DOI:10.2214/AJR.05.1168
AJR 2007; 188:462-471
© American Roentgen Ray Society
CTA and MRA in Mesenteric Ischemia: Part 2, Normal Findings and Complications After Surgical and Endovascular Treatment
Ming-Chen Paul Shih1,2,
John F. Angle3,
Daniel A. Leung3,4,
Kenneth J. Cherry5,
Nancy L. Harthun5,
Alan H. Matsumoto3 and
Klaus D. Hagspiel1,3
1 Division of Noninvasive Cardiovascular Imaging, University of Virginia Health
System, 1215 Lee St., PO Box 800170, Charlottesville, VA 22908.
2 Present address: Department of Medical Imaging, Kaohsiung Medical University
Hospital, Kaohsiung, Taiwan.
3 Division of Interventional Radiology, University of Virginia Health System,
Charlottesville, VA.
4 Present address: Division of Interventional Radiology, Medical College of
Virginia, Richmond, VA.
5 Division of Thoracic and Cardiovascular Surgery, Department of Surgery,
University of Virginia Health System, Charlottesville, VA.
Received July 6, 2005;
accepted after revision December 7, 2005.
Address correspondence to K. D. Hagspiel
(kdh2n{at}virginia.edu).
Abstract
OBJECTIVE. A number of surgical and endovascular options exist for
the treatment of acute and chronic mesenteric ischemia. Both surgical and
endovascular treatments necessitate close clinical and imaging follow-up
because the consequences of acute occlusions can be catastrophic. MDCT
angiography (CTA) and contrast-enhanced MR angiography (MRA) are the preferred
imaging techniques in this setting.
CONCLUSION. We review the appearance of the normal and complicated
surgical and endovascular treatment on CTA and MRA.
Keywords: abdominal imaging • angiography, CT • angiography, MR • gastrointestinal imaging • ischemia • mesentery • stents
Introduction
Therapeutic treatment of ischemic bowel is based on relief of causes
and consequences of arterial obstruction. The type of treatment depends
largely on the clinical presentation, with time being the most important
factor determining viability before irreversible damage occurs to the bowel
[1,
2]. In acute mesenteric
ischemia, the viability of the bowel is usually in doubt, which necessitates
an open surgical approach to assess for bowel infarction and to urgently
revascularize the bowel. Percutaneous endovascular procedures are more
appropriate in patients with chronic mesenteric ischemia
[3,
4].
A number of surgical and endovascular therapeutic options exist for the
treatment of patients with acute or chronic mesenteric ischemia
[5-7].
Although these techniques are valuable in restoring mesenteric blood flow,
they all can lead to complications and all may be subject to early or late
failure. Therefore, clinical followup is mandatory, and high-quality vascular
imaging is essential. MDCT angiography (CTA) and, to a lesser extent,
contrast-enhanced MR angiography (MRA) are the most suitable noninvasive
techniques
[8-10].
In this pictorial essay we review the normal appearance of surgical and
endovascular treatments of mesenteric ischemia and their complications as seen
on CTA and contrast-enhanced MRA. All scanning was performed on 4-, 8-, or
16-MDCT scanners and 1.5-T high-performance MR scanners. Image reconstruction
was performed on Carestream PACS (Eastman Kodak) and Aquarius workstations
(TeraRecon).
Surgical Techniques
Embolectomy and Thrombectomy
Surgical embolectomy or thrombectomy, together with resection of nonviable
bowel, is the procedure of choice for emboli and graft thromboses that cause
acute mesenteric ischemia. Early postoperative studies may show residual
emboli or branch occlusions. Dissections can be also seen associated with
embolectomy.
Late stenoses can develop at the arteriotomy site or diffusely as a
consequence of embolectomy balloon-associated intimal injury.
Endarterectomy
Endarterectomy is the surgical removal of plaque from an artery that has
become narrowed or blocked, which usually occurs as a consequence of chronic
atherosclerosis. The first successful treatment of chronic mesenteric ischemia
by superior mesenteric thromboendarterectomy was reported in 1958
[7] (Fig.
1A,
1B). It is performed when
atherosclerosis of the supra- and infraceliac aorta and the ostia of the
visceral arteries would make placement of bypass graft difficult
[11,
12]. Endarterectomy is also
performed in cases of bowel perforation and contamination of the surgical
field [12].
