AJR 2002; 178:1462-1464
© American Roentgen Ray Society
Perigraft Seroma of Open Aortic Reconstruction
Evelyn Kat1,
D. Neil Jones1,
Jim Burnett2,
Robert Foreman2,
Robin Chok2 and
Michael R. Sage1
1 Division of Medical Imaging, Flinders Medical Centre, Bedford Park, SA 5042,
Australia.
2 Division of Vascular Surgery, Flinders Medical Centre, Bedford Park, SA 5042,
Australia.
Received August 3, 2001;
accepted after revision December 6, 2001.
Address correspondence to E. Kat.
Introduction
Perigraft seroma is a persistent enlarging sterile fluid collection
confined in a nonsecretory fibrous pseudomembrane surrounding an intact
prosthetic vascular graft [1,
2]. When a vascular graft in a
native vessel is involved, such as in open abdominal aortic aneurysm repair,
the accumulating collection expands the vessel diameter, but no demonstrable
graft leak is seen on imaging. This clinicopathologic entity is not well
described in the radiology literature. However, as more aortic reconstructions
are performed and the consequent imaging surveillance increases, it is
postulated aortic reconstruction perigraft seromas, although they rerely
occur, may be more frequently recognized. The mechanism of development of this
entity may have relevance to endoluminal aortic reconstructions and the
increasingly recognized complication of continued abdominal aortic aneurysm
growth in the absence of a demonstrable endoleak. We report a case of
perigraft seroma complicating an open aortoiliac graft in one patient and
similar imaging findings and clinical course in another.
Case Reports
A 60-year-old man presented with abdominal pain 5 years after undergoing
uneventful elective repair of a 7.5-cm infrarenal nonleaking abdominal aortic
aneurysm (Fig. 1A) with a
polytetrafluoroethylene aortoiliac graft. He was afebrile with a normal WBC
and erythrocyte sedimentation rate. Contrast-enhanced helical CT revealed an
intact undilated aortoiliac graft. However, the aneurysm had expanded. It
measured 11.5 cm in the maximal transverse diameter and had a wide-based focal
wall protrusion anteriorly, presumably a form of vascular hernia at the site
of previous aortic wall surgery (Fig.
1B). Sonography revealed the heterogeneous nature of the perigraft
collection, which had anechoic pockets of fluid in solid components and septa
(Figs. 1C and 1D). Conventional
angiography confirmed aortoiliac graft patency, and no vascular leak was
seen.
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Fig. 1A. —60-year-old man with periaortoiliac graft seroma seen 5 years
after elective open reconstruction of abdominal aortic aneurysm.
Contrast-enhanced CT scan obtained before elective surgery shows infrarenal
fusiform abdominal aortic aneurysm with maximal transverse diameter of 7.5 cm.
Intraluminal thrombus and wall calcification may be seen. Aortic wall is
thickened anterolaterally, thought to be result of previously contained leak
or inflammatory aneurysm that caused wall inflammation and fibrosis.
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Fig. 1B. —60-year-old man with periaortoiliac graft seroma seen 5 years
after elective open reconstruction of abdominal aortic aneurysm.
Contrast-enhanced helical CT scan obtained 5 years after A shows intact
nondilated aortoiliac graft. Aneurysm wall has expanded to 11.5 cm in
transverse diameter. Wider-based focal protrusion may be seen anteriorly,
presumably at site of previous aortic wall surgery.
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Fig. 1C. —60-year-old man with periaortoiliac graft seroma seen 5 years
after elective open reconstruction of abdominal aortic aneurysm. Sonogram
shows heterogeneous nature of perigraft collection. Note anechoic pockets of
fluid in solid components and septa.
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At laparotomy, the aortic sac wall appeared thickened and inflamed; the
duodenum and proximal jejunum adherent to the wall required resection of the
small bowel. When the aortic wall was opened, tense gelatinous material was
revealed surrounding the intact arterial graft. The proximal and distal
anastomoses were intact. The sac contents were evacuated, and the sac was
closed tightly around the graft.
Histologic examination of the aortic sac wall showed atheromatous change
and a fibrinous exudate over the luminal surface; a patchy chronic
inflammatory infiltrate was found only in the deeper layers near the
adventitia. No evidence was found of acute infection in the sac wall or in the
gelatinous contents. The gelatinous material contained no cells and was
sterile. The patient's symptoms improved. Findings on routine follow-up CT
performed 3 months after surgery revealed that the sac had returned to its
preoperative size.
