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Urinalysis

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Also Known As

UA, U/A, Urine Analysis, Routine Urinalysis, Urine Test, Urine Examination, Urinary Analysis

Definition

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

Clinical Context

Urinalysis is a versatile diagnostic tool employed across various clinical scenarios. It is primarily used in the assessment of urinary tract infections (UTIs), kidney diseases, diabetes, liver disorders, and as part of routine health screenings.14

In urologic practice, urinalysis serves as a first-line investigation for patients presenting with symptoms such as dysuria, frequency, urgency, hematuria, or flank pain.15 The presence of leukocyte esterase and nitrites on dipstick testing suggests bacterial UTI, while microscopic hematuria may indicate urolithiasis, glomerular disease, or urinary tract malignancy.16

For patient selection, urinalysis is recommended for all patients with suspected UTI, those with symptoms of kidney disease, pregnant women during prenatal visits, and patients with diabetes for monitoring glycosuria and ketonuria.17 It is also valuable in preoperative assessments, particularly before urologic procedures.

The procedure itself is non-invasive when using the clean-catch midstream technique, which is the most common collection method.18 For patients unable to provide a clean specimen (such as young children or those with urinary incontinence), catheterization or suprapubic aspiration may be necessary, though these carry additional risks.19

Expected outcomes from urinalysis vary based on the clinical question being addressed. In UTI diagnosis, positive leukocyte esterase and nitrite tests have a positive predictive value of approximately 80%, allowing for empiric treatment without culture in uncomplicated cases.20 For kidney disease screening, the presence of proteinuria, hematuria, and cellular casts can help differentiate between glomerular, tubular, and interstitial pathologies.21

In monitoring chronic conditions, serial urinalysis provides valuable information about disease progression or treatment response. For instance, decreasing proteinuria in patients with chronic kidney disease often indicates successful therapy, while persistent microhematuria may warrant further investigation with cystoscopy or imaging studies.22

Urinalysis is particularly valuable in resource-limited settings due to its low cost, rapid results, and minimal equipment requirements, making it an essential tool in global healthcare delivery.23

Scientific Citation

[1] Armstrong JA. Urinalysis in Western culture: a brief history. Kidney Int. 2007 Mar;71(5):384-7. DOI: 10.1038/sj.ki.5002057

[2] Diamandopoulos A, Goudas P, Oreopoulos D. Thirty-six Hippocratic aphorisms of nephrologic interest. Am J Kidney Dis. 2009 Jul;54(1):143-53. DOI: 10.1053/j.ajkd.2009.01.277

[3] Echeverry G, Hortin GL, Rai AJ. Introduction to urinalysis: historical perspectives and clinical application. Methods Mol Biol. 2010;641:1-12. DOI: 10.1007/978-1-60761-711-2_1

[4] Wu X. Urinalysis: a review of methods and procedures. Crit Care Nurs Clin North Am. 2010 Mar;22(1):121-8. DOI: 10.1016/j.ccell.2009.10.012

[5] Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. Am Fam Physician. 2005 Mar 15;71(6):1153-62. PMID: 15791892

[6] Delanghe JR, Speeckaert MM. Preanalytics in urinalysis. Clin Biochem. 2016 Dec;49(18):1346-1350. DOI: 10.1016/j.clinbiochem.2016.10.016

[7] Wilson LA. Urinalysis. Nurs Stand. 2005 May 11-17;19(35):51-4. DOI: 10.7748/ns.19.35.51.s55

[8] Queremei Milani DA, Jialal I. Urinalysis. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557685/

[9] Levey AS, Becker C, Inker LA. Glomerular filtration rate and albuminuria for detection and staging of acute and chronic kidney disease in adults: a systematic review. JAMA. 2015 Feb 24;313(8):837-46. DOI: 10.1001/jama.2015.0602

[10] Ponka D, Baddar F. Top 10 forgotten diagnostic procedures: suprapubic bladder aspiration. Can Fam Physician. 2013 Jan;59(1):50. PMID: 23341660

[11] Utsch B, Klaus G. Urinalysis in children and adolescents. Dtsch Arztebl Int. 2014 Sep 12;111(37):617-25. DOI: 10.3238/arztebl.2014.0617

[12] Filice CE, Green JC, Rosenthal MS, Ross JS. Pediatric screening urinalysis: a difference-in-differences analysis of how a 2007 change in guidelines impacted use. BMC Pediatr. 2014 Oct 10;14:260. DOI: 10.1186/1471-2431-14-260

[13] Patel HP. The abnormal urinalysis. Pediatr Clin North Am. 2006 Jun;53(3):325-37. DOI: 10.1016/j.pcl.2006.02.004

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