<s>
Endoscopic	B-Algorithm
ultrasound	I-Algorithm
(	O
EUS	O
)	O
or	O
echo-endoscopy	O
is	O
a	O
medical	O
procedure	O
in	O
which	O
endoscopy	B-Application
(	O
insertion	O
of	O
a	O
probe	O
into	O
a	O
hollow	O
organ	O
)	O
is	O
combined	O
with	O
ultrasound	B-Application
to	O
obtain	O
images	O
of	O
the	O
internal	O
organs	O
in	O
the	O
chest	O
,	O
abdomen	O
and	O
colon	O
.	O
</s>
<s>
Endoscopic	B-Algorithm
ultrasonography	I-Algorithm
is	O
most	O
commonly	O
used	O
in	O
the	O
upper	O
digestive	O
tract	O
and	O
in	O
the	O
respiratory	O
system	O
.	O
</s>
<s>
For	O
the	O
patient	O
,	O
the	O
procedure	O
feels	O
almost	O
identical	O
to	O
the	O
endoscopic	B-Application
procedure	O
without	O
the	O
ultrasound	B-Application
part	O
,	O
unless	O
ultrasound-guided	B-Application
biopsy	I-Application
of	O
deeper	O
structures	O
is	O
performed	O
.	O
</s>
<s>
For	O
endoscopic	B-Algorithm
ultrasound	I-Algorithm
of	O
the	O
upper	O
digestive	O
tract	O
,	O
a	O
probe	O
is	O
inserted	O
into	O
the	O
esophagus	O
,	O
stomach	O
,	O
and	O
duodenum	O
during	O
a	O
procedure	O
called	O
esophagogastroduodenoscopy	B-Application
.	O
</s>
<s>
Endoscopic	B-Algorithm
ultrasound	I-Algorithm
is	O
performed	O
with	O
the	O
patient	O
sedated	O
.	O
</s>
<s>
Endoscopic	B-Algorithm
ultrasound	I-Algorithm
can	O
also	O
be	O
used	O
in	O
conjunction	O
with	O
endoscopic	B-Application
retrograde	O
cholangio	O
pancreatography	O
(	O
ERCP	B-Algorithm
)	O
.	O
</s>
<s>
The	O
ultrasound	B-Application
probe	O
is	O
used	O
to	O
locate	O
gall	O
stones	O
which	O
may	O
have	O
migrated	O
into	O
the	O
common	O
bile	O
duct	O
.	O
</s>
<s>
Echo-endoscopy	O
can	O
also	O
be	O
used	O
for	O
imaging	O
of	O
the	O
rectum	O
and	O
colon	O
,	O
although	O
these	O
applications	O
are	O
lesser	O
known	O
.	O
</s>
<s>
An	O
endoscopic	B-Algorithm
ultrasound	I-Algorithm
probe	O
placed	O
in	O
the	O
esophagus	O
can	O
also	O
be	O
used	O
to	O
visualize	O
lymph	O
nodes	O
in	O
the	O
chest	O
surrounding	O
the	O
airways	O
(	O
bronchi	O
)	O
,	O
which	O
is	O
important	O
for	O
the	O
staging	O
of	O
lung	O
cancer	O
.	O
</s>
<s>
Ultrasound	B-Application
can	O
also	O
be	O
performed	O
with	O
an	O
endoscopic	B-Application
probe	O
inside	O
the	O
bronchi	O
themselves	O
,	O
a	O
technique	O
known	O
as	O
endobronchial	O
ultrasound	B-Application
.	O
</s>
<s>
However	O
,	O
high	O
frequency	O
ultrasound	B-Application
does	O
not	O
penetrate	O
as	O
well	O
as	O
lower	O
frequency	O
ultrasound	B-Application
so	O
that	O
the	O
examination	O
of	O
the	O
nearby	O
organs	O
may	O
be	O
more	O
difficult	O
.	O
</s>
