Virtual Medical Centre

Oesophageal candidiasis refers to candidiasis that occur in the food pipe. It may cause difficulty or pain when swallowing.

Oesophagitis is a general term for any inflammation, irritation, or swelling of the esophagus, the tube that leads from the back of the mouth to the stomach.

Oesophagogastroduodenoscopy (OGD) or gastroscopy for short, refers to endoscopic investigation of the upper gastrointestinal tract.  The procedure involves passing a thin, flexible tube fitted with a camera through the mouth to the duodenum (the initial curved segment of the small intestine).

Oestrogen is a female sex hormone which develops and maintains female reproductive structures.

A condition in which sperm concentration, the proportion of morphologically normal sperm and the proportion of motile sperm are all lower than the WHO reference values;

More on male reproductive system.

More on sperm analysis.

Oligodendrocytes form sheaths around the axons of the central nervous system (CNS) that serve as insulation. These sheaths are made of myelin, which is a white material that enables the conductiong of electrical impulses.

Oligohydramnios is a condition in pregnancy characterised by a deficiency in amniotic fluid.

Seminal fluid in which the concentration of sperm is lower than the WHO reference values.

More on male reproductive system.

More on sperm analysis.

Omega 3 fatty acids are essential fatty acids which the body cannot produce through chemical reactions. Instead, omega 3 fatty acids must be consumed from plant or animal sources. Fish is the best available source of omega 3 fatty acids.

Onchocerciasis is a worm infection which primarily affects the glands such as the lymph nodes, skin and eyes. This tends to cause itchy rashes, small lumps under the skin to form, loss of skin elasticity, enlarged glands in the armpits, groin and/or neck and a gritty/painful eye.

Oocytes are the female gametes, also sometimes referred to as eggs.

More on female reproductive system.

An opaque object is one which cannot be seen through.

Oppositional defiant disorder (ODD) is a behavioural disorder characterised by a ongoing pattern of defiant, disobedient, and hostile behaviour beginning in childhood or adolescence. It is part of a group of disruptive behaviour disorders that also includes attention deficit hyperactivity disorder (ADHD) and conduct disorder. Of these three, ODD is seen as the most gentle.

The oral mucosa is the mucous membrane inside the mouth, including the gums.

Oral mucositis (OM) refers to an inflammatory, erosive, and/or ulcerative process inside the mouth caused mainly by radiation and chemotherapy for those with head and neck cancer.

More information on oral mucositis.

Oral sex is sexual activity involving contact between the genitals and the mouth.

Orchidometers are a series of oval shaped beads which gradually increase in size. They are used for assessing the size and volume of human testes. Testicular size is assessed by placing the beads of the orchidometer along side the man's testicles, in order to identify the bead which is closest in size to the testicle.

Orchitis is a condition characterised by painful inflammation of the testicles. It often occurs following infections of the genital system.

Organ donation is a procedure in which one person receives organs or human tissues from another person. These organs are transplanted into the person in hospital to save or improve the quality of his or her life.

For more information, see Organ and Tissue Donation.

Organic is a term used to describe symptoms or body functions that are resulting from or related to the organs.
(Compare with psychogenic)

Oropharyngeal means of or pertaining to the lower part of the pharynx, or the part of the pharynx below the mouth but above the larynx.

Orthostatic hypotension, also known as postural or resting hypotension, refers to a type of low blood pressure caused by a sudden fall in blood pressure that occurs when a person stands up rapidly after a prolonged period of rest.

Symptoms which generally occur after sudden standing include dizziness, lightheadedness, headache, blurred or dimmed vision (possibly to the point of momentary blindness), generalized (or extremity) numbness or tingling, fainting, and, in rare, extreme cases, syncope.

Ototoxicity refers to drug or chemical-related damage to the inner ear resulting in impairment the organs responsible for hearing and balance. Such damage can result in temporary or permanent hearing loss and/or disequilibrium. Ototoxic substances include several therapeutic medicines such as aminoglycoside antibiotics, some platinum based anti-cancer agents, loop diuretics, anti-malarial drugs and aspirin as well as other environmental substances such as mercury, lead and arsenic.

Ovarian drilling, also known as laparoscopic ovarian diathermy, is a surgical procedure used to induce ovulation in an anovulatory woman. It involves "drilling" small holes in the ovaries, and is usually performed via laparoscopy.

Ovarian follicles are the follicles in the ovaries which contain oocytes, and in which oocytes are matured prior to release during ovulation.

Over-the-counter medicines are medicines which are sold to consumers without a doctor's prescription.

Ovulation refers to the release of the female's egg from its follicle in the ovary during the menstrual cycle.

For more information, see Female Reproductive System and Menstruation.

Oxyacetylene welding, commonly referred to as oxy welding, is a welding process in which acetylene and oxygen are used to generate the heat required to heat the metals for welding.