Similar imaging findings were noted in a 73-year-old man 5 years 6 months
after he underwent open abdominal aortic aneurysm repair with a GORE-TEX (W.
L. Gore, Flagstaff, AZ) graft for a 14-cm nonleaking infrarenal aneurysm.
Imaging performed after surgery revealed a progressively enlarging abdominal
aortic aneurysm (Fig.
2A,2B,2C,2D).
No evidence of a graft leak was seen on multislice CT angiography. The patient
has remained symptomatic from the mass effect of the aneurysm, experiencing
back pain and constipation but no further sequelae. He is considered a poor
surgical candidate.
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Fig. 2A. —73-year-old man with periaortoiliac graft seroma monitored
for 5 years 6 months after elective infrarenal abdominal aortic aneurysm
repair. Contrast-enhanced CT scan obtained before surgery shows huge
nonleaking infrarenal abdominal aortic aneurysm. Transverse diameter measures
14 cm, with intraluminal thrombus with minor laminated calcification. We found
no pelvic extension.
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Fig. 2B. —73-year-old man with periaortoiliac graft seroma monitored
for 5 years 6 months after elective infrarenal abdominal aortic aneurysm
repair. Contrast-enhanced helical CT scans obtained 5 years 6 months after
A show further enlargement of aneurysm sac wall to 16 cm in transverse
diameter, but now with considerable inferior extension of seroma into
pelvis.
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Fig. 2C. —73-year-old man with periaortoiliac graft seroma monitored
for 5 years 6 months after elective infrarenal abdominal aortic aneurysm
repair. Contrast-enhanced helical CT scans obtained 5 years 6 months after
A show further enlargement of aneurysm sac wall to 16 cm in transverse
diameter, but now with considerable inferior extension of seroma into
pelvis.
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Fig. 2D. —73-year-old man with periaortoiliac graft seroma monitored
for 5 years 6 months after elective infrarenal abdominal aortic aneurysm
repair. Sonogram shows loculated nature of collection with solid and fluid
components.
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Discussion
Fluid between the open aortic graft and the sac wall is a normal finding on
imaging in the period immediately after surgery. However, after 3 months, any
perigraft hematoma or fluid should have resolved, and the vessel wall should
approximate the graft. Uncomplicated graft incorporation involves
periprosthetic fibrosis
[1].
In the early postoperative phase, perigraft fluid cannot be differentiated
from infection on the basis of imaging
[3]. In the absence of a
demonstrable leak, the differential diagnoses of the perigraft fluid
collection are graft infection or a sterile fluid collection—lymphatic
or serous. Most graft infections are clinically apparent, and imaging
techniques are used primarily for diagnostic confirmation and surgical
planning.
Lymphatic fluid collections are well recognized after vascular surgery when
surgical disruption of lymphatic channels has occurred in regions of high
interstitial fluid (ischemic legs and femoral—popliteal grafts) where
lymph flow is high, or after renal transplantations when external iliac
lymphatic chains has been disrupted. Lymphatic fluid collections have been
documented, using electrophoresis, as perigraft reactions surrounding Dacron
(DuPont, Wilmington, DE) velour axillofemoral or femoral—femoral grafts
[4,
5]. In the six cases described
[4,
5], an associated intense
inflammatory reaction (vascular proliferation, lymphocyte, plasma cells, and
foreign body macrophages) was seen. Lymphatic perigraft fluid appears to be a
delayed allergic hypersensitivity reaction to the graft by the host
[4,
5].
The pathogenesis of perigraft seromas involves both failure of graft
incorporation into the native vessel wall and increased graft porosity.
Failure of perigraft fibrosis in the surrounding connective tissue or vessel
wall [1,
2] is associated with a slowly
expanding collection caused by transudation of an ultrafiltrate of serum
through the graft wall into the extrinsic milieu
[2]. Unlike lymphatic
collections, perigraft seromas contain no acute inflammatory cells or foreign
body giant cells [2]. Reports
have varied in their descriptions of the consistency of this material from
clear dilute fluid [2] to a
gelatinous coagulum identified histologically as compacted fibrin and
proteinaceous material [6]
surrounded by a pseudocapsule
[2].
Perigraft seroma is a rare, late complication of polytetrafluoroethylene
and Dacron grafts [1,
2], rarely involving autologous
saphenous vein grafts [2].
