Medical Dictionary: I, J, and K

ice-pick headache: A sudden, brief, severe stab of pain in the head.

ileum: The section of the small intestine between the jejunum and the beginning of the large intestine.

iliopsoas muscles: Two muscles, each of which is located on and attached to each side of the lumbar vertebrae as well as being attached to the inside of the pelvis and to the thighbone.

immunoglobulin E (IgE): The antibody responsible for the majority of allergic reactions. Triggered by allergens, IgE on the surface of mast cells fires up the explosive release of histamine.

immunoglobulin: Proteins produced by lymphocytes. Also known as antibodies.

immunologically privileged site: A part of the body, such as the womb, in which the immune system doesn’t seem to function the way it does elsewhere.

immunotherapy (allergy shots): A long-term program of desensitization that induces tolerance to an identified allergen. This treatment is commonly used for allergic rhinitis, asthma, allergies to stinging insects, and conjunctivitis.

impaction: Hardened feces blocking the rectum or colon.

impaired fasting glucose: A condition diagnosed with a fasting plasma glucose test; blood glucose levels are higher than normal but not yet diabetic.

impaired glucose tolerance: A condition similar to impaired fasting glucose, but diagnosed with an oral glucose tolerance test.

in situ: Latin for “in place.” As part of the term “ductal carcinoma in situ,” it means that cancer cells exist and are still contained within the ducts of the milk-producing gland.

inactivated (“killed”) vaccines: Vaccines containing microbes that have been killed and are therefore unable to cause disease.

infiltrating cancer: A cancer that has spread from its site of origin into surrounding tissue.

inflammation: A response to injury or foreign invasion designed to protect the body; the symptoms are heat, redness, swelling, and pain.

infusion: An herbal product or tea made by soaking or steeping an herb in water. Flowers or leaves are most often used.

ingrown toenail: A condition in which the side of a toenail penetrates the skin, causing pain, inflammation, and sometimes infection.

injectable fillers: Materials derived from non-animal sources, purified animal or human tissue, fat, or other substances that are injected to fill in wrinkles or scars and add plumpness to the face or lips.

innate immunity: The response of phagocytes and other early defenses to invading pathogens.

inner ear: The deepest part of the ear, consisting of the cochlea and the labyrinth.

insomnia: The inability to fall asleep or remain asleep long enough to feel rested.

insulin resistance: An illness in which the body does not respond normally to insulin, the hormone that ferries sugar from the blood into the cells. Insulin resistance can lead to type 2 diabetes and heart disease.

insulin: An anabolic (growth-promoting) hormone produced by the beta cells in the pancreas; it directs the passage of glucose, amino acids, and fatty acids into cells and promotes their storage.

intense pulsed light (IPL): A nonlaser device emitting broadband light used in photorejuvenation to improve skin.

interferons: A family of cytokines that interferes with the progress of viral invasion.

interleukins: A family of cytokines produced by leukocytes, a general name for white blood cells.

interpersonal therapy: A form of therapy that concentrates on illuminating and ironing out problems in current relationships.

intervertebral disk: One of the small, shock-absorbing cushions located between the vertebrae of the spine.

intervertebral foramen: The opening between vertebrae through which a spinal nerve exits the spinal column (plural: foramina).

intolerance: A reaction that has similar symptoms to an allergic reaction but does not engage the immune system and so is not an allergy.

intracerebral hemorrhage: A hemorrhagic stroke that occurs when a blood vessel ruptures and bleeds into the brain tissue.

intradiscal electrothermal annuloplasty (IDET): A procedure to relieve the pain of certain disk problems, in which a heated catheter — inserted via a needle placed in the affected disk — sears or cauterizes the nerve fibers along the disk wall.

intraocular lens: A small artificial lens permanently fixed inside the eye to replace the natural lens during cataract surgery.

intrinsic factor: A quality or ability, such as vision, hearing, or proprioception, that originates within someone’s body or depends on the functioning of particular organs and tissues.

intrinsic sphincter deficiency: Inability of the urinary sphincter to close completely.

iris: The colored ring in front of the lens that controls the size of the pupil and how much light enters the eye.

irritants: Substances (tobacco or wood smoke, perfumes, and so on) that cause allergy-like symptoms, although the response is not an allergic reaction.

ischemia: A temporary or longer-lasting interruption in blood flow that can be the trigger for angina, heart attacks, and many strokes.

ischemia: Decreased blood flow that compromises the supply of oxygen and nutrients to organs or tissues.

ischemic stroke: A stroke caused by an interruption in the flow of blood to the brain; almost always caused by a blood clot blocking a blood vessel.

islets of Langerhans: Clusters of hormone-producing cells, including alpha and beta cells, that appear throughout the pancreas.

isolated systolic hypertension: A form of hypertension characterized by elevated systolic blood pressure and normal diastolic pressure.

jejunum: The section of the small intestine between the duodenum and the ileum.

Kegel: An exercise for the pelvic floor muscles; used to prevent and treat incontinence.

ketones: By-products of fat metabolism.

kidney failure: The final stage of chronic kidney disease, when kidney function falls to less than 10%–15% of normal and the kidneys can no longer rid the body of waste products; treatment is with dialysis or kidney transplant.

kyphoplasty: A minimally invasive procedure to alleviate pain from spinal compression fractures. An orthopedic balloon is placed in the affected vertebra and is inflated; the resulting cavity is filled with bone cement in order to stabilize the vertebral fracture.