Urine, Uric acid Quantitative (24 hrs Urine Sample), Uricosuria
Uric acid Quantitative in urine
Sample for Uric acid Quantitative
- This test is done in the urine.
- Collect urine for 24 hours.
- Discard the first sample (empty the urinary bladder), then collect all urine samples until 24 hours are completed.
- Also, add the last sample (empty the urinary bladder) to the container.
- Do not refrigerate the urine; add NaOH (10 mL) to keep the urine alkaline.
- The urine will be stable at 22 °C to 24 °C for three days if there is no bacterial growth.
Indications for Uric acid Quantitative
- To find if kidney stones are due to high uric acid levels in the body.
- Evaluates uric acid metabolism in gout.
It helps to evaluate the effect of uricosuric drugs.
Precautions for Uric acid Quantitative
- Some drugs increase the uric acid level like:
- Vitamin C.
- Cytotoxic drugs are used to treat cancers (leukemias and lymphomas).
- Strenuous exercise.
- A diet high in purines.
- Allopurinol decreases the uric acid level.
Pathophysiology of Uric acid Quantitative
- Uric acid is the major product of catabolism of :
- Purine Nucleosides.
- Nucleic acid precursors are purines, adenosine, and guanosine.
- Dietary nucleic acid forms purines directly converted to uric acid.
- Endogenous nucleic acid forms purines; these are excreted as uric acid into the urine.
- Uric acid is readily filtered through the glomerulus.
- Uric acid is absorbed + excreted by the kidney; only 6% to 12% of filtrate is uric acid in urine.
- Most of the uric acid is excreted by the kidney and a small amount by the intestinal tract.
- Normally 1/3 of the uric acid formed is degraded in the intestine by bacteria.
- Excess of uric acid is related to dietary intake of purines or endogenous uric acid production.
- Uric acid is more soluble at a pH of > 5.75.
- Uric acid is undissociated at a pH of < 5.75.
- Most uric acid is excreted in the urine, and the rest passes out in the stool.
Clinically hyperuricemia may lead to gout.
- This is also called gouty arthritis.
- It appears in common sites in large toes, feet, ankles, knees, and elbows.
- There is severe pain in the joints.
- There is stiffness in the joints.
- There are limited movements of the joints.
- Joints are deformed.
- There are redness and swelling of the joints.
- There may be uric acid deposits called gouty tophi.
- There are more chances for the formation of uric renal stones.
Normal Uric acid in urine/24 hours
|The average on a normal diet||250 to 750 (1.48 to 4.43 mmol/day)|
|Purine free diet|
|Male||<420 0r (<2.48 mmol/day)|
|High purine||<1000 ( <5.90 mmol/day)|
- Urine = 250 to 750 mg/24 hours or
- 1.48 to 4.43 mmol/24 hours
- Men = 250 to 800 mg /24 hours
- Women = 250 to 750 mg /24 hours
- With a purine-free diet = <400 mg / 24 hours.
- With a high purine diet = <1000 mg / 24 hours.
Raised urine uric acid level (Uricosuria) is seen in:
- Renal calculi.
- Cancers (widespread disease).
- Chronic myelogenous leukemia.
- Multiple myelomas.
- Viral hepatitis.
- High–purine diet.
- Wilson’s disease.
- Sickle cell anemia.
- Polycythemia vera.
Decreased urine uric acid level seen in:
- Long-term alcohol abuse.
- Chronic glomerulonephritis (chronic kidney disease).
- Lead poisoning.
- Folic acid deficiency.
- Cytotoxic drugs.
Acidosis (ketotic or lactic).
Normal urine picture:
|Physical features||Chemical features||Microscopic findings|
Questions and answers:
Question 1: At what pH of urine uric acid is soluble?
Uric acid is soluble at pH of >5.75.