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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3748_Библиотеки_им_академика_М_И_Перельмана
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endovascular intervention, or one in which endovascular intervention is thought to
have limited durability. Additionally, open operations are performed for recurrent
symptoms and recurrent disease following a previous endovascular intervention.
Some of the unfavorable anatomic criteria for endovascular intervention would
include extensive occlusions, severe calcication, tandem lesions, small size blood
vessels, or occluded stents or stent-grafts. When the surgeon is encountering one of
these clinical situations, the options for revascularization are primarily three: antegrade mesenteric revascularization, retrograde mesenteric revascularization, and
local mesenteric endarterectomy/trapdoor aortic endarterectomy. Each of these
operations has specic indications with disadvantages and advantages in their use
and selection for the patient with CMI.Additionally, when one is considering open
mesenteric revascularization, the following operative axioms apply: (1) multivessel
revascularization is favored over single-vessel revascularization, and (2) prosthetic
grafts fare better than venous grafts when bypass is performed.
T. J. Nypaver
Acute Mesenteric Ischemia
Acute mesenteric ischemia (AMI) is a distinctly different clinical entity which
necessitates a different algorithmic approach. However, the management of AMI
may require a similar open operation as to that performed for CMI.Most AMI is
managed in an endovascular fashion with a combination of thrombolysis, mechanical thrombectomy, and catheter-based angioplasty with stent or stent-graft insertion.
A hybrid intervention is also an attractive method of revascularization which entails
open SMA exposure and retrograde endovascular angioplasty or stenting. Lastly, in
AMI, it may become necessary to avoid prosthetic grafts due to the presence of
bowel infarction or contamination, in which case a venous bypass would be
preferred.
Preoperative Planning andSurgical Anatomy
Preoperative Planning
Preprocedural imaging involves either computed tomographic arteriography (CTA)
or magnetic resonance angiography (MRA) with adequate imaging of the thoracic
aorta, perivisceral aorta, infrarenal aorta, and pelvis along with high-quality imaging of all mesenteric vessels (celiac axis, SMA, and inferior mesenteric artery) and
their branches. Severe cardiopulmonary disease, a heavily calcied supraceliac
(SC) aorta or infrarenal aorta, and prior abdominal operations are risk factors which
increase overall morbidity. The SC aorta to mesenteric antegrade bypass has the
advantages of excellent patency, anatomic ow direction, and reduced risk of graft
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redundancy or kinking. However, it does usually require a prosthetic graft and has a
risk of signicant physiologic insult to the patient with the potential for increased
cardiopulmonary complications. The retrograde bypass is a less invasive procedure
which may be ideal for a high-risk patient. Disadvantages include the possibility of
graft kinking and reduced patency when compared to antegrade bypass. Lastly, the
trapdoor aortic endarterectomy is a complex procedure with longer SC aortic crossclamp times and should be reserved for the good risk patient who has severe local
anatomic disease with perivisceral aortic disease and disease conned to or within
2–3cm of the celiac and SMA origins. It is advantageous in that no prosthetic graft
is required and patency rates are excellent.
Surgical Anatomy
The SC Aorto-mesenteric Bypass (Antegrade Bypass)
The SC aorto-mesenteric bypass can be performed through two separate distinct
surgical approaches and exposures. The rst is a transperitoneal approach which
entails an anterior exposure of the SC aorta through the lesser sac with a division of
the gastrohepatic ligament (Fig.27.1) and the diaphragmatic crus (Fig.27.2). This
exposure is preferred in patients who have signicant weight loss, a low body mass
index (BMI), and no prior abdominal operations. However, it does require discordant exposure of the SMA below the inferior border of the pancreas, performed
through a separate plane of dissection to that of the SC aorta. Alternately, the left
ank retroperitoneal exposure through the ninth intercostal space allows for complete exposure of the SC aorta as well as all mesenteric vessels, all within the same
plane. This approach may be problematic if the occlusive disease extends out to a
signicant degree, greater than 6cm on the SMA, as it may be more difcult to
Fig. 27.1 Anterior
exposure of supraceliac
aorta using an incision in
gastrohepatic omentum
282
Fig. 27.2 Opening of the
diaphragmatic crus
T. J. Nypaver
Fig. 27.3 Skin incision for retroperitoneal exposure
expose the SMA distally via this approach. In general, we have preferred the left
ank retroperitoneal approach as patients tolerate this well, and the operative procedure can be performed through a single plane exposure. This is accomplished
through a left ank incision in the ninth intercostal space extending from the intercostal space to the lateral rectus sheath with division of the musculature of the
abdominal wall and entry into the retroperitoneal space (Fig.27.3). Mobilization of
the peritoneum and intraperitoneal contents to the midline ensues, maintaining the
psoas muscle on the posterior aspect of the exposure and then developing a plane
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anterior to the left kidney. The kidney remains in an anatomic position with identication of the left renal artery and then the vein coursing over the aorta (Figs.27.4
and 27.5). The dissection continues superiorly to the level of the diaphragmatic crus
which is then divided allowing exposure of the SC aorta. The crus can be divided
