Click on the alphabet and there you go!

Rabid: Having contracted the rabies virus. (Whereas a sports fan can be rabid without being physically sick, in medicine a rabid individual has rabies.)

Rabies: Virus disease of warmblooded animals transmitted to people by a bite (or other means). Animals capable of carrying rabies include dogs, bats, cats, racoons and skunks. In Latin, rabies means madness or rage.

Rad: A unit of energy. A rad is like a roentgen ® but is based on absorbed energy from an ionizing or nonionizing source.

Radial: In anatomy, radial pertains to the radius, the smaller of the two bones on the thumb's side of the forearm. (The bigger one is the ulna). The word radius comes unchanged from the Latin meaning a spoke in a wheel which this bone was thought to resemble. The word radiation is derived from the same Latin word, radius.

Radial aplasia-thrombocytopenia syndrome: Aplasia (absence) of the Radius (the long bone on the thumb-side of the forearm) and Thrombocytopenia (low blood platelets) are key features characterizing this syndrome. There is phocomelia (flipper-limb) with the thumbs always present. The fibula (the smaller bone in the lower leg) is often absent. The risk of bleeding from too few platelets is high in early infancy but lessens with age. The condition is inherited in an autosomal recessive trait with one gene (on a non-sex chromosome) coming from each parent to the child affected with the disease. Alternative names include thrombocytopenia-absent radius syndrome, TAR syndrome, and tetraphocomelia-thrombocytopenia syndrome.

Radiation: The word radiation is derived from the Latin word radius meaning a spoke in a wheel. The same Latin word radius was given by the Romans to the smaller of the two bones in the forearm since it was thought to look like a spoke in a wheel.

Radiation fibrosis: The formation of scar tissue as a result of radiation therapy to the lung.

Radiation oncologist: A doctor who specializes in using radiation to treat cancer.

Radiation therapy: Radiation therapy is the use of special high energy x-ray beams to kill rapidly growing cells, such as cancer cells. It is a generally a painless treatment and is given in an outpatient setting without the need for hospitalization.

Radical cystectomy: Surgery to remove the bladder as well as nearby tissues and organs.

Radical, free: In biochemistry, it is a group of atoms bonded together into an entity that is extremely reactive and shortlived. (A free radical is not a political extremist on parole.)

Radical mastectomy, modified: Breast cancer treatment involving removal of the breast, lymph nodes (the "glands") in the armpit and associated skin and subcutaneous tissue. It differs from total radical mastectomy in that the pectoral (chest) muscles are preserved.

Radical mastectomy, total: Breast cancer treatment involving removal of the breast, the pectoral (chest) muscles, lymph nodes (the "glands") in the armpit and associated skin and subcutaneous tissue.

Radical surgery: Surgery designed to remove all possible diseased tissue, for example, all possible tumor tissue.

Radicle: Radicle is the diminutive derived from the Latin radix meaning root so it is therefore a little root. A nerve radicle is the smallest extension of a nerve.

Radiculitis: Inflammation of the root of a spinal nerve. The Latin radix means root.

Radioactive: Giving off radiation.

Radioactive iodine: Iodine that gives off radiation. See radioiodine.

Radioallergosorbent test (RAST): An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances. RAST stands for RadioAllergoSorbent Test.

Radiograph: Medical term for an X-ray. A film produced by X-ray.

Radiography: Film records (radiographs) of internal structures of the body. Radiography is made possible by X-rays (or gamma rays) passing through the body to act on a specially sensitized film.

Radioimmunoassay: A very sensitive, specific laboratory test (assay) using radiolabeled (and unlabeled) substances in an immunological (antibody-antigen) reaction.

Radioinsensitive: Not sensitive to X-rays and other forms of radiant energy. For example, a tumor may unfortunately be radioinsensitive. The opposite of radiosensitive.

Radioiodine: A radioactive isotope of iodine. (An isotope is an alternate version of a chemical element that has a different atomic mass). Radioiodine can be used in diagnostic tests as well as in radiotherapy of the thyroid. For hyperthyroidism, radioiodine is administered in capsule form on a one-time basis. It directly radiates thyroid tissues thereby destroying them. It takes 8-12 weeks for the thyroid to become euthyroid (normal) after treatment. The majority of patients undergoing this treatment eventually become hypothyroid, which is easily treated using thyroid hormones (levothyroxine). Radioiodine is contraindicated during pregnancy and breast feeding.

Radioisotope: A radioactive isotope. (An isotope is an alternate version of a chemical element that has a different atomic mass).

Radiologic: Having to do with radiology.

Radiology: The science of radiation, both ionizing (like X-ray) and nonionizing (like ultrasound), applied to the diagnosis and treatment of disease. Radiology is also known as roentgenology after Wilhelm Conrad Roentgen who discovered X-rays in 1895.

Radiolucent: X-rays shine right through things that are radiolucent ( lucere in Latin means to shine). Radiolucent structures appear black on exposed X-ray film.

Radiopaque: X-rays cannot penetrate things that are radiopaque (opaque to X-ray). Radiopaque structures appear white on exposed X-ray film.

Radionuclide scan: An exam that produces pictures (scans) of internal parts of the body. The patient is given an injection or swallows a small amount of radioactive material. A machine called a scanner then measures the radioactivity in certain organs.

Radiosensitive: Sensitive to X-rays and other forms of radiant energy. For example, a tumor may be radiosensitive. The opposite is radioinsensitive.

Radiotherapy: The treatment of disease with ionizing radiation. Synonymous with radiation therapy.

Radium: The celebrated radioactive element discovered by Marie and Pierre Curie in 1898.

Radius: In anatomy, the radius is the smaller of the the two bones on the thumb's side of the forearm. (The bigger one is the ulna). The word radius comes unchanged from the Latin meaning a spoke in a wheel which this bone was thought to resemble. The word radiation is derived from the same Latin word, radius.

Radon: A radioactive element formed as a gas during the breakdown of radium.

Ragweed: Any of a number of weedy composite herbs that produce a pollen that is a frequent cause of allergies. Of all allergy sufferers in the United States, 75% are allergic to ragweed.

