or profuse sweating reduces urinary output; ahigh-protein diet tends to increase it. Daytime urineoutput is normally two to four times greater thannighttime output.PRESERVATION OF URINE SPECIMENSTo delay decomposition of urine, use the followingmethods of preservation:RefrigerationPreservatives—Hydrochloric acid—Boric acid—Glacial acetic acidOther preservatives used include formaldehyde,toluene, and thymol. The preservative used must beidentified on the label of the container. If nopreservative is used, this, too, should be noted.NOTE: Before adding a preservative to aurine specimen, contact the laboratoryperforming the test to find out whatpreservative to use and the quantity toadd. Preservative requirements vary fromlaboratory to laboratory.ROUTINE URINE EXAMINATIONA routine urinalysis includes the examination ofphysical characteristics, chemical characteristics, andmicroscopic structures in the sediment. A sample forurinalysis (routine and microscopic) should be at least15 ml in volume (adult), and either a random or firstmorning specimen. Children may only be able toprovide a small volume, but 10-15 ml is preferred.Physical CharacteristicsPhysical characteristics evaluated during a routineurinalysis include color, appearance, and specificgravity.COLOR.—The normal color of urine varies fromstraw to light amber. Diluted urine is generally pale;concentrated urine tends to be darker. The terms usedto describe the color of urine follow.ColorlessLight strawStrawDark strawLight amberAmberDark amberRedThe color of urine may be changed by the presenceof blood, drugs, or diagnostic dyes. Examples are:red or red-brown (smokey appearance), causedby the presence of blood.yellow or brown (turning greenish with yellowfoam when shaken), caused by the presence ofbile.olive green to brown-black, caused by phenols(an extremely poisonous compound, used as anantimicrobial agent).milky white, caused by chyle. (Chyle, whichconsists of lymph and droplets of triglyceride, isa milky fluid taken up by lacteal vessels from thefood in the intestine during digestion.)dark orange, caused by Pyridium® (a topicalanalgesic used in the treatment of urinary tractinfections).blue-green, caused by methylene blue (used as astain or dye for various diagnostic tests).APPEARANCE.—Urine’s appearance may bereported as clear, hazy, slightly cloudy, cloudy, or verycloudy. Some physicians prefer the term “turbidity”instead of “transparency,” but both terms areacceptable.Freshly passed urine is usually clear ortransparent. However, urine can appear cloudy whensubstances such as blood, phosphates, crystals, pus, orbacteria are present. A report of transparency is ofvalue only if the specimen is fresh. After standing, allurine becomes cloudy because of decomposition, salts,and the action of bacteria. Upon standing and cooling,all urine specimens will develop a faint cloudcomposed of mucus, leukocytes, and epithelial cells.This cloud settles to the bottom of the specimencontainer and is of no significance.SPECIFIC GRAVITY.—The specific gravity ofthe specimen is the weight of the specimen comparedto an equal volume of distilled water. The specificgravity varies directly with the amount of solidsdissolved in the urine and normally ranges from 1.015to 1.030 during a 24-hour period.7-34
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