King Edward Medical University

MEDICAL DICTIONARY
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

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Iatr(o)-: Prefix relating to a physician or medicine. From the Greek word "iatros" meaning physician (healer).

Iatrapistic: A lack of faith in doctors. Entirely from the Greek: "iatr-" indicating a relationship to a physician or medicine + "a" meaning lack + "pisteuo" meaning I trust in.

-iatrics: Suffix meaning healing. From the Greek "iatros" meaning healer or physician. Pediatrics is the healing of children. And geriatrics is the healing (or at least the treatment) of disorders characteristic of the aged.

Iatrogenic: Due to the activity of a physician or therapy. From the Greek "iatros" meaning physician + "gennao" meaning I produce. Iatrogenic is defined by Merriam-Webster's Collegiate Dictionary as: "induced inadvertently by a physician or surgeon or by medical treatment or diagnostic procedures." For example, an iatrogenic illness is one caused by a medicine or doctor.

Iatromelia: Ineffective or negligent medical treatment. From "iatro-" meaning a relationship to a physician or medicine + the Greek "meleos" meaning fruitless or vain.

Iatromisia: An intense dislike of doctors. From "iatro-" indicating a relationship to a physician or medicine + the Greek "miseo" meaning I hate.

-iatry: Suffix meaning medical treatment. From the Greek "iatreia" meaning healing, which came from "iatros" meaning treatment (or physician). Psychiatry is literally the medical treatment of the psyche.

IgE: Immunoglobulin E. The E stands for erythema or redness. See Immunoglobulin E.

Ileus: Part of the small intestine beyond the jejunum and before the large intestine (colon).

Ileitis, terminal: Crohn’s disease, a chronic inflammatory disease of the intestine involving only the end of the small intestine (the terminal ileum). Crohn’s disease affects primarily the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease often strikes persons in their teens or early twenties. It tends to be chronic, recurrent with periods of remission and exacerbation. In the early stages. It causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.

Ileocolitis, Crohn’s: Crohn’s disease involving both the ileum (the furtherest part of the small intestine just before the colon) and the large intestine (the colon). Crohn’s disease is a chronic inflammatory condition of the intestine primarily involving the small and large intestines but which can occur anywhere in the digestive system between the mouth and the anus. Named after Burrill Crohn who described the disease in 1932. The disease usually affects persons in their teens or early twenties. It tends to be a chronic, recurrent condition with periods of remission and exacerbation. In the early stages, Crohn’s disease causes small scattered shallow crater-like areas (erosions) called apthous ulcers in the inner surface of the bowel. With time, deeper and larger ulcers develop, causing scarring and stiffness of the bowel and the bowel becomes increasingly narrowed, leading to obstruction. Deep ulcers can puncture holes in the bowel wall, leading to infection in the abdominal cavity (peritonitis) and in adjacent organs. When only the large intestine (colon) is involved, the condition is called Crohn’s colitis. When only the small intestine is involved, the condition is called Crohn’s enteritis. When only the end of the small intestine (the terminal ileum) is involved, it is termed terminal ileitis. Abdominal pain, diarrhea, vomiting, fever, and weight loss can be symptoms. Crohn’s disease can be associated with reddish tender skin nodules, and inflammation of the joints, spine, eyes, and liver. Diagnosis is by barium enema, barium x-ray of the small bowel, and colonoscopy. Treatment includes medications for inflammation, immune suppression, antibiotics, or surgery.

Iliac horns: Symmetrical bilateral central posterior iliac processes. In other words, horn-like malformations of the crest of both iliac bones of the pelvis. A characteristic finding in the nail-patella syndrome.

Immune system: A complex system that is responsible for distinguishing us from everything foreign to us and for protecting us against infections and foreign substances.

Immunity: The condition of being immune. Immunity can be innate (for example,humans are innately immune to canine distemper) or conferred by a previous infection or immunization.

