anatomy and disease~common diagnostics
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Anatomy and Disease
The human body is remarkably well designed. Most of its organs have a great deal of extra capacity or
reserve: They can still function adequately even whendamaged. For example, more than two thirds of the liver
must be destroyed before serious consequences occur, and a
person can usually live with only one lung or kidney.
Other organs can tolerate little damage before theymalfunction and symptoms occur. For example, if an artery
in the brain becomes blocked or ruptures (stroke) and even a
small amount of tissue in a vital part of the brain is destroyed,a person may be unable to speak, move a limb, or maintain
balance. If a heart attack destroys a small amount of tissue in
the part of the heart that creates or carries the signals to beat,
the heart rate may become dangerously slow and the person
may even die.
Disease often affects anatomy, and changes in anatomycan cause disease. If the blood supply to a tissue is
blocked or cut off, the tissue dies (infarction), as in a
heart attack (myocardial infarction) or stroke (cerebral
infarction). An abnormal heart valve can cause heart
malfunction. Trauma to the skin may damage its ability
to act as a barrier, which may lead to infection.
Abnormal growths, such as cancer, can directly destroy
normal tissue or produce pressure that ultimatelydestroys it.
Because of the relationship between disease andanatomy, methods of seeing into the body have become
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a mainstay in the diagnosis and treatment of disease.
The first breakthrough came with x-rays, which enabled
doctors to see into the body and examine internal
structures without surgery. Another major advance was
computed tomography (CT), in which x-rays are linkedwith computers. A CT scan produces detailed cross-
sectional (two-dimensional) images of the body's
interior.
Other methods of producing images of internalstructures include ultrasound scanning, which uses
sound waves; magnetic resonance imaging (MRI),
which uses the movement of atoms in a magnetic field;
and radionuclide imaging, which uses radioactive
chemicals injected into the body. These are noninvasive
ways to see into the body, in contrast to surgery, which
is an invasive procedure.
Common Medical Tests
A large number of tests are widely availableMany tests are specialized for a particular disease
or group of related diseases
Generally, specialized tests are described with theappropriate diseases. However, other tests are
used commonly for a wide range of diseases
Tests are performed for a variety of reasons,including screening, diagnosing a disease,
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evaluating the severity of a disease so that
treatment can be planned, and monitoring the
response to treatment
Sometimes, a test may be used for more than onepurpose. A blood test may reveal that a person has
too few red blood cells (anemia), and then the
same test may be repeated after treatment to check
that the number of red blood cells has returned to
normal
In some instances, a condition can be treated atthe same time a screening or diagnostic test is
performed. For example, when colonoscopy, a test
in which a flexible viewing tube is used to
examine the inside of the large intestine, reveals
growths (polyps), they can be removed before
colonoscopy is completed
Types of Tests
Medical tests generally fall into one of six categories: analysis ofbody fluids,
imaging tests, endoscopy,measurement of body functions,
biopsy, and
analysis of genetic material in cells analysis of body fluids
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In many instances, the lines that separate thecategories become blurred. For example, endoscopy
of the stomach enables the examiner to view the inside
of the stomach as well as obtain tissue samples for
examination in a laboratory.
Analysis of body fluids: most often consists of tests of the blood,
urine, and fluid that surrounds the spinal cord and brain
(cerebrospinal fluid). Less often, fluids such as sweat and saliva
and fluid from the digestive tract (for example, gastric juices) are
analyzed.
Sometimes, the fluids analyzed are present only if a disease ispresent, such as when fluid collects in the abdomen (ascites) or in
the space between the two membranes covering the lungs (pleural
effusion).
Imaging: consists of tests that provide a picture of the inside of the
body, either in its entirety or only of certain parts. Ordinary x-rays
are the most common imaging tests, but others include ultrasound,
radioisotope (nuclear) scans, computed tomography (CT) scans,magnetic resonance imaging (MRI) scans, and positron emission
tomography (PET) scans.
Endoscopy: is the use of a viewing tube to directly observe the
inside of body organs or spaces (cavities). Most often, the
endoscope is flexible, although a few types are rigid. The tip of the
endoscope is usually equipped with a light and a camera, so images
can be seen on a television monitor while the examiner is
observing through the endoscope. Tools are often passed through achannel in the endoscope. One type of tool is used to cut and
remove tissue samples.
Endoscopy usually consists of passing the viewing tube through an
existing body opening. For example, esophagogastroduodenoscopy
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(EGD) is accomplished by passing a viewing tube through the
mouth. Colonoscopy involves passing a viewing tube through the
anus. However, sometimes an opening in the body must be created.
