A complete urinalysis has four
parts:
Part 1
GROSS EXAMINATION
Color
Normal urine usually ranges from a light yellow to
a dark amber color that may vary according to the concentration and the type
of food and drugs that are ingested. The color of urine is attributed to its
chief pigment, "urochrome". Changes in urine may be due to disease, but can
also be caused by food and drugs ingested.
Transparency
Freshly voided urine is usually clear. Samples
exposed to room temperature for more than an hour or two may become cloudy
bur to bacterial growth or precipitation of phosphates or urates. Possible
transparency are the presence of kidney stones, bacteria, sperm, yeasts, or
stool contamination.
Odor
The odor of a fresh urine sample is normally
Aromatic. The odor, when unusual (Ammonia-like sweet and fruity), may be due
to a urinary tract infection, or the presence of ketone bodies as in
Diabetes, starvation, strenuous exercise, vomiting, diarrhea, malnutrition;
or may be due to the ingestion of certain food or to the contamination of
the urine container.
Part 2
SPECIFIC GRAVITY
The specific gravity of urine depends on the
gravity and number of molecules dissolved in solution of the urine sample.
The normal urinary specific gravity may range from 1.002 to 1.030. Most of
the molecules dissolved in the urine are made of Sodium Chloride and Urea.
Urine is usually More concentrated in the morning which, is a normal
phenomenon. Abnormally diluted urine may be present in kidney disease
whereas very concentrated urine with high specific gravity may be present in
diabetes, vomiting, diarrhea, and fever.
Part 3
BIOCHEMICAL TESTING
Leukocytes
Leukocytes are one of the white (Leuko) cells (Cytes)
present in blood stream which defend the body from bacterial invasion. When
present in the urine may suggest the presence of an underlying mild urinary
tract infection. A repeated presence of leukocytes indicate the needs for
further testing such as cultures or blood test.
Nitrates
The presence of nitrates in the urine is due to the
conversion of nitrates in food by the action of the bacteria. Therefore, a
positive nitrate test is a good indicator for the presence of a significant
amount of bacteria in urine. This may be associated with a urinary tract
infection of a bladder or urethral the tube which connects the bladder to
the outside) infection. Significant bacteriuria is estimated to affect 1%-2%
of young girls,5%-10% of pregnant women and is also associated with
diabetes, hypertension, herniation of the urinary bladder, Prostate problems
and the use of a catheter for drawing certain anatomic abnormalities.
Ph
Normally freshly voided urine is acid. Therefore,
the PH which is a measure of acidity may range from 4.0-7.0. People who eat
high protein diets produce a more acid urine than those that consume mostly
fruits and vegetables. Increased urinary acidity (lower PH) may also be
present in diabetes, fever, pulmonary emphysema, diarrhea and dehydration.
Alkaline PH (Higher PH) may also be noted in chronic inflammation of the
urinary bladder, acute or chronic kidney failure, or for intoxication of
salicylate ( such as aspirin) or other drugs.
Proteins
The presence of proteins in the urine is called "Proteinuria"
and is an important sign of renal disease. Proteinuria can be due to an
increased permeability of the walls of the filtering components of the
kidneys (The glomerulus). Proteins may be present in a number of kidney
diseases. However a small amount of proteins, mostly albumin, may appear in
the urine in response to excessive muscular exertion, exposure to colds, or
with extra ingestion of proteins with food. In some people the presence of
proteins in the urine may occur upon arising from a sitting position. This
is called " Orthostatic Proteinuria". Proteinuria may also be present in
acute inflammation of the kidneys as acute nephritis, or in the presence of
malignant hypertension, heart failure and diabetes.
Ketones
Ketones are called "Ketone bodies" and include
acetone, diacetic acid and beta hydrobutyric acid and and appear in normal
urine of patients on a carbohydrate-deficent diet. When the body can not
find sufficient sugar for its metabolism it turns to its fat stores for
energy which in turn are reduced to ketone bodies. Ketone bodies appear in
urine before they increase significantly in blood and this is called "Ketonuria".
The presence of ketones in the urine may occur in uncontrolled diabetes and
hyperthyroidism.
