Ask Dr. M: Why do I need a urine test?

Question: My doctor ordered me to take a urine test, which I’ve never done before. Why does my urine need to be tested?

Urine, produced by the kidneys, contains filtered water, electrolytes and cells, amongst other things. Testing urine allows your doctor to see how your kidneys and urinary system are functioning, or identify substances in your body.

To help you understand why your doctor may order a urine test, let me break down the most common types of tests done, how to provide accurate samples, and what they may reveal about your health.

Common Urine Collection Methods

Clean Catch Midstream

The important aspect of this collection method is to ensure the urine is not exposed to external factors. Thus washing your hands, cleaning the genital area, then urinating a little before you start collection and keeping the lid as free from touching a surface is really important.

Double Voided Urine

This test provides a sample of recently drunken fluids. Peeing, then drinking water and waiting 30–40 minutes to collect the sample is the most common method.

24-hour Urine Collection

Starting in the morning, your first pee does not get collected, however the time of it should be noted. Each time you urinate afterwards, this should be collected in the large container that your provider supplied you with.

The most important thing to remember, no matter what collection method you’ve been instructed to use, is that you do not contaminate the results. This includes allowing toilet paper, menstrual blood, stool, or other foreign materials to enter the samples.

Common Tests Performed on Urine Samples

Once sent to the lab, here are the common things that laboratories are looking for within your urine samples.

Urinalysis

A urinalysis is used to detect and manage a wide range of disorders, such as urinary tract infections, kidney disease and diabetes. A urinalysis involves checking the appearance, concentration and content of urine. Abnormal urinalysis results may point to a disease or illness.

Physical Examination

Colour

Detection of hydration status, kidney, liver, genetic diseases, diabetes or presence of blood. Normal results: Pale to dark yellow.

Clarity

Determine presence of pus, blood, sperm, bacteria, yeast, crystals, mucus or parasites (such as STIs). Normal results: Clear.

Odour

Foods and drugs may alter odour. Diabetes, Urinary Tract Infections (UTI)s, maple syrup disease will also alter the smell. Normal results: Slightly Nutty.

Volume

Reported for 24-hour collection only. Determines amount of urine produced; too little or too much can indicate issues present. Normal results: 800–2,000 mL/day*.

Qualities looked for in a physical urine examination.

Chemical Examination

Specific Gravity

High results indicate dehydration, loss of fluid or substances in the urine (sugar or protein). Low results indicate dilute urine, indicating well hydrated, severe kidney disease or use of medications to increase urine production. Normal results: 1.005–1.030*.

pH

Foods can affect urine pH level. High pH can be a result of vomiting, kidney disease, UTIs or asthma. Low pH levels can be caused by lung disease, uncontrolled diabetes, aspirin overdose, diarrhea, dehydration, starvation, consuming alcohol or antifreeze. Normal results: 4.6–8.0*.

Bilirubin

Detection of bilirubin in urine is indicative of liver disease or biliary obstruction. Normal results: Negative.

Glucose

Too much glucose in the urine may be caused by uncontrolled diabetes, an adrenal gland problem, liver damage, brain injury, certain types of poisoning, some types of kidney diseases, exposure to some IV fluids or in healthy pregnant women. Normal results: None or 60–830 mcmol/L in a 24-hour sample*.

Blood

Additional studies are often required to determine the source of blood in urine. It may indicate kidney stones, a urinary tract infection, and, in older patients, malignancy should be excluded. Normal results: Negative.

Ketones

Ketones in the urine can mean uncontrolled diabetes, very low-carbohydrate diet, starvation or eating disorders, alcoholism, or drinking rubbing alcohol. Ketones are often found in the urine when a person does not eat (fasts) for 18 hours or longer. Low levels of ketones are sometimes found in the urine of healthy pregnant women. Normal results: None.

Protein

Protein in the urine may indicate kidney damage, an infection, cancer, high blood pressure, diabetes, lupus, or kidney inflammation is present. Protein in the urine could also indicate heart failure, leukemia, poison (lead or mercury poisoning), or preeclampsia (if you are pregnant) exist. Normal results: None.

Nitrite

Nitrites are a metabolic product of certain bacteria, so a positive nitrite test is strongly suggestive of urinary tract infection. However, negative doesn’t necessarily mean there is no infection. Normal results: ≥105 organisms/mL*.

Leukocytes

Suggest infection present for example UTI, urethritis etc. Normal results: 10 or more leukocytes/hpf*.

Chemicals looked for in a chemical urine examination.

Microscopic Examination

White Blood Cells (WBC)

White blood cells (pus) in the urine may be caused by a UTI, bladder tumour, inflammation of the kidneys, lupus, or inflammation of the genitals. Normal results: Few to none.

Red Blood Cells (RBC)

May be caused by kidney or bladder injury, kidney stones, UTI, inflammation of the kidneys, a kidney or bladder tumour, or lupus. Normal results: Few to none.

Bacteria, Yeast, Parasites

Any can indicate a UTI. Normal results: None.

Casts

Can indicate kidney inflammation or damage, metal poisoning (such as lead or mercury), heart failure, or a bacterial infection. Normal results: None.

Crystals

Large amounts of crystals, or types of crystals, can indicate kidney stones, kidney damage, or problems with metabolism. Some medications or types of urinary tract infections can increase the number of crystals in urine. Normal results: A few.

Epithelial or Squamous Cells

If present, the test should be re-administered. Normal results: None.

Mucus

May indicate presence of pus or blood. Normal results: None.

What is looked for in a microscopic urine examination.

Although this is a comprehensive look at urine testing, there are many other substances and tests that can be done on urine to detect substance use and abuse, or detect various abnormalities or diseases. It’s critical that urine tests are done with a specific question in mind, or to address certain symptoms. Urinalysis frequently comes back abnormal, and it can be difficult to tell if it’s a concern, or if it’s due to contamination, since urine tests are so easily contaminated.

For example: if a urine sample looks like it shows signs of infection (presenting with white blood cells, and some bacteria), but you do not have any symptoms (like burning/pain when peeing, or abnormal urinary frequency or urgency) then don’t necessarily trust the test. On the other hand, some kidney diseases (especially in the early stages) are asymptomatic (meaning show no symptoms), so the urine tests should be correlated with appropriate blood work and/or imaging.

As always, the best way to know why a urine test is being ordered, and what the results mean, is to ask your physician.

Dr. Shaun Mehta is a medical resident and Dot Health’s team physician
shaun@dothealth.ca

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