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Cor pulmonale

The Cor pulmonale - Enlargement of, and strain upon, the right side of the heart, that is caused by one of several chronic lung diseases. Damage to the lungs leads to pulmonary hypertension (abnormally high blood pressure in the arteries that supply the lungs).

The resulting “back pressure” of blood puts strain on the heart, and may eventually cause right-sided heart failure with oedema.
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coroner

The coroner - A public officer appointed to inquire into a cause of death when it is unknown or when unnatural causes are suspected.
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Coronary thrombosis

The coronary thrombosis - A condition in which a thrombus (blood clot) narrows or blocks one of the coronary arteries, thereby preventing sufficient oxygen from reaching a section of the heart muscle.

In most cases, the thrombus forms in a blood vessel that has already been narrowed by atherosclerosis. Sudden blockage of a coronary artery will cause a myocardial infarction (heart attack).

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coronary care unit

The coronary care unit - A specialist ward for the care of acutely ill patients who may have suffered a myocardial infarction (heart attack) or another serious cardiovascular disorder.
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Coronary artery disease

The coronary artery disease - Narrowing of the coronary arteries, which supply blood to the heart, leading to damage or malfunction of the heart. The most common heart disorders due to coronary artery disease are angina pectoris (chest pain due to insufficient oxygen reaching the heart) and myocardial infarction (heart attack).

CAUSES:
The usual cause is atherosclerosis, in which fatty plaques develop on artery linings. An affected vessel can becometotally blocked if a blood clot forms or lodges in the narrowed area. Atherosclerosis has many interrelated causes, including smoking, a high-fat diet, lack of exercise, being overweight, and raised blood cholesterol levels. Other risk factors include a genetic predisposition and diseases such as diabetes mellitus and hypertension.

SYMPTOMS:
In its early stages, coronary artery disease often produces no symptoms. The first sign is frequently the chest pain of angina, or an actual heart attack.

The disease may also cause arrhythmias (abnormalities in the heartbeat); in severe cases, arrhythmia can cause cardiac arrest (in which the heart stops beating). In elderly people, it may lead to heart failure, in which the heart gradually becomes less and less efficient.

TREATMENT:
Drugs are given to help the heart to function more efficiently and to relieve symptoms. These include glyceryl trinitrate and other nitrate drugs; calcium channel blockers; beta-blockers; potassium channel activators; and vasodilator drugs.

If drug treatment fails to relieve the symptoms of coronary artery disease, or if there is extensive narrowing of the coronary arteries, blood flow may be improved by balloon angioplasty or coronary artery bypass surgery.
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coronary artery bypass

coronary artery disease

The coronary artery bypass - A major heart operation that is carried out in order to bypass coronary arteries that have become narrowed or blocked (usually as a result of atherosclerosis). The procedure involves using additional blood vessels (such as a mammary artery or a vein from the leg) to improve blood flow to the heart muscle.

A coronary artery bypass is performed if symptoms of coronary artery disease have not been relieved by drugs, or if balloon angioplasty (a surgical procedure used to widen blocked arteries) is inappropriate or has failed. Before surgery, sites of blockage are identified using an imaging procedure called angiography. Usually, a heart–lung machine is needed to maintain the circulation during the operation, although sometimes minimally invasive surgery may be used to bypass the artery, thereby avoiding the need to stop the heart.

The long-term outlook is good following a coronary artery bypass. However, the grafted vessels may also eventually become blocked by atherosclerosis. (See also Coronary artery bypass box, overleaf.)
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coronary artery

The coronary artery - Either of the two main arteries that supply the heart tissues with oxygen-rich blood. These vessels, known as the left and right main coronary arteries, arise directly from the aorta (the main artery in the body).

