DOI:10.2214/AJR.05.0408
AJR 2006; 187:W524-W527
© American Roentgen Ray Society
MDCT Angiography of Middle Mesenteric Artery with Associated Bowel Nonrotation Complicating Management of Abdominal Aortic Aneurysm
Courtney A. Woodfield1 and
Drew A. Torigian1
1 Both authors: Department of Radiology, Hospital of the University of
Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104-4283.
Received March 7, 2005;
accepted after revision May 2, 2005.
Address correspondence to D. A. Torigian
(Drew.Torigian{at}uphs.upenn.edu).
WEB
This is a Web exclusive article.
Keywords: abdominal aortic aneurysm • abdominal arteries • bowel nonrotation • MDCT angiography • middle mesenteric artery
Introduction
A middle mesenteric artery is a very rare mesenteric arterial anomaly
resulting from incomplete regression of the primitive paired segmental ventral
arteries of the dorsal abdominal aorta which supply variable amounts of the
small and large bowel
[1-8].
We report the imaging findings of a middle mesenteric artery with associated
bowel nonrotation in a patient undergoing preoperative MDCT angiography for a
known abdominal aortic aneurysm (AAA). The patient was subsequently excluded
from aortic stent-graft repair because the middle mesenteric artery was
originating from the proximal aspect of the AAA, which, to our knowledge, has
not previously been reported. In addition, findings of a middle mesenteric
artery with associated bowel nonrotation on MDCT angiography examination have
not been previously reported in the literature.
Case Report
A 72-year-old asymptomatic man with a history of diabetes mellitus,
hypertension, and coronary artery disease presented to our affiliated Veterans
Affairs Medical Center for evaluation of chronic renal insufficiency (serum
creatinine level of 2.1 mg/dL). Physical examination revealed a nontender,
pulsatile abdominal mass inferior in relation to the umbilicus, and subsequent
evaluation with retroperitoneal sonography showed a 7.9-cm infrarenal AAA.
The patient was subsequently brought to our hospital for MDCT angiography
examination of the abdomen and pelvis to preoperatively assess for
endovascular aortic stent-graft repair. Before the MDCT angiography
examination, the patient received IV hydration and N-acetylcysteine
therapy. The examination was performed on a 16-MDCT scanner using an MDCT
angiography protocol for AAA. Initially, unenhanced images were obtained using
the following parameters: 120 kVp; effective milliampere-seconds, 150; slice
collimation, 1.5 mm; slice width, 5 mm. Subsequently, 100 mL of nonionic
contrast material was administered IV at a rate of 4 mL/s, and images were
obtained from just above the level of the celiac artery to the level of the
common femoral bifurcation during the arterial phase of enhancement via bolus
triggering using the following parameters: 120 kVp; effective
milliampere-seconds, 180; slice collimation, 0.75 mm; slice width, 2 mm;
reconstruction interval, 1 mm. Three-dimensional multiplanar reformatted
images were created using maximum-intensity-projection and volume-rendering
techniques on a dedicated 3D workstation.
The MDCT angiography examination showed an 8.4 x 7.5 cm infrarenal
AAA that was 12.2 cm in craniocaudal length with a neck length (i.e., distance
from the most inferior renal artery to the start of the aneurysm) of 2.4 cm
and distal extension to the aortic bifurcation. Areas of curvilinear high
attenuation were visualized on unenhanced images within the mural thrombus of
the AAA, in keeping with a crescent sign, which signifies impending aneurysm
rupture.
Three right renal arteries, a single left renal artery, the celiac artery,
and the superior mesenteric artery were patent. The superior mesenteric artery
supplied the proximal half of the small bowel. An anomalous middle mesenteric
artery was noted to arise from the most proximal anterior aspect of the AAA,
5.8 cm inferior in relation to the celiac artery, 4.6 cm inferior in relation
to the superior mesenteric artery, 11.6 cm superior in relation to the
inferior mesenteric artery, and 2.4 cm inferior in relation to the
inferior-most right renal artery. Mild to moderate ostial stenosis of the
middle mesenteric artery was present, and branches of the middle mesenteric
artery supplied the distal half of the small bowel along with the cecum,
ascending colon, hepatic flexure, transverse colon, and splenic flexure (Figs.