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Fig. 1A —43-year-old woman with history of Takayasu's arteritis, descending
thoracic aortic aneurysm (not shown), and premature atherosclerosis. Her
clinical complaint was classic triad of mesenteric ischemia. Thin-slab
maximum-intensity-projection MDCT angiograms before (A) and after
(B) surgery show that aortic endarterectomy was performed at distal
thoracic aorta and celiac trunk (arrowhead) as well as at origin of
superior mesenteric artery and paravisceral abdominal aorta through a
thoracoretroperitoneal approach. Note widely patent postoperative lumen.
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Fig. 1B —43-year-old woman with history of Takayasu's arteritis, descending
thoracic aortic aneurysm (not shown), and premature atherosclerosis. Her
clinical complaint was classic triad of mesenteric ischemia. Thin-slab
maximum-intensity-projection MDCT angiograms before (A) and after
(B) surgery show that aortic endarterectomy was performed at distal
thoracic aorta and celiac trunk (arrowhead) as well as at origin of
superior mesenteric artery and paravisceral abdominal aorta through a
thoracoretroperitoneal approach. Note widely patent postoperative lumen.
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Bypass Placement
Bypass grafts can be antegrade from the supraceliac abdominal aorta or
retrograde from the infraceliac abdominal aorta, the common iliac arteries, or
previous grafts. Most vascular surgeons prefer antegrade or retrograde bypass
grafts to thrombectomy or endarterectomy
[11], mainly because of the
shorter clamping times and greater technical ease.
Both vein grafts and synthetic grafts are used, but synthetic grafts are
superior because they have better patency
[4,
12] (Figs.
2 and
3A,
3B). Differentiating these
bypass materials is not essential, but they have several specific
characteristics. Vein grafts appear to be of relatively small caliber.
Postoperative synthetic grafts should be of a uniform size.
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Fig. 2 —56-year-old woman with claudication and intermittent abdominal pain.
Postoperative volume-rendered MDCT angiogram shows aortobifemoral bypass with
14 x 7 mm PTFE (polytetrafluoroethylene) graft, retrograde 6-mm PTFE
superior mesenteric artery bypass off aortobifemoral bypass graft
(arrowhead), and inferior mesenteric artery reimplantation
(arrow).
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Fig. 3A —58-year-old man who underwent placement of supraceliac bypass to
superior mesenteric artery (SMA) using reversed greater saphenous vein for
typical symptoms of chronic mesenteric ischemia. One year after surgery,
symptoms recurred that were found to be caused by stenosis of proximal graft
anastomosis and 70% stenosis in SMA just distal to graft anastomosis on
catheter angiography (not shown). Patient underwent recanalization of occluded
proximal native SMA and placement of balloon-expandable stent as well as
percutaneous transluminal angioplasty (PTA) of SMA just distal to anastomosis.
Stenosis in graft was not treated. MDCT angiogram immediately after
intervention shows vein graft stenosis (arrowhead), stent in proximal
SMA (solid arrow), and widely patent SMA after successful PTA
(black arrow).
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Fig. 3B —58-year-old man who underwent placement of supraceliac bypass to
superior mesenteric artery (SMA) using reversed greater saphenous vein for
typical symptoms of chronic mesenteric ischemia. One year after surgery,
symptoms recurred that were found to be caused by stenosis of proximal graft
anastomosis and 70% stenosis in SMA just distal to graft anastomosis on
catheter angiography (not shown). Patient underwent recanalization of occluded
proximal native SMA and placement of balloon-expandable stent as well as
percutaneous transluminal angioplasty (PTA) of SMA just distal to anastomosis.
Stenosis in graft was not treated. Follow-up MDCT angiogram 1 year later shows
that antegrade graft is now occluded, presumably because of progression of
intimal hyperplasia and reduced flow caused by patent SMA.
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A single-vessel bypass to the superior mesenteric artery is generally
effective in providing symptomatic relief even in patients with multiple
vessel occlusions (Fig. 3A,
3B). However, a higher
incidence of graft failure and recurrence of symptoms occurs after single as
opposed to multiple-vessel revascularizations
[13]. If revascularization of
two or more visceral branches is performed, bifurcated grafts (Fig.
4A,
4B,
4C) and jump grafts (Fig.
5A,
5B) can be used instead of
several individual grafts.
