Urinalysis

Urinalysis is a comprehensive diagnostic screening test that involves the physical, chemical, and microscopic examination of urine.¹ The term “urinalysis” derives from two Greek words: “ouron,” which means urine, and “skopeō,” which means to ‘behold, contemplate, examine, inspect’.² Around 6,000 years ago, laboratory medicine began with the analysis of human urine, originally termed “uroscopy,” which later evolved into what we now call urinalysis.³

A complete urinalysis consists of three components or examinations:

1. Physical examination describes the volume, color, clarity, odor, and specific gravity of the urine sample.⁴

2. Chemical examination identifies pH, red blood cells, white blood cells, proteins, glucose, urobilinogen, bilirubin, ketone bodies, leukocyte esterase, and nitrites.⁵

3. Microscopic examination encompasses the detection of casts, cells, crystals, and microorganisms.⁶

Urinalysis is an invaluable diagnostic tool in clinical practice, providing clinicians with crucial information about the general health status of a patient, including hydration, urinary tract infection, diabetes mellitus, and liver or renal disease.⁷ For some healthcare providers, urinalysis is considered the most common, simple, and relevant screening exam available.⁸ It serves as a formidable and cost-effective tool to obtain crucial information for diagnostic purposes.⁹

The procedure requires proper collection techniques to maintain sample integrity. Urine samples collected from the first void or “morning urine” are considered the best representative for testing, as the urine accumulated overnight in the bladder is more concentrated, providing insight into the kidneys’ concentrating capacities and allowing for the detection of trace substances that may not be present in more diluted samples.¹⁰ Ideally, urine should be examined within the first hour after collection due to the instability of some urinary components (cells, casts, and crystals).¹¹

Urinalysis results can be affected by various factors including light and temperature, bacterial growth, alkaline pH, glucose presence, contrast agents, exercise, foods and drugs, and preservatives.¹² These interfering factors must be considered when interpreting results to avoid false-positive or false-negative findings.

As one of the oldest diagnostic tests in medicine, urinalysis continues to be a fundamental component of patient assessment, providing valuable insights into both urologic and systemic conditions.¹³