Rale: A type of abnormal lung sound heard through a stethescope. Rales may be sibilant (whistling), dry (crackling) or wet (more sloshy) depending on the amount and density of fluid refluxing back and forth in the air passages. The word rale is a straight steal from the French rale (minus the circumflex accent over the a). In French, a rale was originally restricted to the death rattle (le rale de mort). After Laennec invented the stethescope in France in 1815, he borrowed the word rale to apply it to the less ominous, albeit still abnormal, lung sounds he heard through his newfangled instrument.

Ramus: A standard medical dictionary contains over 13 pages full of entries to the word ramus. Why? Because ramus in Latin means a branch and all sorts of anatomic items such as blood vessels and nerves quite naturally have branches. So, for example, medicine is plagued with the likes of the ramus acetabularis arteriae circumflexae femoris medialis which is simply the branch of an artery that goes to the acetabulum (the socket) of the hip joint.

Ramus of the mandible: The mandible (the lower jaw bone) is shaped like a horseshoe. The back parts of the horseshoe that stick up are the two ramuses, or more properly, the rami of the mandible.

Random mating: Totally haphazard mating with no regard to the genetic makeup (genotype) of the mate so that any sperm has an equal chance of fertilizing any egg. This rarely, if ever, occurs but the concept is impoortant in population genetics. Also called panmixus.

Range: In medicine (and statistics), the range is the difference between the lowest and highest numerical values. For example, if premature infants are born weighing 2, 3, 4, 4, and 5 pounds, the range of their birth weights is 2-5 pounds.

Range, normal: Normal results can fall outside the normal range. By convention, the normal range is set to cover ninety-five percent (95%) of values from a normal population. Five percent (5%) of normal results therefore fall outside the normal range.

Range of motion: The range through which a joint can be moved, usually its range of flexion and extension. Due to an injury, the knee may for example lack 10 degrees of full extension.

Rash: Breaking out (eruption) of the skin. Medically, a rash is referred to as an exanthem.

RAST: An allergy test done on a sample of blood. The aim with RAST, as with skin tests, is to check for allergic sensitivity to specific substances. RAST stands for RadioAllergoSorbent Test.

Rat-flea typhus: Murine typhus, an acute infectious disease with fever, headache, and rash, all quite similar to, but milder than, epidemic typhus, caused by a related microoganism, Rickettsia typhi (mooseri), transmitted to humans by rat fleas (Xenopsylla cheopis). The animal reservoir includes rats, mice and other rodents. Murine typhus occurs sporadically worldwide but is more prevalent in congested rat-infested urban areas. Also known as endemic typhus and urban typhus of Malaya.

Rate, basal metabolic: A measure of the rate of metabolism. For example, someone with an overly active thyroid will have an elevated basal metabolic rate.

Rate, birth: The birth rate is usually given as the number of live births divided by the average population (or the population at midyear). This is termed the crude birth rate. In 1995, for example, the crude birth rate per 1,000 population was 14 in the United States, 16.9 in Australia, etc.

Rate, death: The number of deaths in the population divided by the average population (or the population at midyear) is the crude death rate. In 1994, for example, the crude death rate per 1,000 population was 8.8 in the United States, 7.1 in Australia, etc. A death rate can also be tabulated according to age or cause.

Rate, erythrocyte sedimentation: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.

Rate, fetal mortality: The ratio of fetal deaths divided by the sum of the births (the live births + the fetal deaths) in that year. In the United States, the fetal mortality rate plummeted from 19.2 per 1,000 births in 1950 to 9.2 per 1,000 births in 1980.

Rate, heart: Number of heart beats per minute. The normal resting adult heart beats regularly at an average rate of 60 times per minute. (Young children’s hearts beat faster). The speed of the heartbeat (heart rate) is governed by the speed of electrical signals from the pacemaker of the heart, the SA node, located in the right atrium (upper chamber of the heart). The electrical signals from the SA node travel across the atria and cause these two upper heart chambers to contract, delivering blood into the lower heart chambers, the ventricles. The electrical signals then pass through the AV node to reach the ventricles. Electrical signals reaching the ventricles cause these chambers to contract, pumping blood to the rest of the body, generating the pulse. During rest, the speed of electrical signals originating from the SA node is slow, so the heart beats slowly. During exercise or excitement, the speed of signals from the SA node increases, and the heartbeat quickens.

Rate, infant mortality: 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.

Rate, maternal mortality: The number of maternal deaths related to childbearing divided by the number of live births (or by the number of live births + fetal deaths) in that year. The maternal mortality rate in the United States in 1993 (and 1994) was 0.1 per 1,000 live births, or 1 mother dying per 10,000 live births.

Rate, neonatal mortality: The number of children dying under 28 days of age divided by the number of live births that year. The neonatal mortality rate in the United States, which was 8.4 per 1,000 live births in 1980, declined to 5.8 per 1,000 live births in 1990.

Rate, pulse: The pulse rate is most often taken at the wrist. It measures the number of pulsations in the radial artery each minute.

Rate, respiratory: The number of breaths per minute (or, more formally, the number of movements indicative of inspiration and expiration per unit time). In practice, the respiratory rate is usually determined by counting the number of times the chest rises (or falls) per minute. By whatever means, the aim is to determine if the respirations are normal, abnormally fast (tachypnea), abnormally slow (technically termed bradypnea), or nonexistent (apnea).

Rate, sed: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.

Rate, sedimentation: A sedimentation rate, or "sed rate", is a blood test that detects and is used to monitor inflammation activity. It is measured by recording the rate at which red blood cells (RBCs) sediment in a tube over time. It increases (the RBCs sediment faster) with more inflammation.

Rattlesnake bite: A venomous (poisonous) snake bite. All rattlesnakes are venomous and secrete poisonous venom.

