Uric Acid Stones Workup

Author: Sahar Fathallah-Shaykh, MD; Chief Editor: Craig B Langman, MD more...

Updated: Aug 3, 2011

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Laboratory Studies
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Laboratory Studies

Any child with a stone should have a 24-hour urine sample collected for analysis of calcium, magnesium, uric acid, citrate, sodium, and urine volume. A spot urine pH level should be obtained.

Serum uric acid, 24-hour acid excretion, urine uric acid, creatinine, and serum creatinine can be used to assess uric acid production and excretion.

Blood should be obtained for measurement of BUN, creatinine, calcium, phosphorus, bicarbonate, uric acid, and parathyroid hormone levels.

These test results are used to estimate the fractional excretion of uric acid.
Reference range values for uric acid excretion by children and infants are shown in the table above.
Results are used to determine if the elevated urinary uric acid concentration is caused by uric acid overproduction, decreased net renal tubular uric acid reabsorption, or increased net renal tubular uric acid secretion.
Overproduction is indicated by high uric acid excretion for 24 hours with high or reference range serum uric acid levels and reference range or increased fractional excretion of uric acid.
Decreased net renal tubular reabsorption or increased net tubular secretion is indicated by reference range or low uric acid excretion with low or low-normal serum uric acid and high fractional excretion of uric acid.

Once the problem is recognized as overproduction or increased tubular secretion or decreased net tubular reabsorption, specific testing for the primary cause can be undertaken.

For children, renal ultrasonography and abdominal flat plate radiography are as effective as intravenous pyelography (IVP) for identifying stones and do not expose the child to the risk of contrast agents. In addition, the radiation exposure is less. Renal ultrasonography is nonpainful, noninvasive, and creates no radiation exposure. Ultrasonography can reveal hydronephrosis and, frequently, acoustic shadowing produced by a renal stone. Although the stone position can be identified, its composition cannot be determined using ultrasonography.
Noncontrast CT scanning (spiral CT scanning) is the most sensitive and specific study to search for uric acid stones.

Any stones collected should be sent for crystallographic analysis.

Retrograde pyelography may be necessary to delineate upper tract anatomy and localize small or radiolucent calculi.

Proceed to Treatment & Management

Contributor Information and Disclosures

Author

Sahar Fathallah-Shaykh, MD Assistant Professor in Pediatric Nephrology, University of Alabama at Birmingham School of Medicine; Consulting Staff, Division of Pediatric Nephrology, Medical Director of Pediatric Dialysis Unit, Children's of Alabama

Sahar Fathallah-Shaykh, MD is a member of the following medical societies: American Society of Nephrology and American Society of Pediatric Nephrology

Disclosure: emedecine Honoraria Other

Coauthor(s)

Richard Neiberger, MD, PhD Director of Pediatric Renal Stone Disease Clinic, Associate Professor, Department of Pediatrics, Division of Nephrology, University of Florida College of Medicine and Shands Hospital

Richard Neiberger, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Federation for Medical Research, American Medical Association, American Society of Nephrology, American Society of Pediatric Nephrology, Christian Medical & Dental Society, Florida Medical Association, International Society for Peritoneal Dialysis, International Society of Nephrology, National Kidney Foundation, New York Academy of Sciences, Shock Society, Sigma Xi, Southern Medical Association, Southern Society for Pediatric Research, and Southwest Pediatric Nephrology Study Group

Disclosure: The Osler Institute Honoraria Speaking and teaching

Specialty Editor Board

Uri S Alon, MD Director of Bone and Mineral Disorders Clinic and Renal Research Laboratory, Children's Mercy Hospital of Kansas City; Professor, Department of Pediatrics, Division of Pediatric Nephrology, University of Missouri-Kansas City School of Medicine

Uri S Alon, MD is a member of the following medical societies: American Federation for Medical Research

Disclosure: Nothing to disclose.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Frederick J Kaskel, MD, PhD Director of the Division and Training Program in Pediatric Nephrology, Vice Chair, Department of Pediatrics, Montefiore Medical Center and Albert Einstein School of Medicine