The term “coronary artery” is also applied to any of the arteries that branch off from the main coronary arteries, such as the left circumflex artery and the left anterior descending artery. Blockage of a coronary artery as a result of atherosclerosis (an accumulation of fatty deposits in the artery) can lead to myocardial infarction. (See also coronary artery disease.)
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coronary

The coronary - Any structure that encircles another like a crown. The term is usually used to refer to the coronary arteries, which surround the heart and supply it with blood It is also sometimes used as a nonmedical term for a heart attack (see myocardial infarction).
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corneal ulcer

The corneal ulcer - A break, erosion, or open sore in the cornea. It usually affects the outer layer of the cornea, but in some cases may penetrate down to the middle layer.

Corneal ulcers are commonly caused by a corneal abrasion. They may also be due to chemical damage, or infection with bacteria, fungi, or viruses (particularly herpes virus).

Eye conditions such as keratoconjunctivitis sicca and eyelid deformities such as entropion or ectropion increase the risk of an ulcer. Ulcers are revealed by introducing fluorescein dye into the eye. Infections and predisposing eye conditions are treated according to their cause.

A superficial, noninfectious ulcer usually heals quickly; if it fails to do so, it may be treated with a “bandage’’ contact lens or with tarsorrhaphy (temporary sealing of the eyelids).
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corneal graft

The corneal graft - The surgical transplantation of donor corneal tissue to replace a damaged cornea. In most grafts, tissue is taken from a human donor after death.

The success rate of corneal grafts is generally high, because the cornea has no blood vessels; this reduces access for white blood cells, which could otherwise cause rejection of the donor tissue.
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corneal abrasion

The corneal abrasion -  A scratch or defect in the epithelium (outer layer) of the cornea caused by a small, sharp particle in the eye (see eye, foreign body in) or by an injury. Corneal abrasions usually heal quickly but may cause severe pain and photophobia.

Treatment of a corneal abrasion includes covering the eye with a patch and analgesics to relieve pain. If the ciliary muscles go into spasm, eyedrops containing cycloplegic drugs may be used to paralyse the ciliary muscle. Antibiotic eyedrops are usually given to prevent bacterial infection (which can lead to a corneal ulcer).
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Cornea

Location of cornea

The Cornea - The transparent, thin-walled surface that forms the front of the eyeball. The cornea has two main functions. It helps to focus light rays on to the retina at the back of the eye, and protects the front of the eye from debris and injury.

The cornea is joined at its circumference to the sclera (white of the eye); the black pupil and the coloured iris are visible beneath it. There are five layers. The outermost layer (the epithelium) protects the eye and absorbs oxygen and nutrients from tears. The central layer (the stroma) is by far the thickest and gives the cornea its form.The inner layer (the endothelium) expels excess fluid from the cornea, thus keeping the tissues transparent.

For the cornea to stay healthy, it must be kept moist and clean. It is kept moist by a film of tears, which are produced by the lacrimal gland and by the mucusand fluid-secreting cells in the eyelids and conjunctiva. Further protection is provided by the eyelids, which blink or close to keep out debris. In addition,
the cornea is very sensitive, and immediately registers the presence of any injury or foreign body.

DISORDERS OF THE CORNEA:
Various injuries or conditions can affect the sensitive cornea.

Injury:
A corneal abrasion (scratch) can become infected and progress to a corneal ulcer. Penetrating corneal injuries can cause scarring, which may lead to impairment of vision. Chemical injuries can result from contact with a corrosive substance such as an acid or alkali. In actinic keratopathy, the outer layer of the cornea is damaged by ultraviolet light. In exposure keratopathy, damage occurs as a result of reduced protection from the tear film and blink reflex.

Infection:
The cornea can be infected by viruses, bacteria, or fungi. Some infections can cause ulceration, the herpes simplex virus being especially dangerous.

Congenital defects:
Rare congenital defects include microcornea (a cornea that is smaller than normal) or megalocornea (one that is bigger than normal) and buphthalmos, or “ox-eye’’, in which the entire eyeball is distended as a result of glaucoma (raised fluid pressure in the eyeball).

