AJR 2005; 184:1524-1531
© American Roentgen Ray Society
Intraoperative Sonogram in Mesenteric Revascularization: Spectrum of Findings
Thanila A. Macedo1,
Gustavo S. Oderich2,
Robert A. Lee1 and
Jean M. Panneton2
1 Department of Radiology, Mayo Clinic and Foundation, 200 First Street SW,
Rochester, MN 55905.
2 Division of Vascular Surgery, Mayo Clinic and Foundation, Rochester, MN
55905.
Received June 25, 2004;
accepted after revision October 15, 2004.
Address correspondence to T. A. Macedo
(macedo.thanila{at}mayo.edu).
Abstract
OBJECTIVE. The role of intraoperative sonography is to detect and
prompt revision of technical defects that may adversely affect results. Our
objective is to describe the technique and illustrate normal and abnormal
findings in intraoperative sonography of mesenteric revascularization.
CONCLUSION. An abnormality on a gray-scale image associated with
hemodynamic changes is a significant finding. Awareness and recognition of
major abnormalities should prompt immediate surgical revision and improved
outcome.
Introduction
Intraoperative sonogram has been used as a valuable tool to enhance
outcomes in arterial revascularization. The examination is accomplished as
part of the operative procedure. In carotid, renal, and infrainguinal arterial
revascularizations, correction of significant defects prevents early
complications and contributes to long-term success
[1–3].
This rationale has been extended to mesenteric revascularization, although
only a small number of cases have been reported. The role of an intraoperative
sonogram is to detect and prompt revision of technical defects that may
adversely affect results. Unrepaired significant technical defects in
mesenteric revascularization can lead to bowel necrosis, the need of bowel
resection, and long-term parenteral nutrition. Our purpose is to illustrate
the spectrum of findings in an intraoperative sonogram of mesenteric
revascularization.
Technique
After the completion of revascularization and before closing the abdomen,
an intraoperative sonogram is performed in the operating room by the
radiologist under sterile conditions. We use a Sequoia 512 (Acuson Solutions)
and, typically, an 8–15 MHz linear array transducer. A sterile plastic
cover with acoustic gel is placed over the sonogram transducer, and
examination of the exposed revascularized segment is performed. Machine
settings are controlled with the help of the sonographer. Sterile saline is
poured in the abdominal cavity for acoustic coupling. The aorta proximal to
the graft is evaluated, followed by proximal anastomosis, entire graft length,
distal anastomosis, and native distal vessels (celiac and/or superior
mesenteric artery [SMA]). Images are first acquired in both transverse and
longitudinal planes with grayscale images. Color Doppler screening followed by
spectral analysis is used to determine if a hemodynamically significant defect
is present.
There are different types of mesenteric arterial revascularization (Fig.
1A,
1B,
1C,
1D), and awareness of the type
performed helps to guide the examination. A supraceliac aorta to celiac and/or
SMA bypass is the preferred option, offering antegrade flow with excellent
long-term patency rates. However, patients who are poor surgical candidates or
those with hostile anatomy (e.g., previous aortic operation, extensive aortic
wall calcification precluding clamping) are best treated with retrograde
bypasses originating from the infrarenal aorta or iliac artery (e.g.,
retrograde aorta or iliac to SMA bypass). In addition, patients with
mesenteric and renal ostial lesions requiring revascularization because of
extensive aortic atherosclerosis are ideal candidates for transaortic renal
and mesenteric endarterectomy.
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Fig.1A. —llustrations show most common types of mesenteric arterial
revascularization. Bifurcated supraceliac aorta to celiac and superior
mesenteric artery (SMA) is most common type of revascularization
performed.
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Findings
Normal
A normal mesenteric intraoperative sonogram consists of a detailed
gray-scale examination that reveals no intraluminal filling defects (Fig.
2A,
2B,
2C,
2D) and screening color Doppler
and spectral analysis confirming no hemodynamic disturbance.
