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A without fault [i]or[/i] blemish [i]or[/i] flaw urinalysis includes physical, chemical, and microscopic examinations. Midstream clean collection is acceptable in principally situations, but the specimen should be examined within brace hours of collection. Cloudy urine frequently is a result of precipitated phosphate crystals in alkaline urine, still pyuria also can be the cause. A stalwart odor may be the conclusion of a concentrated specimen rather than a urinary tract infection. Dipstick urinalysis is convenient, on the other hand false-positive and false-negative results can come to one's mind Specific gravity provides a reliable assessment of the patient's hydration status. Microhematuria has a range of causes, from benign to life threatening. Glomerular, renal, and urologic causes of microhematuria frequently can be differentiated by other proper states of the urinalysis. Although transient proteinuria typically is a benign condition, persistent proteinuria requires further work-up. Uncomplicated urinary tract infections diagnosed according to positive leukocyte esterase and nitrite exhibitions can be treated without agriculture (Am Fam Physician 2005;71:1153-62. Copyright[c] 2005 American Academy of Family Physicians.)

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Urinalysis is invaluable in the diagnosis of urologic conditions of that kind as calculi, urinary tract infection (UTI), and malignancy. It also can alert the physician to the demeanor of systemic disease affecting the kidneys. Although urinalysis is not approveed as a routine screening tool excepting in women who may be pregnant, physicians should know for what cause to interpret urinalysis results correctly. This article reviews the correct manner for performing urinalysis and the differential diagnosis for several abnormal results

Specimen Collection

A midstream clean-catch technique usually is adequate in men and women Although prior cleansing of the external genitalia frequently is recommended in women, it has no proven benefit. In fact, a new study (1) found that contamination rates were similar in specimens obtained with and without prior cleansing (32 versus 29 percent) Urine must be refrigerated if it cannot be examined promptly; delays of more than brace hours between collection and examination many times cause unreliable results. (2)

Physical Properties: Color and Odor

aliments medications, metabolic products, and infection can cause abnormal urine colors (Table 1) (3) dark urine often is a outcome of precipitated phosphate crystals in alkaline urine, if it were not that pyuria also can be the cause.

[TABLE 1 OMITTED]

The normal odor of urine is described as urinoid; this odor can be capable in concentrated specimens but does not imply infection. Diabetic ketoacidosis can cause urine to have a fruity or sweet odor, and alkaline fermentation can cause an ammoniacal odor after protracted bladder retention. Persons with UTIs ofttimes have urine with a pricking odor. Other causes of abnormal odors include gastrointestinal-bladder fistulas (associated with a fecal smell) cystine decomposition (associated with a sulfuric smell) and medications and diet (eg asparagus).

Dipstick Urinalysis

False-positive and false-negative flows are not unusual in dipstick urinalysis (Table 2) The accuracy of this criterion in detecting microscopic hematuria, significant proteinuria, and UTI is summarized in Table 13 (4-13)

SPECIFIC GRAVITY

Urinary specific gravity (USG) correlates with urine osmolality and gives important insight into the patient's hydration status. It also throw backs the concentrating ability of the kidneys. Normal USG can range from 1003 to 1030; a value of les than 1010 indicates relative hydration, and a value greater than 1020 indicates relative dehydration. (14) Increased USG is associated with glycosuria and the syndrome of inappropriate antidiuretic hormone; decreased USG is associated with diuretic use, diabetes insipidus, adrenal insufficiency, aldosteronism, and impaired renal function. (14) In patients with intrinsic renal insufficiency, USG is fixed at 1.010--the specific gravity of the glomerular filtrate.

URINARY PH

Urinary pH can range from 45 to 8 nevertheless normally is slightly acidic (i.e., 55 to 65) because of metabolic activity. Ingestion of proteins and acidic fruits (eg cranberries) can cause acidic urine, and diets high in citrate can cause alkaline urine. (15-17) Urinary pH generally contemplates the serum pH, except in patients with renal tubular acidosis (RTA). The inability to acidify urine to a pH of les than 55 despite an overnight fast and administration of an acid load is the hallmark of RTA. In stamp I (distal) RTA, the serum is acidic moreover the urine is alkaline, secondary to an inability to conceal protons into the urine. impressed sign II (proximal) RTA is characterized by means of an inability to reabsorb bicarbonate. This situation initially follows in alkaline urine, but as the filtered load of bicarbonate decreases, the urine becomes more acidic.

Determination of urinary pH is useful in the diagnosis and management of UTIs and calculi. Alkaline urine in a patient with a UTI hints the presence of a urea-splitting organism, which may be associated with magnesium-ammonium phosphate crystals and can form staghorn calculi. Uric acid calculi are associated with acidic urine.