Degeneration:
Degenerative conditions of the cornea include calcium deposition, thinning, and spontaneous ulceration. Such conditions occur mainly in elderly people, and are more common in previously damaged eyes.

Other disorders:
Other disorders include: keratomalacia, which may result from vitamin A deficiency; keratoconjunctivitis sicca (dry eye); corneal dystrophies, such as keratoconus, in which the cornea becomes thinner and cone-shaped; and oedema, in which fluid builds up inside the cornea and impairs vision.
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corn

cross section of a corn

The corn - A small area of thickened skin on a toe or other part of the foot. A corn is caused by the pressure of a tight-fitting shoe. The dead skin cells form a hard plug that extends down into the skin tissues.

Pressure on this plug can cause pain. If a corn is painful, a spongy ring or corn pad can be placed over it to relieve the pressure. If the corn persists, the area of thickened skin can be removed by a chiropodist.

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Cordotomy

The Cordotomy - A surgical procedure in which certain bundles of nerve fibres within the spinal cord are severed.

Cordotomy is carried out to relieve persistent, severe pain that has not responded to other treatment. It is most frequently performed to treat pain occurring in the lower trunk and legs, especially in people who have cancer.
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co-proxamol

The co-proxamol - An analgesic drug (painkiller) containing paracetamol and the weak opioid analgesic drug dextropropoxyphene.

Co-proxamol is used to relieve mild to moderate pain that has not responded to paracetamol or other nonopioid analgesics alone. Side effects include dizziness, drowsiness, constipation, and nausea. The drug may be habit-forming if taken over a long period.
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Copper

The Copper - A metallic element that is an essential part of several enzymes (substances that regulate chemical reactions in the body).

Copper is required by the body in only minute amounts (see trace elements). An excess in the body may occur as a result of the rare inherited disorder Wilson’s disease.
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COPD

The COPD - The abbreviation for chronic obstructive pulmonary disease (see pulmonary disease, chronic obstructive).
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Convulsion, febrile

The convulsion, febrile - Twitching or jerking of the limbs with loss of consciousness that occurs in a child after a rapid rise in body temperature. Febrile convulsions are common and usually affect children between the ages of six months and five years.

CAUSES:
The convulsions are due to immaturity of the temperature-lowering mechanism in the brain; the mechanism allows the child’s body temperature to rise too rapidly in response to infections such as measles or influenza.

TREATMENT AND PREVENTION:
Treatment involves lowering the temperature by sponging the child’s face and body with tepid water and using a fan. Seizures can often be prevented in susceptible children by giving paracetamol at the first signs of fever.

OUTLOOK:
Most children who have one or more febrile convulsions suffer no long-term effects. However, there is a very small risk of developing epilepsy, which is increased in children with a pre-existing abnormality of the brain or nervous system, or children with a family history of epilepsy.
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conversion disorder

The Conversion disorder - A psychological disorder, formerly called hysteria, in which repressed emotions appear to be unconsciously converted into physical symptoms such as blindness, loss of speech, or paralysis. Conversion disorder is generally treated by psychotherapy.
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convergent squint

The convergent squint - A type of squint in which the abnormal eye is directed too far inwards towards the other eye.
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convalescence

The convalescence - The period of recovery following an illness or a surgical operation during which the patient gradually regains strength before returning to their normal activities.
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contusion

The contusion - Bruising to the skin and underlying tissues from a “blunt” injury such as an abrasion (graze) or an impact.

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controlled trial

The controlled trial - A scientific method of testing the effectiveness of new treatments or of comparing different treatments.

In a typical controlled drug trial, two comparable groups of patients with the same illness are given courses of apparently identical treatment. Only one group, however, actually receives the new treatment; the second group (known as the control group) is given a placebo (a harmless substance containing no active ingredients). Alternatively, the control group may be given an established drug that is already known to be effective. After a predetermined period, the two groups are assessed medically. If the patients on the new treatment show a greater improvement than those on the placebo (or those on an existing treatment), this result proves that the drug has a beneficial effect.