Immunization: Immunizations, or vaccinations, work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Immunizations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed. To immunize against bacterial diseases, it is generally possible to use only a small portion of the dead bacteria to stimulate the formation of antibodies against the whole bacteria. In addition to the initial immunization process, it has been found that the effectiveness of immunizations can be improved by periodic repeat injections or "boosters." Also see Immunizations (in the plural) and Immunization of a specific type (such Immunization, Polio).

Immunization, anthrax: A series of six shots over six months and booster shots annually, the anthrax vaccine now in use in the USA was first developed in the 1950s and approved by the Food and Drug Administration for general use in 1970. It is produced by the Michigan Biologic Products Institute of Michigan’s Department of Health and is given routinely to veterinarians and others working with livestock. In December, 1997 it was announced that all US military would receive the vaccine, as do the military in the UK and Russia, the reason being concern that anthrax might be used in biologic warfare.

Immunization, children’s: In the United States, it is recommended that all children receive vaccination against:

Hepatitis B
Diphtheria, tetanus, pertussis
Haemophilus influenzae type B (HIB)
Poliovirus
Measles, mumps, rubella
Varicella zoster virus (chickenpox).
Every child in the U.S. should have these vaccinations except when there are special circumstances and the child’s doctor advises specifically against a vaccination.
Immunization, chickenpox: This vaccine prevents the common disease known as chickenpox (varicella zoster). While chickenpox is often considered a trivial illness, it can cause significant lost time on the job and in school and have serious complications including ear infections, pneumonia, and infection of the rash with bacteria, inflammation of the brain (encephalitis) leading to difficulty with balance and coordination (cerebellar ataxia), damaged nerves (palsies), and Reye’s syndrome, a potentially fatal complication. The vaccination requires only one shot given at about a year of age. If an older person has not had chickenpox, the shot may be given at any time. There have been few significant reactions to the chickenpox vaccine. All children, except those with a compromised immune system, should have the vaccination.

Immunization, DPT: DPT immunization protects from diphtheria, pertussis (whooping cough), and tetanus and is given in a series of 5 shots at 2, 4, 6, 18 months of age and 4-6 years of age. Thanks to vaccination programs, these diseases have become less common. However, there are still unvaccinated individuals capable of carrying and passing diphtheria and pertussis to others who are not vaccinated. Tetanus bacteria are prevalent in natural surroundings, such as contaminated soil. See also Immunization, DTaP.

Immunization, DTaP: Like DPT, DTaP protects from diphtheria, pertussis (whooping cough) and tetanus. DTaP is the same as DTP, except that it contains only acellular pertussis vaccine which is thought to cause fewer of the minor reactions associated with immunization and is also probably less likely to cause the more severe reactions occasionally seen following pertussis vaccination. DTaP is currently recommended only for the shots given at 18 months and 4-6 years of age.

Immunization, DT: DT (diphtheria and tetanus) vaccine does not protect from pertussis and is usually reserved for individuals who have had a significant adverse reaction to a DPT shot or who have a personal or family history of a seizure disorder or brain disease.

Immunization, flu: The flu (influenza) vaccine is recommended for persons at high risk for serious complications from influenza infection, including everyone 65 or over; people with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia; residents of nursing homes and other chronic-care facilities, children and teenagers taking aspirin therapy (and who may therefore be at risk for developing Reye syndrome after an influenza infection), and those in close or frequent contact with anyone at high risk. Persons with an allergy to eggs should not receive influenza vaccine.

Immunization, hepatitis A: When immediate protection against hepatitis A (infectious hepatitis) is needed, immunoglobulins are used. Protection is effective only if given within 2 weeks of exposure and lasts but 2-4 months. Immunoglobulins can be used to protect household contacts of someone with acute viral hepatitis and travelers to regions with poor sanitation and high hepatitis A rates, when the traveler has to depart sooner than the vaccines can take effect (about 2 weeks). Travelers can receive the immunoglobulin and vaccine simultaneously and be protected immediately and for longer term. When immediate protection is not needed, hepatitis A vaccines are considered for individuals in high-risk settings, including frequent world travelers, sexually active individuals with multiple partners, homosexual men, individuals using illicit drugs, employees of daycare centers, and certain health care workers, and sewage workers. Two hepatitis A vaccines called HAVRIX and VAQTA are commercially available in the U.S. Both are highly effective and provide protection even after only one dose. Two doses are recommended for adults and 3 doses for children (under 18 years of age) to provide prolonged protection.

