Hyperuricosuria and Gouty Diathesis Workup

  • Author: Bijan Shekarriz, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS   more...
 
Updated: Nov 23, 2011
 

Laboratory Studies

  • Laboratory evaluation should include urinalysis and urine culture. In patients with known uric acid stones, urinary pH should be recorded using pH paper. Blood chemistry tests should include calcium, phosphorus, electrolyte, creatinine, uric acid, and parathormone levels.
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Imaging Studies

  • All patients with questionable urinary calculi should undergo a baseline radiologic evaluation, including a scout film (ie, kidneys, ureters, bladder [KUB]). The scout film is useful not only as a baseline for tracking radiopaque calculi, but also for establishing radiolucency of possible uric acid stones.
  • Pure uric acid stones are relatively radiolucent and are a bright-white signal on noncontrast CT scans. The diagnosis of uric acid stones can be suggested by a persistent urinary pH of less than 5.5, uric acid crystals visible on microscopic urinalysis, hyperuricemia, a KUB study that fails to show a calcific stone, or a history of gout or previous uric acid calculi. CT scan demonstrating right partial staghorn uric CT scan demonstrating right partial staghorn uric acid calculus. Uric acid stones appear dense on CT scan and radiolucent on kidneys, ureters, and bladder (KUB) imaging (not shown). Follow-up CT scan of patient in the image above (iFollow-up CT scan of patient in the image above (ie, with partial staghorn uric acid calculus) 1 year later. This patient was treated with oral urinary alkalinization with sodium bicarbonate. Note only a small residual fragment is present (right image).
  • Intravenous urography (ie, intravenous pyelography [IVP]) or renal ultrasonography may be useful. Contrast is used for IVP, which can make a uric acid stone appear as a filling defect, especially in the renal pelvis. Ultrasonography is a very good tool for identifying and tracking larger uric acid calculi, especially in the renal pelvis, because their radiolucency does not affect sonograms. This modality is less useful for ureteral calculi.
  • Noncontrast CT scanning is the imaging modality of choice for the differential diagnoses of urinary calculi. With noncontrast CT scanning, uric acid calculi, despite being radiolucent on conventional radiographs, appear as bright-white images, as do other calculi. The average density readings of uric acid stones on CT scans are substantially less than calcium-containing stones but are still well above the threshold of optical visualization as anything but a bright-white spot. In these cases, performing KUB imaging at the same time as CT scanning is essential to help indicate that the stone is relatively radiolucent and therefore likely to be composed of uric acid. If the stone is located in the kidney, ultrasonography can be particularly useful for tracking the progress or dissolution of the stone.
  • In rare circumstances (eg, intravenous contrast allergy, unavailability of CT scanning), retrograde pyelography may help to confirm the diagnosis.
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Other Tests

  • Perform a 24-hour urine collection for volume, pH, calcium, uric acid, oxalate, citrate, phosphorus, sodium, and creatinine analysis after the acute stone event has resolved. This test should help elucidate the metabolic abnormality associated with stone formation. The most common urinary abnormalities in patients with uric acid stones are persistently acidic urine (< 5.5), low volume, and hyperuricosuria.
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Staging

  • Staghorn calculi are stones in the renal pelvis that extend into at least 2 calyceal groups. A complete staghorn calculus fills the entire renal collecting system.
  • Proximal ureteral calculi are stones in the ureter distal to the ureteropelvic junction and anterior to the superior edge of the sacroiliac joint.
  • Midureteral calculi are stones in the ureter that overlie the sacroiliac joint as seen on KUB images.
  • Distal ureteral calculi are stones in the ureter below the inferior margin of the sacroiliac joint down to the ureterovesical junction.
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Contributor Information and Disclosures
Author

Bijan Shekarriz, MD  Director, Laparoscopy and Minimally Invasive Surgery, Associate Professor of Urology, Department of Urology, State University of New York Upstate Medical University

Bijan Shekarriz, MD is a member of the following medical societies: American Urological Association and Endourological Society

Disclosure: Nothing to disclose.

Coauthor(s)

Marshall L Stoller, MD  Professor and Vice Chairman, Medical Director of Urinary Stone Center, Department of Urology, University of California, San Francisco, School of Medicine

Marshall L Stoller, MD is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

Brian H Eisner, MD  Instructor in Surgery, Department of Urology, Massachusetts General Hospital-Harvard Medical School; Fellow in Endourology, Department of Urology, University of California

Brian H Eisner, MD is a member of the following medical societies: American Urological Association and Endourological Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Allen Donald Seftel  MD, Professor of Urology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School; Head, Division of Urology, Director, Urology Residency Training Program, Cooper University Hospital

Allen Donald Seftel is a member of the following medical societies: American Urological Association

Disclosure: lilly Consulting fee Consulting; sanofi-aventis Consulting fee Consulting; auxilium Consulting fee Consulting; solvay Consulting fee Consulting; plethora Grant/research funds clinical trial; endo Consulting fee Consulting; nature publishing journal editor

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

J Stuart Wolf Jr, MD, FACS  The David A Bloom Professor of Urology, Director, Division of Endourology and Stone Disease, Department of Urology, University of Michigan Medical School

J Stuart Wolf Jr, MD, FACS is a member of the following medical societies: American College of Surgeons, American Urological Association, Catholic Medical Association, Endourological Society, Society for Urology and Engineering, Society of Laparoendoscopic Surgeons, Society of University Urologists, and Society of Urologic Oncology

Disclosure: Nothing to disclose.

Chief Editor

Bradley Fields Schwartz, DO, FACS  Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine

Bradley Fields Schwartz, DO, FACS is a member of the following medical societies: American College of Surgeons, American Urological Association, Association of Military Osteopathic Physicians and Surgeons, Endourological Society, Society of Laparoendoscopic Surgeons, and Society of University Urologists

Disclosure: Nothing to disclose.

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CT scan demonstrating right partial staghorn uric acid calculus. Uric acid stones appear dense on CT scan and radiolucent on kidneys, ureters, and bladder (KUB) imaging (not shown).
Follow-up CT scan of patient in the image above (ie, with partial staghorn uric acid calculus) 1 year later. This patient was treated with oral urinary alkalinization with sodium bicarbonate. Note only a small residual fragment is present (right image).
 
 
 
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