Controlled trials must be conducted “blind’’ (meaning that the patients do not know which treatment they are receiving). In a “double-blind’’ trial, neither the patients nor the doctors who assess them know who is receiving which treatment.
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Controlled drug

The Controlled drug - One of a number of drugs that are subject to restricted use because of their potential for abuse. Controlled drugs include opiates such as cocaine and morphine, amphetamine drugs, and barbiturate drugs.
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contrast medium

The contrast medium - A substance that is opaque to X-rays and is introduced into hollow or fluid-filled parts of the body to render them visible on X-ray film. Barium is one of the most commonly used contrast media (see barium X-ray examinations).
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contrast enema

The contrast enema - A contrast medium (opaque substance), which is introduced through the anus, that enables the colon and rectum to be seen in outline on an X-ray. (See also barium X-ray examinations.)
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contraindication

The contraindication - Factors in a patient’s condition that would make it unwise to pursue a certain line of treatment.
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Contracture

The contracture - A deformity that is caused by shrinkage of tissue in an area of skin, muscle, or a tendon and that may restrict the movement of a joint. Skin contractures commonly occur as a result of scarring following extensive burns or other injuries.

Other types of contracture are caused by inflammation and shrinkage of connective tissues; examples of these include Dupuytren’s contracture and Volkmann’s contracture.
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contractions, uterine

The contractions, uterine - Rhythmic, squeezing muscular spasms that occur in the walls of the uterus before and during childbirth in order to expel the baby from the uterus. Regular contractions indicate the start of labour and increase in strength and frequency throughout the first stage. (See also Braxton Hicks’ contractions.)
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contraceptives, injectable

The contraceptives, injectable - A hormonal method of contraception in which long-acting progestogen drugs are injected every two to three months. Injectable contraceptives are very effective, but they may cause menstrual disturbances, weight gain, headaches, and nausea, especially in the first few months.
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contraceptive implant

The contraceptive implant - A hormonal method of contraception in which a long-acting progestogen drug is inserted under the skin inside the upper arm. An implant consists of a small, flexible rod that steadily releases the drug into the bloodstream. It functions continually for several years.
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Methods of contraception, natural

The Methods of contraception, natural -Methods of avoiding conception that do not involve the use of any contraceptive hormones or devices. These methods are based on attempts to pinpoint a woman’s fertile period around the time of ovulation, so that sexual intercourse can be avoided at this time.

The calendar method is based on the assumption that ovulation takes place around 14 days before menstruation. Due to its high failure rate, it has been largely superseded by other methods. The temperature method is based on the normal rise of a woman’s body temperature in the second half of the menstrual cycle, after ovulation has occurred. The woman takes her temperature each day using an ovulation thermometer.

Sex is considered to be safe only after there has been a rise in temperature lasting at least three days. The cervical mucus method involves attempting to pinpoint the fertile period by charting the appearance and amount of cervical mucus during the menstrual cycle. Certain recognized changes in the mucus occur before and often at ovulation. The symptothermal method is a combination of the temperature and mucus methods.
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Methods of contraception, hormonal

The Methods of contraception, hormonal - The use by women of synthetic progestogen drugs, often combined with synthetic oestrogens, to prevent conception. The combined pill (see oral contraceptives), the best-known form of hormonal contraception, contains both an oestrogen and a progestogen; it acts by suppressing ovulation (the release of an egg from an ovary).

Progestogen drugs make cervical mucus thick and impenetrable to sperm. They also cause thinning of the endometrium (lining of the uterus), which reduces the chance of a fertilized egg implanting successfully. Progestogens can be given as pills, as contraceptive implants under the skin, or by injection (see contraceptives, injectable), or they can be released into the uterus by some IUDs.
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contraception, emergency

The contraception, emergency - Measures to avoid pregnancy following unprotected sexual intercourse. There are two main methods: hormonal and physical. In the first, oral contraceptives (the “morning after” pill) should be taken in a high dose as soon as possible after unprotected sexual intercourse: preferably within 12 hours, but no later than 72 hours afterwards.

