation, patients who are at high risk for stones because of medical history, children and adolescents, patients with a solitary kidney, and first-time adult stone formers who want to know more about the stone's origin.

A simple metabolic evaluation should be performed, including at least one, and preferably two, 24-hour urine collections associated with a random diet. Urine analysis should include total volume, pH, calcium, oxalate, uric acid, citrate, sodium, potassium, and creatinine. The 24-hour urine provides the basis for dietary measures, said Pearle.

Dietary therapies for patients with kidney stones include:

• Fluid intake sufficient to achieve a urine volume of at least 2.5 L/day
• Limited sodium intake
• Consumption of 1,000 to 1,200 mg/day of dietary calcium
• Limit intake of nondairy animal protein to reduce the risk of uric acid or calcium stones associated with high urinary uric acid

Medication for stones should be chosen on the basis of stone type. Thiazide diuretics should be offered to patients who have high or relatively high urine calcium and a history of recurrent calcium stone formation. For patients with calcium stones and low urinary citrate, the guideline panel recommends potassium citrate.

Allopurinol is recommended for patients with calcium oxalate stones associated with hyperuricosuria and normal urinary calcium.

Thiazide diuretics, potassium citrate, or both should be offered to patients who have recurrent calcium stones and no other metabolic abnormalities or abnormalities that have been addressed and stone formation persists, said Pearle. Allopurinol should not be offered routinely as first-line therapy for uric acid stones.

Follow-up should be based on improvement in urinary risk factors and a reduction in stone formation. The guideline panel recommends serial urine collections to assess changes in risk factors for stone disease. Changes in urinary composition probably precede stone recurrence, Pearle noted.

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