This can be done by making a small cut (incision) through the skin
and through layers of tissue beneath the skin, so that the endoscopecan be passed into a body cavity. For example, in arthroscopy, an
endoscope is passed through an incision to view a joint, such as the
knee or shoulder.
Measurement of body functions: often involves recording and
analyzing the activity of various body organs. For example,
electrical activity of the heart is measured with electrocardiography
(ECG), and electrical activity of the brain is measured withelectroencephalography (EEG).
Biopsy: involves removing tissue samples and examining them,
usually with a microscope. The examination often focuses on
finding abnormal cells that might provide evidence of
inflammation or of a disease, such as cancer. Tissues that are
commonly examined include skin, breast, lung, liver, kidney, and
bone.
Analysis of genetic material: usually involves testing cells from
skin, blood, or bone marrow. Genetic testing consists of an
examination for abnormalities of chromosomes, genes, or both.
Examination of genes includes analysis of DNA. Fetuses may
undergo genetic testing to determine whether they have a genetic
disorder. Children and young adults often undergo genetic testing
to determine whether they themselves have a disease or are at risk
of a disease. Adults sometimes undergo genetic testing to help
determine the likelihood that their relatives, such as children or
grandchildren, will develop certain diseases.
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Risks and Results
Every test has some risk The risk may be only the need for further testing if the
result is abnormal, or it may be the possibility of injuryduring the test
Doctors weigh the risk of a test against the usefulnessof the information it will provide
Normal test result values are expressed as a range, which is based
on the average values in a healthy population; 95% of healthy
people have values within this range, but average values are
slightly different for women and men and also may vary by age.
These values also vary somewhat among laboratories.
Blood Tests
Test Reference Range/Threshold
(Conventional Units)
Acidity (pH) 7.35-7.45
Alcohol (ethanol) 0 mg/dL (more than 0.1 mg/dLusually indicates intoxication)
Ammonia 15-50 units/L
Amylase 53-123 units/L
Antinuclear antibodies (ANA;
other antibodies can also be
identified)
0 (negative result)
Ascorbic acid 0.4-1.5 mg/dL
Bicarbonate (carbon dioxidecontent)
18-23 mEq/L
Bilirubin Direct: up to 0.4 mg/dL
Total: up to 1.0 mg/dL
Blood volume 8.5-9.1% of body weight
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Calcium 8.5-10.5 mg/dL (slightly higher
in children)
Carbon dioxide pressure
(expressed as a comparison
with how high the level of
mercury [Hg] rises in a tube
due to air pressure at sea
level)
35-45 mm Hg
Carboxyhemoglobin (carbon
monoxide in hemoglobin)
Less than 5% of total
hemoglobin
CD4 cell count 500-1500 cells/L
Ceruloplasmin 15-60 mg/dL
Chloride 98-106 mEq/L
Complete blood cell count
(CBC)
See individual tests:
Hemoglobin, hematocrit, mean
corpuscular hemoglobin, mean
corpuscular hemoglobin
concentration, mean corpuscular
volume, platelet count, white
blood cell count
Copper 70-150 g/dLCreatine kinase (CK or CPK) Male: 38-174 units/L
Female: 96-140 units/L
Creatine kinase isoenzymes 5% MB or less
Creatinine 0.6-1.2 mg/dL
Electrolytes See individual tests: Electrolytes
routinely tested include calcium,
chloride, magnesium, potassium,
and sodium
Erythrocyte sedimentation
rate (ESR)
Male: -13 mm/hr
Female: 1-20 mm/hr
Glucose Fasting: 70-110 mg/dL
Hematocrit Male: 45-52%
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Female: 37-48%
Hemoglobin Male: 13-18 gm/dL
Female: 12-16 gm/dL
Iron 60-160 g/dL (higher in males)
Iron-binding capacity 250-460 g/dL
Lactate (lactic acid) Venous: 4.5-19.8 mg/dL
Arterial: 4.5-14.4 mg/dL
Lactic dehydrogenase 50-150 units/L
Lead 20 g/dL or less (much lower in
children)
Lipase 10-150 units/L
Lipids:Cholesterol Less than 225 mg/dL (for age
40-49 yr; increases with age)
High-density lipoprotein
(HDL)
30-70 mg/dL
Low-density lipoprotein
(LDL)
60 mg/dL
Triglycerides 40-200 mg/dL (higher in males)
Triglycerides 40-200 mg/dL (higher in males)Liver function tests Include bilirubin (total),
