radial keratotomy - a surgical procedure in which incisions are made into the epithelium of the cornea to correct refractive error.

radiation - use of high-energy radiation from x-rays, neutrons, and other sources to kill cancer cells and shrink tumors.

radical mastectomy - surgical removal of the entire breast, the pectoral muscles, and the ancillary lymph nodes.

radical prostatectomy - surgery to remove the prostate along with the two seminal vesicle glands attached to the prostate.    

radical retropubic prostatectomy - an operation to remove the entire prostate gland and seminal vesicles through the lower abdomen.

radiculopathy - pinched nerve usually from a herniated, or slipped, disk; can cause a shooting pain often described as an electrical feeling.

radioisotope - a radioactive material injected into the body so that a nuclear scanner can make pictures.

radionuclide scan - an imaging scan in which a small amount of radioactive substance is injected into the vein. A machine measures levels of radioactivity in certain organs, thereby detecting any abnormal areas or tumors.

radionuclide ventriculography - a diagnostic procedure used to determine the shape and size of the heart's chambers.

range of motion - measurement of the extent to which a joint can go through all of its normal range of movements.

rectal manometry - test that uses a thin tube and balloon to measure pressure and movements of the rectal and anal sphincter muscles.

rectocele - condition in which weakening of the lower vaginal wall causes the rectum to bulge into the vagina.

rectum - lower end of the large intestine, leading to the anus.

reflex sympathetic dystrophy (RSD) - caused by an abnormal sympathetic muscle reflex, giving rise to a response that is out of proportion to, and inconsistent with, the injury.

reflux (Also called regurgitation.) - condition that occurs when gastric juices, or small amounts of food from the stomach, flow back into the esophagus and mouth.

reflux esophagitis - irritation of the esophagus due to stomach contents flowing back into the esophagus.

refractive error - the degree to which light reaches the back of the eye; includes myopia, hyperopia, and astigmatism.

regional anesthetic - an anesthetic used to numb a portion of the body.

regional enteritis - see Crohn's disease.

rehabilitation - the process of restoring a part of the body or a person to near-normal functioning after an injury or disease. 

required surgery - an operation which is necessary to continue quality of life. Required surgery may not have to be done immediately, like emergency surgery.

respiration - gas exchange from air to the blood and from the blood to the body cells.   

respiratory system - the group of organs responsible for carrying oxygen from the air to the bloodstream and for expelling carbon dioxide.   

resting tremor - a tremor of a limb that increases when the limb is at rest.

retching - dry vomiting.

retrolisthesis - posterior slippage of one vertebra onto another.

rheumatic fever - a childhood disease that may damage the heart valves or the outer lining of the heart.

rhinitis - an inflammation of the mucous membrane that lines the nose; often due to allergy to pollen, dust, or other airborne substances; causes sneezing, itching, a runny nose, and nasal congestion.

RICE (rest, ice, compression, and elevation) - treatment plan for acute injury to prevent inflammatory processes from becoming uncontrolled and to speed up the recovery process by eliminating swelling; acute injury management.

rigidity - increased resistance to the passive movement of a limb.

rotator cuff - muscles and their insertional tendons that form a cuff over the shoulder joint, on their way to attaching from the scapula to the humorous; major function is to control, and produce, rotation of the shoulder.

round window - membrane separating the middle ear and inner ear.

rupture - break or tear in any organ or soft tissue.