Immunization, hepatitis B: Hepatits B (hep B) vaccine gives prolonged protection, but 3 shots over a half year are usually required. In the U.S., all infants receive hep B vaccine. Two vaccines (ENGERIX-B, and RECOMBIVAX-HB) are available in the US. The first dose of hep B vaccine is frequently given while the newborn is in the hospital or at the first doctor visit following birth. The second dose is given about 30 days after the initial dose. A booster dose is performed approximately six months later. Babies born to mothers testing positive for hep B receive, in addition, HBIG (hep B immune globulin) for prompt protection. Older children (11-12 years) are advised to receive a hep B booster as are adults in high-risk situations including healthcare workers, dentists, intimate and household contacts of patients with chronic hep B infection, male homosexuals, individuals with multiple sexual partners, dialysis patients, IV drug users, and recipients of repeated transfusions. Health care workers accidentally exposed to materials infected with hep B (such as needle sticks), and individuals with known sexual contact with hep B patients are usually given both HBIG and vaccine to provide immediate and long term protection.

Immunization, HIB: This vaccine is to prevent disease caused by the Haemophilus influenzae type B (HIB) bacteria. The H. influenzae (H. flu) bacteria can cause a range of serious diseases including meningitis with potential brain damage and epiglottitis with airway obstruction poisoning. The HIB vaccine is usually given at 2, 4 and 6 months of age. A final booster is given at 12-15 months of age. HIB vaccine rarely causes severe reactions.

Immunization, MMR: The standard vaccine given to prevent measles, mumps and rubella (German measles). The MMR vaccine is now given in two dosages. The first should be given at12-15 months of age. The second vaccination should be given at 4-6 years (or, alternatively, 11-12 years) of age. Most U.S. colleges require proof of a second measles or MMR vaccination prior to entrance. Most children should receive MMR vaccinations. Exceptions may include children born with an inability to fight off infection, some children with cancer, on treatment with radiation or drugs for cancer, on long term steroids (cortisone). People with severe allergic reactions to eggs or the drug neomycin should probably avoid the MMR vaccine. Pregnant women should wait until after delivery before being immunized with MMR. People with HIV or AIDS should normally receive MMR vaccine. Measles, mumps, and rubella vaccines may be administered as individual shots, if necessary, or as a measles-rubella combination.

Immunization, pneumococcal pneumonia: This vaccine, which prevents one of the most common and severe forms of pneumonia, is usually given only once in a lifetime, usually after the age of 55, to someone with ongoing lung problems (such as chronic obstructive pulmonary disease (COPD) or asthma) or other chronic diseases (including those involving the heart and kidneys). This vaccination would rarely be given to children.

Immunization, polio: The vaccines available for vaccination against polio are OPV (Oral Polio Vaccine) and IPV (Inactivated Polio Vaccine). OPV is still the preferred vaccine for most children. As its name suggests, it is given by mouth. IPV, or Inactivated Polio Vaccine is given as a shot in the arm or leg. Infants and children should be given four doses of OPV. The doses are given at 2 months, 4 months, 6-18 months and 4-6 years of age. Persons allergic to eggs or the drugs neomycin or streptomycin should receive OPV, not the injectable IPV. Conversely, IPV should be given If the vaccine recipient is on long-term steroid (cortisone) therapy, has cancer, or is on chemotherapy or if a household member has AIDS or there is an unimmunized adult in the house.

Immunization, Td: Td is the vaccine given to children over six and adults as boosters for immunity to diphtheria and tetanus.

Immunocompetant: Able to develop an immune response. The opposite of immunodeficient.

