• sodium
• potassium
• calcium
• magnesium
• chloride
• phosphorus
• sulfate
• citrate excretion
• oxalate
• pH
• creatine
• osmolality
• ammonium
• urea nitrogen
• protein catabolic rate

Diagnosis and management of patients with renal lithiasis:

• Predicting the likely composition of the stone, in patients who have a radiopaque stone, for whom stone analysis is not available. This may help in designing a treatment program.
• Aiding in identification of specific risk factors for stones using a 24-hour urine collection
• Monitoring the effectiveness of therapy by confirming that the crystallization potential has indeed decreased
• Evaluating kidney excretion of acid and urine pH
• Estimating a patient's protein intake

X-ray dyes and contrast media will affect uric acid test results.

• If a kidney X-ray with dye or computerized tomography (CT) scan with contrast has been performed, patient should wait a minimum of 1 day before starting collection.
• If a cholangiography (bile duct X-ray) has performed, patient should wait 7 days before starting collection.
• Urine must be collected before tablets have been taken for gallbladder X-ray, otherwise patient should wait 7 days before starting collection.

24-hr urine collection container, no additive

• Collect a single 24-hour urine collection without preservative.
• Refrigerate specimen throughout the collection period.

How to collect a 24-hr urine sample

1. Measure the total volume
2. Mix well
3. Transfer 50 mL aliquot of the collection to a screw cap plastic containers, (no preservative)
4. Write total volume of 24 hour collection on aliquot with other clinical information on each container
5. Refrigerate

Screw cap plastic container (sterile)

1. 24-Hour volume is required.
2. Patient's height in centimeters and weight in kilograms are required if patient is younger than 18 years.

Refrigerated (preferred) - 14 days

Frozen - 14 days

Ambient - 3 days

The major analytes evaluated are potassium, calcium, phosphorus, oxalate, uric acid, citrate, magnesium, sodium, chloride, sulfate, ammonium, urea nitrogen and pH. The protein catabolic rate is calculated from urine urea nitrogen using the formula:

Protein catabolic rate (g/day) =[(UUN+4)* 6.25] g

Given the measured urine concentrations of these analytes and the known affinity constants of the ions for each other at the given pH, a computer program (EQUIL2) calculates a supersaturation for each ion pair of interest (eg, calcium oxalate). Results are expressed as a Delta G (DG) value for each ion pair. DG is the Gibbs free energy of transfer from a supersaturated to a saturated solution.(Werness PG, Brown CM, Smith LH, Finlayson B: EQUIL2: a BASIC computer program for the calculation of urinary saturation. J Urol. 1985 Dec;134(6):1242-1244; Moreira DM, Friedlander JI, Hartman C, Elsamra SE, Smith AD, Okeke Z: Using 24-hour urinalysis to predict stone type. J Urol. 2013 Dec;190(6):2106-2111)