The Golden Rules of Urinalysis

Understanding Urinalysis Testing: A Guide for Healthcare Professionals

Urinalysis is a fundamental diagnostic tool in clinical practice, offering valuable insights into a patient’s overall health. As a non-invasive and cost-effective procedure, urinalysis is widely used to screen for and monitor a variety of medical conditions. For healthcare professionals, understanding the intricacies of urinalysis testing is essential for accurate diagnosis and effective patient management.

An artistic rendering of a Urinalysis being performed during evening shift when co-workers call in sick.

The Basics of Urinalysis Testing

Urinalysis (a contraction of urine-analysis) involves the examination of urine to detect abnormalities that could indicate disease or dysfunction. The test is typically divided into three main components: physical, chemical, and microscopic analysis. Each component provides distinct information about the patient's health. The urinalysis consists of three parts:

Step one: Just Eyeball It

Physical analysis evaluates the urine’s color and clarity which can reveal signs of dehydration, hematuria, or infection. If it's bright red, there is likely blood in the urine. If it's orange, it's orange, that probably because of a drug. If it's cloudy, then either it's a raging UTI, or it could just be that it was in the refrigerator. You will usually result the color and clarity in your reporting.

Step two: The Dipstick

Chemical analysis uses reagent strips to measure various parameters such as pH, protein, glucose, ketones, and bilirubin, offering clues about metabolic and systemic conditions. Watch out though, the dipstick is usually color-based, so any colors in the urine (such as red or orange listed above) can cause inaccurate results.

Step three: The Microscopic (This is not microbiology! Don't get these confused)

Microscopic analysis involves examining urine sediment for the presence of red blood cells, white blood cells, epithelial cells, casts, and crystals, which can help identify infections, poor kidney function, trauma, or other underlying conditions. This step takes lots of practice to get right, so get some reps and train that eye.

A strip used in a urine dipstick test.

Reporting guidelines graded by color. This is automated when you use even very basic analyzers.

Indications for Urinalysis

Urinalysis is performed for several reasons, ranging from routine health assessments to the diagnosis of specific conditions. For this reason, it is collected on a vast array of patients coming into the Emergency Department. It is commonly used to screen for urinary tract infections (UTIs), monitor kidney function, and detect metabolic disorders such as diabetes. In pregnancy, urinalysis is an essential component of prenatal care, helping to identify conditions like preeclampsia or gestational diabetes. It is also utilized in drug screening and in monitoring the effects of certain medications that may impact renal function.

How to do a Proper Urine Microscopic

The first step of doing the microscopic is to centrifuge the urine. Centrifuge the sample at 1,500-2,000 RPM for 5 minutes. This process separates the sediment from the supernatant. You will dump out all but one mL at the bottom and mix that well with a disposable pipette. Take one drop of this and put it on a microscope slide and place a cover slip over the top.

Look at the sample under 40x dry objective. Now report what you see. When you are a beginner, keep a urinalysis textbook with picture with you. The books are really good and you can get them online for cheap. The internet is not good and very confusing. These elements may include any of the following:

Cells

Red Blood Cells (RBCs): Indicates hematuria, which may result from trauma, infection, stones, or glomerular disease.

White Blood Cells (WBCs): Suggests inflammation or infection (e.g., urinary tract infection or interstitial nephritis).

Epithelial Cells:

• Squamous Epithelial Cells: Indicative of contamination (e.g., from the external genitalia).

• Transitional Epithelial Cells: May arise from the bladder, ureters, or renal pelvis; occasionally associated with malignancy.

• Renal Tubular Epithelial Cells: Suggest tubular damage (e.g., acute tubular necrosis).

  
  

Casts (Formed in the renal tubules)

Hyaline Casts: Usually non-specific, seen in normal individuals or during dehydration.

Granular Casts: Indicative of renal disease or tubular damage.

Cellular Casts:

• RBC Casts: Suggest glomerulonephritis.

• WBC Casts: Seen in pyelonephritis or interstitial nephritis.

• Epithelial Cell Casts: Indicate tubular injury.

Fatty Casts: Seen in nephrotic syndrome.

Waxy Casts: Associated with chronic kidney disease or severe tubular injury.

Mixed Casts: Contain a combination of different cell types.

Crystals (May indicate normal or pathological conditions)

Normal Crystals:

• Uric Acid

• Calcium Oxalate

• Triple Phosphate (Struvite)

• Amorphous Urates or Phosphates

Abnormal Crystals:

• Cystine: Suggestive of cystinuria.

• Tyrosine: Seen in severe liver disease.

• Leucine: Also indicative of liver dysfunction.

• Cholesterol: Associated with nephrotic syndrome.

• Drug-Induced Crystals: Sulfonamides, ampicillin, or radiographic contrast agents.

Microorganisms

Bacteria: Indicates infection; must correlate with symptoms and culture results.

Yeast: Suggests fungal infections, particularly in immunocompromised patients or diabetics.

Parasites: Includes Trichomonas vaginalis, which appears as motile, flagellated organisms.

Other Elements

Spermatozoa: Can be seen in male urine or as contamination in female urine.

Mucus: Generally non-specific, often seen in normal urine.

Artifacts: Fibers, talc, starch granules, or other contaminants that might be mistaken for pathological findings.

Proper Sample Collection and Handling

As they say, "garbage in, garbage out" and urinalysis results will only be as good as the sample that is collected. Accurate urinalysis results depend on proper sample collection and handling. Healthcare professionals should ensure that patients are educated on the correct methods of collection, such as the clean-catch midstream technique, to minimize contamination. For infants and non-ambulatory patients, alternative collection methods, such as urine bags or catheters, may be necessary. Once collected, urine samples should be processed promptly or stored appropriately to preserve the integrity of the sample. Delayed analysis can lead to erroneous results due to bacterial overgrowth or chemical changes in the urine.

Urine samples should be at room temperature for no more than one hour or refrigerated for no more than 24 hours. Alternately, the urine may be aliquoted into specific tube with boric acid to extend its useful life up to a week.

Interpreting Urinalysis Results

Interpreting urinalysis results requires a comprehensive understanding of the potential implications of each parameter. For example, the presence of leukocytes and nitrites often points to a UTI, while elevated protein levels may indicate kidney damage or systemic disease. Abnormal glucose or ketone levels are frequently associated with diabetes, whereas blood in the urine (hematuria) can suggest conditions ranging from urinary tract trauma to malignancies. Healthcare professionals must also consider factors such as patient history, clinical symptoms, and concurrent laboratory findings to ensure accurate diagnosis and treatment.

A beautiful golden waterfall.

Limitations and Pitfalls

While urinalysis is a powerful diagnostic tool, it is not without limitations. False-positive or false-negative results can occur due to factors such as improper sample collection, contamination, or the use of certain medications. For instance, high levels of vitamin C can interfere with the detection of glucose or blood in the urine. Additionally, urinalysis results should not be interpreted in isolation but rather in the context of the patient’s overall clinical picture. When in doubt, further diagnostic tests or imaging studies may be required to confirm findings and guide treatment.

Advances in Urinalysis Technology

Newer, large analyzers can automatically do both the dipstick and microscopic parts. The analyzer will take pictures of all the cells and classify them. Any that it cannot classify may need the help of a human. But as artificial intelligence becomes more integrated with lab systems, the human part may be less needed. But for most small labs, the process remains labor intensive with lots of aliquoting, centrifuging, and microscope work. But isn't that why we studied science? To look at peepee, or course.