Graft–vessel mismatch is considered an unavoidable finding in some
patients and is characterized by a change in caliber noted on gray-scale
images and elevated velocities that are not focal in the smaller caliber
native vessel distal to the graft (Fig.
3A,
3B). The size discrepancy
between the larger graft and smaller native vessel is responsible for the
elevated velocities. To maintain constant flow volumes, the velocity in the
smaller native vessel has to increase. In this case, velocity measurements
obtained at different points in the native vessel will all be elevated. In
contrast, anastomotic stenosis will result in focally increased velocity at
the anastomosis site and normal velocity distally in the native vessel.
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Fig. 2A. —58-year-old woman who underwent supraceliac bifurcated aorta
celiac and superior mesenteric artery (SMA) bypass graft. Intraoperative
sonogram findings were normal. Longitudinal gray-scale image shows no
technical defect in proximal graft anastomosis (aorta = narrow arrow,
graft body = wide arrow, bifurcated limbs = arrowheads).
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Fig. 2B. —58-year-old woman who underwent supraceliac bifurcated aorta
celiac and superior mesenteric artery (SMA) bypass graft. Intraoperative
sonogram findings were normal. Longitudinal gray-scale image reveals widely
opened distal anastomosis of graft limb (arrow) and native SMA
(arrowhead).
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Fig. 2C. —58-year-old woman who underwent supraceliac bifurcated aorta
celiac and superior mesenteric artery (SMA) bypass graft. Intraoperative
sonogram findings were normal. Subsequent color Doppler screening confirms
absence of hemodynamic disturbance.
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Fig. 2D. —58-year-old woman who underwent supraceliac bifurcated aorta
celiac and superior mesenteric artery (SMA) bypass graft. Intraoperative
sonogram findings were normal. Spectral analysis confirms absence of
hemodynamic disturbance.
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Fig. 3A. —73-year-old woman with aorta to celiac artery bypass graft.
Intraoperative sonogram with longitudinal views of distal anastomosis
evaluation is shown. Spectral Doppler waveform at distal graft limb shows
velocity of about 0.4 m/sec.
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Fig. 3B. —73-year-old woman with aorta to celiac artery bypass graft.
Intraoperative sonogram with longitudinal views of distal anastomosis
evaluation is shown. Spectral Doppler waveform in native artery reveals
significant increase in peak systolic velocity up to 2.5 m/sec associated with
significant change in caliber. Elevated velocities were seen throughout
vessel, and no filling defect was detected. These findings are characteristic
of graft–vessel mismatch.
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Abnormal
Abnormal findings are classified as minor or major
(Table 1). This classification
has management implications. A minor abnormality is thought to be an
insignificant finding for which revision is not recommended. These
abnormalities include mild graft kink
(Fig. 4), residual mild
stenosis, and small intimal flap not associated with hemodynamic disturbance
or elevated velocity. Major findings are abnormalities that should be promptly
addressed, such as narrowing with elevated velocity at the distal anastomosis
(Fig. 5A,
5B,
5C), elevated velocity
associated with filling defect found to be thrombus (Figs.
6A,
6B,
6C,
6D and
7A,
7B,
7C,
7D) or intimal flap (Fig.
8A,
8B,
8C,
8D), occlusive thrombus in
distal native vessel (Fig. 9),
intraluminal defect in proximal anastomosis and decreased flow with little
diastolic flow indicative of distal thrombosis (Fig.
10A,
10B), and flow limiting
dissection (Fig. 11). A major
finding consists of an abnormality on gray-scale image associated with
hemodynamic changes on Doppler interrogation. It is difficult to determine a
specific abnormal threshold velocity because of the variations in graft and
native vessel size. The accepted normal peak systolic velocity for the SMA
(2.75 m/sec) and celiac artery (2.0 m/sec) should be used with caution in this
scenario. More important is analysis of the waveform and velocities in
conjunction with gray-scale findings. Although major abnormalities are
generally revised, one should weigh the risks and benefits of further surgical
intervention. Factors such as additional organ ischemia due to prolonged
clamping time, technical difficulty, and patient comorbidities are important
in this decision. After revision of major defects, a repeat sonogram is
usually performed to document correction of the abnormality. In our previous
report [4], minor findings were
present in 6% (8/120) and major findings were found in 8% (10/120) of the
arteries studied.