Raynaud’s phenomenon: A condition resulting in discoloration of fingers and/or toes when a person is exposed to changes in temperature (cold or hot) or emotional events. Skin discoloration occurs because an abnormal spasm of the blood vessels causes a diminished blood supply. Initially, the digits involved turn white because of diminished blood supply, then turn blue because of prolonged lack of oxygen and finally, the blood vessels reopen, causing a local "flushing" phenomenon, which turns the digits red. This three-phase color sequence (white to blue to red), most often upon exposure to cold temperature, is characteristic of Raynaud’s phenomenon. Named for the French physician Maurice Raynaud (1834-1881).

Reabsorption: Absorbing again. For example, the kidney selectively reabsorbs substances such as glucose, proteins, and sodium which it had already secreted into the renal tubules. These reabsorbed substances return to the blood.

Reaction, allergic: A reaction that occurs when the immune system attacks a usually harmless substance (an allergen) that gains access to the body. The immune system calls upon a protective substance called immunoglobulin E (IgE) to fight these invading allergic substances ( allergens). Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -in fact, too many for their own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens. As is often the case in war, innocent bystanders are affected by this battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of strong chemicals including histamine into the tissues and blood that frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice.

Reactive arthritis: Reiter’s syndrome is also called "reactive arthritis" since it is thought to involve the immune system which is "reacting" to the presence of bacterial infections in the genital, urinary, or gastrointestinal systems. Accordingly, certain people’s immune systems are genetically primed to react aberrantly when these areas are exposed to certain bacteria. The aberrant reaction of the immune system leads to inflammation in the joints and eyes.

Reading frame: One of the three possible ways to read a nucleotide sequence in DNA (depending upon whether reading starts with the first, second or third base in a triplet).

Reading frame, open: An open reading frame in DNA has no termination codon, no signal to stop reading the nucleotide sequence, and so may be translated into protein.

Reagent: A substance used to produce a chemical reaction to detect, measure, produce, etc. other substances.

Rebound: Just like a rebound in basketball when the ball reverses its course and bounces back off the backboard, in medicine a rebound is a reversal of response upon withdrawal of the stimulus.

Rebound effect: The characteristic of a drug to produce reverse effects when the effect of the drug has passed or the patient no longer responds to it.

Recalcitrant: Stubborn. For example, a recalcitrant case of pneumonia stubbornly resists treatment.

Receptor: In cell biology, a receptor is a structure on the surface of a cell or inside a cell that selectively receives and binds a specific substance. There are, for example, insulin receptors, low-density lipoprotein (LDL) receptors, etc. However, in neurology, a receptor is the terminal of a sensory nerve that (receives and) responds to stimuli.

Receptor, visual: The layer of rods and cones, the visual cells, of the retina.

Recessive: A recessive gene expresses itself only when there is no other type of gene present at that locus (spot on the genetic code or chromosome). For example, cystic fibrosis (CF) and Duchenne muscular dystrophy (DMD) are both recessive disorders. A CF child has the CF gene on both chromosome 7’s (and so is said to be homozygous for CF). The DMD boy has the DMD gene on his sole X chromosome (and so is said to be hemizgous for DMD).

Recessive, autosomal: A gene on a nonsex chromosome (an autosome) that expresses itself only when there is no different gene present at that locus (spot on the chromosome). For example, cystic fibrosis (CF) is an autosomal recessive disorder. A CF child has the CF gene on both chromosome 7’s (and so is said to be homozygous for CF).

Recessive, X-linked: A gene on the X chromosome that expresses itself only when there is no different gene present at that locus (spot on the chromosome). For example, Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder. A DMD boy has the DMD gene on his sole X chromosome (and so is said to be hemizgous for DMD). Although it is much rarer, a girl can have DMD (by several different means as, for example, if she has the DMD gene on both her X chromosomes and so is homozygous for DMD).

Recipient: In medicine, a recipient is someone who receives something like a blood transfusion or an organ transplant. The recipient is beholden to the donor.

Reciprocal treanslocation: Mutual exchange of chromosome segments between two nonhomologous chromosomes (chromosomes that do not belong to the same pair).

Recombinant: A person with a new combination of genes, a combination of genes not present in either parent, due to parental recombination of those genes.

Recombinant clones: Clones containing recombinant DNA molecules.

Recombinant DNA molecules: A combination of DNA molecules of different origin that are joined using recombinant DNA technology.

Recombinant DNA technology: A series of procedures used to join together (recombine) DNA segments. A recombinant DNA molecule is constructed (recombined) from segments from 2 or more different DNA molecules. Under certain conditions, a recombinant DNA molecule can enter a cell and replicate there, autonomously (on its own) or after it has become integrated into a chromosome.

Recombination: The trading of fragments of genetic material between chromosomes before the egg and sperm cells are created. Key features of recombination include the point-to-point association of paired chromosomes (synapsis) followed by the visible exchange of segments (crossing over) at X-shaped crosspoints (chiasmata). Recombination is the principal way of creating genetic diversity between generations. By shuffling the genetic deck of cards, recombination ensures that children are dealt a different genetic hand than their parents.

RECOMBIVAX-HB: A vaccine against hepatitis B (hep B) to stimulate the body’s immune system to produce antibodies against the hep B virus.

Recrudescence: Reappearance. In Latin, recrudescere meant to become raw or sore again. Recrudescence has broadened out so there can now be the recrudescence of a rash, of arthritis, etc.

Rectal: Having to do with the rectum.

Rectal cancer: A malignant tumor arising from the inner wall of the large intestine. The third leading cause of cancer in males, fourth in females in the U.S. Risk factors include heredity (family history), colon polyps, and long-standing ulcerative colitis. Most colorectal cancers develop from polyps. Colon polyp removal can prevent colorectal cancer. Colon polyps and early cancer can have no symptoms so regular screening is important. Diagnosis of colorectal cancer can be made by barium enema or by colonoscopy with biopsy confirmation of cancer.

Rectum: The last 6 to 8 inches of the large intestine. The rectum stores solid waste until it leaves the body through the anus. The word rectum comes from the Latin rectus meaning straight (which the human rectum is not).

Recuperate: To recover health and strength. From the Latin recuperare meaning to regain, get back, recover. To recuperate is to convalesce.

