Page 383 - The Veterinary Laboratory and Field Manual 3rd Edition

352 Susan C. Cork, Willy Schauwers and Roy Halliwell

urine samples may become cloudy due to the ing traces of protein. To look for leucocytes, put
presence of phosphates. A cloudy fresh urine a drop of urine in the counting chamber of a
sample will often indicate a renal tract pathol- haemocytometer slide, and count the cells, as if
ogy. counting cells in a blood sample. Use the follow-
ing procedure.

biochemical analysis of urine
Method
Kidneys excrete water and many waste substances 1 Collect a clean midstream specimen of urine.
from the blood. One of the more important 2 Mix the specimen well. If the urine is not well
waste substances is urea. Substances which mixed, leucocytes may settle at the bottom of
are not waste products sometimes get into the the bottle.
urine because something is wrong systemically 3 Put a cover slip on a haemocytometer count-
(for example, a metabolic or toxic problem) or ing chamber.
with the urinary tract. Urine should be examined 4 Fill the counting chamber with urine using a
visually before testing to determine the colour Pasteur pipette.
and consistency. Any abnormalities should be 5 Count the cells in four corners of the cham-
recorded including any abnormal odour. ber as for a white blood cell count (W). (See
The presence of sugar in the urine is called Chapter 5.)
‘glycosuria’ and can indicate diabetes mellitus
(due to insufficient insulin). The presence of Some of the elements seen in the sediments of
protein in the urine is referred to as ‘protein- urine samples are shown in Figure 7.13. White
uria’. If protein is found it can indicate one of blood cells will appear much larger than red
several diseases of the urinary tract including blood cells, although neutrophils often disinte-
urogenital infection, inflammatory disease of grate. Different white blood cells (WBC) may
the kidneys or chronic kidney (renal) or bladder not be readily distinguished but neutrophils are
damage. A sample containing protein will usu- usually numerically more common. Red blood
ally be cloudy. Urine may sometimes be a deep cells may appear faintly yellowish-red in urine
brownish green due to the presence of bile pig- and are often crenated (distorted). Epithelial
ments and it may be coloured by drugs or certain cells, usually from the lining of the urinary tract,
dietary additives. The presence of haemoglobin will appear much larger and flatter and usually
or blood, results in red urine, this is abnormal, have a nucleus that is easily seen. Sometimes
however, it is important to rule out contamina- they appear as sheets of cells.
tion from the reproductive tract.
IntErPrEtatIon
In excess of 2–3 WBC per high power field or 10
Microscopic examination of urine cells per microlitre can be considered abnormal
sediment but it is necessary to assess this alongside other
test results. Note, however, that cells from the
When the urinary tract is infected, protein, bac- reproductive tract may contaminate urine.
teria and/or pus cells are usually present in the
urine. Finding pus cells (leucocytes especially LookInG at a cEntrIFuGEd dEPoSIt
neutrophils) in urine (pyuria) is a much more For more detailed examination of the cellular
certain sign of urinary tract infection than find- components of a urine sample it should be cen-

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