Understanding Urinalysis

Clues for the Obstetrician-Gynecologist

Sarah Coad; Boris Friedman; Roxana Geoffrion

Disclosures

Expert Rev of Obstet Gynecol. 2012;7(3):269-279. 

In This Article

Abstract and Introduction

Abstract

The observation of urine has been used for centuries to diagnose and follow many disease states. It continues to be an important test in modern medicine. Various diseases such as pelvic and bladder malignancies, liver dysfunction, renal disease, infection and some pregnancy-related pathologies such as placenta percreta and preeclampsia may be suspected on the basis of an abnormal urinalysis result. The obstetrician–gynecologist must have a good understanding of urinalysis, as correct interpretation is important for optimal patient care. In this review, we will detail the components of basic urinalysis routine and microscopy. We will discuss both basic science and clinical correlations, with a focus on diseases commonly encountered by the obstetrician–gynecologist.

Introduction

Urinalysis is one of the most commonly used diagnostic tests in modern medicine.[1] It is also one of the few laboratory tests still consistently performed in the office setting.[2] This is likely attributable to the ease of specimen collection and testing. Observation of urine has been used for more than 6000 years, by many civilizations, to diagnose a variety of ailments.[3] Hippocrates wrote about urine examination as early as 400 BC and correctly identified urine as a filtrate of blood.[4] The modern era of reagent strip, or dipstick testing, began in 1956 and has constantly improved since then.[5]

In an obstetrics and gynecology practice, most patients will have a urinalysis at some step in their care, either during a prenatal evaluation, or in response to urinary symptoms in the office or in the emergency department. It is therefore important that care providers develop a good understanding of the different components of urinalysis and the pathologic abnormalities it reflects.

Urinalysis (routine and microscopy) typically consists of reagent strip (dipstick) analysis and microscopic evaluation of a sample of urine. Dipstick analysis detects the following: urine-specific gravity (USG), pH, leukocyte esterase, nitrites, protein, glucose, ketones, urobilinogen, bilirubin, blood and hemoglobin. Microscopic analysis detects cells and formed elements, such as casts and crystals, which provide further diagnostic clues.

In this review, we will describe the general characteristics, chemical composition and formed elements of a typical urinalysis, routine and microscopy. We will focus on common abnormalities seen by the obstetrician–gynecologist and provide practical recommendations for further diagnosis and management.

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