Webster's New World Medical Dictionary

retrograde intrarenal surgery
A procedure for
performing surgery within the kidney by using a
viewing tube called a fiber-optic endoscope.
Abbreviated RIRS. In RIRS, the scope is placed
through the urethra into the bladder and then
through the ureter, into the urine-collecting part of
the kidney. RIRS may be done to remove a stone. The
stone can be seen through the scope, manipulated or
crushed by an ultrasound probe, evaporated by a
laser probe, or grabbed with small forceps. RIRS is
performed by a specialist, a urologist with special
expertise in RIRS (endourologist). The procedure is
usually done under general or spinal anesthesia. The
advantages of RIRS over open surgery include a
quicker solution of the problem, the elimination of
prolonged pain after surgery, and much faster recov-
ery. Also known as kidney scoping.
retropubic prostatectomy
Surgical removal of
the prostate through an incision in the abdomen.
retrosternal
Behind the sternum (breastbone).
retrovirus
A virus that is composed not of DNA
but of RNA. Retroviruses have an enzyme, called
reverse transcriptase, that gives them the unique
property of transcribing their RNA into DNA after
entering a cell. The retroviral DNA can then inte-
grate into the chromosomal DNA of the host cell,
to be expressed there. HIV is a retrovirus.
Rett syndrome
A neurological disease that affects
girls only and is one of the most common causes of
mental retardation in females. Girls with the syn-
drome show normal development during the first 6
to 18 months of life, followed first by a period of
stagnation and then by rapid regression in motor
and language skills. The hallmark of Rett syndrome
is the loss of purposeful hand use and its replace-
ment with stereotyped hand wringing. Other symp-
toms include slowed brain and head growth,
seizures, and gait abnormalities. Rett syndrome is an
X-linked dominant trait and is due to mutation in the
MECP2 gene on the X chromosome. The vast major-
ity of cases are sporadic and result from a new muta-
tion in the girl with Rett syndrome. Males with
MECP2 mutation suffer severe brain disease and die
shortly after birth. See also 
X-linked dominant.