Microscopic examination of urine

A standard urinalysis should be obtained in the initial assessment of a patient. Microscopic examination of the urine should be performed by preparation of a Gram stain of unspun or centrifuged urine. The presence of at least one organism per oil-immersion field in a properly collected uncentrifuged specimen correlates with more than 100,000 bacteria/mL of urine. 

It is usually unnecessary to obtain a microscopic examination on all urinalyses unless there are reasons to believe that important information and data may be lost. This is particularly true after it has been demonstrated that the test treatment does not affect the parameters measured in the microscopic evaluation of urine. 

Microscopic examination of the sediment obtained from the centrifugation of a fresh urine sample wiU show the presence of a few cells (erythrocytes, leukocytes, and cells derived from the kidney and urinary tract), casts (composed predominantly of Tamm-HorsfaU glycoprotein [THG]), and possibly fat or pigmented particles. An increase in red cells or casts unplies hematuria, possibly caused by glomerular disease white cells or casts imply the presence of white cells in the tubules. Inflammation of the upper urinary tract may result in polymorphonuclear leukocytes and various types of casts, and in lower urinary tract inflammation the casts will not be present. In acute glomerulonephritis, hematuria may... 

Microscopic examination of the urine for leukocytes is also used to determine the presence of pyuria. The presence of pyuria in a symptomatic patient correlates with significant bacteriuria. Pyuria is defined as a white blood cell (WBC) count of greater than 10 WBCs/mm of urine. A count of 5 to 10 WBCs/mm is accepted as the upper limit of normal. It should be emphasized that pyuria is nonspecific and signifies only the presence of inflammation and not necessarily infection. Thus patients with pyuria may or may not have infection. Sterile pyuria has long been associated with urinary tuberculosis, as well as chlamydial and fungal urinary infections. 

Urine microscopy The microscopic examination of the urine sediment provides enhanced diagnostic efficiency. Hematuria The normal number of erythrocytes in resuspended urine sediment is no more than 1 to 2 per high-powered field. When an abnormal number... 

Heematnria.—Blood may appear in the urine in the form of corpuscles, free haemoglobin (haemoglobinuria), and abnormal derivatives (methaemoglobin, and haematoporphyrin). In haematuria the urine often has a smoky, reddish colour that is very characteristic. Microscopic examination of the sediment may show the presence of blood corpuscles if they have escaped haemolysis. 

The presence of leucocytes or pus in urine (pyuria) is most easily confirmed by microscopical examination of the sediment. 

Bladder tumor-associated antigen (BTA), a human complement factor H, is produced by bladder cancer cells (men two to three times as often as women). Cancer cells are sometimes seen in urine samples by microscope cytoscopy (examination of the bladder with an instrument inserted into the urethra), which can reveal abnormal areas. Biopsy is needed to confirm the diagnosis. Early stage cancer confined to the bladder wall can often be removed with a cytoscope. If several tumors are present, they are removed by infusing the bladder with a solution containing bacteria able to stimulate the immune system. 

Differential Diagnosis of Acute Renal Failure on the Basis of Urine Microscopic Examination Findings... 

Most clinical laboratories have established a standard battery of tests that includes most or all of the basic parameters listed in Table 20.12. If a dipstick is used to test the urine for several parameters, it is useful to use one that measures occult blood, even if a microscopic examination will count the number of red blood cells per high-power field. The means of obtaining the specimen should be indicated (i.e., normal voiding sample, clean catch, midstream, catheterization, suprapubic tap, or cytoscopy), especially in clinical trials in which an antidiuretic or antibiotic (or other relevant drug) is being tested. 

Experimental design Rats (7-13 male and 10-13 female) were exposed to 1,4-dichlorobenzene vapors for 7 hours a day, 5 days a week at concentrations of 0, 96, or 158 ppm for a total of 126-139 exposures. At the end of the exposure period, the animals were sacrificed, body and organ weights determined, and tissues examined microscopically. Hematology (parameters not specified), analysis of urine (blood, glucose, albumin, and sediment) and measurement of blood urea nitrogen were conducted for females exposed to the lowest concentration of 1,4-dichlorobenzene. 

The type of urine specimen to be collected is dictated by the tests to be performed. Untimed or random specimens are suitable for only a few chemical tests usually, urine specimens must be collected over a predetermined interval of time, such as 1,4, or 24 hours. A clean, early morning, fasting specimen is usually the most concentrated specimen and thus is preferred for microscopic examinations and for the detection of abnormal amounts of constituents, such as proteins, or of unusual compounds, such as chorionic gonadotropin. The clean timed specimen is one obtained at specific times of the day or during certain phases of the act of micturition. Bacterial examination of the first 10 mL of urine voided is most appropriate to detect urethritis, whereas the midstream... 

Examination of the urine is often the first step in the assessment of a patient suspected of having, or confirmed to have, deterioration in kidney function. In the laboratory, urine is examined visually, chemically, and microscopically. New instrumental techniques are also being used to examine urine. 

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