Immunodeficiency: Inabillity to mount a normal immune response. Immunodeficiency can be due to a genetic disease or acquired as in AIDS due to HIV.

Immunogenetics: The genetics (inheritance) of the immune response. For example, the study of the Rh, ABO and other blood groups or the HLA system important to kidney and other transplants.

Immunoglobulin E (IgE): Antibody of a specific class used to fight invading allergic substances (allergens). An allergic person frequently has elevated blood levels of IgE. IgE antibodies attack and engage the invading army of allergens.

Immunology: The study of all aspects of the immune system including its structure and function, disorders of the immune system, blood banking, immunization and organ transplantation.

Immunosuppression: Lowering the immune response, for example, with radiation or medications.

Immunotherapy, allergy: Stimulation of the immune system with gradually increasing doses of the substances to which a person is allergic, the aim being to modify or stop the allergy "war" (by reducing the strength of the IgE and its effect on the mast cells). This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (eg, bees, hornets, yellow jackets, wasps, velvet ants, fire ants). Allergy immunotherapy usually takes 6 months to a year to become effective and "shots" (injections) are usually required for 3-5 years.

Impaction, dental: Teeth pressing together. For example, molar teeth (the large teeth in the back of the jaw) can be impacted, cause pain and require pain medication, antibiotics, and surgical removal.

Impotence: An inability to sustain an erection sufficient for sexual intercourse or to achieve ejaculation, or both. Impotence usually has a physical cause, such as disease, injury, drug side-effects, or a disorder that impairs blood flow in the penis. Impotence can also have an emotional cause. Impotence is treatable in all age groups.

Imperforate anus: Birth defect where the rectum is a blind alley and there is no anus.

Imprinting: A remarkable genetic phenomenon. The gist is that gene expression depends on the sex of the transmitting parent. There is, for example, increased severity of neurofibromatosis when the gene for it came from the mother.

Inborn errors of metabolism: Term coined by A. Garrod in 1908 applying to heritable disorders of biochemistry. Examples include albinism, cystinuria (a cause of kidney stones) and phenylketonuria (PKU) are a few of the hundreds of inborn errors of metabolism.

Inbreeding: The mating of two closely related persons. Also called consanguinity.

Inbreeding, coefficient of: A statistical way of gauging how close two people are as to their genes. The coefficient of inbreeding (symbolized as F) is the probability that a person with two identical genes received both genes from an identical ancestor. Take, for example, first cousins. They share a set of grandparents. For any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. For any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and ½ that she transmits that gene to the child so 1/8 X ½ = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding F =1/16. The added risks to the offspring of first cousins depend not only upon this coefficient of inbreeding but also upon the genetic family history and, in some cases, upon test results (as to beta thalassemia, for instance, for first cousins of Italian descent). There are always added risks from the mating of closely related persons.

Incest: Sexual activity between individuals so closely related that marriage is prohibited. Incest involving a child is a form of child abuse.

Inch: In length, 1/12th of foot or 1/36 of a yard or, metrically, 2.54 centimeters. The inch, along with the foot and yard, are Old World creations to which the USA has stubbornly clung. The inch was originally about the length of the last bone (distal phalanx) in a man’s thumb and served as a measurement of land. The etymology (word history) of "inch" is remarkable. It originally meant "one twelfth". The abbreviation is "in."

Incontinence: Inability to control excretions. Urinary incontinence is inability to keep urine in the bladder. Fecal incontinence is inability to retain feces in the rectum.

Incontinence, fecal: Inability to hold feces in the rectum. This is due to failure of voluntary control over the anal sphincters permitting untimely passage of feces and gas. Also called rectal incontinence.

Incontinence of urine: Inability to hold urine in the bladder. This is due to failure of voluntary control over the urinary sphincters resulting in involuntary passage of urine (wetting).

Incontinence, rectal: Inability to hold feces in the rectum due to failure of voluntary control over the anal sphincters with involuntary passage of feces and gas. Also called fecal incontinence.

