<s>
A	O
computed	B-Algorithm
tomography	I-Algorithm
urography	I-Algorithm
(	O
CT	B-Algorithm
urography	I-Algorithm
or	O
CT	B-Algorithm
urogram	I-Algorithm
)	O
is	O
a	O
computed	O
tomography	O
scan	B-Application
that	O
examines	O
the	O
urinary	O
tract	O
after	O
contrast	B-Application
dye	I-Application
is	O
injected	O
into	O
a	O
vein	O
.	O
</s>
<s>
In	O
a	O
CT	B-Algorithm
urogram	I-Algorithm
,	O
the	O
contrast	O
agent	O
is	O
through	O
a	O
cannula	O
into	O
a	O
vein	O
,	O
allowed	O
to	O
be	O
cleared	O
by	O
the	O
kidneys	O
and	O
excreted	O
through	O
the	O
urinary	O
tract	O
as	O
part	O
of	O
the	O
urine	O
.	O
</s>
<s>
Plain	O
CT	B-Algorithm
urography	I-Algorithm
(	O
without	O
contrast	O
)	O
is	O
used	O
to	O
evaluate	O
stone	O
diseases	O
,	O
calcifications	O
within	O
kidneys	O
,	O
density	O
of	O
renal	O
masses	O
and	O
presence	O
of	O
any	O
bleeding	O
before	O
contrast	O
is	O
given	O
.	O
</s>
<s>
Then	O
iodinated	B-Algorithm
contrast	I-Algorithm
is	O
given	O
intravenously	O
to	O
evaluate	O
kidney	O
tumours	O
(	O
if	O
any	O
)	O
and	O
urinary	O
tract	O
.	O
</s>
<s>
CT	O
scan	B-Application
is	O
then	O
taken	O
at	O
30	O
to	O
70	O
seconds	O
(	O
when	O
the	O
contrast	O
reaches	O
the	O
renal	O
cortex	O
and	O
renal	O
medulla	O
)	O
to	O
evaluate	O
the	O
perfusion	O
and	O
vascularity	O
of	O
the	O
kidneys	O
.	O
</s>
<s>
CT	O
scan	B-Application
taken	O
at	O
90	O
to	O
180	O
seconds	O
(	O
when	O
the	O
contrast	O
perfused	O
the	O
whole	O
kidney	O
)	O
to	O
evaluate	O
the	O
characteristics	O
of	O
kidney	O
masses	O
.	O
</s>
<s>
Taking	O
a	O
CT	O
scan	B-Application
at	O
this	O
time	O
is	O
useful	O
to	O
evaluate	O
any	O
strictures	O
or	O
masses	O
from	O
within	O
the	O
ureters	O
or	O
from	O
outside	O
but	O
compressing	O
on	O
the	O
ureters	O
.	O
</s>
<s>
Contrast	O
CT	B-Algorithm
urography	I-Algorithm
is	O
also	O
useful	O
to	O
monitor	O
whether	O
a	O
tumour	O
is	O
responding	O
to	O
treatment	O
.	O
</s>
<s>
CT	B-Algorithm
urography	I-Algorithm
(	O
CTU	O
)	O
is	O
commonly	O
used	O
in	O
the	O
evaluation	O
of	O
hematuria	O
,	O
and	O
specifically	O
tailored	O
to	O
image	O
the	O
renal	O
collecting	O
system	O
,	O
ureters	O
and	O
bladder	O
in	O
addition	O
to	O
the	O
renal	O
parenchyma	O
.	O
</s>
<s>
An	O
intravenous	O
cannula	O
is	O
inserted	O
and	O
contrast	B-Application
dye	I-Application
is	O
injected	O
through	O
this	O
during	O
the	O
scan	B-Application
.	O
</s>
<s>
The	O
scan	B-Application
involves	O
a	O
person	O
lying	O
down	O
on	O
a	O
table	O
that	O
is	O
put	O
through	O
a	O
CT	O
Scanner	O
.	O
</s>
<s>
The	O
CT	O
scan	B-Application
will	O
image	O
the	O
urinary	O
tract	O
,	O
including	O
the	O
kidney	O
,	O
ureters	O
,	O
bladder	O
,	O
and	O
urethra	O
.	O
</s>
<s>
The	O
scan	B-Application
itself	O
usually	O
involves	O
a	O
CT	O
scan	B-Application
without	O
contrast	O
(	O
a	O
non-contrast	O
phase	O
)	O
,	O
a	O
CT	O
scan	B-Application
while	O
the	O
contrast	O
is	O
within	O
the	O
kidneys	O
(	O
a	O
parenchymal	O
phase	O
)	O
,	O
and	O
a	O
CT	O
scan	B-Application
taken	O
while	O
the	O
contrast	O
travels	O
through	O
the	O
renal	O
tract	O
(	O
an	O
excretory	O
phase	O
)	O
.	O
</s>
<s>
A	O
person	O
may	O
have	O
an	O
allergy	O
to	O
the	O
contrast	B-Application
dye	I-Application
.	O
</s>
<s>
The	O
contrast	B-Application
dye	I-Application
may	O
not	O
all	O
go	O
inside	O
the	O
vein	O
at	O
the	O
cannula	O
site	O
,	O
and	O
if	O
it	O
extravasates	O
,	O
it	O
may	O
cause	O
pain	O
or	O
bruising	O
to	O
the	O
local	O
area	O
.	O
</s>
<s>
The	O
scan	B-Application
involves	O
radiation	O
,	O
which	O
may	O
increase	O
the	O
risk	O
of	O
future	O
cancers	O
by	O
a	O
very	O
small	O
amount	O
,	O
or	O
prove	O
damaging	O
to	O
a	O
pregnancy	O
.	O
</s>
