Urinalysis is the physical and chemical examination of a urine sample. It is a common procedure that can be done quickly and yields important clinical information. This article will teach you the three key steps to perform this procedure and interpret the results.
This article includes a quick visual summary, a video demonstration, and a detailed explanation on urinalysis.
Contents
Visual summary
Video demonstration
Equipment
- Gloves
- Apron
- Urine sample
- Urine test strips (or dipsticks)
- Urinalysis colour chart (usually found on the test strip container)
- Paper towels
- Timer (e.g., clock, stopwatch, phone)
Urine dipsticks and colour chart
A urine dipstick is a thin strip of paper/plastic covered in 10 different coloured squares and a blank end for you to hold. Each square is covered in a reagent which will react with the urine’s contents and change colour depending on the presence and concentration of each chemical.
The colour chart is in the same order as the reagent squares on the dipstick. Their order is based on how long it takes for the chemical reaction to occur (i.e when the result can be read). The colour change will provide a semi-quantitative result of each substance.
Source: Hxa098020, Wikimedia Commons, 28 Oct 22.
Procedure
Step 1: Physical inspection
- Wash your hands. Put on gloves and an apron.
- Check that the urine sample belongs to the correct patient.
- Observe and record the sample’s colour, clarity, and odour.
- Colour
- Observe how pale or dark the urine appears.
- Check for red or brown urine.
- Clarity
- Take note of any cloudiness or frothiness.
- Inspect carefully for any sediment.
Step 2: Urine dipstick
- Check the expiry date on the dipstick container.
- Remove a dipstick by holding the blank end and reseal the container.
- Over a paper towel, insert the dipstick into the urine sample, making sure all the squares are covered and then remove immediately. Tap off or wipe off any excess urine from the dipstick against the rim of the urine container to prevent the reagents from mixing.
- Lay the dipstick flat on a paper towel face up and start a timer.
- After each time interval on the colour chart passes, compare the colour on the dipstick to the chart. Hold them side by side to avoid misreading.
- Once all the tests have been interpreted, dispose of the dipstick, gloves, apron, and paper towel in a clinical waste bin and then wash your hands.
- You may also discard the urine sample if no further investigations are required.
Step 3: Record and interpret the results
- Document your findings and use the tables below to interpret the results.
- Suggest further investigations based on the results and other clinical information.
Urinalysis interpretation
| Urine colour | Potential causes |
| Pale straw/light yellow | Normal (hydrated) |
| Dark yellow | Dehydrated |
| Colourless | Excess hydration Diabetes insipidus |
| Red | Blood Medication (e.g rifampicin) Food (e.g beetroot) |
| Brown | Hyperbilirubinaemia (think causes of jaundice) Myoglobin (think causes of rhabdomyolysis) |
| Urine clarity | Potential causes |
| Clear | Normal |
| Cloudy | Urinary tract infection (UTI) Crystals (think causes of renal stones) Proteinuria (e.g nephrotic syndrome) |
| Frothy | Proteinuria (e.g nephrotic syndrome) |
| Testing reagent | Clinical relevance | Normal result | Abnormal result causes |
| Leukocyte esterase | An enzyme produced by white blood cells, its presence in urine suggests infection or inflammation. Easily susceptible to false positives. | Absent | UTI Urinary tract inflammation (think causes of haematuria) |
| Nitrite | Produced by bacteria in urine that reduce nitrate to nitrites. These bacteria can be seen in urinary tract infections. Poor sensitivity. | Absent | UTI |
| Urobilinogen | Urobilinogen is produced by the breakdown of conjugated bilirubin in the intestine and reabsorbed by the gut and excreted by the kidneys. | 0.2-1.0 mg/dL | Low urobilinogen (biliary obstruction) High urobilinogen (think causes of haemolysis e.g haemolytic anaemia) |
| Protein | Usually filtered by the glomerulus and reabsorbed in the renal tubules. Damage to glomeruli disrupts filtration and reabsorption. Diseases which produce excess protein can cause overflow proteinuria. | Absent or trace amounts | Renal disease (think causes of nephrotic syndrome and chronic kidney disease) Excess proteinaemia or overflow proteinuria (e.g multiple myeloma, rhabdomyloysis, haemolysis) UTI |
| pH | Depends on the physiological state and varies significantly with diet. In acidosis the kidnes will excrete more H+ causing lower urinary pH. In alkalosis the kidneys will excrete less H+ causing higher urinary pH. Note: urine pH does not accurately reflect patient acid-base balance. | 4.5-8.0 | Low pH (think causes of acidosis): – Diabetic ketoacidosis – Sepsis High pH : – Vomiting – UTI |
| Blood | Detects haemoglobin and myoglobin. Susceptible to false positives such as menstruation and vigorous exercise. | Absent | UTI Renal stones Urinary tract malignancy Nephritic syndrome Rhabdomyolysis Trauma (e.g catheterisation, pelvic injury) |
| Specific gravity | Measures the amount of solute dissolved in urine compared to water. | 1.003-1.035 mOsm/kg | Low specific gravity: – Excess fluid intake – Diabetes insipidus – Acute tubular necrosis High specific gravity: – Dehydration – Diabetes mellitus – Syndrome of inappropriate anti-diuretic hormone (SIADH) – Nephrotic syndrome – Contrast dyes |
| Ketones | Ketones are produced by fatty acid metabolism. | Absent | Starvation Diabetic ketoacidosis |
| Bilirubin | Bilirubin is produced from the breakdown of haemoglobin and then converted to water soluble conjugated bilirubin in the liver. | Absent | Biliary obstruction (think causes of jaundice) |
| Glucose | Glucose is water soluble and passes through the glomerulus. The vast majority is reabsorbed in the proximal tubule. | Absent | Diabetes mellitus Medication (e.g SGLT2 inhibitors) Renal tubular disease |
Written and edited by Jesse Chan (FY3)
Video created by Alice Murphy (CTF), Ashmal Qamar (CTF)
Visual summary created by Brian Ng (FY3)
