Do iatrogenic serosal tears result in small bowel perforation in a rabbit model
Date
2016-02-26
Authors
Tsai, Ming - Chih
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Introduction
A
common
decision
faced
by
surgeons
during
laparotomy
is
how
to
manage
iatrogenic
small
bowel
serosal
tears.
Surgical
dogma
dictates
that
serosal
tears
should
be
repaired;
as
not
doing
so
may
result
in
the
bowel
becoming
ischemic
and
likely
perforation.
This
would
result
in
significant
morbidity
and
potentially
mortality
and
re
-‐
laparotomy
with
either
repair
of
the
perforation
or
bypass
management
options.
However,
we
do
not
know
if
serosal
tears
result
in
a
localised
area
of
bowel
ischaemia
as
no
study
has
been
performed
to
test
this
assumption.
Methods
I
designed
two
experiments
wherein
I
determined
whether
or
not
serosal
tears
result
in
localized
bowel
ischemia
in
a
rabbit
model
using
adult
-‐
size
white
rabbits.
The
first
experiment
demonstrated
the
intra
-‐
luminal
pressure
required
for
perforation
to
occur
at
the
site
of
a
small
bowel
serosal
tear.
In
the
second
experiment
I
investigated
whether
delayed
serosal
tears
occur
in-‐vivo.
The
WITS
Animal
Ethics
Committee
approved
both
experiments.
The
rabbit
model
consisted
of
adult
-‐
sized
white
rabbits
were
subjected
to
a
mid
–
line
laparotomy
under
ketamine
-‐
xylazine
anaesthesia
with
the
assistance
of
the
Central
Animal
Service
veterinary
nurses
and
staff.
Serosal
tears
of
various
lengths
and
circumferences
were
created
while
wearing
2.5x
surgical
loupes.
Rabbits
were
euthanized
at
the
end
of
the
procedure.
The
bowel
was
harvested
for
histology
to
check
for
viability
of
the
mucosa.
iv
Experiment
1.
Twelve
rabbits
were
used
in
this
experiment.
In
order
not
to
compromise
the
vascular
supply
of
the
bowel,
the
bowel
was
clamped
approximately
3cm
away
on
either
side
of
the
serosal
tear.
Two
18
gauge
jelcos
were
inserted
into
the
isolated
bowel
lumen.
One
jelco
was
used
to
incrementally
infuse
the
normal
saline
solution.
The
other
jelco
was
connected
to
a
manometer
or
a
pressure
transducer
and
used
to
measure
intraluminal
pressure
generated
by
the
normal
saline.
Experiment
2.
A
mid
–
line
laparotomy
was
performed
as
above
on
another
ten
rabbits,
of
which
a
4
cm
x
100
%
circumferential
serosal
tear
was
created
on
a
segment
of
small
bowel.
Their
abdomens
were
closed
with
PDS
suture
and
the
rabbits
were
observed
after
the
operation
for
signs
of
bowel
perforation
and
then
terminated
at
either
72
hours
or
120
hours
to
harvest
the
bowel
for
histological
examination.
Results
The
mean
intraluminal
pressure
for
bowel
perforation
was:
26.4
cm
H₂O
for
sham
rabbits,
23.0
cm
H₂O
for
1cm
serosal
tears
in
length
and
23.3
cm
for
4cm
in
length.
There
is
no
statistically
difference
between
the
mean
intraluminal
pressures
of
1cm
and
4
cm.
For
serosal
tears
involving
the
circumference
with
1
cm
in
length,
the
intraluminal
pressure
of
perforation
was:
27.7
cm
H₂O
for
25
%
circumference,
30.6
cm
H₂O
for
50
%
circumference,
23.8
cm
H₂O
for
75
%
circumference,
25.4
cm
for
100
%
circumference.
At
normal
physiological
intraluminal
pressure
of
6
–
8
cm
H₂O
during
peristalsis,
no
perforation
of
the
serosal
tear
present
in
this
experiment.
Findings
of
the
second
experiment
also
demonstrated
no
obvious
bowel
perforation
at
72
hours
and
120
hours
after
the
operation.
Histological
examination
of
the
small
bowel
serosal
tear
site
also
showed
that
the
mucosa
and
the
submucosal
layers,
at
the
tear
sites,
were
intact
and
viable
without
signs
of
ischemia.
Conclusion
In
the
acute
setting,
small
bowel
serosal
tears
up
to
4
cm
in
length
or,
up
to
100%
of
the
bowel
circumference
did
not
perforate
at
physiological
pressures
of
6
-‐
8
cm
H₂0,
which
are
encountered
during
normal
peristalsis.
Furthermore,
serosa
of
the
small
bowel
does
not
appear
to
affect
the
tensile
strength
of
the
bowel
wall
nor
does
it
contribute
significantly
to
mucosal
and
submucosal
blood
supply.
No
small
bowel
perforation
occurred
within
72
-‐
120
hours
after
creating
serosal
tears.