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Fig. 4. —66-year-old man with bifurcated supraceliac aorta to superior
mesenteric artery (SMA) bypass. Intraoperative sonogram with spectral Doppler
waveform shows elevated velocity and turbulence associated with area of
angulation at proximal SMA graft anastomosis. On gray-scale image, lumen in
area of angulation remains widely opened, and velocity distal and proximal to
area of turbulence was not significantly lower. Therefore, findings were
thought to be insignificant and attributed to mild graft kinking.
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Fig. 5A. —Intraoperative sonogram of 50-year-old woman with
longitudinal views of distal anastomosis of supraceliac aorta to superior
mesenteric artery bypass graft. Doppler interrogation of distal graft limb
reveals normal waveform.
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Fig. 5B. —Intraoperative sonogram of 50-year-old woman with
longitudinal views of distal anastomosis of supraceliac aorta to superior
mesenteric artery bypass graft. Doppler sampling at distal anastomosis reveals
elevated velocity and focal narrowing. This was thought to be hemodynamically
significant focal narrowing that warranted revision.
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Fig. 5C. —Intraoperative sonogram of 50-year-old woman with
longitudinal views of distal anastomosis of supraceliac aorta to superior
mesenteric artery bypass graft. Postrevision image reveals resolution of
abnormal findings. Graft anastomosis narrowing was found.
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Fig. 6A. —Intraoperative sonogram of 62-year-old man with redo
bifurcated aorta to common hepatic artery and superior mesenteric artery (SMA)
bypass graft. Gray-scale sonogram reveals echogenic line (small
arrow) at anastomosis of new SMA graft limb (arrow) to old graft
(arrowhead).
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Fig. 6B. —Intraoperative sonogram of 62-year-old man with redo
bifurcated aorta to common hepatic artery and superior mesenteric artery (SMA)
bypass graft. Color and spectral Doppler sonogram reveals associated focal
elevated velocity and turbulence in proximal SMA graft.
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Fig. 6C. —Intraoperative sonogram of 62-year-old man with redo
bifurcated aorta to common hepatic artery and superior mesenteric artery (SMA)
bypass graft. Postrevision sonogram reveals resolution of echogenic line found
to be thrombus.
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Fig. 6D. —Intraoperative sonogram of 62-year-old man with redo
bifurcated aorta to common hepatic artery and superior mesenteric artery (SMA)
bypass graft. Postrevision color and spectral Doppler reveals normalization of
waveform.
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Fig. 7A. —75-year-old woman who had intraoperative sonogram after
transaortic endarterectomy of superior mesenteric artery (SMA). Gray-scale
image shows echogenic material within proximal SMA (arrow).
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Fig. 7B. —75-year-old woman who had intraoperative sonogram after
transaortic endarterectomy of superior mesenteric artery (SMA). Color and
spectral Doppler sonogram reveals associated turbulent flow with elevated
velocity.
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Fig. 7C. —75-year-old woman who had intraoperative sonogram after
transaortic endarterectomy of superior mesenteric artery (SMA). Postrevision
Doppler with spectral analysis reveals resolution of echogenic material and
normalization of velocity.
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Fig. 7D. —75-year-old woman who had intraoperative sonogram after
transaortic endarterectomy of superior mesenteric artery (SMA). Postrevision
color Doppler image reveals widely patent proximal anastomosis and resolution
of thrombus found to be associated with intimal flap.
