AJR 2005; 184:S73-S74
© American Roentgen Ray Society
Paraprosthetic Extravasation of Enteric Contrast: A Rare and Direct Sign of Secondary Aortoenteric Fistula
Ryan M. Peirce,
Richard H. Jenkins and
Peter MacEneaney
University of Chicago, Department of Radiology, 5841 S. Maryland Ave.,
Chicago, IL 60637.
Received February 26, 2004;
accepted after revision June 1, 2004.
Address correspondence to R. M. Peirce
(rpeirce{at}radiology.bsd.uchicago.edu).
Introduction
An aortoenteric fistula is a communication between the aorta and the
gastrointestinal tract. This condition is a rare cause of massive,
life-threatening gastrointestinal hemorrhage. Primary aortoenteric fistulas
are typically caused by arteriosclerosis and occur in the elderly. Secondary
aortoenteric fistulas (SAEFs) are uncommon complications of vascular surgical
procedures. Presentations of SAEF can be straightforward but are notorious for
elusive and temporally remote presentations.
The symptoms of SAEF are variable and depend on the site of the graft
infection. Infected femoral components in a patient may present with a fever,
local tenderness, and, occasionally, purulent drainage through a sinus tract
in the thigh. Intraabdominal infections tend to be more nebulous; malaise,
back pain, elevated white blood cell count (WBC), and abdominal complaints are
the usual presentation. These features mimic more common disease entities,
making diagnosis difficult.
Proving the existence of an SAEF radiographically can be difficult. In this
article, paraprosthetic extravasation of enteric contrast, a rare and direct
sign of SAEF, verified aorto-to-enteric communication on CT.
Case Report
A 72-year-old woman arrived at our emergency department with a fever,
elevated WBC count, abdominal pain, and purulent groin drainage (Figs.
1A,
1B,
1C). The patient had
aortobifemoral prosthesis placement at an outside institution 6 weeks earlier.
Because of abnormal renal function, a CT scan of the abdomen and pelvis was
performed with enteric contrast only (meglumine diatrizoate [Gastrografin],
Mallinckrodt).
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Fig. 1A. —72-year-old woman with aortobifemoral prosthesis placement 6
weeks earlier presented with fever, elevated WBC count, abdominal pain, and
purulent groin drainage. CT (with enteric contrast only) reveals ring of
high-contrast material surrounding left iliac limb of graft.
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Fig. 1B. —72-year-old woman with aortobifemoral prosthesis placement 6
weeks earlier presented with fever, elevated WBC count, abdominal pain, and
purulent groin drainage. More caudal CT shows direct contact between sigmoid
colon and left limb of graft. Communication between iliac limb of graft and
sigmoid colon was confirmed at laparotomy.
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Fig. 1C. —72-year-old woman with aortobifemoral prosthesis placement 6
weeks earlier presented with fever, elevated WBC count, abdominal pain, and
purulent groin drainage. More proximal CT reveals large air-fluid collection
anterior to graft, representing an abscess. Air and enteric contrast material
are present around bifurcation of aortic component of graft.
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CT revealed a ring of high-contrast material and air in the paraprosthetic
space of the left iliac limb of the graft. The contrast and air tracked
superiorly, to the level of the aortic portion of the graft and inferiorly
into the groin. This represented leakage of enteric contrast from the
bowel.
CT findings indicated an aortoenteric fistula and were confirmed at
surgical exploration. Laparotomy revealed an infected aortobifemoral graft
with a large intraabdominal collection of purulent fluid just behind the
duodenum, anterior to the graft. The infected fluid collection extended into
the left limb of the graft, with associated erosion into the adjacent sigmoid
colon. The infected graft was removed and an aorto-to-popliteal bypass graft
was inserted. Culture of the wound drainage revealed mixed bowel flora. The
patient was treated with IV antibiotics and experienced a complicated
postoperative course. However, the patient fully recovered and returned home
weeks later.
Discussion
Secondary aortoenteric fistulas are complications of aortic vascular
procedures and were first described by Brock
[1] in 1953. These fistulas
represent an abnormal communication from the gastrointestinal tract to the
suture line of a vascular graft and most commonly affect the proximal graft
anastomosis. As enteric contents surround the anastomosis, infection often
follows. Graft infection occurs in 1.3-6.0% of vascular procedures
[2,
3], leading to breakdown of the
anastomotic site and eventual hemorrhage. The reported incidence is
approximately 0.6-1.5% of aortic bypass graft procedures
[4]. Perigraft infections have
mortality rates of 25-75% [5]
and mimic other common emergency department diagnoses.
Subtle and confusing presentations can make diagnosis of deep perigraft
infections difficult. The diagnosis of perigraft infection should be
considered in all patients with a history of graft placement and clinical
features of abdominal pain and infection.
Because of its availability and speed, CT is the initial diagnostic
technique of choice to evaluate SAEF
[6]. Specific early imaging
features have been described to aid diagnosis and include perigraft fluid,
perigraft air, perigraft extravasation of IV contrast, focal bowel wall
thickening, and pseudoaneurysm
[6,
7]. Peigraft fluid or
soft-tissue attenuation and perigraft air are the more commonly seen, although
less specific, signs of SAEF. To our knowledge, this is the first report in
the radiologic literature of CT revealing extravasation of enteric contrast
material from the adjacent bowel
[8]. This sign showed direct
visualization of enteric contents encasing the vascular graft. Our real-time
demonstration of active enteric extravasation around the graft is direct
evidence of a fistulous connection between the bowel and vascular bed. In our
case, the active SAEF was confirmed at surgery. Most of the classic signs can
represent normal postoperative findings, depending on the timing of the
examination relative to surgery. For example, perigraft fluid and air are
considered normal findings for weeks after surgery. Perigraft fluid has been
reported for up to a year without being infected
[9]. Although this sign was
previously unreported in radiologic literature, paraprosthetic extravasation
of enteric contrast is never a normal finding. In addition, many of the
aforementioned signs can present with simple aortic graft infections and SAEF.
Enteric extravasation into the fluid surrounding the aortic graft is rare but
should be considered a highly specific sign of SAEF.
References
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infections: radiologic manifestations and implications for management.
RadioGraphics2000; 20:977
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- Kukora JS, Rushton FW, Cranston PE. New computed tomographic signs
of aortoenteric fistula. Arch Surg1984; 119:1073
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Introduction
Case Report
