Urinalysis

Written by Yasmin Bashir

Introduction

Introduce yourself, stating your name and role, and confirm the patient's name and date of birth. Explain the procedure, check the patient’s understanding and obtain consent.

A urine dipstick is a very useful diagnostic tool. It is easy to perform and is inexpensive. It is commonly used to detect urinary tract infections, renal disease, liver disease, diabetes mellitus and many metabolic diseases.

A urine dipstick is comprised of 10 squares containing reagents which change colour when dipped in the urine and allowed to dry. Each square tests for a different variable (leukocyte esterase, nitrite, urobilinogen, protein, pH, blood, specific gravity, ketones, bilirubin, glucose).

Due to its broad utility, a urine dipstick can be used in a range of healthcare settings:

Collecting the urine sample

Explain to the patient the purpose of a midstream urine (MSU) sample, that is, a collection of the middle part of the urine stream, but not the first and last part of the stream. Stress that in order to get reliable results only the middle part of the urine stream should be collected.

An MSU sample serves many purposes: it can be tested with a urine dipstick, sent off for a urine drug screen, and also for culture and microscopy if a urinary tract infection (UTI) is suspected. As a result of the latter, it is very important that the sample is not contaminated by pathogens which may be present externally at the end of the urethra. Collecting the middle of the urine stream reduces this risk of contamination. Urine is sterile, and hence if any bacteria are found, this signifies a UTI.

The sampling process

Hand the patient a sample pot for urine collection. Explain to them how to collect a midstream urine (MSU) sample and then check their understanding.

First, the patient will need to wash their hands and clean their external genitalia with water and gauze or tissue paper. They should then begin to pass urine into the toilet. Without stopping the flow, they should collect a sample of urine in the sample pot and then finish passing the rest of the urine into the toilet. They should then close the lid of the sample pot.

Once the patient has brought their sample pot, pour the urine into a labelled urine specimen bottle (in case it needs to be sent off for microscopy) and proceed to test the urine using a dipstick.

If you wish, you can just hand the patient the specimen bottle to use instead of the pot. However, if you do this it is important to inform them that they must not touch the inside of the container with any body part as this can contaminate the sample and interfere with the results. They must also close the lid as soon as the sample is collected for the same reasons.

Equipment

Gather your equipment. In addition to the urine sample, you will need the following:

Equipment preparation

Once you have gathered your equipment, check the expiry date on the urine dipsticks. Then, wash your hands and put on a pair of non-sterile gloves and an apron.

Testing the urine

Before testing the sample, make sure that the sample is from the correct patient. Remember to mix the urine sample well.

Inspection

Appearance

Hold up the urine sample to the light and inspect it closely.

Begin by observing the colour, the urine should be yellow, and may appear light or dark depending on the patient’s hydration status. Specifically look for any presence of blood (haematuria). The most common causes of visible (macroscopic) haematuria are UTIs and renal stones.

Check for cloudiness, as this is indicative of infection and any sedimentation as this can indicate infection, bladder stones or diabetes. Urinary sediment is an accumulation of substances (including erythrocytes, leukocytes, bacteria and protein) at the bottom of the urine sample.

Dark yellow: Indicates highly concentrated urine usually due to dehydration.

Red: Suggestive of macroscopic haematuria, haemoglobinuria or myoglobinuria.

Brown: Urine can either be brown/black due to blood and so this would be suggestive of haematuria. Or it could be due to the presence of bile pigments. It could indicate acute tubular necrosis (ATN) or liver failure.

Green: This suggests a pseudomonas infection; the gram-negative bacteria produce blue-green pigments such as pyocyanin, which then makes its way into the urine, thus turning the urine green.

Odour

You may wish to open the bottle and smell the urine. Foul smelling urine is usually associated with infection, whereas sweet smelling urine is associated with diabetic ketoacidosis.

In practice, this is very rarely performed, as it fails to add much to your diagnosis.

Procedure

Remove one dipstick without touching the reagent squares. Promptly replace the lid as the dipsticks can oxidise. Immerse the dipstick in the urine sample for 2-3 seconds, making sure that all of the squares on the dipstick are covered. Remove the dipstick and tap the edge along the rim of the sample container to get rid of any excess urine.