1A,
1B, and
1C). The inferior mesenteric
artery was proximally occluded and distally reconstituted via a branch of the
middle mesenteric artery, which predominantly supplied the descending colon,
sigmoid colon, and proximal rectum. Nonrotation of the bowel was also seen by
small-bowel location in the right abdomen, large-bowel location in the left
abdomen, lack of crossing of the duodenum through the midline, and inversion
of the normal superior mesenteric artery and superior mesenteric vein
relationship (Figs. 1D and
1E).
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Fig. 1A —72-year-old man with history of diabetes mellitus,
hypertension, and chronic renal insufficiency presents for evaluation of
abdominal aortic aneurysm (AAA) as detected on prior retroperitoneal
sonography. Frontal (A) and right lateral (B) 3D volume-rendered
contrast-enhanced MDCT angiography images of abdominal aorta show middle
mesenteric artery (M) with focal ostial stenosis (black arrow,
A, and white arrow, B) arising from anterosuperior
aspect of AAA (A) below level of celiac artery (C) and superior mesenteric
artery (S). Note branches of superior mesenteric artery directed rightward to
location of proximal nonrotated small bowel and branches of middle mesenteric
artery directed both rightward and leftward to locations of distal nonrotated
small bowel and proximal nonrotated large bowel, respectively. Proximally
occluded inferior mesenteric artery (white arrows, A) is
distally reconstituted by distal branch of middle mesenteric artery.
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Fig. 1B —72-year-old man with history of diabetes mellitus,
hypertension, and chronic renal insufficiency presents for evaluation of
abdominal aortic aneurysm (AAA) as detected on prior retroperitoneal
sonography. Frontal (A) and right lateral (B) 3D volume-rendered
contrast-enhanced MDCT angiography images of abdominal aorta show middle
mesenteric artery (M) with focal ostial stenosis (black arrow,
A, and white arrow, B) arising from anterosuperior
aspect of AAA (A) below level of celiac artery (C) and superior mesenteric
artery (S). Note branches of superior mesenteric artery directed rightward to
location of proximal nonrotated small bowel and branches of middle mesenteric
artery directed both rightward and leftward to locations of distal nonrotated
small bowel and proximal nonrotated large bowel, respectively. Proximally
occluded inferior mesenteric artery (white arrows, A) is
distally reconstituted by distal branch of middle mesenteric artery.
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Fig. 1C —72-year-old man with history of diabetes mellitus,
hypertension, and chronic renal insufficiency presents for evaluation of
abdominal aortic aneurysm (AAA) as detected on prior retroperitoneal
sonography. Axial contrast-enhanced maximum-intensity-projection MDCT image
through portion of AAA shows distal portions of superior mesenteric artery (S)
and middle mesenteric artery (M) adjacent to AAA (A), with distal branches
supplying nonrotated small and large bowels as described for A and
B.
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Fig. 1D —72-year-old man with history of diabetes mellitus,
hypertension, and chronic renal insufficiency presents for evaluation of
abdominal aortic aneurysm (AAA) as detected on prior retroperitoneal
sonography. Axial contrast-enhanced MDCT images through upper (D) and
mid (E) abdomen show inversion of normal superior mesenteric artery (S,
D) and superior mesenteric vein (V, D) relationship, along with
small bowel (SB, E) location on right and large bowel (LB, E) on
left in keeping with bowel nonrotation.
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Fig. 1E —72-year-old man with history of diabetes mellitus,
hypertension, and chronic renal insufficiency presents for evaluation of
abdominal aortic aneurysm (AAA) as detected on prior retroperitoneal
sonography. Axial contrast-enhanced MDCT images through upper (D) and
mid (E) abdomen show inversion of normal superior mesenteric artery (S,
D) and superior mesenteric vein (V, D) relationship, along with
small bowel (SB, E) location on right and large bowel (LB, E) on
left in keeping with bowel nonrotation.
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Because the middle mesenteric artery was originating from the proximal end
of the AAA, the patient was excluded as a candidate for endovascular aortic
stent-graft repair. The patient subsequently underwent open surgical repair of
the AAA at our affiliated Veterans Affairs Medical Center, with a
20-mm-diameter polyethylene terephthalate fiber (Dacron, DuPont) straight
graft prosthesis via a left retroperitoneal approach, and reimplantation of
the middle mesenteric artery without complication. Surgical correction of the
bowel nonrotation was not performed.