Incontinence, urinary: Inability to hold urine in the bladder. This is due to failure of voluntary control over the urinary sphincters resulting in involuntary passage of urine (wetting).

Incontinent: Unable to control excretions, to hold urine in the bladder or keep feces in the rectum. (This is the usual medical meaning of the word incontinent, not continent. Incontinent can also refer to a lack of self-restraint in the sexual arena, failure to refrain from sexual intercourse.)

Incontinentia pigmenti (IP): A genetic disease with blisters that develop soon after birth on the trunk and limbs, then heal, but leave dark (hyperpigmented) streaks and marble-like whorls on the skin. (The name came from the erroneous idea that the skin cells were incontinent of pigment and could not contain it normally.) Other key features of IP include dental and nail abnormalities, bald patches, and (in about 1/3rd of cases) mental retardation. IP is an X-linked dominant with male lethality. The IP gene is in band q28 on the X chromosome. Mothers with IP have an equal chance of having a normal or IP daughter or a normal son. The IP sons die before birth. IP is also known as Bloch-Sulzberger syndrome.

Index case: A person who first draws attention to their family. For example, if my eye doctor discovers I have glaucoma and subsequently other cases of glaucoma are found in my family, I am the index case. Also called the propositus (if male) or proposita (if female).

Infant: The child up to 24 months of age. The word infant is from the Latin meaning not speaking.

Infant mortality rate: The number of children dying under a year of age divided by the number of live births that year. The infant mortality rate in the United States, which was 12.5 per 1,000 live births in 1980, fell to 9.2 per 1,000 live births in 1990.

Infection, urinary tract (UTI): An infection in the urinary system that begins when microorganisms cling to the opening of the urethra (the canal from the bladder) and begin to multiply. Most UTIs are due to one type of bacteria, E. (Escherichia) coli, a normal denizen of the colon. An infection in the urethra leads to inflammation called urethritis. From there bacteria may move up, causing a bladder infection (cystitis) and if the infection is not treated promptly, bacteria may go up the ureters to infect the kidneys (pyelonephritis). Factors leading to UTI include any abnormality of the urinary tract (such as a urinary tract malformation or a kidney stone) that obstructs the flow of urine, an enlarged prostate gland that slows the flow of urine, catheters (tubes) in the bladder, diabetes (due to changes of the immune system), and any disorder that suppresses the immune system. Women have more UTI than men, probably because a woman’s urethra is shorter (allowing bacteria quick access to the bladder) and nearer sources of bacteria from the anus and vagina. For many women, sexual intercourse seems to trigger an infection, as may the use of a diaphragm. Not everyone with a UTI has symptoms but symptoms commonly include a frequent urge to urinate and a painful, burning when urinating (dysuria). The urine may look milky or cloudy, even reddish if blood is present. Kidney infection can cause pain in the back or side below the ribs. In children, symptoms may be easily missed or misunderstood. A child with a UTI may be irritable, not eat normally, have an unexplained fever, have incontinence or loose bowels, or just not thrive.

Infectious mononucleosis: A specific viral infection (with the Epstein-Barr virus) in which there is an increase of white blood cells that are mononuclear (with a single nucleus)"Mono" and "kissing disease" are popular terms for this very common illness caused by the Epstein-Barr virus (EBV). By the time most people reach adulthood, an antibody against EBV can be detected in their blood meaning they have been infected with EBV. The illness is less severe in young children. The infection can be spread by saliva. The incubation period for "mono" is 4 to 8 weeks. Symptoms include fever, fatigue, sore throat, and swollen lymph glands. "Mono" can cause liver inflammation (hepatitis) and spleen enlargement. Vigorous contact sports should be avoided to prevent spleen rupture.

Inferior: In medicine, inferior means below or downward. The opposite of superior.

Infertility: Diminished or absent ability to conceive and bear offspring (fertility).

Infiltrate: To penetrate. If an IV infiltrates, the IV fluid penetrates the surrounding tissue.

Inflammation: Inflammation is localized redness, warmth, swelling and pain as a result of infection, irritation or injury.