Recur: To occur again. To return. Any symptom (such as fatigue), any sign (such as a heart murmur), or any disease can recur.

Recurrence: The return of a sign, symptom or disease after a remission. The reappearance of cancer cells at the same site or in another location is, unfortunately, a familiar form of recurrence.

Recurrence risk: In medical genetics, the recurrence risk is the chance that a genetic (inherited) disease present in the family will recur in that family and affect another person (or persons). It is the chance of "lightning striking twice" (or thrice, etc.).

Recurrent: Back again. A recurrent fever is a fever that has returned after an intermission: a recrudescent fever.

Recurrent laryngeal nerve: A branch of a nerve (the vagus nerve) that comes down the neck and turns back ("recurs") to supply the larynx (the "voice box").

Red blood cells: Red blood cells (RBCs) are cells that carry oxygen in the blood. They are also called red corpuscles.

Red cells: Short for red blood cells, the oxygen/carbon dioxide carrying cells in blood. Also known acronymically as RBC’s, red corpuscles or erythrocytes (literally, red hollow vessels).

Red corpuscles: Red corpuscles are cells that carry oxygen in the blood. They are also called red blood cells or "RBCs."

Reduction division: The first cell division in meiosis, the process by which germ cells are formed. A unique event in which the chromosome number is reduced from diploid (46 chromosomes) to haploid (23 chromosomes). Also called first meiotic division or first meiosis.

Reed-Sternberg cell: A type of cell that appears in patients with Hodgkin's disease. The number of these cells increases as the disease advances.

Referral: The recommedation of a medical or paramedical professional. If you get a referral, for example, to ophthalmology, you are sent to the eye doctor. The earliest recorded use of the word referral in medicine was in 1927.

Reflex: A reaction that is involuntary. The corneal reflex is the blink that occurs with irritation of the eye. The nasal reflex is a sneeze.

Reflex sympathetic dystrophy syndrome (RSDS): A condition that features a group of typical symptoms, including pain (often "burning" type), tenderness, and swelling of an extremity associated with varying degrees of sweating, warmth and/or coolness, flushing, discoloration, and shiny skin.

Reflux: The term used when liquid backs up into the esophagus from the stomach.

Reflux disease, gastroesophageal (GERD): The stomach contents regurgitate and back up (reflux) into the esophagus The food in the stomach is partially digested by stomach acid and enzymes. Normally, the partially digested acid content in the stomach is delivered by the stomach muscle down into the small intestine for further digestion. With esophageal reflux, stomach acid content refluxes back up into the esophagus, occasionally reaching the breathing passages, causing inflammation and damage to the esophagus, as well as to the lung and larynx (the voice box). 10% of patients with GERD develop Barrett’s esophagus, a risk fractor in cancer of the esophagus.

Reflux, esophageal: A condition wherein stomach contents regurgitate or back up (reflux) into the esophagus (a long cylindrical tube that transports food from the mouth to the stomach). The food in the stomach is partially digested by stomach acid and enzymes. Normally, the partially digested acid content in the stomach is delivered by the stomach muscle into the small intestine for further digestion. In esophageal reflux, stomach acid content refluxes backwards up into the esophagus, occasionally reaching the breathing passages, causing inflammation and damage to the esophagus, as well as to the lung and larynx (the voice box). The overall process is medically termed gastroesophageal reflux disease (GERD). 10% of patients with GERD develop a Barrett’s esophagus which can increase the risk of cancer of the esophagus.

Reflux laryngitis: Inflammation of the voice box (larynx) caused by stomach acid backing up into the esophagus. Reflux laryngitis can cause chronic hoarseness and be associated with other symptoms of inflammation of the esophagus, such as heartburn. Many treatment options are available.

Refraction: Checking the eyes for refractive errors (nearsighted, farsighted, astigmatism) and correcting those errors.

Refractory: Not yielding (at least not yielding readily) to treatment.

Refractory anemia: Anemia (a shortage of red blood cells) unresponsive to treatment.

Refsum’s disease: A genetic disorder of the fatty acid phytanic acid which accumulates and causes a number of progressive problems including polyneuritis (inflammation of numerous nerves), diminishing vision (due to retinitis pigmentosa), and wobbliness (ataxia) caused by damage to the cerebellar portion of the brain (cerebellar ataxia).

Regenerate: To reproduce or renew something lost. For example, after an injury, the liver has the capacity to regenerate.

Regimen: With the accent on the first syllable (reg as in Reggie Jackson), a regimen is a plan, a regulated course such as a diet, exercise or treatment, designed to give a good result. A low-salt diet is a regimen.

Region, regulatory: See: Regulatory sequence.

Regional eneteritis: Crohn’s disease, a chronic inflammatory disease of the intestine primarily in 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 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.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. When both the small intestine and the large intestine are involved, the condition is called Crohn’s enterocolitis (or ileocolitis). 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. (The disease is also called granulomatous enteritis).

Registry: Although a registry was originally the place (like Registry House in Edinburgh) where information was collected (in registers), the word registry has also come to mean the collection itself. A registry is usually organized so the data can be analyzed. For example, analysis of data in a tumor registry maintained at a hospital may show a rise in lung cancer among women.

Regress: To return or go back. For example, if a 5-year-old child begins to regress (and function like a much younger child), that is worrisome.

Regulatory gene: A gene that regulates the expression of other genes. A regulatory gene is a nosy gene whose prime preoccupation is to horn in on other genes and control the rate at which they make products.

Regulatory region: See: Regulatory sequence.

Regulatory sequence: A sequence of bases in DNA that controls gene expression.

Regurgitation: A backward flowing. For example, of food. Or the sloshing of blood back into the heart (or between chambers of the heart) when a heart valve is incompetant and does not close effectively.

Rehab: Short for Rehabilitation.

Rehabilitation: The restoration of skills by a person who has suffered an illness or injury so they regain maximum self-sufficiency. After a stroke, rehabilitation may be important to walk again and speak clearly again.