Urobilinogen
A small presence of urobilinogen is normal
and is formed from bilirubin by the action of the intestinal
bacteria. Bilirubin is a substance which is produced by the
breakdown of red blood cells. The majority of urobilinogen is
excreted in the stool but a small amount is reabsorbed into
circulation. Thus traces of urobilinogen may be normally present in
the urine. Most of the urobilinogen is re-excreted again by a normal
liver. In the presence of liver tissue damage like viral hepatitis,
secondary hepatitis or cirrhosis of the liver one may find an
increased amount of urobilinogen in the urine. A large amount of
urobilinogen may be present in blood disorders such as hemolytic
anemia, pernicious anemia or other forms of anemia. Urobilinogen may
be reduced during antibiotic therapy and maybe absent when there is
an obstruction of the biliary duct which conducts the bile from the
liver and gallbladder to the intestine
Glucose
Glucose (sugar) is a key indicator of
carbohydrate metabolism. Normally there is no detectible glucose in
the urine. Glucose is reabsorbed by the kidney after it has passed
through the glomerular filter. The maximum reabsorption capacity is
about 160 milligrams per deciliter (md/dl). If the blood sugar
concentration rises above this level glucose begins to spill into
the urine. The presence of glucose in the urine is called "glycosuria".
Diabetes mellitus is the major cause of glycosuria. Therefore people
with diabetes may test the urine for sugar to monitor their therapy.
Other common causes of glycosuria are pain, excitement, thyroid
gland hyperactivity or toxicity, resection of the stomach, liver
damage, shock, head injury, and acute inflammation of the pancreas.
Glycosuria may also be noted after general anesthesia or
administration of morphine or strychnine.
Bilirubin
The presence of bilirubin in the urine
helps in the detection of biliary obstruction (the duct which
carries the bile from the liver to the intestines) or liver disease.
Bilirubin is formed from the breakdown of the pigment contained in
the red blood cells which is called "hemoglobin". Bilirubin is then
transported to the liver where it is conjugated and is then excreted
through the biliary tract into the intestines and reduced to
urobilinogen (see above) by intestinal bacteria. Normally there is
no bilirubin present in the urine. When bilirubin is present this
condition is called "Bilirubinuria" and can occur in liver disease
and obstruction of the bile duct and associated with "jaundice".
However when jaundice is due to increased breakdown of red blood
cells an increased presence of bilirubin in the urine will not be
present. Bilirubin in the urine may also occur in hepatitis,
sclerosis of the liver, cancer of the head of the pancreas,
poisoning due to toxic fumes and heart failure when associated with
jaundice.
Blood
The presence of blood in the urine is a
warning sign of renal disease or of cancer of the urinary tract.
Normally a few red blood cells may be present in the urine. However,
if there are more than 8 or 10 red blood cells in a high-power field
on the microscope this is considered an abnormal finding. The
presence of occult blood in the urine is called "hematuria" (when
whole red blood cells are present) to distinguish it from "hemoglobinuria"
(when the red cells are broken down) or "myoglobinuria" (when
pigment coming from the destruction of muscle tissues is present in
the urine). Hematuria is present in many kidney disorders such as
acute inflammation of the kidney, presence of stones, malignant
tumors or chronic kidney infections. Also some drugs like the sulfur
drugs or anti-coagulants may cause the presence of blood in the
urine.
Hemoglobin
Hemoglobin is the main component of
red blood cells and is a molecule which carries oxygen from the
lungs to all parts of the body. Hemoglobin is made of four units of
"heme" (an iron containing element) and of a "globin" (a protein).
The presence of hemoglobin in the urine indicates the breakdown of
red cells and is called "hemoglobinuria". Hemoglobin may normally
appear in the urine after heavy physical exertion. In these cases
blood (whole red cells) is not present. Hemoglobin may also be
present as a reaction to a blood transfusion, injury due to
electrical current or severe bums. This test may positive also in
the presence of "myoglobin" as it occurs in muscle tissue disorders,
trauma or a crush injury.
Part 4
MICROSCOPY & SEDIMENT EXAMINATION
Cells
To identify urinary sediment
cells is a difficult task. Some cells have characteristic features,
therefore easily identifiable. On the other hand, some cells, even
with sophisticated stains, remain a challenge. The diversity of
cells that one can meet is notable. . Urinary cells can originate
from the kidney or from the lower urinary tract, from the
superficial lining or from a deeper source. In an adult male, cells
can also originate from the prostate and the urethra.
