an infectious viral disease primarily affecting animals; can be transmitted to humans through an infected animal's bite; if untreated, can result in paralysis and death

Radial keratotomy

a surgical procedure for correcting near-sightedness in which tiny cuts are made in the cornea to change its shape and focusing properties


a variety of types of energy, such as X-rays and ultraviolet

Radiation therapy

treatment of a disease, such as cancer, using forms of radioactivity that damage or destroy abnormal cells

Radical surgery

treatment of disease by surgically removing all tissue that is or may be affected


any disease of the nerve roots; can be caused by disk prolapse, arthritis, and other problems

Radioallergosorbent test

a blood test performed to help determine the cause of an allergy by detecting the presence of antibodies to various allergens


the formation of images of the inside of the body using radiation projected through the body and onto film; a radiograph is also called an X-ray

Radionuclide scanning

an imaging technique in which a radioactive substance is introduced into the body and its emitted radiation is detected; specific organs can be studied according to the amount of the radioactive substance that they absorb


one of the two long bones of the forearm, located on the thumb side of the arm


a colourless, odourless, tasteless radioactive gas that is produced by materials in soil, rocks, and building materials; suspected of causing cancer


abnormal crackling or bubbling sounds heard in the lungs during breathing


an area of inflammation or a group of spots on the skin

Raynaud's disease

a condition in which the fingers and toes become pale when exposed to cold or emotional stress, owing to sudden narrowing of the arteries that supply them with blood


a nerve cell that responds to a stimulus and produces a nerve impulse; also refers to the area on the surface of a cell that a chemical must bind to in order to have its effect

Recessive gene

a gene that does not produce its effect when it occurs with a dominant gene, but produces its effect only when there are two copies of it

Reconstructive surgery

surgery to rebuild part of the body that has been damaged or defective from birth

Rectal prolapse

bulging of the lining of the rectum through the anus, usually due to straining during a bowel movement


a short tube located at the end of the large intestine, which connects the intestine to the anus

Red blood cell

a doughnut-shaped blood cell that carries oxygen from the lungs to body tissues

Reduction of fracture

the realignment of the broken ends of a bone

Referred pain

pain felt in a part of the body remote from the site where pain originates


an automatic, involuntary response of the nervous system to a stimulus

Reflux oesophagitis

the backflow of gastric acid from the stomach to the lower oesophagus, owing to a defect in the valve that separates them


the backflow of fluid; can refer to food and drink flowing back up from the stomach into the mouth or blood flowing back into the heart through a defective heart valve


treatment for an injury or illness aimed at restoring physical abilities


treatment for dehydration (an abnormally low level of water in the body) in which levels are restored by taking fluids containing water, salt, and glucose by mouth or, if severe, through a vein

Reiter's syndrome

a disorder characterised by inflammation of the joints, urethra, and sometimes the conjunctiva


the return of a disease or symptom after it had disappeared

REM sleep

rapid eye movement sleep; the stage of sleep in which dreaming occurs


the temporary disappearance of a disease or its symptoms, either partially or completely; also refers to the time period in which this occurs

Renal cell carcinoma

the most common type of kidney cancer

Renal colic

severe pain on one side of the lower back, usually as a result of a kidney stone

Renal tubular acidosis

inability of the kidneys to remove sufficient amounts of acid from the body, making the blood more acidic than normal


an enzyme that plays a role in increasing a low blood pressure

Repetitive strain injury

an injury that occurs when the same movement is repeated continuously

Reproductive system

the organs and structures that allow men and women to have sexual intercourse and produce children


partial or complete surgical removal of a diseased organ or structure


the process by which oxygen is taken in and used by tissues in the body and carbon dioxide is released


another term for a ventilator

Respiratory arrest

a condition in which a person suddenly stops breathing

Respiratory distress syndrome

a condition experienced after an illness or injury damages the lungs, causing severe breathing difficulty and resulting in a life-threatening lack of oxygen in the blood

Respiratory failure

the failure of the body to exchange gases properly, which leads to a build-up of carbon dioxide and a lack of oxygen in the blood

Respiratory system

the organs that carry out the process of respiration

Resting pulse

the pulse rate when a person is not experiencing any physical activity or mental stress


an immature red blood cell


a membrane lining the inside of the back of the eye that contains light-sensitive nerve cells that convert focused light into nerve impulses, making vision possible