Influenza: The flu is caused by viruses that infect the respiratory tract which are divided into three types, designated A, B, and C. Most people who get the flu recover completely in 1 to 2 weeks, but some people develop serious and potentially life-threatening medical complications, such as pneumonia. Much of the illness and death caused by influenza can be prevented by annual influenza vaccination.

Influenza vaccine: The flu (influenza) vaccine is recommended for persons at high risk for serious complications from influenza infection, including everyone age 65 or more; people with chronic diseases of the heart, lung or kidneys, diabetes, immunosuppression, or severe forms of anemia; residents of nursing homes and other chronic-care facilities, children and teenagers receiving long-term aspirin therapy (and who may therefore be at risk for developing Reye syndrome after an influenza virus infection), people in close or frequent contact with anyone at high risk. People with an allergy to eggs should not receive influenza vaccine.

Informatics: The application of computers and statistics to the management of information. For example, in the Human Genome Project, informatics includes the development and use of methods to search databases quickly, analyze DNA sequence information, and predict protein sequence and structure from DNA sequence data.

Inguinal canal: A passage in the lower anterior abdominal wall which in the male allows passage of the spermatic cord and in the female contains the round ligament. Because of the weakness it creates in the abdominal wall, it is the most frequent site for a hernia.

Insect stings: Stings from large stinging insects such as bees, hornets, yellow jackets and wasps can trigger allergic reactions varying greatly in severity. Avoidance and prompt treatment are essential. In selected cases, allergy injection therapy is highly effective. (The three "A’s" of insect allergy are Adrenaline, Avoidance and Allergist.)

Insertion: Chromosome abnormality due to insertion of a segment from one chromosome into another chromosome.

In situ hybridization: The use of a DNA or RNA probe to detect the complementary DNA sequence.

Insulin: A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood.

Interatrial septum: The partition separating the upper chambers (the atria) of the heart.

Intercostal muscle: Muscle tissue between two ribs. This muscle is a type called skeletal muscle.

Interferon: A substance used in biological therapy. Interferon helps the immune system slow the rate of growth and division of cancer cells, causing them to become sluggish and die. There are a number of interferons. All are proteins (lymphokines) produced by the body in response to infection. these substances interfere with cell infection. There are 3 main classes of interferon, alpha, beta, and gamma. The interferons have been synthesized using recombinant DNA technology.

Interleukins: Substances used in biological therapy. Interleukins stimulate the growth and activities of certain kinds of white blood cells.

Interleukin-2: A type of interleukin, a chemical messenger, a substance that can improve the body’s response to disease. It stimulates the growth of certain disease-fighting blood cells in the immune system. Also called IL-2.

Internal medicine: A medical specialty dedicated to the diagnosis and medical treatment of adults. A physician who specializes in internal medicine is referred to as an internist. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal medicine include allergy and immunology, cardiology (heart), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumatology (arthritis and musculoskeletal disorders).

Internal radiation therapy: Radiation therapy in which radioactive material is placed in or near a tumor.

Internist: A physician who specializes in the diagnosis and medical treatment of adults. This specialty, called internal medicine, is dedicated to adult medicine. A minimum of seven years of medical school and postgraduate training are focused on learning the prevention, diagnosis, and treatment of diseases of adults. Subspecialties of internal medicine include allergy and immunology, cardiology (heart), endocrinology (hormone disorders), hematology (blood disorders), infectious diseases, gastroenterology (diseases of the gut), nephrology (kidney diseases), oncology (cancer), pulmonology (lung disorders), and rheumatology (arthritis and musculoskeletal disorders).

Interphase: The interval in the cell cycle between two cell divisions when the individual chromosomes cannot be distinguished, interphase was once thought to be in resting phase but it is far from a time of rest for the cell. It is the time when DNA is replicated in the cell nucleus.

Interstitial cystitis (IC): Disease that involves inflammation or irritation of the bladder wall. This inflammation can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes IC, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments.