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Fig. 4A —47-year-old woman with mesenteric ischemia who received supraceliac
bifurcated bypass graft to celiac artery and superior mesenteric artery (SMA)
using 12 x 7 mm Hemashield Dacron graft (Boston Scientific). On
postoperative day 2, patient complained of abdominal pain. MDCT angiography
was performed and showed graft thrombosis. Sagittal multiplanar reformation
shows stump of graft (arrowhead) as well as two separate areas of
occlusion in SMA (arrows). Patient underwent emergent embolectomy
that restored patency of bifurcated graft. Hepatic graft anastomosis was
revised by inserting interposition graft.
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Fig. 4B —47-year-old woman with mesenteric ischemia who received supraceliac
bifurcated bypass graft to celiac artery and superior mesenteric artery (SMA)
using 12 x 7 mm Hemashield Dacron graft (Boston Scientific). On
postoperative day 2, patient complained of abdominal pain. MDCT angiography
was performed and showed graft thrombosis. Sagittal multiplanar reformation
(B) and volume-rendered MDCT angiogram (C) show patent
anastomosis and two patent limbs of Y-graft (arrowheads, C)
after successful surgical revision.
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Fig. 4C —47-year-old woman with mesenteric ischemia who received supraceliac
bifurcated bypass graft to celiac artery and superior mesenteric artery (SMA)
using 12 x 7 mm Hemashield Dacron graft (Boston Scientific). On
postoperative day 2, patient complained of abdominal pain. MDCT angiography
was performed and showed graft thrombosis. Sagittal multiplanar reformation
(B) and volume-rendered MDCT angiogram (C) show patent
anastomosis and two patent limbs of Y-graft (arrowheads, C)
after successful surgical revision.
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Fig. 5A —63-year-old woman with history of postprandial pain, 50-lb [22.5-kg]
weight loss, and aversion to food underwent MDCT angiography for assessment of
mesenteric circulation. Volume-rendered CT angiogram reveals severe celiac
artery stenosis as well as 4-cm-long proximal occlusion of superior mesenteric
artery (SMA) (arrows). Inferior mesenteric artery was prominent and
supplied SMA territory via Riolan's arch (arrowhead).
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Fig. 5B —63-year-old woman with history of postprandial pain, 50-lb [22.5-kg]
weight loss, and aversion to food underwent MDCT angiography for assessment of
mesenteric circulation. Volume-rendered CT angiogram after surgery shows
placement of supraceliac jump grafts in coronary artery and SMA using
Hemashield Dacron (Boston Scientific), which resulted in complete symptomatic
relief despite stenosis just distal to anastomosis with SMA
(arrowhead).
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Reimplantation of the inferior mesenteric artery (IMA) during aortic
reconstructive surgery is usually performed if there is intraoperative lack of
backbleeding from the dissected IMA because that indicates inadequate
collateralization (Fig. 6).
Not reimplanting the IMA in these cases would put the patient at risk for
mesenteric ischemia.
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Fig. 6 —86-year-old man who underwent placement of aortobiiliac graft and
inferior mesenteric artery (IMA) reimplantation (arrowhead) for
aneurysmal disease of aorta with insufficient intraoperative backbleeding from
IMA. Note right internal iliac artery aneurysm (arrow).
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Median Arcuate Ligament Syndrome
The treatment of medial arcuate ligament syndrome is surgical and consists
of release of the ligament with or without placement of a bypass
(Fig. 7). Endovascular
therapies have proven to be ineffective because stents are crushed by the
ligament [14].
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Fig. 7 —45-year-old woman with median arcuate ligament syndrome who
underwent surgical median arcuate ligament release with antegrade celiac
artery bypass. Patient developed stenosis at proximal anastomosis
(arrowhead) that was subsequently treated with percutaneous
transluminal angioplasty.
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Complications of Surgical Therapy
Kinking
Antegrade bypasses are less prone to kinking and compression than
retrograde ones, but antegrade bypasses have been associated with renal
ischemia because of the need for suprarenal aortic clamping. Retrograde
bypasses from the infrarenal abdominal aorta or iliac artery are technically
easier and avoid renal ischemia, but they are more prone to reduced inflow and
graft kinking [7,
11].