Urine is not a favorable media for maintaining cell structures. Most
cells undergo rapid changes that profoundly affect the visual aspect
of the cell. These changes are more pronounced if the cell comes
from the higher urinary tract. The best preserved cells are usually
bladder cells, while a well preserved proximal renal tubular cell is
exceptional. Some pathologies, like inflammation, metaplasia,
neoplasia, are known to affect the cellular aspect.
Casts
Casts are elements of the
urinary sediment, mainly composed of protein excreted by that
section of the kidney which includes the thick ascending branch of
the loop of Henle and the first part of the distal tubules and which
takes the shape of the site of its formation (casting).
Casts are formed, after the loop, in the late section of the distal
tubules and the early section of the collecting tubes. The formation
site is the kidney section where the dilution is maximal.
Some factors (found in abnormal urines) seem to promote casts
formation while others (found in normal urines) have an inhibiting
effect. Casts are formed when the equilibrium between promoters and
inhibitors is broken. Factors known to be promoters of cast
formation are the presence of albumin, stagnant urine, cellular
debris and low urine filtration rate through the kidneys and acid
urine.
Many different types of casts have been described and may appear as
coarsely granular, finely granular or waxy and relations between
these casts and some clinical conditions have also been described.
They are divided as blood casts, cellular casts, fatty casts and
granular casts and they can relate to diseases of different sections
of the kidneys.
Crystals
Except for the cystine
crystals and a few others, the majority of crystals found in the
urinary sediment are of limited clinical value. It is tempting to
associate crystals with a risk of kidney stones but many benign
situations can provoke crystal formation.
In the majority of cases, the crystals found in urine are not
present in the freshly voided specimen. Alkalization and
refrigeration are promoters of crystals formation.
Drug crystals are sometimes found in urine. In most cases, these
findings are of little clinical value. The sediment's picture may at
times, indicate a possible renal obstruction. Crystal casts are
typical of this situation.
Crystals related to kidney stones are, except for cystine, usual and
easy to identify. Calcium is found in 80 to 95% of kidney stones,
mostly as oxalate or phosphate crystals. Many stones are not
homogeneous. Some have a nucleus of a different composition from the
surrounding matrix.
Formation of crystals can be due to a decreased dilution like in a
case of insufficient water intake or could also be caused by a high
elimination.
Critters
"Critters" are
usually Bacteria, Yeast, Parasites, Viruses, Sperm and Mucous and
they may suggest the presence of a urinary tract infection (UTI).
The presence of many white blood cells and bacteria is
characteristic of this situation. On the other hand, urine specimens
for routine examination are not usually obtained through a sterile
technique with the result that old specimens can have a lot of
bacteria with only a few leukocytes. Bacteria associated with
urinary tract infection are mostly bacillus (E. Coli).
Bacteria-coated urethral cells are frequent in cystitis. This
situation is different from Clue Cells, which are vaginal cells
coated with a coccobacillus (Gardnerella Vaginalis), forming a crust
over the cell.
Like bacteria, the presence of yeast in the urine sediment may
indicate an infection. A frequently seen yeast in urine is Candida.
Identification of this organism is relatively easy because of its
usual club shape. In a number of specimens, the presence of yeast is
the result of a contamination with vaginal secretion. Yeasts are
often observed in specimens that contain sugar. It is important to
be careful with these specimens because a yeast infection is a
frequent finding with diabetic patients. Yeast containing casts have
a very high clinical value; these are typical of kidney infection.
The parasite that is the more frequently seen in urine is
Trichomonas. Usually, this cell comes from genital secretions
contaminating the specimen. But Trichomonas should be mentioned
because cases of bladder and prostate colonization by this organism
have been reported in the literature
Some cellular manifestations of viral infection can be seen in the
urine sediment. Herpes simplex is the most observed viral
manifestation.
Urinary spermatozoa is a contamination arising from sexual activity.
With a male subject, these represent a residual drainage while with
a female, these have a vaginal contamination source.
Mucus is a frequent finding of the urinary sediment. The exact
function of mucus is unknown. Some think that this substance is a
protection against bacterial infection.