slowly with Bovie cauterization with a right-angle clamp protecting the underlying
aorta. The celiac axis is then identied and circumferentially dissected with vessel
loop control. Likewise, the SMA at the site of the anticipated distal anastomosis is
dissected free. The patient is systemically anticoagulated, and the graft is chosen;
typically, a 12 × 6, 14 × 7, or 16 × 8 bifurcated Dacron graft is selected. The proximal anastomosis is performed rst. The author favors complete cross clamping of
Fig. 27.4 Retroperitoneal
exposure with the kidney
in anatomical position
Fig. 27.5 Diagrammatic
representation of dissection
plane for retroperitoneal
exposure with left kidney
in anatomical position
284
Fig. 27.6 Exposure of
SMA with bifurcation graft
to the celiac and SMA
T. J. Nypaver
the SC aorta (as opposed to a side biting clamp) (Fig.27.6). An aortotomy is made
extending slightly medially distally, and the anastomosis is performed in a parachute fashion starting at the heel of the anastomosis, using 4-0 proline suture. The
clamps are released, and the anastomosis is checked for hemostasis. A graft clamp
(Fogarty Hydragrip Clamp) has been placed on the graft main body, and then the
right limb is cut appropriately for the celiac axis anastomosis. An end-to-end anastomosis to the distal celiac axis is accomplished with 4-0 proline suture. This graft
limb is relatively short. The proximal celiac axis is ligated and oversewn. Lastly, the
SMA anastomosis is performed with the graft lying in the retroperitoneal space
extending down to the intended SMA anastomotic site, anterior to the left renal
artery and vein. In general, this is performed in an end-to-end fashion. If there are
branches more proximal to the desired anastomotic site, then an end-to-side anastomosis should be considered (Fig.27.6). Flow is reestablished into the SMA, and
hemostasis is achieved. The tissues are allowed to fall back into the retroperitoneal
space, and the abdominal musculature layers are closed together with PDS. The
remaining incision is closed in the usual fashion. As the pleural cavity has been
entered, a thoracostomy tube is placed, typically a 20 French chest tube.
Alternately, if a transperitoneal approach has been chosen, a midline incision is
made. The left lobe of the liver is mobilized and retracted to the patient’s right
(Fig.27.1). A nasogastric tube is in place which allows identication of the esophagus which is retracted to the patient’s left. The gastrohepatic ligament is divided as
are the crura tissues exposing the anterior surface of the SC aorta which is dissected
in a nearly circumferentially fashion to allow for complete cross clamp application
(Fig.27.2). The celiac axis is dissected with exposure of the proximal portion of the
celiac. In general, an end-to-end anastomosis is attempted (Fig.27.7); if the disease
extends signicantly beyond the orice of the celiac, then the anastomosis can be
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Fig. 27.7 Completed
aortoceliac and mesenteric
bypass in relationship to
pancreas
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performed to the hepatic artery. The SMA will need to be exposed in a separate
plane. This is accomplished by tracing the transverse mesocolon back with identication of the middle colic artery. A transverse incision near the origin of the middle
colic artery is undertaken with exposure of the SMA at the inferior border of the
pancreas just medial to the superior mesenteric artery vein. The bypass will need to
be a tunneled in an infra-pancreatic position connecting the two surgical planes with
the bypass extending in the retro-pancreatic position to the SMA (Fig. 27.7).
Otherwise, the procedure is performed identical to the retroperitoneal exposure.
Retrograde Bypass
The retrograde bypass from the iliac to the SMA is selected in high-risk patients for
whom an endovascular option does not exist. Additional indications include patient
with calcic disease involving the SC aorta or those high-risk patients who have
failed prior endovascular revascularization. The operation is performed transperitoneally, and the author has adopted the C-shaped graft conguration. The inow
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T. J. Nypaver
artery is either one of the common iliac arteries (the right iliac is favored with better
conguration of the graft), whereas the distal anastomosis is most often constructed
to a single vessel, that being the SMA.The author has favored the use of 8mm
external supported PTFE.The SMA is exposed via a lateral approach with mobilization of the duodenum to the patient’s right and dissection immediately cephalad
to the duodenum with exposure and mobilization of the SMA up to the level of the
left renal vein (Fig.27.8). Importantly, the tunnel created is on the left side of the
retroperitoneum and follows a gentle curve over to the SMA.The distal anastomosis
(the SMA anastomosis) is created rst in an end-to-side fashion with 5-0 proline
suture. The bowel contents are allowed to fall back, and a gentle curve without
excessive redundancy is fashioned with the graft coursing under the retroperitoneum to the right common iliac artery. The aorta can also be chosen as the inow
site, useful in the setting of calcic disease involving both iliacs. An end of graft to
side of iliac is created with the common iliac arteriotomy positioned slightly medially. As the possibility of graft kinking is one of the potential drawbacks to this
Fig. 27.8 Exposure of
SMA cephalad to left
renal vein
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Fig. 27.9 Retrograde
bypass from common iliac
artery to SMA
287
procedure, attention to the appropriate length and course of the graft is essential
(Fig. 27.9). Routine post bypass reconstruction assessment with intraoperative
Doppler is accomplished, and the retroperitoneum is closed over the graft.
