Citrate – Urine 24 hours

Overview

The Citrate – Urine 24 Hours test measures the total amount of citrate excreted in urine over a 24-hour period. Citrate is an organic acid produced from the metabolism of carbohydrates and fats and is also present in citrus fruits. It serves as a critical urinary buffer, maintaining acid-base balance and preventing excessive acidity or alkalinity that contributes to calcium kidney stone formation.

Citrate performs multiple biological functions:

1. Inhibits calcium stone formation by binding and solubilizing calcium, reducing supersaturation of calcium salts.
2. Acts as a calcium chelator and metabolic regulator.
3. Plays a role in renal, hepatic, and coagulation processes.
4. Supports systemic calcium homeostasis, bone mineralization, energy metabolism, and immune function.
5. Functions as an intermediate in the Krebs (TCA) cycle, aiding lipid and protein synthesis, insulin secretion, and tissue formation.

Low urinary citrate (hypocitraturia) significantly increases the risk of calcium kidney stones, while normal or high citrate levels provide a protective effect.

The test is indicated for assessing kidney stone risk, diagnosing disturbances in citrate metabolism, and monitoring patients undergoing treatment for renal tubular acidosis or calcium stone disease.

Symptoms

While the Citrate – Urine 24 Hours test does not diagnose symptoms directly, the PDF outlines situations in which symptoms suggest the need for this test.

Symptoms Suggesting Kidney Stones:

1. Sharp pain in the back or side
2. Blood in urine (hematuria)
3. Nausea and vomiting
4. Fever (if infection is associated)
5. These symptoms typically arise due to low citrate levels that contribute to stone formation.

Symptoms Suggesting Renal Tubular Acidosis (RTA):

1. Growth failure in children
2. Bone deformities
3. Muscle weakness
4. Signs of kidney dysfunction

These symptoms indicate inadequate acid-base regulation, often accompanied by low urinary citrate levels.

Causes

The PDF provides detailed information on biological and pathological causes of abnormal urinary citrate levels.

Causes of Low Urinary Citrate (Hypocitraturia):

1. Acidosis
2. Renal tubular acidosis
3. Altered metabolism affecting citrate production
4. Renal tubular disorders leading to impaired citrate excretion
5. Low urine pH, contributing to calcium stone formation

Low urinary citrate increases calcium stone risk by reducing citrate’s ability to bind calcium.

Causes of High Urinary Citrate:

1. High dietary citrate intake
2. Metabolic alkalosis
3. High citrate levels are protective and reduce the risk of kidney stones.

Testing Accuracy Issues (Causes of Incorrect Results):

1. Incomplete 24-hour urine collection
2. Dietary fluctuations during collection
3. Medications influencing citrate excretion
4. Underlying conditions affecting citrate metabolism
5. The PDF emphasizes that incomplete collection is the most common reason for unreliable results.

Risk Factors

Risk factors influence either the development of low/high urinary citrate levels or increase the need for this test.

Risk Factors for Low Urinary Citrate:

1. History of recurrent calcium kidney stones
2. Family history of stones
3. Conditions affecting kidney acid-base balance, such as RTA
4. High-acid dietary patterns
5. Underlying metabolic disturbances
6. Bone remodeling abnormalities
7. Chronic kidney disease

Risk Factors Suggesting Need for the Test:

1. Symptoms of kidney stones (pain, hematuria, fever)
2. Symptoms of RTA
3. Patients undergoing treatment for stone prevention
4. Monitoring individuals with known metabolic disorders

Prevention

Prevention described in the PDF focuses on proper patient preparation, correct sample collection, and strategies that support accurate citrate measurement.

Patient Preparation (Strictly From PDF):

1. Avoid foods and beverages containing citrate (citrus fruits, juices, sodas),
2. Avoid alcohol, caffeine, and tobacco
3. For at least 24 hours before and during the urine collection period.

Proper Sample Collection:

1. Collect 24-hour urine and refrigerate during the entire period.
2. Use a clean plastic container with 30 mL of 6N HCl preservative.
3. Send the sample promptly to the laboratory.
4. For metabolic evaluation, also collect 3.0 mL blood in an EDTA (lavender-capped) tube and separate plasma early.

Analytical Methods Mentioned in the PDF:

1. Nuclear Magnetic Resonance (NMR)
2. UV Assay
3. Enzymatic Methods
4. Spectrophotometry
5. Ion Chromatography
6. Titration

Clinical Prevention:

1. Ensure complete 24-hour urine collection to avoid false results.
2. Monitor citrate levels in patients with kidney stones or RTA undergoing therapy.
3. Use citrate measurement to track responses to dietary or medical interventions.