Anatomy and Disease~Common Diagnostics

7/27/2019 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

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Anatomy and Disease~Common Diagnostics