Trapdoor Aortic Endarterectomy
The trapdoor aortic endarterectomy is a well-established means of revascularization
in the setting of chronic mesenteric ischemia associated with a signicant component of the perivisceral aortic disease. It is most useful in instances where the occlusive disease is conned to or within 2–3cm of the origins of the SMA and celiac
axis. It is major operation indicated in low-risk patients with suitable anatomic pattern of disease. This operation is generally not used in the setting of acute mesenteric ischemia.
The patient’s aorta is approached through the left ank retroperitoneal approach
with the incision made in the ninth intercostal space (Fig. 27.3). The abdominal
musculature is divided sequentially with Bovie cauterization taking care to maintain
the retroperitoneal position and not violate the peritoneal cavity. The lumber vein
off the left renal vein is identied and divided to enhance mobilization the left kidney anteriorly. Dissection in the retroperitoneum proceeds cautiously with the division of retroperitoneal tissue using a combination of Bovie cauterization, hemoclips,
ties, or the harmonic scalpel. The diaphragmatic crus is identied and divided,
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T. J. Nypaver
exposing the underlying SC aorta. The SC aorta is dissected circumferentially as are
the origins of the visceral vessels, i.e., the celiac axis and the SMA.The aorta below
the SMA is dissected circumferentially. It is the preference of the author to either
include the lumbar vessels within the aortic cross clamp (preferential) or individually control each of the lumbar vessel. Once the patient is anticoagulated, the aorta
proximally is clamped as is the aorta below the SMA; typically, the clamps are
positioned 2–4cm above the celiac axis and 2–3cm below the SMA.The clamp
may be positioned below the left renal artery dependent upon its positioning and
origin in relation to the SMA.The patient routinely receives intravenous mannitol,
25g (or 0.5g/kg). The celiac axis and the SMA are controlled with double-looped
vessel loops. The aortotomy is performed extending below the SMA to above the
origin of the celiac. A plaque elevator is required to initiate a plane, and one needs
to be certain that the aortic wall being left behind is not too thin. The plaque is
divided superiorly in a circumferential fashion with a stepdown from the diseased
aorta proximally to the endarterectomized aorta. This rarely requires tacking sutures.
The same is performed for the distal site, and one frequently can allow this to feather
out circumferentially; occasionally tacking sutures are required. Finally, the eversion endarterectomy of the celiac and SMA is performed with gentle traction and an
eversion technique employed ensuring a clean distal endpoint (Fig.27.10). The aor-
totomy is rapidly closed with a running suture of 4-0 proline suture on a small
needle. Prior to completing the anastomosis, the distal camp is released, and ow
Fig. 27.10 Trapdoor aortic
endarterectomy
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restored distally into the aorta then into the celiac and nally the SMA.Hemostasis
is conrmed, and then the ank incision is closed as delineated above.
Complications
If bowel ischemia is in question (AMI), one should strongly consider autogenous
vein reconstruction. Although this is more time consuming and can be fraught with
kinking, redundancy, or twisting, autogenous grafts are more resistant to infection.
This is especially the case when one encounters bowel contamination and an endovascular or hybrid approach cannot be performed successfully. One needs to be
aware of the course of the graft as any redundancy or kinking of the graft is not well
tolerated and can lead to graft occlusion. This applies to both prosthetic graft and
vein bypasses. This is especially true as the graft is frequently sewn to the mesenteric vessels in a position which will be different once the bowel is able to return to
its anatomical position. Graft patency results are excellent with secondary patency
of 97% achievable. Mortality is not inconsequential, in the range of 5–8%. Ischemiareperfusion with open bypass or reconstructions for CMI is a factor which inuences outcome as postoperative pathophysiologic derangements are common
including respiratory failure, renal insufciency, hyperbilirubinemia, coagulopathy,
and thrombocytopenia.
Take-Home Points
1. Endovascular revascularization is the preferred method of initial mesenteric
2. Open mesenteric revascularization is utilized in instances of recurrent disease
not amenable to repeat intervention, failure of attempted endovascular intervention, and anatomic pattern of disease which does not render itself to endovascular intervention.
3. The bypass selected is tailored to the patient’s anatomy, comorbid conditions,
acuity of presentation, and whether there is any issue with infarcted bowel.
4. The key to avoid graft elongation, angulation, or kinking of the graft is to cut the
graft to length with the SMA in a nearly anatomic position.
5. Antegrade SC aorta to mesenteric bypass is overall the preferred method of
revascularization; however, one needs to be aware of other open surgical options
to optimize patient care and outcome. This can be performed through either a
retroperitoneal or transperitoneal approach.
6. Two-vessel reconstruction is preferred over single-vessel revascularization. Open
bypass or endarterectomy do have superior patency when compared to endovascular operations. A preoperative plan involving a detailed review of the anatomy,
an evaluation of the patient’s cardiopulmonary reserve, and selection of the
appropriate revascularization method are integral to a successful patient outcome.
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