Discussion
The middle mesenteric artery is a very rare mesenteric arterial anomaly,
arising from the infrarenal abdominal aorta between the superior mesenteric
artery and inferior mesenteric artery
[2-8].
This fourth mesenteric artery results from abnormal regression of the
primitive paired segmental ventral arteries of the dorsal aorta. Normally,
only the 10th, 13th, and 22nd ventral segmental arteries persist to form the
celiac artery, the superior mesenteric artery, and the inferior mesenteric
artery, respectively [1].
Review of the medical literature revealed seven prior reports of a middle
mesenteric artery
[2-8].
In 1963, Benton and Cotter [2]
first described a middle mesenteric artery with branches to the transverse and
proximal descending colon in a 71-year-old male cadaver. Three subsequent
articles reported detection on conventional angiography of a middle mesenteric
artery that supplied the transverse colon and splenic flexure in two cases and
the distal ileum through the splenic flexure in the remaining case
[3-5].
In 1999, Koizumi et al. [7]
reported the appearance on conventional angiography and MDCT angiography
maximum-intensity-projection images of a middle mesenteric artery that
supplied the cecum through the splenic flexure in a 55-year-old woman with
renovascular hypertension.
Only two prior reports of a middle mesenteric artery occurring in
association with bowel nonrotation appear in the literature. In 1998, Higashi
and Hirai [6] described a
middle mesenteric artery that supplied the distal small bowel through the
splenic flexure with bowel nonrotation in a 74-year-old female cadaver; and in
2004, Uchida et al. [8]
reported a middle mesenteric artery that supplied the distal ileum through the
hepatic flexure on conventional angiography and axial CT images, along with
bowel nonrotation, in a 57-year-old man undergoing preoperative evaluation for
known colon carcinoma. Higashi and Hirai also suggested that the presence of a
middle mesenteric artery may have led to bowel nonrotation during
embryogenesis, although bowel nonrotation was not present in the other five
(71%) of seven reported cases of a middle mesenteric artery
[2-8].
In the present case, the middle mesenteric artery arose in the setting of
bowel nonrotation and an AAA, which were well depicted on the MDCT angiography
examination. At our institution, MDCT angiography of the abdomen and pelvis is
routinely performed as part of the preoperative evaluation for AAA. When
compared with conventional CT, MDCT, with shorter scanning times, thinner
collimation, and rapid administration of IV contrast material, has been shown
to improve mesenteric vessel opacification and depiction of both major and
small mesenteric vessel anatomy and pathology on both axial source and 3D
reformatted images [9].
MDCT angiography, with arterial and venous phases of acquisition, can also
accurately show AAA size and morphology; aortic branch vessel patency, size,
and morphology, including that of the iliac and femoral arteries; venous
anatomy; and hollow and solid organ abnormalities. Any of these may
potentially alter the therapeutic approach to AAA repair
[10,
11]. At our institution, the
most common MDCT angiography findings that prevent a patient from undergoing
endovascular stent-graft repair for AAA are small caliber of the common or
external iliac artery and inadequate infrarenal AAA neck length (< 10-15
mm). However, in the present case, the patient was excluded from undergoing
endovascular repair because of a middle mesenteric artery originating from the
proximal aspect of the AAA. In this patient, the middle mesenteric artery
contributed most of the blood flow to the small and large bowel, supplying
both the distal small bowel and the colon from the cecum through to and
including the splenic flexure. In the absence of an anastomotic vessel between
the superior mesenteric artery and the middle mesenteric artery, and with the
middle mesenteric artery reconstituting a proximally occluded inferior
mesenteric artery, accidental coverage of the patient's middle mesenteric
artery after placement of an endovascular aortic stent-graft would have placed
the patient at high risk for both proximal and mid large-bowel and distal
small-bowel infarction.
In summary, we report the MDCT angiography imaging findings of a middle
mesenteric artery with associated bowel nonrotation in a 72-year-old man
undergoing preoperative evaluation for AAA repair. Detection of the middle
mesenteric artery altered the surgical management of the AAA from potential
endovascular aortic stent-graft repair to an open graft repair. This case
emphasizes the importance of detecting and characterizing such vascular and
nonvascular anomalies and reporting them to the surgeon in a timely manner
because patient management may be significantly affected.
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- Benton RS, Cotter WB. A hitherto undocumented variation of the
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Introduction
Case Report