The pills contain a high dose of the hormone progesterone. In the physical method, an IUD is inserted by a doctor within five days of unprotected sex. Both methods are thought to work by preventing a fertilized egg from implanting in the uterus.
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barrier methods of contraception

The barrier methods of contraception - The use of a device and/or a chemical that will physically stop sperm from reaching an ovum, thus preventing fertilization and pregnancy. Barrier methods and spermicides (preparations that kill sperm), when used together correctly, can be highly effective in preventing conception. Barrier methods of contraception also help to prevent the sexual transmission of diseases such as HIV, genital herpes (see herpes, genital), and viral hepatitis (see hepatitis, viral).

The male condom, a latex sheath that covers the penis, is one of the most widely used barrier contraceptives. The female condom (see condom, female), which lines the vagina, is similar to the male condom but is larger.

Other barrier methods that are used by women include the diaphragm and the cap. The diaphragm (see diaphragm, contraceptive) is a hemispherical dome of thin rubber with a metal spring in the rim to hold it in place against the vaginal wall, blocking the entrance to the cervix. It is used with a spermicide. A cervical cap (see cap, cervical) is an alternative to the diaphragm.

Spermicides, in the form of aerosol foams, creams, gels, and pessaries, are placed in the vagina as close as possible to the cervix shortly before sexual intercourse. Although some condoms are precoated with spermicide, not all types of spermicide should be used with rubber barrier devices.
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contraception

Method of contraception

The contraception - The control of fertility to prevent pregnancy. Contraception can be achieved by a variety of methods. Some forms prevent ovulation in the woman; others stop sperm from meeting an ovum in the fallopian tube (preventing fertilization), or prevent a fertilized ovum from implanting in the uterus.

Some contraceptive methods involve changes in sexual activity; such methods include total or periodic abstinence from intercourse (see contraception, natural methods of) and coitus interruptus, in which sexual intercourse is stopped before ejaculation occurs. Other methods, known as barrier methods (see contraception, barrier methods of), in volvethe use of condoms to prevent sperm from coming into contact with eggs.

Hormonal methods, including the use of oral contraceptives, implants, and injections (see contraceptives, injectable), prevent conception by altering the hormone balance in a woman’s body. Further forms of contraception include the use of intrauterine devices (see IUDs); postcoital methods (see contraception, emergency); or sterilization of the male (see vasectomy) or female (see sterilization, female).
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continuous positive pressure ventilation (CPPV)

The continuous positive pressure ventilation (CPPV) - A rarely used method of ventilation (mechanically assisted breathing) in which positive pressure is applied to the airways to produce each inhalation.
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continuous positive airway pressure (CPAP)

The continuous positive airway pressure (CPAP) - A method of ventilation (mechanically assisted breathing) in which the air pressure inside a patient’s airways is kept above atmospheric pressure.
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contagious

The contagious - A term used to describe a disease that can be transferred from person to person by ordinary social contact. All contagious diseases, such as the common cold or chickenpox, are infectious. The term “contagious” does not apply to the many infectious diseases, such as typhoid, syphilis, or AIDS, which are spread by other means.
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contact tracing

The contact tracing -  A service provided by clinics treating sexually transmitted infections, in which all contacts of a person diagnosed as having a sexually transmitted infection are traced and then encouraged to be examined and treated. Contact tracing is also used in cases of other infections, especially tuberculosis, meningitis, and imported tropical diseases.
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contact lenses

CARE AND INSERTION OF CONTACT LENSES

The contact lenses - Thin, shell-like, transparent discs fitted over the cornea of the eye that are used to correct defective vision. Contact lenses are most commonly used for the correction of myopia (shortsightedness) and hypermetropia (longsightedness). In addition, noncorrective lenses are available for cosmetic use, for example to change eye colour.