Interstitial radiation: Radiation therapy in which a radioactive material is placed directly into a tumor.

Interventricular septum: The stout wall separating the lower chambers (the ventricles) of the heart fromone another. A hole in the interventricular septum is termed a ventricular septal defect (VSD).

Intestine: The long, tubelike organ in the abdomen that completes the process of digestion. It consists of the small and large intestines.

Intestinal gas: The complaint referred to as "intestinal gas" is a common one and the discomfort can be quite significant. Everyone has gas and eliminates it by burping or passing it through the rectum. In many instances people think they have too much gas when in reality they have normal amounts. Most people produce 1 to 3 pints of intestinal gas in 24 hours and pass gas an average of 14 times a day. It is made up primarily of odorless vapors such as carbon dioxide, oxygen, nitrogen, hydrogen, and in some families, methane. The unpleasant odor is due to bacteria in the large intestine that release small amounts of gases containing sulfur.

Intracranial: Inside the skull (the cranium). Intracranial hemorrhage A bleed inside the head.

Intractable: Unstoppable. For example, intractable diarrhea or intractable pain.

Intraepithelial: Within the layer of cells that forms the surface or lining of an organ.

Intraocular: In the eye. The intraocular pressure is the pressure within the eye.

Intraoperative radiation therapy: Radiation treatment given during surgery. Also called IORT.

Intraperitoneal: Within the peritoneal cavity, the area that contains the abdominal organs.

Intraperitoneal chemotherapy: Treatment in which anticancer drugs are put directly into the abdomen through a thin tube.

Intrathecal chemotherapy: Treatment with drugs that are injected into the fluid surrounding the brain and spinal cort (cerebrospinal fluid).

Intrauterine contraceptive device (IUD): A device inserted into the uterus (womb) to prevent conception (pregnancy). The IUD can be a coil, loop, triangle, or T-shape. It can be plastic or metal.

Intravenous pyelogram: An x-ray of the kidneys and urinary tract. Structures are made visible by the injection of a substance that blocks x-rays. Also called IVP.

Intron: Part of a gene that is initially transcribed into the primary RNA transcript but then removed from it when the exxon sequences on either side of it are spliced together. Also called an intervening sequence.

Intussusception: A segment of intestine is prolapsed (telescoped) within another, which may lead to intestinal obstruction.

Invasive cervical cancer: Cancer that has spread from the surface of the cervix to tissue deeper in the cervix or to other parts of the body.

Inversion: A chromosome segment is clipped out, turned upside down and reinserted.

In situ: In the normal location. An in situ tumor is one that is confined to its site of origin and has not invaded neighboring tissue or metastasized elsewhere.

Invest: In medicine, this has nothing to do with the stock market. It means to envelop, cover, or embed.

In vitro: The opposite of in vivo, it literally means in glass, that is in a test tube, in the laboratory. An in vitro test is one done in the lab, not in a living organism.

Involution: A retrograde change. After treatment, a tumor may involute. With advancing age, there may be physical and emotional involution.

Iodide: The form to which iodine in the diet is reduced before it is absorbed through the intestinal wall into bloodstream and carried to the thyroid gland. See Iodine.

Iodine: Essential element in the diet. The thyroid gland uses iodine to make thyroid hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3). Thyroxine (T4) has four iodine molecules attached to its structure, while triiodothyronine (T3) has three iodine molecules attached. Iodine is found in seafood, bread, salt, and seaweed.

Iodine deficiency: Iodine is a natural requirement of our diets. Iodine deficiency can lead to inadequate production of thyroid hormone from the thyroid gland (hypothyroidism). For example, in some parts of Zaire, Ecuador, India, and Chile, remote, mountainous areas, such as in the Alps (in the past), Andes and the Himalayas have a particular predisposition to severe iodine deficiency, goiter, and hypothyroidism. Since the addition of iodine to table salt, iodine deficiency is rarely seen in the United States.