Intimal Hyperplasia
All bypasses are prone to develop stenoses due to intimal hyperplasia,
especially at the anastomotic sites. Stenosis usually develops within the
first 3-6 months after surgery. Advanced stages of intimal hyperplasia can
ultimately lead to graft thrombosis
[7,
11] (Figs.
3A,
3B,
8, and
9).
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Fig. 8 —66-year-old man who underwent placement of aortobiiliac graft and
retrograde graft to superior mesenteric artery (SMA). He presents with acute
onset of abdominal pain. Sagittal multiplanar reformatted MDCT angiogram shows
occlusion of retrograde graft close to anastomosis caused by acute thrombus
(arrow). Anastomotic stenosis was identified at surgery as underlying
culprit lesion.
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Fig. 9 —26-year-old woman with Takayasu's arteritis who underwent placement
of extraanatomic aortic bypass for abdominal aortic occlusion (solid
arrow). Superior mesenteric artery (SMA) is supplied by graft off left
iliac artery (arrowheads), and right and left kidneys, via graft from
supraceliac aorta and extraanatomic aortic graft, respectively. Note old
thrombosed graft off right common iliac artery that previously supplied SMA
and celiac artery (open arrows).
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Early Graft Occlusion
Graft occlusion in the immediate postoperative period is almost always due
to technical or surgical problems such as kinking, twisting, or inadequate
anastomoses [7] (Fig.
4A,
4B). Hypercoagulable states are
occasionally responsible, with no identifiable underlying anatomic cause.
Surgical revision is almost always indicated in all cases of early graft
occlusion. Early and late graft occlusion can be catastrophic events resulting
in bowel necrosis.
CT can show bowel-wall thickening and pneumatosis
[8]. Both CTA and
contrast-enhanced MRA are excellent for visualizing grafts and graft
anastomoses. Rarely, surgical clips cause streak artifact on CT or signal void
on MRI that reduce the diagnostic usefulness of these studies. Graft
thrombosis and occlusion can be reliably diagnosed
[8,
10] (Figs.
8 and
9).
Reperfusion Syndrome
Both surgical and endovascular revascularization can result in massive
hyperemia of the bowel and visceral organs, resulting in severe complications
such as pancreatitis, liver failure with ascites, and food intolerance
[15]. CTA shows massive
hyperemia of the bowel and the abdominal organs (Fig.
10A,
10B,
10C).
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Fig. 10A —64-year-old woman with severe postprandial abdominal pain and weight
loss who underwent successful recanalization with percutaneous transluminal
angioplasty and stenting of celiac artery and superior mesenteric artery
(SMA), resulting in temporary reperfusion syndrome with ascites and
pancreatitis. Abdominal aortogram shows total occlusion of celiac trunk, SMA,
and inferior mesenteric artery at their ostia ("bald aorta").
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Fig. 10B —64-year-old woman with severe postprandial abdominal pain and weight
loss who underwent successful recanalization with percutaneous transluminal
angioplasty and stenting of celiac artery and superior mesenteric artery
(SMA), resulting in temporary reperfusion syndrome with ascites and
pancreatitis. Coronal subvolume maximum-intensity-projection (MIP) MDCT
angiogram after endovascular revascularization shows massive mesenteric
hyperemia as evidenced by strong portal venous enhancement in this arterial
phase scan.
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Fig. 10C —64-year-old woman with severe postprandial abdominal pain and weight
loss who underwent successful recanalization with percutaneous transluminal
angioplasty and stenting of celiac artery and superior mesenteric artery
(SMA), resulting in temporary reperfusion syndrome with ascites and
pancreatitis. Subvolume MIP of same MDCT angiogram shows ascites
(arrowhead) and enlarged pancreatic vessels (arrow). Liver
function abnormalities, pancreatitis, abdominal pain, and inability to
tolerate food normalized after 5 days, and patient was discharged with no
symptoms.
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Endovascular Therapy
Endovascular techniques, including catheter-directed thrombolysis,
mechanical thrombectomy, angioplasty, stenting, and endoluminal stent-graft
placement, are important therapeutic options for the treatment of mesenteric
ischemia.
Thrombolysis and Embolectomy
Thrombi and emboli can be effectively treated with either pharmacologic or
mechanical thrombectomy
[14].
