Bma Illustrated Medical Dictionary

tract. The procedure involves intravenous
infusion of a contrast mediuminto the
arm. The medium is carried in the blood
to the urinary system, where it passes
through the kidneys, ureters, and bladder
to be excreted in the urine. X-rays taken
at intervals show outlines ofthe urinary
system. IVUdetects abnormalitiessuch
as tumours and obstructions, and signs
of kidney disease.
intrinsic factorA chemical produced
by the stomach lining that is necessary
for the absorption of vitamin B 12.
introitusA general term for the en-
trance to a body cavity or space, most
commonly used for the vagina.
introvertA person more concerned
with his or her inner world. Introverts
prefer to work alone, are shy, quiet, and
withdrawn when under stress. (See also
extrovert; personality.)
intubationMost commonly, the pro-
cess of passing an endotracheal tube
(breathing tube) into the trachea (wind-
pipe). Endotracheal intubation is carried
out if mechanical ventilationis needed
to deliver oxygen to the lungs. The tube
is passed through the mouth or nose
and down the throat.
The term intubation is also used to
refer to the placement of a gastric or
intestinal tube in the stomach for pur-
poses of suction or the giving of nutrients
(see feeding, artificial).
intussusceptionA condition in which
part of the intestine telescopes in on
itself, forming a tube within a tube, usu-
ally resulting in intestinal obstruction
(see intestine, obstruction of). The condi-
tion usually affects the last part of the
small intestine, where it joins the large
intestine. In some cases there is an
association with a recent infection. In
other cases, it may start at the site of a
polypor Meckel’s diverticulum.
Intussusception occurs most common-
ly in children under the age of 2. An
affected child usually develops severe
abdominal colic; vomiting is common,
and blood and mucus are often found
in the faeces. In severe cases, the blood
supply to the intestine becomes blocked
and gangrene, followed by peritonitisor
perforation, may result. In some cases,
an enemacan be used to force the

abnormal area of bowel back into a nor-

mal position. In other cases, surgery may

be necessary to reposition the bowel.

invasiveTending to spread throughout

body tissues; the term is usually ap-

plied to cancerous tumours or harmful

microorganisms. In an invasive medical

procedure, body tissues are penetrated

by an instrument. (See also minimally

invasive surgery andnoninvasive.)

inverted nippleAn indrawing of the

nipple, which can be longstanding or

may develop in later life as a result of

changes in the breast. Causes include

normal changes associated with aging

or, in some cases, an underlying cancer.

in vitroThe performance of biological

processes in a laboratory rather than

within the body. The term in vitro liter-

ally means “in glass”.

in vitro fertilization A method of treat-

ing infertilityin which an egg (ovum) is

surgically removed from the ovary and

fertilized outside the body.

The woman is given a course of fertility

drugsto stimulate release of eggs from

the ovary. This is followed by ultrasound

scanningto check the eggs, which are

collected by laparoscopyimmediately

before ovulation. They are then mixed

with sperm in the laboratory. Two, or

sometimes more, fertilized eggs are

replaced into the uterus. If they become

safely implanted in the uterine wall, the

pregnancy usually continues normally.

Only about 1 in 10 couples undergoing

in vitro fertilization achieves pregnancy

at the 1st attempt, and many attempts

INTRINSIC FACTOR IN VITRO FERTILIZATION

I

Intussuscepted

segment

Large

intestine

LOCATION

Appendix

Small

intestine

INTUSSUSCEPTION