Iodine excess: Just as too little iodine can cause thyroid disease, so may prolonged intake of too much iodine also lead to the development of goiter (swelling of the thyroid gland) and hypothyroidism (abnormally low thyroid activity). Certain foods and medications contain large amounts of iodine. Examples include seaweed; iodine-rich expectorants (such as SSKI and Lugol’s solution) used in the treatment of cough, asthma, chronic pulmonary disease; and amiodarone (CARDORONE), an iodine-rich medication used in the control of abnormal heart rhythms (cardiac arrhythmias).

Ipsilateral: On the same side. The opposite of contralateral (the other or opposite side). For example, a tumor involving the right side of the brain may affect vision ipsilaterally (that is, in the right eye).

IPV: Inactivated Polio Vaccine. The polio virus in IPV has been inactivated (killed). Also called the Salk vaccine (after the American physician-virologist Jonas Salk). See Immunization, polio.

Iritis: Inflammation of the iris. The iris is the circular, colored curtain in the front of the visible of the eye. (The opening of the iris forms the pupil.)

Iron: An essential mineral. Iron is necessary for the transport of oxygen (via hemoglobin in red blood cells) and for oxidation by cells (via cytochrome). Deficiency of iron is a common cause of anemia. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men. Iron overload can damage the heart, liver, gonads and other organs. Iron overload is a particular risk in people who may have certain genetic conditions (hemochromatosis) sometimes without knowing it and also in people receiving recurrent blood transfusions. Iron supplements meant for adults (such as pregnant women) are a major cause of poisoning in children.

Iron deficiency: Deficiency of iron results in anemia because iron is necessary to make hemoglobin, the key molecule in red blood cells responsible for the transport of oxygen. In iron deficiency anemia, the red cells are unusally small (microcytic) and pale (hypochromic). Characteristic features of iron deficiency anemia in children include failure to thrive (grow) and increased infections. The treatment of iron deficiency anemia , whether it be in children or adults, is with iron and iron-containing foods. Food sources of iron include meat, poultry, eggs, vegetables and cereals (especially those fortified with iron). According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men.

Iron excess:Iron overload can damage the heart, liver, gonads and other organs. Iron overload is a particular risk in people who may have certain genetic conditions (hemochromatosis) sometimes without knowing it and also in people receiving recurrent blood transfusions. According to the National Academy of Sciences, the Recommended Dietary Allowances of iron are 15 milligrams per day for women and 10 milligrams per day for men.

Iron poisoning: Iron supplements meant for adults (such as pregnant women) are a major cause of poisoning in children. Care should be taken to keep iron supplements safely away from children.

Irritable bowel syndrome (IBS): A common gastrointestinal disorder, also called spastic colitis, mucus colitis or nervous colon syndrome, IBS is an abnormal condition of gut contractions (motility) characterized by abdominal pain, bloating, mucous in stools, and irregular bowel habits with alternating diarrhea and constipation, symtoms that tend to be chronic and wax and wane over the years. Although IBS can cause chronic recurrent discomfort, it does not lead to any serious organ problems. Diagnosis usually involves excluding other illnesses. Treatment is directed toward relief of symptoms and includes high fiber diet, exercise, relaxation techniques, avoidance of caffeine, milk products and sweeteners, and medications.

Ischemia: Inadequate blood supply (circulation) to a local area due to blockage of the blood vessels to the area.

Isochromosome: An abnormal chromosome with two identical arms due to duplication of one arm and loss of the other arm. (Found in some girls with Turner syndrome and in tumors.)

Isodisomy: Remarkable situation where both chromosomes in a pair are from one parent and neither from the other. Isodisomy causes some birth defects and, we suspect, plays a role in cancer. Also called uniparental disomy.

Isolate: A group in which mating is always between members of the group. For example, the Amish.

Isotope: A form of a chemical element with a different atomic mass. Isotopes are used in a number of medical tests.

itis: Word ending (suffix) meaning inflammation. For example, colitis is literally colon inflammation or figuratively inflammation of the colon. The ending -itis is one of the building blocks derived from Greek (in this case) or Latin used to construct medical terms.