What is the role of 24-hour urine profile in the diagnosis of nephrolithiasis?

Updated: Jun 21, 2018
  • Author: Chirag N Dave, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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Answer

To identify urinary risk factors, a 24-hour urine profile, including appropriate serum tests of renal function, uric acid, and calcium, is needed. Such testing is available from various commercial laboratories. This study is designed to provide more information about the exact nature of the chemical problem that caused the stone. This information is useful not only to allow more specific and effective therapy for stone prevention but also to identify patients with renal calculi who might have other significant health problems.

Keep in mind that all of the 24-hour urine chemistry findings may be within the reference range in patients who actively form stones and who are at high risk for stones. In these cases, optimizing the levels is beneficial and certain pharmacologic interventions may be suggested to prevent further stone formation

The following are objective indications for a metabolic evaluation with a 24-hour urinalysis:

  • Residual calculi after surgical treatment

  • Initial presentation with multiple calculi

  • Initial presentation before age 30 years

  • Renal failure

  • Solitary kidney (including renal transplant)

  • Family history of calculi

  • More than 1 stone in the past year

  • Bilateral calculi

  • Patient preference: An important consideration in determining whether to perform a 24-hour urine study is the patient’s interest. If a patient is strongly motivated to follow a protracted stone-prevention treatment plan (involving diet, supplements, medications, or a combination), obtain the study. If a patient is unlikely or unwilling to follow a long-term treatment plan, a metabolic evaluation is probably unwarranted. Patients have to understand that stone disease is a chronic disease. If they do not commit to helping themselves in behavior modification, dietary changes, or medical compliance, they are prone to more frequent calculi formation.

The most common findings on 24-hour urine studies include hypercalciuria, hyperoxaluria, hyperuricosuria, hypocitraturia, and low urinary volume. Other factors, such as high urinary sodium and low urinary magnesium concentrations, may also play a role. A finding of hypercalcemia should prompt follow-up with an intact parathyroid hormone study to evaluate for primary and secondary hyperparathyroidism.


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