Urinalysis is a simple, inexpensive means of detecting urologic and systemic conditions such as infection, urolithiasis, malignancy, and metabolic diseases. Urinalysis can be outsourced or performed in the office by clinical staff. Familiarity with a visual inspection of the urine, dipstick testing, and point-of-care microscopy is an important diagnostic skill for family physicians. This article reviews and updates the practical use of office-based urinalysis and the differential diagnosis for abnormal results.

Setting Up In-Office Urinalysis

Urine dipstick test kits are widely available and easy to use. Results may be interpreted visually off the dipstick or by an automated machine.¹ Microscopic analysis requires a centrifuge and microscope, with commonly used 10×, 40×, and 100× (oil immersion) objectives. Phase-contrast and polarized microscopes help identify casts and crystals, respectively, but are not commonly used in office settings.²

The Clinical Laboratory Improvement Amendments (CLIA) regulate medical testing, and dipstick urinalysis can be performed in a physician’s office by obtaining a CLIA certificate of waiver. Clinician-performed microscopy is considered moderate complexity testing and requires a demonstration of quality assurance by proficiency testing or split sampling.² The American Academy of Family Physicians has published detailed guidance for navigating this process.³

Specimen Collection

The American Society for Microbiology recommends midstream urine collection with genital cleansing when possible, regardless of age and sex, despite a lack of evidence that this strategy decreases contamination.⁴ The American Urological Association also recommends midstream collection for evaluation of microhematuria.⁵ Urine should be refrigerated or tested promptly after collection to avoid incorrect results.⁶

In clinically stable infants and children, the initial urinalysis can be performed using a convenient collection method, such as a urine collection bag specimen. Urine culture of a bag specimen is not recommended. Alternatively, successful midstream urine collection has been described using suprapubic and lumbosacral stimulation, such as the Quick-Wee approach.⁷ If urinalysis shows the presence of leukocyte esterase or nitrites, follow-up urinalysis using clean urine collection by urethral catheterization or suprapubic aspiration should be performed.⁸ An online risk calculator can help in the assessment of urinary tract infection (UTI) in infants (https://uticalc.pitt.edu).

Visual Appearance and Odor

The yellow color of urine is caused by urochrome generated from the breakdown of hemoglobin. Foods, drugs, metabolic products, and infections can cause an abnormal urine appearance (Table 1).^6,9–11 Cloudy urine suggests an infection (positive likelihood ratio = 3) but can indicate alkaline urine with precipitated phosphate crystals.^6,12 Gross hematuria is concerning for malignancy. Visible feces in the urine can suggest an enterovesical fistula, whereas nonfeculent brown urine may indicate ingestion of fava beans. Fluorescence by Wood lamp can demonstrate porphyrins in heme biosynthesis disorders. Purple urine bag syndrome can occur in patients with long-term indwelling catheters because of metabolites from certain types of bacterial overgrowth (Figure 1).¹¹

Dehydration leads to concentrated, strong-smelling urine. A fruity or sweet odor can indicate diabetic ketoacidosis. Foul smells such as ammonia can indicate a UTI or an infected kidney stone. Although a feculent odor suggests a fistula, a sulfur-like odor can be attributed to ingestion of a sulfa medication or asparagus.⁶

Dipstick Urinalysis

Dipsticks visually display results after a sufficient time in contact with urine. The color change is compared with a reference standard to determine the concentration of the analyte being measured.¹ The dipstick result is usually read after 60 to 120 seconds. The leukocyte esterase dipstick test is the most sensitive to time. Substances and medical conditions can also affect dipstick results. Nitrite results can be inaccurate when the dipstick is left unpackaged in the open air (Figure 2).