Bma Illustrated Medical Dictionary

most common around puberty. It is

more likely to occur if the testis is

unusually mobile within the scrotum.

Diagnosis is by physical examination.

Surgery is performed to untwist the testis

and anchor it in the scrotum with small

stitches to prevent recurrence. If irrever-

sible damage has occurred, orchidectomy

is performed. In either case, the other tes-

tis is anchored to the scrotum to prevent

torsion on that side. With prompt treat-

ment, recovery of the testis is complete.

testis, undescendedA testis that has

failed to descend from the abdomen to

the scrotum. The condition usually affects

only 1 testis and occurs in about 1 per

cent of full-term and 10 per cent of pre-

mature male babies. An undescended

testis often descends within months of

birth but rarely descends after this time.

An undescended testis does not de-

velop normally, is incapable of normal

sperm production, and is at increased

risk of developing testicular cancer (see

testis, cancer of). If both testes are

undescended, infertilityresults.

A diagnosis is made during a physical

examination after birth or later in infancy.

Treatment is by orchidopexy, which usu-

ally reduces the risk of later infertility or

testicular cancer (see testis, cancer of). A

poorly developed undescended testis

may be removed if the other is normal.

test mealA procedure to measure the

output of acid by the stomach. A naso-

gastric tubeis passed into the stomach

after an overnight fast, and a sample of

gastric fluid is sucked up through the

tube. An injection of histamineor, more

usually, pentagastrin (a synthetic prepa-

ration of the hormone gastrin) is given;

further samples of stomach fluid are

taken at intervals for up to 2 hours and

analysed for hydrochloric acid content.

The test is used for people thought to

be suffering from Zollinger–Ellison syn-

drome, and to confirm the absence of

stomach acid in people with pernicious

anaemia (see anaemia, pernicious).

testosteroneThe main androgen hor-

mone(male sex hormone). It stimulates

bone and muscle growth and sexual

development. It is produced by the testes

and, in very small amounts, the ovaries.

Synthetic or animal testosterone is

used to stimulate delayed pubertyor

treat some forms of male infertility.

tests, medicalTests may be performed

to investigate the cause of symptoms

and establish a diagnosis, to monitor

the course of a disease, or to assess

response to treatment. A medical test-

ing programme carried out on apparently

healthy people to find disease at an early

stage is known as screening.

The accuracy of a test is based on its

sensitivity (ability to correctly identify

diseased subjects), specificity (ability to

correctly identify healthy subjects), and

predictive value. The predictive value is

determined by a mathematical formula

that involves the number of accurate

test results and the total number of tests

performed. The best tests have both

high specificity and high sensitivity, and

therefore high predictive value.

tetanusA serious, sometimes fatal, dis-

ease of the central nervous systemcaused

by infection of a wound with spores of

the bacterium CLOSTRIDIUM TETANI. The

spores live mainly in soil and manure

but are also found elsewhere, including

in the human intestine. When the spores

infect poorly oxygenated tissues they

multiply and produce a toxinthat acts

on the nerves controlling muscle acti-

vity. The most common symptom of this

is trismus(commonly known as lockjaw).

Other symptoms include stiffness of the

abdominal and back muscles, and con-

traction of facial muscles, producing a

fixed grimace. There may also be a fast

TESTIS, UNDESCENDED TETANUS

T

TESTIS, TORSION OF

Twisted

spermatic

cord

Vas

deferens

Blood

vessels

Scrotum

Testis

twisted

around

Penis