When focusing with the high-power lens, the red
cells show a distinct circle; the white cells tend to
appear granular with a visible nucleus.
One drop of 5% acetic acid added to the urine
sediment disintegrates any red cells, but it does
not affect the white cells (except that the nuclei
become more distinct).
Casts.These urinary sediments are formed by
coagulation of albuminous material in the kidney
tubules. Casts are cylindrical and vary in diameter.
The sides are parallel, and the ends are usually
rounded. Casts in the urine always indicate some form
of kidney disorder and should always be reported. If
casts are present in large numbers, the urine is almost
sure to be positive for albumin.
There are seven types of casts.
They are as
Hyaline casts are the most frequently occurring
casts in urine. Hyaline casts can be seen in even
the mildest renal disease. They are colorless,
homogeneous, transparent, and usually have
Red cell casts indicate renal hematuria. Red cell
casts may appear brown to almost colorless and
are usually diagnostic of glomerular disease.
White cell casts are present in renal infection
and in noninfectious inflammation.
majority of white cells that appear in casts are
Granular casts almost always indicate
significant renal disease.
casts may be present in the urine for a short time
following strenuous exercise.
that contain fine granules may appear grey or
pale yellow in color. Granular casts that contain
larger coarse granules are darker. These casts
often appear black because of the density of the
Epithelial casts are rarely seen in urine because
renal disease that primarily affects the tubules is
infrequent. Epithelial casts may be arranged in
parallel rows or haphazardly.
Waxy casts result from the degeneration of
granular casts. Waxy casts have been found in
patients with severe chronic renal failure,
malignant hypertension, and diabetic disease of
the kidney. Waxy casts appear yellow, grey, or
colorless. They frequently occur as short, broad
casts, with blunt or broken ends, and often have
cracked or serrated edges.
Fatty casts are seen when there is fatty
degeneration of the tubular epithelium, as in
degenerative tubular disease. Fatty casts also
result from lupus and toxic renal poisoning. A
typical fatty cast contains both large and small
The small fat droplets are
yellowish-brown in color.
Clinical laboratory medicine is a very dynamic
field of medicine, with new testing procedures and
equipment being invented all the time. The goal of this
chapter is to introduce you to some basic laboratory
tests that do not require state-of-the-art equipment and
that can be easily performed in isolated duty stations
and aboard naval vessels. These tests will assist you in
establishing diagnoses and will enable you to provide
the best possible medical care for your patients.