Retinal artery occlusion

obstruction of an artery that supplies blood to the retina, resulting in some degree of temporary or permanent blindness

Retinitis pigmentosa

gradual loss of the field of vision, owing to a degeneration of the light-sensitive nerve cells of the retina


a hereditary, cancerous tumour of the retina affecting infants and children


a substance resembling vitamin A that is used to treat skin conditions such as acne and has been reported to reduce skin wrinkling


any disease or disorder of the retina; usually refers to damage to the retina caused by high blood pressure or diabetes mellitus


a method of determining focusing errors of the eye in which light is shined through the pupil and the reflected beam is measured


a group of viruses that are made up of RNA instead of DNA, including HIV and the virus that causes T-cell leukaemia

Reverse T3 (rT3)

Triiodothyronine (T3) is the active thyroid hormone which governs metabolism in our cells. It is produced from T4 by the removal of an atom of iodine. At times, the wrong atom is removed resulting in Reverse T3. Reverse T3 can block the action of T3 in our cells. Small amounts of rT3 are normal and actually regulate T3 uptake in our cells, but in times of stress more rT3 is produced which limits the action of T3. This can cause symptoms associated with an underactive thyroid even though blood test levels of T4 and T3 may be normal.

Reye's syndrome

a rare disorder mainly affecting those under the age of 15 that is characterised by brain and liver damage following a viral infection such as chickenpox or the flu; may be linked to taking aspirin to treat a viral infection

Rh blood group

a blood group classifying whether the substances called Rhesus (Rh) factors are present on the surface of red blood cells; the "positive" or "negative" designation in blood classification (for example, "O negative")

Rh immunoglobulin

a substance used to prevent a woman who is Rh incompatible with her foetus from becoming Rh sensitised

Rh incompatibility

a condition in which a pregnant woman's Rh factor does not match that of the foetus; can lead to the production of antibodies by the mother that destroy the foetus' red blood cells

Rh sensitised

a condition in which a woman who has a negative Rh factor develops permanent antibodies against Rh-positive blood as a result of exposure to the blood of her foetus; can cause foetal haemolysis in subsequent pregnancies

Rheumatic fever

a disorder that follows a throat infection by the streptococcus bacteria and causes inflammation in body tissues

Rheumatoid arthritis

a condition in which joints in the body become inflamed, stiff, painful, and sometimes deformed because of the body's own immune system attacking the tissues

Rheumatoid factors

antibodies that are present in about 80% of people with rheumatoid arthritis; their detection through blood testing can help to diagnose the disorder


inflammation of the mucous membrane lining the nose, which can cause sneezing, runny nose, congestion, and pain; when caused by substances in the air, it is called allergic rhinitis or hay fever


a bulb-shaped deformity and redness of the nose as a result of severe rosacea


surgery that changes the structure of the nose, either to improve appearance or to correct a deformity or injury

Rhythm method

a method of preventing pregnancy in which a couple does not have sexual intercourse during the days of the menstrual cycle during which fertilisation can occur


a vitamin belonging to the vitamin B complex that is important in many processes in the body and helps to maintain healthy skin


a childhood disease in which bones lack calcium and are deformed as a result of vitamin D deficiency (vitamin D helps the body absorb calcium)

Rigor mortis

the stiffness that occurs in the body after death


a skin infection caused by a fungus that spreads out in an even circle, characterised by ring-like, scaly patches of red skin

Rinne's test

a test that uses a tuning fork to diagnose hearing loss resulting from poor conduction of sound from the outer to the inner ear


ribonucleic acid, which helps to decode and process the information contained in DNA

Rocky mountain spotted fever

a rare disease transmitted to humans through the bites of ticks; characterised by small pink spots on the wrists and ankles that spread to other parts of the body, become larger, and bleed


a skin disorder that is characterised by patches of red skin on the nose and cheeks and acne-like bumps; most commonly occurs in middle-aged women

Roseola infantum

a common disease in young children characterised by a sudden fever and rash

Rotator cuff

a structure made up of four muscle tendons that reinforces the shoulder joint


a group of worms that includes many of the major human parasites


a mild viral infection (also known as German measles) that produces a rash and fever; dangerous when it infects a woman during the early stages of pregnancy, when it can spread causing birth defects in the foetus


another term for measles


a tear or break in an organ or tissue

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