Percutaneous Transluminal Angioplasty
The first percutaneous transluminal angioplasty (PTA) in the mesenteric
circulation was performed in 1980
[16]. Since then, PTA of the
superior mesenteric artery, the IMA, and the celiac trunk has been reported in
many patients. Both CTA and contrast-enhanced MRA allow visualization of
vessel patency after PTA. Possible complications are vessel occlusion, emboli,
dissection, and rupture
[14].
Stent Placement
Stents are generally used in cases of PTA failure, and they are
particularly suitable for ostial lesions (Fig.
11A,
11B). Their use results in
higher technical and clinical success rates than PTA alone. Their patency
appears also to be superior to PTA in the long term, with one group reporting
a primary patency rate of 74% at 18 months and an assisted patency rate of 83%
at 3 years [5] (Figs.
11A,
11B,
12A,
12B,
13A,
13B,
14A,
14B,
15A,
15B). Only CTA can be used for
follow-up of stents because stent-induced artifacts preclude assessment of
stent patency on contrast-enhanced MRA
[17] (Figs.
10A,
10B,
10C,
11A,
11B,
12A,
12B,
13A,
13B,
14A,
14B).
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Fig. 11A —70-year-old woman with history of hypercholesterolemia and bilateral
renal stents presents with intermittent abdominal pain, nausea, and diarrhea.
Catheter angiography showed ostial 90% celiac artery stenosis with pressure
gradient greater than 60 mm Hg that was successfully treated with
balloon-expandable stent dilated to 7 mm. Control angiogram immediately after
stent placement shows widely patent proximal celiac artery.
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Fig. 11B —70-year-old woman with history of hypercholesterolemia and bilateral
renal stents presents with intermittent abdominal pain, nausea, and diarrhea.
Catheter angiography showed ostial 90% celiac artery stenosis with pressure
gradient greater than 60 mm Hg that was successfully treated with
balloon-expandable stent dilated to 7 mm. Multiplanar reformation of MDCT
angiogram obtained day after intervention also shows widely patent stent.
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Fig. 12A —81-year-old woman with occlusion of celiac trunk and superior
mesenteric artery (SMA) as well as high-grade inferior mesenteric artery (IMA)
stenosis who underwent treatment with placement of two balloon-expandable
stents in IMA. Curved multiplanar reformation of MDCT angiogram after
revascularization shows widely patent stent lumen.
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Fig. 12B —81-year-old woman with occlusion of celiac trunk and superior
mesenteric artery (SMA) as well as high-grade inferior mesenteric artery (IMA)
stenosis who underwent treatment with placement of two balloon-expandable
stents in IMA. Volume-rendered image shows IMA stent (arrowhead) and
reconstitution of SMA and celiac trunk via Riolan's arch and
pancreaticoduodenal arcades, respectively.
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Fig. 13A —56-year-old man with calcified high-grade ostial superior mesenteric
artery stenosis who was treated with balloon-expandable stent. Angiogram after
completion of stent placement shows mild stenosis at inferior stent border due
to noncompressible plaque (arrowhead).
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Fig. 13B —56-year-old man with calcified high-grade ostial superior mesenteric
artery stenosis who was treated with balloon-expandable stent. Curved
multiplanar reformation of MDCT angiogram shows heavily calcified plaque
causing incomplete stent expansion (arrowhead).
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Fig. 14A —76-year-old woman who presented with persistent nausea, vomiting,
abdominal pain, and diarrhea of approximately 2 months' duration. Catheter
angiogram reveals 90% stenosis of superior mesenteric artery (SMA), large
calcified plaque at its ostium, and 50% celiac artery stenosis. After
successful stenting of SMA origin, patient experienced almost immediate
symptomatic relief from her abdominal pain.
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Fig. 14B —76-year-old woman who presented with persistent nausea, vomiting,
abdominal pain, and diarrhea of approximately 2 months' duration. Follow-up
MDCT angiogram shows widely patent stent. Nonocclusive protrusion of calcified
aortic plaque was present proximal to stent but could not be seen on
angiographic films.
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Fig. 15A —83-year-old woman with chronic occlusion of celiac trunk and
superior mesenteric artery (SMA) and high-grade stenosis of inferior
mesenteric artery (IMA) who underwent treatment with placement of
balloon-expandable stent in IMA (not shown). Preprocedure-rendered MDCT
angiogram shows IMA (arrowhead) and reconstitution of SMA and celiac
trunk via Riolan's arch and pancreaticoduodenal arcades, respectively. Patient
did well after discharge but presented 4 months later in emergency department
with acute abdomen.