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Fig. 8A. —59-year-old woman with supraceliac bifurcated aorta to celiac
and superior mesenteric artery (SMA) bypass graft. Longitudinal gray-scale
image at distal graft to SMA anastomosis shows echogenic line in lumen
(arrow).
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Fig. 8B. —59-year-old woman with supraceliac bifurcated aorta to celiac
and superior mesenteric artery (SMA) bypass graft. Color spectral Doppler
confirms hemodynamic disturbance with turbulent flow and focally elevated
velocity greater than 4 m/sec.
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Fig. 8C. —59-year-old woman with supraceliac bifurcated aorta to celiac
and superior mesenteric artery (SMA) bypass graft. Postrevision image reveals
resolution of echogenic line, thought to be intimal flap that resolved after
dilator was passed.
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Fig. 8D. —59-year-old woman with supraceliac bifurcated aorta to celiac
and superior mesenteric artery (SMA) bypass graft. Color and spectral analysis
Doppler shows resolution of hemodynamic abnormality. Abnormality on gray-scale
image associated with elevated velocity was significant, and revision was
recommended.
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Fig. 9. —78-year-old man with supraceliac bifurcated aorta to celiac
and superior mesenteric artery bypass graft. Intraoperative sonogram with
color Doppler reveals occlusive thrombus (arrow) in proximal common
hepatic artery, 2 cm beyond distal graft anastomosis. Embolectomy was
performed, and completion sonogram was normal. Occlusive thrombus is
significant finding that should prompt revision.
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Fig. 10A. —73-year-old man with supraceliac bifurcated aorta to splenic
artery and superior mesenteric artery bypass graft. Gray-scale image reveals
linear bright echo (arrow) at distal anastomosis with splenic artery
(arrowhead).
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Fig. 10B. —73-year-old man with supraceliac bifurcated aorta to splenic
artery and superior mesenteric artery bypass graft. Spectral Doppler waveform
was abnormal with minimal flow distally and high resistance, indicating distal
occlusion or significant stenosis. Surgeon elected not to revise this
abnormality because of prolonged operating and clamping time and significant
patient comorbidities. Graft occluded the following day and patient underwent
additional operation.
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Fig. 11. —Intraoperative sonogram of 78-year-old man after supraceliac
aorta to celiac and superior mesenteric artery bypass graft. Longitudinal
sonogram with spectral Doppler analysis reveals intraluminal flap
(arrow) associated with elevated velocity consistent with a
flow-limiting dissection in native common hepatic artery just beyond distal
anastomosis. These findings are consistent with major abnormality and should
prompt revision. After revision with repair of intimal flap, repeat sonogram
was normal.
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Conclusion
In summary, a sonogram is an accessible, relatively inexpensive, and
accurate tool to evaluate the adequacy of arterial revascularizations.
Mesenteric intraoperative sonography has a wide spectrum of findings. An
abnormality on a gray-scale image associated with hemodynamic changes is a
significant finding. Awareness and recognition of major abnormalities should
prompt immediate surgical revision and improved outcome.
References
- Okuhn SP, Reilly LM, Bennett JB, et al. Intraoperative assessment
of renal and visceral artery reconstruction: the role of duplex scanning and
spectral analysis. J Vasc Surg1987; 5:137
–147[Medline]
- Dougherty MJ, Hallett JW, Naessens JM, et al. Optimizing technical
success of renal revascularization: the impact of intraoperative color-flow
duplex ultrasonography. J Vasc Surg1993; 17:849
–857[Medline]
- Bandyk DF, Johnson BL, Gupta AK, Esses GE. Nature and management of
duplex abnormalities encountered during infrainguinal vein bypass grafting.
J Vasc Surg1996; 24:430
–438[Medline]
- Oderich GS, Panneton JM, Macedo TA, et al. Intraoperative duplex
ultrasound of visceral revascularizations: optimizing technical success and
outcome. J Vasc Surg2003; 38:684
–691[Medline]
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Abstract
Introduction
