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186. Proteinuria, haematuria, casts.
Proteinuria is the abnormal presence of protein in the urine, and more than 150 mg of protein/day is
considered pathological. A large quantity of protein can make your urine appear frothy. Protein in the
urine indicates damage to kidneys, either from a glomerular membrane permeability defect or a defect in
the renal tubules-- where filtered proteins are normally reabsorbed. A common method of testing for
proteinuria is a chemically treated diptstick that changes color in the urine sample based on how much
protein is present. The small amount of physiological protein appearing in the urine (less than 150
mg/day) consists of uromodulin (Tamm-Horsfall protein-secreted by tubular epithelium), albumin, and
low molecular weight proteins (beta-2 microglobulin) and amino acids. One exception of physiological
proteinuria is orthostatic proteinuria, most common in young adult males and is associated with
prolonged upright posture throughout the day. Can yield a positive dipstick test, but with otherwise
normal renal functions. Proteinuria exceeding 3500mg/day is termed nephritic syndrome.
Proteinuria can be also be classified as selective or non-selective, depending on the extent of the
derangement of the glomerular membrane. In non-selective proteinuria, the membrane damage is severe
and even large and electrically charged proteins are excreted.
(http://www.patient.co.uk/showdoc/40000542/ and Professor Necas)
Haematuria is the abnormal presence of red blood cells in the urine. The source of the RBCs can be
post-glomerular –from the urinary tract (caused by inflammation, stones, tumors) or the glomerular
capillaries (accompanied by massive proteinuria). In theory, no RBCs should be found in the urine, and
haematuria can be classified as macroscopic (red colored urine) or microscopic, where the RBCs can be
detected using a chemically treated dipstick or microscopically.
(http://en.wikipedia.org/wiki/Hematuria and Professor Necas)
Urinary casts are formed when debris in the renal tubules aggregate into a cylindrical shape in the distal
tubules, dislodge and pass into the urine. They can be identified microscopically (bright field or phase
contrast) and used as prognostic indicators of kidney disorders. Some casts might require staining for
differentiation (WBCs). The debris composing the casts can be acellular (hyaline, granular, waxy, fatty,
pigment, crystal) or cellular elements (RBCs, WBCs, bacterial cells, epithelial cells). All casts contain
uromodulin (Tamm-Horsfall mucoprotein) which is normally secreted from the tubular epithelial cells of
the distal tubules, plus whatever other debris adheres or is included. The urine sample should be
centrifuged, the and the pellet resuspended in a small amount of supernatant (.2-.5mL) and a drop is
examined on a microscope slide. Casts can be reported quantitatively (number of casts per power field)
and by content (cell type, composition). The samples should be fresh, as casts are prone to break apart if
left standing too long. A few hyaline or granular casts may be considered physiological.
Acellular Casts:
Hyaline casts are solidified Tamm-Horsfall mucoprotein. Low urine flow, concentrated urine, or an
acidic environment can contribute to the formation of hyaline casts, and as such, they may be seen in
normal individuals in dehydration or vigorous exercise.
Granular casts can result either from the breakdown of cellular casts, or the inclusion of aggregates of
plasma proteins (albumin or immunoglobulin light chains). Depending on the size of inclusions, they can
be classified as fine or coarse, though the distinction has no diagnostic significance. Their appearance is
generally more cigar-shaped and of a higher refractive index than hyaline casts. While most often
indicative of chronic renal disease, these casts, as with hyaline casts, can also be seen for a short time
following strenuous exercise.
Waxy casts are thought to represent the end product of cast evolution, waxy casts suggest the very low
urine flow associated with severe, longstanding kidney disease such as renal failure. Additionally, due to
urine stasis and their formation in diseased, dilated ducts, these casts are significantly larger than hyaline
casts. While cylindrical, they also possess a higher refractive index and are more rigid, demonstrating
sharp edges, fractures, and broken off ends. Waxy casts also fall under the umbrella of “broad” casts, a
more general term to describe the wider cast product of a dilated duct.
Fatty casts are formed by the breakdown of lipid rich epithelial cells, these are hyaline casts with fat
globule inclusions, and are yellowish-tan in appearance. If cholesterol or cholesterol esters are present,
they are associated with the “Maltese cross” sign under polarized light. They can be present in various
disorders, including the high urinary protein nephrotic syndrome, diabetic or lupus nephropathy, or larger
scale necrosis or epithelial cell death.
Pigment casts are formed by the adhesion of metabolic breakdown products or drug pigments, these casts
are so named due to their discoloration. Pigments include those produced endogenously, such as
hemoglobin in hemolytic anemia, myoglobin in rhabdomyolysis, and bilirubin in liver disease. Drug
pigments, such as phenazopyridine, may also cause cast discoloration.
Crystal casts are crystallized urinary solutes, such as oxalates, urates, or sulfonamides, and may become
enmeshed within a hyaline cast during its formation, the clinical significance of this occurrence is not felt
to be great.
http://en.wikipedia.org/wiki/Urinary_casts
Cellular Casts:
RBCs in the cast appear yellowish brown and are pathological. Causes include: systemic lupus
erythematosis, post-stretpococcal glomerulonephritis, Goodpasture’s syndrome, renal infarction, and can
be associated with subacute bacterial endocarditis.
WBCs in the cast are indicative of infection (such as pyelonephritis) or inflammation (caused by post
streptococcal glomerulonephritis, acute allergic interstitial nephritis, or nephrotic syndrome)
Bacterial casts often include WBCs, maybe seen with pyelonephritis.
Epithelial cell casts are the tubular lining, which can slough off due to insult or injury, including toxic
ingestion (Hg), tubular necrosis, cytomegalovirus and viral hepatitis.
(Acellular and cellular casts descriptions taken from: Haber, Meryl H. Urinary Sediment: A Textbook
Atlas. American Society of Clinical Pathologists, Chicago. 1981.)
Plagiarism sources 14.6%