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Fig. 15B —83-year-old woman with chronic occlusion of celiac trunk and
superior mesenteric artery (SMA) and high-grade stenosis of inferior
mesenteric artery (IMA) who underwent treatment with placement of
balloon-expandable stent in IMA (not shown). Emergent MDCT angiogram showed
occluded IMA stent (not shown) as well as complete bowel necrosis as evidenced
by extensive pneumatosis. Patient subsequently died.
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Although recurrent symptoms have a slightly higher incidence after
interventional radiologic treatment
[6] than after open surgery,
the former has gained wide popularity, especially in high-risk patients.
Interventional treatment has also been used to minimize the recurrence of
symptoms and organ infarction after graft failure
[7] (Fig.
3A,
3B).
Aortic Dissection
Endovascular techniques attempt to restore flow to the true lumen with
aortic stent-grafts and to the viscera via stenting of the visceral vessels or
fenestration of the dissection membrane. Surgical options include aortic
repair and fenestration. The choice of surgical versus endovascular techniques
depends on the type of dissection, the degree of branch vessel obstruction,
individual anatomy, and preexisting morbidities
[14,
18].
Complications of Endovascular Treatment
Intimal Hyperplasia and Restenosis
Percutaneous interventions can trigger inflammatory reactions leading to
the development of intimal hyperplasia (Fig.
13A,
13B). This reaction is even
more prominent in atheromatous plaques in which inflammatory cells have
already been activated and in stents (Figs.
15A,
15B and
16A,
16B). Untreated restenosis
ultimately leads to thrombosis and occlusion
[19]
(Fig. 17). CTA shows intimal
hyperplasia as hypodense tissue on the inner stent surface.
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Fig. 16B —64-year-old man 16 months after placement of balloon-expandable
stent in superior mesenteric artery (SMA). Curved multiplanar reformation of
MDCT angiogram also shows hypodense intimal hyperplastic tissue in stent
(arrowhead).
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Fig. 17 —64-year-old woman 3 years after placement of balloon-expandable
stent in superior mesenteric artery (SMA). Curved multiplanar reformation of
MDCT angiogram shows stent fracture (arrowhead) and preserved stent
patency in this asymptomatic patient.
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Stent Fracture and Migration
In our experience, migration of a stent is usually a complication that
occurs during placement, whereas stent fracture is an unusual late-term
complication of endovascular treatment. Both can be readily detected on CTA
(Figs. 17 and
18A,
18B).
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Fig. 18A —60-year-old man who underwent stenting of ostial celiac artery
stenosis that was complicated by migration of stent due to undersizing.
Catheter angiogram shows stent free-floating in celiac artery
(arrowhead). Stent was then deployed more distally with larger
balloon but was not covering ostial lesion. A second stent was therefore
placed in ostium.
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Fig. 18B —60-year-old man who underwent stenting of ostial celiac artery
stenosis that was complicated by migration of stent due to undersizing.
Volume-rendered MDCT angiogram shows two stents (arrowheads).
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Summary
Mesenteric ischemia is a life-threatening entity. Even after successful
open or percutaneous therapy, symptoms can recur. Sudden graft failure carries
a high mortality rate. CTA is a technique that is well suited for assessing
the normal and complicated appearances after mesenteric ischemia treatment. In
our opinion, the ability to visualize the lumen of metallic stents, the higher
spatial resolution, and the much faster acquisition times on modern MDCT
scanners make CTA superior to contrast-enhanced MRA in this setting.
Aggressive therapy improves survival but requires imaging surveillance to
detect complications early. Knowledge of the normal and abnormal appearances
after mesenteric ischemia therapy is mandatory for the radiologist involved in
the care of these patients.
References
- English WP, Pearce JD, Craven TE, et al. Chronic visceral ischemia:
symptom-free survival after open surgical repair. Vasc Endovascular
Surg 2004; 38:493
-503[Abstract/Free Full Text]
- Merle C, Lepouse C, De Garine A, et al. Surgery for mesenteric
infarction: prognostic factors associated with early death within 72 hours.
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H. P. Forman
Back to the Beginning
Am. J. Roentgenol.,
February 1, 2007;
188(2):
295 - 296.
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Abstract
Introduction