Rehydrate: To restore water. If a child has severe diarrhea, loses a lot of water in the stools and so becomes seriously dehydrated, it is imperative to rehydrate that child properly and promptly.

Reiter’s syndrome: A chronic form of inflammatory arthritis wherein the following three conditions are combined: (1) arthritis; (2) inflammation of the eyes (conjunctivitis); and (3) inflammation of the genital, urinary or gastrointestinal systems.

Rejection: In transplantation biology, the refusal by the body to accept transplanted cells, tissues or organs. For example, a kidney transplanted may be rejected.

Relapse: The return of signs and symptoms of a disease after a remission.

Relaxant: Something that relaxes, relieves, reduces tension. For example, a muscle relaxant is often administered during abdominal surgery to relax the diaphragm and keep it from moving during the surgery.

rem: In radiation, Roentgen equivalent for man, a roentgen (an international unit of X- or gamma-radiation) adjusted for the atomic makeup of the human body. In ophthalomology, rapid eye movement.

Remedy: Something that consistently helps treat or cures a disease. From the Latin remedium meaning that which heals again (and again).

Remission: Disappearance of the signs and symptoms of cancer or other disease. When this happens, the disease is said to be "in remission." A remission can be temporary or permanent.

Remission induction chemotherapy: The initial chemotherapy a patient with acute leukemia receives to bring about a remission.

Renal: Having to do with the kidney. From the Latin renes (the kidneys), which gave the French les reins which mean both the kidneys and the lower back.

Renal cancer: Childhood kidney cancer is different from adult kidney cancer. The most common symptom of kidney cancer is blood in the urine. The diagnosis of kidney cancer is supported by findings of the medical history and examination, blood, urine, and x-ray tests, and confirmed by a biopsy.

Renal capsule: The fibrous connective tissue that surrounds each kidney.

Renal cell cancer: Cancer that develops in the lining of the renal tubules, which filter the blood and produce urine. Also called renal cell carcinoma.

Renal cell carcinoma: Cancer that develops in the lining of the renal tubules, which filter the blood and produce the urine. Also called renal cell cancer.

Renal osteodystrophy: A combination of bone disorders usually caused by chronic kidney failure (renal disease). Can also occur because of abnormal kidney functioning at birth (congenital). When the kidneys have failed, death is imminent unless dialysis is given. Therefore, patients with osteodystrophy are usually on dialysis therapy. This bone disease, which is also simply called osteodystrophy, is common in patients on chronic hemodialysis.

Renal pelvis: The area at the center of the kidney. Urine collects here and is funneled into the ureter.

Renal tubules: Small structures in the kidney that filter the blood and produce the urine.

rep: Stands for roentgen equivalent physical. A rep is a unit of absorbed radiation approximately equivalent to a roentgen, an international unit of X- or gamma-radiation.

Repair, DNA: The cell has a series of special enzymes to repair mutations (changes) in the DNA and restore the DNA to its original state.

Reperfusion: The restoration of blood flow to an organ or tissue. After a heart attack, an immediate goal is to quickly open blocked arteries and reperfuse the heart muscles. Early reperfusion minimizes the extent of heart muscle damage and preserves the pumping function of the heart.

Repetitive DNA: DNA sequences that are repeated in the genome.

Replication: A turning back, repetition, duplication, reproduction.

Replication, DNA: A wondrous complex process whereby the ("parent") strands of DNA in the double helix are separated and each one is copied to produce a new ("daughter") strand. This process is said to be "semi-conservative" since one of each parent strand is conserrved and remains intact after replication has taken place.

Reporting, anonymous: In public health, anonymous reporting permits the acquisition of certain data such as the proportion of persons with a positive test or with a disease. It is different from anonymous testing, in which no name is used on the test sample.

Reporting, named: In public health, named reporting is the reporting of infected persons by name to public health departments. This is standard practice for the surveillance of many infectious diseases such as syphilis, gonorrhea, and tuberculosis that pose a public health threat. The opposite of named reporting is anonymous testing in which the individual remains nameless.

Reporting, unique identifier: In public health, a system that uses information such as the person’s birth date and part of their identification number (in the U.S., the social security number) to create a unique code that is reported instead of a name. It is an alternative to named reporting that provides some of the surveillance benefits of reporting by name, such as the elimination of duplicate reports, while reducing privacy concerns by avoiding use of a person’s name. This system is used with HIV testing for example in Maryland and Texas.

Reproduction: The production of offspring. Reproduction need not be sexual. Yeast can reproduce by budding.

Reproductive cells: The eggs and sperm are the reproductive cells. Each mature reproductive cell is haploid in that it has a single set of 23 chromosomes.

Reproductive system: In women, the organs that are directly involved in producing eggs and in conceiving and carrying babies.

Resection: Surgical removal of part of an organ.

Reservoir, Ommaya: A device implanted under the scalp and used to deliver anticancer drugs to the fluid surrounding the brain and spinal cord.

Residual: Something left behind. With residual disease, the disease has not been eradicated.

Resistance, antibiotic: The ability of bacteria and other microorganisms to withstand an antibiotic to which they were once sensitive (and were once stalled or killed outright). Also called drug resistance.

Resistance, pulmonary: The opposition of the respiratory tree to air flow.

Resistance, vascular: The opposition to the flow of blood across a vascular bed.

Resolution: In genetics, resolution refers to the degree of molecular detail on a physical map of DNA, ranging from low to high.

Resorb: Literally, to absorb again. To lose substance. Some of a tooth may be resorbed.

Resorption: The process of losing substance. Bone when it is remodeled (reshaped) undergoes both new formation and resorption.

Respiration: Respiration is the act of inhaling and exhaling air in order to exchange oxygen for carbon dioxide.

Respiratory: Having to do with respiration. The word comes from the Latin re- (again) + spirare (to breathe) = to breathe again.

Respiratory rate: The number of breaths per minute (or, more formally, the number of movements indicative of inspiration and expiration per unit time). In practice, the respiratory rate is usually determined by counting the number of times the chest rises (or falls) per minute. By whatever means, the aim is to determine if the respirations are normal, abnormally fast (tachypnea), abnormally slow (technically termed bradypnea), or nonexistent (apnea).

