Uric Acid Nephrolithiasis: A Systemic Metabolic Disorder.
Uric acid nephrolithiasis is characteristically a manifestation of a systemic metabolic disorder. It has a prevalence of about 10% among all stone formers, the third most common type of kidney stone in the industrialized world. Uric acid stones form primarily due to an unduly acid urine; less deciding factors are hyperuricosuria and a low urine volume. The vast majority of uric acid stone formers have the metabolic syndrome, and not infrequently, clinical gout is present as well. A universal finding is a low baseline urine pH plus insufficient production of urinary ammonium buffer. Persons with gastrointestinal disorders, in particular chronic diarrhea or ostomies, and patients with malignancies with a large tumor mass and high cell turnover comprise a less common but nevertheless important subset. Pure uric acid stones are radiolucent but well visualized on renal ultrasound. A 24 h urine collection for stone risk analysis provides essential insight into the pathophysiology of stone formation and may guide therapy. Management includes a liberal fluid intake and dietary modification. Potassium citrate to alkalinize the urine to a goal pH between 6 and 6.5 is essential, as undissociated uric acid deprotonates into its much more soluble urate form.
Division of Nephrology, Baylor University Medical Center, 3500 Gaston Avenue, Dallas, TX 75246, USA.
Department of Internal Medicine, Division of Nephrology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-8885, USA, Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Pub Type(s)Journal Article