phosphatase (alkaline), protein
(total and albumin),
transaminases (alanine and
aspartate), prothrombin
Magnesium 1.5-2.0 mg/dL
Mean corpuscular hemoglobin
(MCH)
27-32 pg/cell
Mean corpuscular hemoglobin
concentration (MCHC)
32-36% hemoglobin/cell
Mean corpuscular volume
(MCV)
76-100 cu m
Osmolality 280-296 mOsm/kg plasma
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Oxygen pressure (expressed as
a comparison with how high
the level of mercury [Hg] rises
in a tube due to air pressure at
sea level)
83-100 mm Hg
Oxygen saturation (arterial) 96-100%
Phosphatase (alkaline) 50-160 units/L (higher in infants
and adolescents, lower in
females)
Phosphorus 3.0-4.5 mg/dL
Platelet count 150,000-350,000/mL
Potassium 3.5-5.0 mEq/L
Prostate-specific antigen
(PSA)
0-4 ng/mL (increases with age)
Protein:
Total 6.0-8.4 gm/dL
Albumin 3.5-5.0 gm/dL
Globulin 2.3-3.5 gm/dL
Prothrombin time (PT) 10-13 seconds
Red blood cell (RBC) count 4.2-5.9 million/mLSodium 135-145 mEq/L
Thyroid-stimulating hormone
(TSH)
0.5-5.0 m units/L
Transaminase:
Alanine (ALT) 1-21 units/L
Aspartate (AST) 7-27 units/L
Troponin:
I Less than 1.6 ng/mLT Less than 0.1 ng/mL
Urea nitrogen (BUN) 7-18 mg/dL
Uric acid 3.0-7.0 mg/dL
Vitamin A (other vitamins can
also be measured)
30-65 g/dL
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White blood cell (WBC) count 4,300-10,800 /mL*Blood can be tested for many other substances as well.
Units are explained in Appendix I. Conventional units can be
converted to international units by using a conversion factor.International units (IU), a different system, is sometimes used by
laboratories.
Diagnostic Procedures
Procedure Body Area or
Sample
Tested
Description
Amniocentesis Fluid from the
sac
surrounding
the fetus
Analysis of fluid to
detect an
abnormality in the
fetus
Arteriography(angiography) Any artery inthe body;
commonly in
the brain,
heart,
kidneys,
aorta, or legs
X-ray study inwhich radiopaque
dye is used to
detect and outline
or highlight a
blockage or defect
of an artery
Audiometry Ears Assessment of the
ability to hear and
distinguish sounds
at specific pitches
and volumes
Auscultation Heart Listening with a
stethoscope for
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abnormal heart
sounds
Barium x-ray studies Esophagus,
stomach,
intestine,rectum
X-ray study to
detect ulcers,
tumors, or otherabnormalities
Biopsy Any tissue in
the body
Removal and
examination of
tissue sample under
a microscope for
cancer or another
abnormality
Blood pressuremeasurement
Usually anarm
Test for high or lowblood pressure
Blood tests Usually a
blood sample
from an arm
Measurement of
substances in the
blood to evaluate
organ function and
to help diagnose
and monitor
various disordersBone marrow aspiration Hipbone or
breastbone
Examination of
marrow under a
microscope for
abnormalities of
blood cells
Bronchoscopy Airways of
the lungs
Direct examination
for a tumor or other
abnormalityCardiac catheterization Heart Study of heart
function and
structure
Chorionic villus sampling Placenta Examination of a
sample under a
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microscope for an
abnormality in the
fetus
Chromosomal analysis Blood Examination under
a microscope todetect a genetic
disease or to
determine a fetus's
sex
Colonoscopy Large
intestine
Direct examination
for a tumor or other
abnormality
Computed tomography(CT)
Any part ofthe body
Computer-enhanced x-ray
study to detect
structural
abnormalities
Cone biopsy Cervix Removal and
examination of a
cone-shaped piece
of tissueCulture Sample from
any area of
the body
(usually a
fluid such as
blood or
urine)
Examination of
microorganisms
grown from a
sample to identify
infection with
bacteria or fungi
Dilation and curettage (Dand C)
Cervix anduterus
Examination of asample under a
microscope for an
abnormality of the
uterine lining
Dual X-ray absorptiometry Skeleton, Study of thickness
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(DEXA) focusing on
specific
regions,
usually hip,
spine, andwrist
of bones using a
type of x-ray
Echocardiography Heart Study of heart
structure and
function using
sound waves
Electrocardiography
(ECG)
Heart Study of the heart's
electrical activity