Respiratory system: The organs that are involved in breathing. These include the nose, throat, larynx, trachea, bronchi, and lungs.

Respiratory therapy: Exercises and treatments that help patients recover lung function, such as after surgery.

Resting phase: More appropriately called interphase. The interval in the cell cycle between two cell divisions when the individual chromosomes cannot be distinguished, interphase was once thought to be the 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.

Restitution: In cytogenetics, the spontaneous rejoining of broken chromosomes to reconstitute the original chromosome configuration.

Restriction endonuclease: An enzyme from bacteria that can recognize specific base sequences in DNA and cut (restrict) the DNA at that site (the restriction site). Also called a restriction enzyme.

Restriction enzyme: An enzyme from bacteria that can recognize specific base sequences in DNA and cut (restrict) the DNA at that site (the restriction site). Also called a restriction endonuclease.

Restriction fragment length polymorphism (RFLP): A difference in DNA between people that can be recognized by the use of a restriction enzyme.

Restriction map: An array of sites in DNA susceptible to cleavage by diverse restriction enzymes.

Restriction site: A sequence in DNA that can be recognized and cut by a specific restriction enzyme.

Retinoblastoma: A malignant eye tumor caused by the loss of a pair of tumor-suppressor genes. An inherited form of retinoblastoma (it typically appears at birth, leads to multiple tumors and affects both eyes) is due to a transmissible (germline) mutation followed by an acquired (somatic) mutation. The sporadic form of retinoblastoma (it has later onset and leads to a single tumor in one eye) is due to acquired (somatic) mutations of both tumor-suppressor genes. When the tumor is detected at an early stage, it can sometimes be treated locally, but it oftren unfortunately requires removal of the eye (enucleation).

Retropubic prostatectomy: Surgical removal of the prostate through an incision in the abdomen.

Retrosternal: Behind the sternum (the breastbone).

Retrovirus: An RNA virus (a virus composed not of DNA but of RNA). Retroviruses have an enzyme called reverse transcriptase that gives them the unique property of transcribing RNA (their RNA) into DNA. The retroviral DNA can then integrate into the chromosomal DNA of the host cell to be expressed there.

Reversal of organs, total: This condition (medically called situs inversus totalis) involves complete transposition (right to left reversal) of the thoracic and abdominal organs. The heart is not in its usual position in the left chest but is on the right. Specifically related to the heart, this is referred to as dextrocardia (literally, right-hearted). And the stomach, which is normally in the left upper abdomen, is on the right. In patients with situs inversus totalis, all of the chest and abdominal organs are reversed and appear in mirror image when examined or visualized by tests such as x-ray filming. Situs inversus totalis has been estimated to occur once in about 6-8,000 births. Situs inversus occurs in a rare abnormal condition that is present at birth (congenital) called Kartagener’s syndrome.

Reverse genetics: In classic genetics, the traditional approach was to find a gene product and then try to identify the gene itself. In molecular genetics, the reverse has been done by identifying genes purely on the basis of their position in the genome with no knowledge whatsoever of the gene product. This revolutionary approach is reverse genetics. Also called positional cloning.

Reverse transcriptase: An enzyme that permits DNA to be made using RNA as the template. A retrovirus (a virus composed of RNA) can propagate by converting its RNA into DNA with the invaluable assistance of reverse transcriptase.

Reye’s syndrome: A sudden, sometimes fatal, disease of the brain (encephalopathy) with degeneration of the liver, occurs in children (most cases 4-12 years of age), comes after the chickenpox (varicella) or an influenza-type illness, is also associated with taking medications containing aspirin. The child with Reye’s syndrome first tends to be unusually quiet, lethargic (stuporous), sleepy, and vomiting. In the second stage, the lethargy deepens, the child is confused, combative and delirious. And things get worse from there with decreasing consciousness, coma, seizures, and eventually death. The prognosis (outlook) depends on early diagnosis and control of the increased intracranial pressure. Reye’s syndrome is a good reason to have your child immunized against chickenpox and not give the child aspirin for fever.

RF: Rheumatoid factor.

RFLP (Restriction Fragment Length Polymorphism ): A difference in DNA between people that can be recognized by the use of a restriction enzyme.

Rh: A blood group system and one of the most complex. A person can be said to be Rh-positive or Rh-negative. Rh stands for rhesus monkeys.

Rhabdomyolysis: A condition whereby skeletal muscle is broken down, releasing intracellular (inside the cell) muscle enzymes and electrolytes. The major risks of this condition are two fold: one is obviously muscle breakdown and the other is kidney failure. The myoglobin, an intracellular component, is toxic to the kidneys and may lead to kidney failure. Rhabdomyolysis is relatively uncommon, but most often occurs as the result of extensive muscle damage, for example crush injury or electrical shock. Other causes many be drug or toxin, for example many of the cholesterol lowering medications have the potential to cause this disorder. Underlying diseases can also lead to rhabdomyolysis, including collagen vascular diseases (such as systemic lupus erythematosus) and others, which if left untreated may also cause this muscle degradation.

Rheumatism: Rheumatism is an older term, used to describe any of a number of painful conditions of muscles, tendons, joints, and bones.

Rheumatoid arthritis: An autoimmune disease which causes chronic inflammation of the joints, the tissue around the joints, as well as other organs in the body. Autoimmune diseases occur when the body tissues are mistakenly attacked by its own immune system. The immune system is a complex organization of cells and antibodies designed normally to "seek and destroy" invaders of the body, particularly infections. Patients with these diseases have antibodies in their blood which target their own body tissues, where they can be associated with inflammation. Because it can affect multiple other organs of the body, rheumatoid arthritis is referred to as a systemic illness and is sometimes called rheumatoid disease. While rheumatoid arthritis is a chronic illness (meaning it can last for years) patients may experience long periods without symptoms.

