Urine Analysis: Part 18 – uric acid Quantitative (24 hrs Urine Sample), Uricosuria
- 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.
- 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.
- Some drugs increase the uric acid level like:
- Vitamin C.
- Cytotoxic drugs are used to treat cancers (leukemias and lymphomas).
- Strenuous exercise.
- Diet high in purines.
- Allopurinol decreases the uric acid level.
- 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.
- The majority of the uric acid is excreted by the kidney and a small amount by the intestinal tract.
- Normally 1/3 of uric acid formed is degraded in the intestine by bacteria.
- Excess of the uric acid is related to dietary intake of purines or endogenous uric acid production.
- Uric acid exists in the more soluble form 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 large toe, feet, ankles, knee, and elbow are common sites.
- There is severe pain in the joints.
- There is the stiffness of 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.
|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 purine free diet = <400 mg / 24 hours.
- With 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
- Color = Pale yellow or amber
- Appearance = Clear to slightly hazy
- pH = 4.5 to 8.0
- Specific gravity = 1.015 to 1.025
- Blood = Negative
- Glucose = Negative
- Ketones= Negative
- Protein = Negative
- Bilirubin = Negative
- Urobilinogen = Negative (±)
- Leucocyte esterase = Negative
- Nitrite for bacteria = Negative
- RBCs = Rare or Negative
- WBC = Rare or Negative
- Epithelial cells = Few
- Cast = Negative (Occasional hyaline)
- Crystal = Negative (Depends upon the pH of the urine)
- Bacteria = Negative