Hold the dipstick horizontally and place it flat onto a paper towel. Let it dry for the time specified on the container.

Keeping the dipstick horizontal prevents the reagents from mixing.

Different variables on the dipstick require different times to dry, ranging from 30 seconds to 2 minutes. These times also vary with the make of the dipsticks.

These are just a guideline. Timings vary with the make so always check the container for correct timings.

Interpretation

Having allowed the strip to dry for the specified time, read the results from the test strip by looking at each square and matching it against the colour coded chart on the side of the container (starting with the ones with the shortest read times). Note the results.

The main variables that the dipstick tests are: Leukocyte esterase, nitrite, urobilinogen, protein, pH, blood, specific gravity, ketones, bilirubin, and glucose.

Leukocyte esterase – enzyme produced by neutrophils, indicating white blood cells in the urine.

Nitrite – breakdown products indicating presence of gram negative bacteria.

Urobilinogen Urobilinogen is produced from bilirubin diglucoronide by intestinal bacteria. In obstructive jaundice, bile doesn't reach the gut, and so it isn't produced.
indicates urobilinogen in urine.

Protein – indicates protein in urine.

pH – indicates acidity of urine.

Blood – indicates red blood cells in urine.

Specific gravity – indicates amount of solute dissolved in urine.

Ketones – breakdown product of fatty acid metabolism, indicating incomplete metabolism of fat.

Bilirubin – indicates presence of bilirubin in urine.

Glucose – indicates presence of glucose in urine.

Completion

Having noted the results, put the lid back on the urine sample and discard the strip in a clinical waste bin. Clean the area, disposing of any rubbish. Remove your gloves and wash your hands.

Thank the patient and present your findings.

Further investigations

After presenting your findings you should suggest further investigations that could be done, such as an FBC, U&Es, TFTs, LFTs, a CRP and urine culture and microscopy. Your choice of investigation will depend on your findings. For example, if results suggest a UTI, offer to send off the urine for culture and microscopy and obtain a FBC, U&Es and a CRP.

Leukocyte esterase:

Nitrite:

Urobilinogen:

Protein:

pH:

Blood:

Specific gravity:

Ketones:

Bilirubin:

Glucose:

List form

Instructions
When assessing each other, please click on each list item as you go along. Doing so will turn the list item green. Make careful note of any steps missed at the end.
We recommend completing any examination or procedure in under 10 minutes, but you can adjust the timer to suit your needs.
:

  1. Introduction: “Hello. I’m SimpleOSCE and I’m a medical student. Could I confirm your full name and DOB?”
  2. Explain procedure and gain consent: “Today I would like to test your urine. If it is okay with you, I would like to explain to you how to collect a sample that we can use?”
  3. Wash hands.
  4. Ask the patient if they have had their urine tested before and explain the purpose.
  5. Proceed to explain to the patient the correct technique for obtaining a mid-stream urine sample.
  6. Hand the patient a sample pot (or specimen bottle).
  7. MSU - Explain the following steps to the patient (7-12)

  8. “Wash your hands.”
  9. “Clean your external genitalia.”
  10. “Pass the first part of your stream of urine into the toilet.”
  11. “Without stopping your flow, pass some urine into the sample pot.”
  12. “Pass the rest of your urine into the toilet.”
  13. “Once finished, close the lid of the sample pot.”
  14. Urine dipstick

  15. Optional: Poor the MSU sample into a suitable tube for testing (usually a specimen bottle).
  16. Gather equipment.
  17. Wash hands and put on non-sterile gloves and an apron.
  18. Check you have the correct sample and it is labelled.
  19. Inspect the urine sample.
  20. Check the expiry date of the dipsticks and take out one strip.
  21. Fully immerse in the urine sample for 2-3 seconds and then tap on edge of sample container to get rid of excess urine.
  22. Place the strip flat on a paper towel and wait for the time specified on the strip container.
  23. Match the squares with the colour coded chart and note findings.
  24. Dispose of rubbish appropriately, remove gloves and wash hands.
  25. Thank the patient.
  26. Present your findings, and if appropriate, suggest further investigations
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