Rheumatoid arthritis, systemic-onset juvenile (Still’s disease): Also known as systemic-onset juvenile chronic arthritis. Still’s disease presents with systemic (bodywide) illness including high intermittent fever, a salmon-colored skin rash, swollen lymph glands, enlargement of the liver and spleen, and inflammation of the lungs (pleuritis) and around the heart (pericarditis). The arthritis may not be immediately apparent but it does appear and may persist after the systemic symptoms are gone.

Rheumatoid factor: Rheumatoid factor is an antibody that is measurable in the blood. It is commonly used as a blood test for the diagnosis of rheumatoid arthritis. Rheumatoid factor is present in about 80% of adults (but a much lower proportion of children) with rheumatoid arthritis. It is also present in patients with other connective tissue diseases (such as systemic lupus erythematosus) and in some with infectious diseases (such as infectious hepatitis).

Rheumatoid nodules: Rheumatoid nodules are firm lumps in the skin of patients with rheumatoid arthritis that usually occur in pressure points of the body, most commonly the elbows

Rheumatology: A subspecialty of internal medicine that involves the non-surgical evaluation and treatment of the rheumatic diseases and conditions. Rheumatic diseases and conditions are characterized by symptoms involving the musculoskeletal system. Many of the rheumatic diseases and conditions feature immune system abnormalities. Therefore, rheumatology also involves the study of the immune system. Classical rheumatology training includes 4 years of medical school, 1 year of internship in internal medicine, 2 years of internal medicine residency, and 2 years of rheumatology fellowship. There is a subspecialty board for rheumatology certification. The American College of Rheumatology is the official organization acting on behalf of the field of rheumatology in the United States.

Rhinitis: Irritation of the nose. Derived from the Greek word rhinos meaning of the nose.

Rhinitis, allergic: The medical term for hayfever. (Hay fever"is a misnomer since hay is not a usual cause of this problem and there is no fever. Many substances cause the allergic symptoms in hay fever. Allergic rhinitis is the correct term for this allergic reaction. Rhinitis means "irritation of the nose" and is a derivative of Rhino, meaning nose.) Symptoms include nasal congestion, a clear runny nose, sneezing, nose and eye itching, and tearing eyes. Post-nasal dripping of clear mucus frequently causes a cough. Loss of smell is common and loss of taste occurs occasionally. Nose bleeding may occur if the condition is severe. Eye itching, redness, and tearing frequently accompany the nasal symptoms.

Rhinitis, allergic, perennial: Allergic rhinitis (hayfever) that occurs throughout the year.

Rhinitis, allergic, seasonal: Allergic rhinitis (hayfever) which occurs during a specific season.

Rhinoplasty: Plastic surgery on the nose, known familiarly as a nose job.

Rhinorrhea: Medical term for a runny nose. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."

Rib: Any one of the twelve paired bones which form the skeletal structure of the chest wall (rib cage). The ribs attach to the building blocks of the spine (vertebrae) in the back. The first seven ribs attach to the sternum in the front and are known as true ribs. The lower five ribs do not directly connect to the sternum and are known as false ribs.

RiboNucleic Acid (RNA): A chemical similar to DNA, The several classes of RNA molecules play important roles in protein synthesis and other cell activities.

Ribosomes: Structures (called organelles) composed of RNA and protein situated outside the nucleus in the cytoplasm of the cell where the cell uses messenger RNA to make up polypeptides.

Rickettsia: A member of a group of microorganisms that (like viruses) require other living cells for growth but (like bacteria) use oxygen, have metabolic enzymes and cell walls, and are susceptible to antibiotics. Rickettsiae cause a series of diseases (See Rickettsial diseases).

Rickettsial diseases: The infectious diseases caused by the rickettsiae fall into 4 groups:(1) typhus: epidemic typhus, Brill-Zinsser disease, murine (endemic) typhus, and scrub typhus; (2) spotted fever—Rocky Mountain spotted fever, Eastern tick-borne rickettsioses, and rickettsialpox; (3) Q fever; and (4) trench fever.

Rickettsialpox: A mild infectious disease first observed in New York City caused by Rickettsia akari, transmitted from its mouse host by chigger or adult mite bites. There is fever, a dark spot that becomes a small ulcer at the site of the bite, swollen glands (lymphadenopathy) in that region, and a raised blistery (vesicular) rash. Also known as vesicular rickettsiosis.

Rickettsioses: The infectious diseases caused by the rickettsiae. See Rickettsial diseases.

Rickettsioses of the eastern hemisphere, tick-borne: Thare are 3 known diseases caused by infection with rickettsial agents> They are North Asian tick-borne rickettsiosis, Queensland tick typhus, and African tick typhus (fièvre boutonneuse).

Rickettiosis, North Asian tick-borne: One of the tick-borne rickettsial diseases of the eastern hemisphere, similar to Rocky Mountain spotted fever, but less severe, with fever, a small ulcer (eschar) at the site of the tick bite, swollen glands nearby (satellite lymphadenopathy), and a red raised (maculopapular) rash.

Rickettsiosis, vesicular: See Rickettsialpox.

Ring chromosome: A structurally abnormal chromosome in which the end of each chromosome arm has been lost and the broken arms have been reunited in ring formation. A ring chromosome is denoted by the symbol r.

Ringworm of the nails: The most common fungus infection of the nails (onychomycosis). Onychomycosis makes the nails look white and opaque, thickened, and brittle. Older women (perhaps because estrogen deficiency may increase the risk of infection). and men and women with diabetes or disease of the small blood vessels (peripheral vacscular disease) are at increased risk. Artificial nails (acrylic or "wraps") increase the risk because when an artificial nail is applied, the nail surface is usually abraded with an emery board damaging it, emery boards can carry infection, and. water can collect under the nail creating a moist, warm environment for fungal growth. Alternative names include tinea unguium and dermatophytic onychomycosis.

Risk factor: Something that increases a person's chances of developing a disease.

Risk of recurrence: In medical genetics, the chance that a genetic (inherited) disease present in a family will recur in that family. The concept in general medicine means the chance that an illness we come back again.

