<s>
In	O
radiology	O
,	O
the	O
tree-in-bud	B-Algorithm
sign	I-Algorithm
is	O
a	O
finding	O
on	O
a	O
CT	O
scan	O
that	O
indicates	O
some	O
degree	O
of	O
airway	O
obstruction	O
.	O
</s>
<s>
The	O
tree-in-bud	B-Algorithm
sign	I-Algorithm
is	O
a	O
nonspecific	O
imaging	O
finding	O
that	O
implies	O
impaction	O
within	O
bronchioles	O
,	O
the	O
smallest	O
airway	O
passages	O
in	O
the	O
lung	O
.	O
</s>
<s>
Histopathologic	O
studies	O
have	O
shown	O
that	O
the	O
tree-in-bud	B-Algorithm
pattern	O
is	O
caused	O
by	O
demarcation	O
of	O
the	O
normally	O
invisible	O
branching	O
course	O
of	O
the	O
peripheral	O
airways	O
,	O
which	O
usually	O
results	O
from	O
bronchioles	O
being	O
plugged	O
or	O
blocked	O
with	O
mucus	O
,	O
pus	O
or	O
fluid	O
.	O
</s>
