A 55-year-old man comes to the emergency department with severe right flank pain. CT scan shows a 5-mm stone in the right ureter and several smaller stones in both renal pelvices. Urinalysis results are as follows:

The patient subsequently passes a stone and analysis shows it to be composed of predominantly uric acid.
Besides high fluid intake, which of the following would be most helpful for this patient to prevent recurrent stones?

Question

A 55-year-old man comes to the emergency department with severe right flank pain.  CT scan shows a 5-mm stone in the right ureter and several smaller stones in both renal pelvices.  Urinalysis results are as follows:

The patient subsequently passes a stone and analysis shows it to be composed of predominantly uric acid.
Besides high fluid intake, which of the following would be most helpful for this patient to prevent recurrent stones?

Quizplus · Accepted Answer

Uric acid stones account for approximately 10%-15% of nephrolithiasis cases. These are most commonly seen in patients with unusually low urine pH (which may be due to a defect in renal ammonia excretion) and hyperuricosuria. Uric acid stones are radiolucent on conventional radiographs but can often be seen on renal ultrasound or CT scan. Treatment of uric acid stones includes hydration, alkalinization of the urine, and a low-purine diet. Alkalinization of the urine to pH 6.0- 6.5 with oral potassium citrate is recommended as uric acid stones are highly soluble in alkaline urine. In addition to alkalinizing the urine, citrate is a stone inhibitor and reduces crystallization. Allopurinol can be added if there are recurrent symptoms despite initial measures, especially if hyperuricosuria or hyperuricemia occurs. (Choice A) A calcium-restricted diet is not beneficial in the management of uric acid stones. It is not advised even in patients with calcium stones, as calcium restriction can potentially cause a negative calcium balance and hyperoxaluria due to the resulting increase in gastrointestinal absorption of oxalate. (Choice B) Furosemide increases urinary calcium excretion, and the resulting hypercalciuria can increase the risk of calcium stone formation. (Choice C) A purine-restricted (not high-protein) diet is indicated in patients with uric acid stones secondary to hyperuricosuria. (Choice D) Hydrochlorothiazide decreases urinary calcium excretion and is used in the management of recurrent hypercalciuric renal stones. Educational objective: Uric acid stones are often radiolucent but may be seen on ultrasound or CT scan. They are highly soluble in alkaline urine; alkalinization of the urine to pH 6.0-6.5 with oral potassium citrate is the treatment of choice. Allopurinol can be added if there are recurrent symptoms despite initial measures, especially if hyperuricosuria or hyperuricemia occurs. __________ References: Uric acid stones and hyperuricosuria. (http://www.ncbi.nlm.nih.gov/pubmed/23089277)

A 55-Year-Old Man Comes to the Emergency Department with Severe