TYPES:
There are several types. Hard plastic lenses give good vision; they are also long-lasting and durable, inexpensive, and easy to maintain. Sometimes, however, these lenses are difficult for the wearers to tolerate and may fall out. Hard gas-permeable lenses are more comfortable because they allow oxygen to pass through to the eye, but are less durable. Soft lenses are the most comfortable because of their high water content. Disposable soft lenses are for single use only; extended-wear lenses are worn for up to a month. Other types of contact lenses include rigid scleral lenses, which cover the whole of the front of the eye and are used to disguise disfigurement; bifocal contact lenses; and toric contact lenses, which have an uneven surface curvature and can correct astigmatism.

PROBLEMS:
Hard plastic lenses may cause abrasion of the cornea if worn for too long. Soft lens wearers sometimes develop sensitivity of the eyes and lids. Any type of contact lens may cause redness of the eye. The most serious complication of using lenses is infection, which can occasionally cause permanent damage to the cornea and affect vision; meticulous hygiene lowers the risk.

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contact dermatitis, allergic

The contact dermatitis, allergic - A type of dermatitis caused by an allergic skin reaction to a substance that is harmless for most people. Common causes include nickel and rubber. (See also irritant dermatitis.)
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consultant

The consultant - In the UK, a doctor, usually attached to a certain hospital, who is a specialist in a particular branch of medicine and who takes full responsibility for the patients in his or her care.
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constipation

The constipation - The infrequent or difficult passing of hard, dry faeces. Constipation may be uncomfortable but in the short term is usually harmless.

CAUSES:
The most common cause of constipation is insufficient fibre in the diet (see fibre, dietary), because fibre assists the propulsion of waste matter through the colon. Other common causes include lack of regular bowel movements due to poor toilet-training in childhood or repeatedly ignoring the urge to move the bowels. Constipation in elderly people may be due to immobility or to weakness of the muscles of the abdomen and the pelvic floor. Occasionally, constipation is a symptom of an underlying disorder. This is especially likely if it is part of a persistent change in bowel habits in someone over the age of 40, or if it is accompanied by other symptoms such as blood in the faeces, pain on moving the bowels, or weight loss. Conditions that may cause constipation include haemorrhoids, anal fissure, irritable bowel syndrome, and narrowing of the colon due to disorders such as diverticular disease or cancer (see colon, cancer of).

TREATMENT:
Self-help measures such as establishing a regular bowel routine, increasing the amount of fibre in the diet, and drinking more fluids are usually beneficial. Prolonged use of laxative drugs should be avoided, because this can impair the normal functioning of the colon.
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consent

The consent - Also sometimes referred to as informed consent, the legal term describing a patient’s agreement to a doctor performing an operation, arranging drug treatment, or carrying out a diagnostic test. The patient’s consent is also needed before a doctor supplies confidential information to an insurance company, an employer, or a lawyer.

Consent is valid only if the patient has been fully informed about the purpose of that particular procedure, the likely outcome, and any complications and side effects. Consent cannot be given by young children or by people who are not considered to be competent, but a relative may give or withhold consent on their behalf.
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consciousness

The consciousness - A state of alertness in which a person is fully aware of his or her thoughts, surroundings, and intentions.
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Conn’s syndrome

The Conn’s syndrome - A disorder caused by the secretion of excessive amounts of the hormone aldosterone. The overproduction of this hormone is caused by a noncancerous tumour of one of the adrenal glands. (See also aldosteronism.)

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connective tissue diseases

The connective tissue diseases -  Certain autoimmune disorders (disorders in which the immune system attacks the body’s own tissues) that often affect blood vessels and produce secondary damage to connective tissue.

Connective tissue diseases include rheumatoid arthritis, polyarteritis nodosa, systemic lupus erythematosus, systemic sclerosis, and dermatomyositis.

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