Frederick J Kaskel, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American Pediatric Society, American Physiological Society, American Society of Nephrology, American Society of Pediatric Nephrology, American Society of Transplantation, Eastern Society for Pediatric Research, Federation of American Societies for Experimental Biology, International Society of Nephrology, National Kidney Foundation, New York Academy of Sciences, Renal Physicians Association, Sigma Xi, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Howard Trachtman, MD Program Director, Pediatrics Research, Schneider Children's Hospital, Department of Pediatrics, Division of Nephrology, Professor, Albert Einstein College of Medicine

Howard Trachtman, MD is a member of the following medical societies: American Society of Hypertension, American Society of Nephrology, American Society of Pediatric Nephrology, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Chief Editor

Craig B Langman, MD The Isaac A Abt, MD, Professor of Kidney Diseases, Northwestern University, The Feinberg School of Medicine; Division Head of Kidney Diseases, Children's Memorial Hospital

Craig B Langman, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Nephrology, and International Society of Nephrology

Disclosure: Merck Grant/research funds None; NIH Grant/research funds None; Raptor Pharmaceuticals, Inc Grant/research funds None; Alexion Pharmaceuticals, Inc. Grant/research funds None

References

Baldree LA, Stapleton FB. Uric acid metabolism in children. Pediatr Clin North Am. Apr 1990;37(2):391-418. [Medline].
Fujita T, Shimooka T, Teraoka Y, Sugita Y, Kaito H, Iijima K, et al. Acute renal failure due to obstructive uric acid stones associated with acute gastroenteritis. Pediatr Nephrol. Dec 2009;24(12):2467-9. [Medline].
Kaneko K, Shimo T, Hirabayashi M, Ito T, Okazaki H, Harada Y. Cause of uric acid stones in rotavirus-associated gastroenteritis. Pediatr Nephrol. Oct 2010;25(10):2187-8. [Medline].
Kato K, Sai S, Hirata T, et al. Two cases of ammonium acid urate urinary stones related to anorexia nervosa and laxative abuse. Hinyokika Kiyo.Mar. 2004;50(3):181-5. [Medline].
Sakhaee K, Maalouf NM. Metabolic syndrome and uric acid nephrolithiasis. Semin Nephrol. Mar 2008;28(2):174-80. [Medline].
Raj GV, Auge BK, Assimos D, Preminger GM. Metabolic abnormalities associated with renal calculi in patients with horseshoe kidneys. J Endourol. Mar 2004;18(2):157-61. [Medline].
[Medline].
Barrat TM, PG Duffy. Nephrocalcinosis and Urolithiasis. In: Pediatric Nephrology. 4^th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999:933-46.
Camron JS, F Moro. Gout, Uric Acid, and Purine Metabolism in Pediatric Nephrology. In: Pediatric Nephrology. Vol 7. 1993:105-18.
Johnson RJ, Kivlighn SD, Kim YG, et al. Reappraisal of the pathogenesis and consequences of hyperuricemia in hypertension, cardiovascular disease, and renal disease. Am J Kidney Dis. Feb 1999;33(2):225-34. [Medline].

Uric acid stones.

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Table 1. Serum Uric Acid levels and Urinary Acid Excretion in Neonates, Children, and Adults [1]

Table 1. Serum Uric Acid levels and Urinary Acid Excretion in Neonates, Children, and Adults^[1]

	Neonates*			Children						Adults
	29-33 wk	34-37 wk	38-40 wk	3-4 y		5-9 y		10-14 y		40-44 y
				Male	Female	Male	Female	Male	Female	Male	Female
Serum uric acid (mg/dL)	7.71±2.65	6.04±2.19	5.19±1.57	3.45±1.01	3.44±0.8	3.63±1.04	3.71±0.92	4.28±1.19	4.09±1.2	5.134±1.25	4.25±1.1
Uric acid excretion (mg/dL GFR^†)	4.8±2.23	2.81±0.93	1.69±0.84	0.34±0.11						0.403±0.095
Uric acid excretion (mg/kg/d)	N/A	N/A	19.6	13.5±3.75 (3 y)		11.5±3.75 (7 y)		9±3.75 (12 y)		10
Fractional excretion of uric acid (%)	61.24±12.21	44.52±15.23	38.19±13.61	12±3.75 (3 y)		10±3 (7 y)		7.6±3.75 (12 y)		7±1.6
*Gestational ages ^† Glomerular filtration rate

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Uric Acid Stones Workup

Laboratory Studies

Imaging Studies

Other Tests

Procedures