Electroencephalography(EEG)
Brain Study of brain'selectrical function
Electromyography Muscles Recording of a
muscle's electrical
activity
Electrophysiologic testing Heart Test to evaluate
rhythm or electrical
conduction
abnormalitiesEndoscopic retrograde
cholangiopancreatography
(ERCP)
Biliary tract X-ray study of the
biliary tract after
injection of a
radiopaque dye
using a flexible
viewing tube to
reach the biliary
tractEndoscopy Digestive
tract
Direct examination
of internal
structures using a
flexible viewing
tube
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Enzyme-linked
immunosorbent assay
(ELISA)
Usually blood The sample is
mixed with a
sample of allergens
or microorganisms
to test for thepresence of specific
antibodies
Fluoroscopy Digestive
tract, heart,
lungs
A continuous x-ray
study that allows a
doctor to see the
inside of an organ
as it functions
Hysteroscopy Uterus Direct examinationof the inside of the
uterus with a
flexible viewing
tube
Intravenous urography Kidneys,
urinary tract
X-ray study of the
kidneys and urinary
tract after
intravenousinjection of a
radiopaque dye
Joint aspiration Joints
between
bones,
especially
shoulder,
elbow,fingers, hips,
knees, ankles,
toes
Examination of
fluid from the space
within joints for
blood cells, crystals
formed from
minerals, andknees, organisms
Laparoscopy Abdomen Direct examination
for diagnosis and
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treatment of
abnormalities in the
abdomen
Magnetic resonance
imaging (MRI)
Any part of
the body
Magnetic imaging
test for anystructural
abnormality
Mammography Breasts X-ray study for
breast cancer
Mediastinoscopy Chest Direct examination
of the area of the
chest between the
lungsMyelography Spinal
column
Simple or
computer-enhanced
x-ray of the spinal
column after
injection of a
radiopaque dye
Nerve conduction study Nerves Test to determine
how fast an impulsetravels
Occult blood test Large
intestine
Test to detect blood
in the stool
Ophthalmoscopy Eyes Direct examination
to detect
abnormalities
inside the eye
Papanicolaou (Pap) test Cervix Examination under a microscope of
cells scraped from
the cervix to detect
cancer
Paracentesis Abdomen Insertion of a
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needle into the
abdominal cavity to
remove fluid for
examination
Percutaneous transhepatic
cholangiography
Liver, biliarytract
X-ray study of theliver and biliary
tract after injection
of a radiopaque dye
into the liver
Positron emission
tomography (PET)
Brain and
heart
Radioactive
imaging to detect
abnormality of
functionPulmonary function tests Lungs Tests to measure
the lungs' capacity
to hold air, to move
air in and out of the
body, and to
exchange oxygen
and carbon dioxide
Radionuclide imaging Many organs Radioactiveimaging to detect
abnormalities of
blood flow,
structure, or
function
Reflex tests Tendons Tests to detect
abnormalities of
nerve functionRetrograde urography Bladder,
ureters
X-ray study of the
bladder and ureters
after infusion of a
radiopaque dye
Sigmoidoscopy Rectum and Direct examination
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last portion of
the large
intestine
to detect tumors or
other abnormalities
Skin allergy tests Usually an
arm or theback
Tests for allergies
Spinal tap (lumbar
puncture)
Spinal canal Test for
abnormalities of
spinal fluid
Spirometry Lungs Test of lung
function that
involves blowing
into a measuringdevice
Stress test (exercise
tolerance)
Heart Test of heart
function with
exertion
Thoracentesis The space that
surrounds the
lungs (pleural
space)
Removal of fluid
from the chest with
a needle to detect
abnormalitiesThoracoscopy Lungs Examination of the
pleura and the
pleural space
through a viewing
tube
Tympanometry Ears Measurement of the
impedance
(resistance topressure) of the
middle ear, which
helps in
determining the
cause of hearing
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loss
Ultrasonography
(ultrasound scanning)
Any part of
the body
Ultrasound imaging
to detect structural
or functional
abnormalities
Urinalysis Kidneys and
urinary tract
Chemical analysis
of urine sample to
detect protein,
sugar, ketones, and
blood cells
Venography Veins X-ray study to
detect blockage of a
vein