Ritter disease: This is the scalded skin syndrome, a potentially serious side effect of infection with the Staph (Staphylococcus) bacteria that produces a specific protein which loosens the "cement" holding the various layers of the skin together. This allows blister formation and sloughing of the top layer of skin. If it occurs over large body regions it can be deadly (just like a large surface area of the body having been burned). It is necessary to treat scalded skin syndrome with intravenous antibiotics and to protect the skin from allowing dehydration to occur if large areas peel off. The disease occurs predominantly in children under 5 years of age. It is known formally as Staphyloccoccal scalded skin syndrome.

RMSF: Rocky Mountain spotted fever.

RNA: Short for ribonucleic acid. A chemical (specifically, a nucleic acid) similar to DNA but containing ribose rather than deoxyribose. RNA is in fact formed upon a DNA template. The several classes of RNA molecules play crucial roles in protein synthesis and other cell activities. (See also messenger RNA, transfer RNA and ribosomal RNA.)

RNA, messenger: A class of RNA that is the template upon which polypeptides are put together. Abbreviated mRNA.

RNA polymerase: Enzyme that catalyzes (speeds) the polymerization of RNA. RNA polymerase uses preexisting nucleic acid templates and assembles the RNA from ribonucleotides.

RNA, ribosomal: A component of ribosomes, ribosomal RNA functions as a nonspecific site for making polypeptides. Ribosomal RNA is abbreviated rRNA.

RNA, transfer: In cooperation with the ribosomes, transfer RNA brings (transfers) activated amino acids into position along the messenger RNA template. The abbreviation for transfer RNA is tRNA.

RNA polymerase: A polymerase is an enzyme that catalyzes the joining of many smaller molecules (called monomers) to form a big molecule (a macromolecule). RNA polymerase is a unique enzyme that makes (synthesizes) thye macromolecule RNA using DNA as the template.

Robertsonian translocation: A type of chromosome rearrangement involving all of the essential genetic material of the long arms of two acrocentric chromosomes. The acrocentric chromosomes (those with the centromere near the end so there is only a tiny short arm) are chromosomes 13-15, 21 and 22 in humans. Named after W.R.B. Robertson who in 1916 first described this kind of chromosome rearrangement (in grasshoppers), Robertsonian translocations are also known as whole-arm or centric-fusion translocations. They are relatively common in humans and contribute to the toll of trisomy 13 syndrome and Down syndrome.

Rocky Mountain spotted fever (RMSF): An acute febrile (feverish) disease initially recognized in the Rocky Mountain states, caused by Rickettsia rickettsii transmitted by hard-shelled (ixodid) ticks. Occurs only in the Western Hemisphere. Anyone frequenting tick-infested areas is at risk for RMSF. Onset of symptoms is abrupt with headache, high fever, chills, muscle pain. and then a rash .The rickettsiae grow within damaged cells lining blood vessels which may become blocked by clots. Blood vessel inflammation (vasculitis) is widespread Early recognition of RMSF and prompt antibiotic treatment is important in reducing mortality. Also called spotted fever, tick fever, and tick typhus.

Roentgen: Named for Wilhelm Conrad Roentgen who discovered X-rays, a roentgen (abbreviated R). An international unit of X- or gamma-radiation.

Roentgenology: Radiology is also known as roentgenology after Wilhelm Conrad Roentgen who discovered X-rays in 1895. Both terms refer to the science of radiation, both ionizing (like X-ray) and nonionizing (like ultrasound), applied to the diagnosis and treatment of disease.

Rooting reflex: When the cheek or lip is touched, a newborn baby automatically roots and turns the face toward the stimulus. The rooting reflex helps with breast-feeding.

Roseola: Short for Roseola infantum, a viral disease of infants and young children with sudden onset of high fever which lasts several days and then suddenly subsides leaving in its wake a fine red rash. The causative agent is herpesvirus type 6 so the disease is known as Sixth Disease. Also as Exanthem subitum (sudden rash), pseudorubella, roseola infantilis.

Roseola infantilis: Another name for Roseola.

Roseola infantum: The full name for Roseola.

Rotavirus: A leading cause of severe diarrhea in early childhood (acute infantile gastroenteritis), rotavirus infection each year causes an estimated 500,000 doctor visits and 50,000 hospital admissions in the United States. Almost everyone catches rotavirus in childhood but, with good nutrition and rehydration, nearly all recover uneventfully. However, in poor countries there are at least 600,000 deaths of children under 5 years from rotavirus diarrhea and dehydration. Rotavirus was discovered in 1973 and took its name from its wheel-like appearance (rota means wheel in Latin). A vaccine has been reported in The New England Journal of Medicine (vol. 337, pp. 1181-7, 1997) to provide a high level of protection against severe diarrhea caused by rotavirus.

Rothmund-Thomson syndrome (RTS): A genetic disorder with numerous features affecting skin (premature aging, excess pigmentation, dilated blood vessels),eyes (juvenile cataract), nose (saddle nose), teeth (maldeveloped), skeletal system (congenital bone defects) hair (abnormal), gonads (underdevelopment) limbs (soft tissue contractures), growth (short stature), blood (anemia) and a tendency to develop a type of bone cancer (osteogenic sarcoma). The RTS gene is on chromosome 8. The syndrome is recessive so to be affected with RTS a child has to have two RTS genes, one from each parent. RTS is also called "poikiloderma atrophicans and cataract".

Rubella immunization: The standard MMR vaccine is 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 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.

Runny nose: Rhinorrhea is the medical term for this common problem. From the Greek words "rhinos" meaning "of the nose" and "rhoia" meaning "a flowing."

Ruptured spleen: Rupture of the capsule of the spleen, an organ in the upper left part of the abdomen, is a potential catastrophe that requires immediate medical and surgical attention. Splenic rupture permits large amounts of blood to leak into the abdominal cavity which is severely painful.and life-threatening. Shock and, ultimately, death can result. Patients typically require an urgent operation. Rupture of a normal spleen can be caused by trauma, for example, in an accident. If an individual’s spleen is enlarged, as is frequent in mononucleosis, most physicians will not allow activities (such as major contact sports) where injury to the abdomen could be catastrophic.