eMedicine Specialties > Pediatrics: General Medicine > Nephrology

Uric Acid Stones: Differential Diagnoses & Workup

Author: Sahar Fathallah-Shaykh, MD, Assistant Professor in Pediatric Nephrology, Northwestern University Feinberg School of Medicine; Consulting Staff, Division of Kidney Diseases, Children's Memorial Hospital
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
Contributor Information and Disclosures

Updated: Jul 8, 2008

Differential Diagnoses

Colic
Sarcoidosis
Cystinosis
Systemic Lupus Erythematosus
Fanconi Syndrome
Tumor Lysis Syndrome
Glycogen-Storage Disease Type I
Urinary Tract Infection
Hematuria
Urolithiasis
Hemorrhagic Fever With Renal Failure Syndrome
Xanthinuria
Hypercalciuria
Nephritis
Pyelonephritis

Other Problems to Be Considered

Include glomerulonephritis in the differential diagnosis.

The differential diagnosis of uric acid urolithiasis includes other items that cause hematuria and flank pain, such as other stones (eg, calcium, cystine), infection (pyelonephritis), tumor (Wilms), and trauma.

In infants or children who present with acute crystal nephropathy, causes of acute renal failure should be included in the differential diagnosis. Causes include prerenal (eg, decreased renal perfusion), intrinsic renal (eg, acute tubular necrosis, interstitial nephritis, glomerulonephritis, vascular lesions, infection), and postrenal (eg, obstruction).

The prevalence of uric acid nephrolithiasis is higher among patients with features of the metabolic syndrome such as obesity and type 2 diabetes mellitus.3 The major determinant in the development of idiopathic uric acid stones is an abnormally low urinary pH.

Patients with calculi in anatomically abnormal kidneys (eg, horseshoe kidney) should be considered for a metabolic evaluation to include workup for uric acid stones.4 These patients may be more prone to have hypercalciuria, hyperoxaluria, hyperuricosuria, and hypocitraturia.

Workup

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.

Imaging Studies

  • 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.

Other Tests

  • Any stones collected should be sent for crystallographic analysis.

Procedures

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

More on Uric Acid Stones

Overview: Uric Acid Stones
Differential Diagnoses & Workup: Uric Acid Stones
Treatment & Medication: Uric Acid Stones
Follow-up: Uric Acid Stones
Multimedia: Uric Acid Stones
References
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References

  1. Baldree LA, Stapleton FB. Uric acid metabolism in children. Pediatr Clin North Am. Apr 1990;37(2):391-418. [Medline].

  2. 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].

  3. Sakhaee K, Maalouf NM. Metabolic syndrome and uric acid nephrolithiasis. Semin Nephrol. Mar 2008;28(2):174-80. [Medline].

  4. 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].

  5. Barrat TM, PG Duffy. Nephrocalcinosis and Urolithiasis. In: Pediatric Nephrology. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999:933-46.

  6. Camron JS, F Moro. Gout, Uric Acid, and Purine Metabolism in Pediatric Nephrology. In: Pediatric Nephrology. Vol 7. 1993:105-18.

  7. 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].

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Further Reading

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Keywords

uric acid stones, radiolucent kidney stones, gouty nephropathy, urate nephropathy, uric acid urolithiasis, uric acid kidney stones, renal insufficiency, uric acid urolithiasis, renal stones, glycogen-storage disease, gross hematuria, leukemia, lymphoma, lung cancer, breast cancer, pancreatic cancer, hyperuricosuria, hypouricemia, familial juvenile gouty nephropathy, renal failure, urinary tract obstruction, insomnia, Lesch-Nyhan syndrome, tumor lysis disease, gout, polycythemia, lead exposure, congestive heart failure, sarcoidosis, purine disorder, laxative abuse, hypoxanthine-guanine phosphoribosyltransferase deficiency, HGPRT deficiency, phosphoribosyl pyrophosphate synthetase, PRPP synthetase, glucose-6-phosphatase deficiency, myeloproliferative disorder, lymphoproliferative disorder

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Contributor Information and Disclosures

Author

Sahar Fathallah-Shaykh, MD, Assistant Professor in Pediatric Nephrology, Northwestern University Feinberg School of Medicine; Consulting Staff, Division of Kidney Diseases, Children's Memorial Hospital
Sahar Fathallah-Shaykh, MD is a member of the following medical societies: American Society of 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

Medical Editor

Uri S Alon, MD, Director of Research and Education, Department of Pediatrics, Division of Pediatric Nephrology, Children's Mercy Hospital of Kansas City; Professor, University of Missouri at Kansas City
Uri S Alon, MD is a member of the following medical societies: American Federation for Medical Research
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

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.

CME Editor

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, Feinberg School of Medicine, Northwestern University; Division Head of Kidney Diseases, Children's Memorial Hospital, Chicago
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: Amgen Grant/research funds None; Altus Pharmaceuticals Grant/research funds None; Genzyme Grant/research funds None; Merck Grant/research funds None; NIH Grant/research funds None

 
 
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