These seromas are most often reported in superficial grafts such as
axillofemoral reconstructions and in hemodialysis arteriovenous fistulas,
because of their easy clinical recognition
[1]. Mediastinal perigraft
seromas have been described in pediatric polytetrafluoroethylene grafts in
modified Blalock-Taussig shunt procedures
[2]. The incidence of perigraft
seromas in open aortic reconstructions may be underreported, possibly because
of lack of imaging surveillance or clinical detection.
Why this entity occurs rarely and sporadically is unknown, but multiple
theories exist [1,
2]. Polytetrafluoroethylene
grafts are chemically inert, highly electronegative and hydrophobic, and
impermeable to whole blood. However, excess wetting of the graft by organic
solvents, such as alcohol, or excess manipulation or forced irrigation through
the walls of the graft before graft insertion are thought to create a
condition conducive to plasma leakage
[6]. Increased permeability of
the graft may also be due to previous infection
[2]. Increased levels of
humoral fibroblast inhibition, antigenically induced by the graft acting as a
foreign body, may have a role in the failure of graft incorporation by
preventing maturation and proliferation of perigraft fibroblasts
[1]. Populations susceptible to
humoral fibroblast inhibition production have not been defined.
Perigraft seromas in any vascular reconstruction are resistant to treatment
and prone to recurrence [1],
thereby posing further treatment dilemmas. Reported, usually unsuccessful,
treatments include aspiration, pseudocapsule resection, graft replacement, and
closed drainage [1]. Injection
of a sclerosing agent is not recommended because of the risk of graft
thombosis [2]. Nevertheless,
case reports of inserting microfibrillar collagen (the end product of mature
fibroblasts) into the space surrounding an axillobifemoral graft have
documented successful graft incorporation into the surrounding tissue with no
fluid reaccumulation [1]. We
know of only one case report that has described a surgical communication
between the seroma and the peritoneal cavity via a polytetrafluoroethylene
membrane that allows the fluid to drain; no recurrence had occurred in that
patient at 10 months after surgery
[7].
Although perigraft seromas have been documented only in open vascular
arterial grafts, we postulate that this finding may have relevance to
endoluminal stent-grafts. Increase in the size of the aneurysmal sac after
endoluminal exclusion of the aortic sac without apparent endoleak has been
documented [6,
8]. In the context of
endoluminal repair, ruptures have occurred in this situation
[8], and they are thought to be
caused by persistent intrasac pressure close to systemic arterial pressure.
This phenomenon is referred to as endotension—that is, continued sac
pressurization as documented via direct pressure lines in open surgery
[6]. Mechanisms leading to
increased sac volume in conjunction with endotension have not been fully
elucidated in the literature
[6]. We propose that increased
graft permeability, failure of graft incorporation into the native vessel
wall, and failure of perigraft fibrosis in the surrounding connective tissue
may be contributing factors, and we think that further research may be
indicated. White et al. [6]
noted a case of expanding aortic aneurysm despite the absence of demonstrable
endoleak of an endovascular abdominal aortic aneurysm repair. The endovascular
graft was replaced with an open graft. Endotension was confirmed at surgery
using a direct pressure line, and a gellike semiliquid thrombus, similar
macroscopically to a perigraft seroma, was noted around the graft. Therefore,
understanding the underlying pathogenesis of a perigraft seroma may aid in
finding a solution to this new treatment dilemma.
Our two patients who underwent open repair (Figs.
1A,1B,1C
and
2A,2B,2C,2D)
had minimal complications and mild symptoms, despite their having aneurysms
that were found on imaging to have increased in size. These outcomes are in
contrast to reports in the literature of endovascular graft rupture caused by
endotension [6].
In the absence of a clinical suspicion of graft infection, perigraft seroma
should be considered in the differential diagnosis of an aneurysmal sac that
increases in diameter after an open aortoiliac graft procedure. The expansion
may be noted incidentally on imaging, or it may be a cause of symptoms
reported by the patient. Its significance lies in its recognition, the
potential complications, and in the treatment dilemma. The underlying
pathogenesis may have relevance to the understanding of complications of
endoluminal aortic aneurysm repair. The apparent contrasting natural history
of aneurysm sac expansion in otherwise macroscopically successful open and
endoluminal aortic repairs is noted.
References
-
Ahn SS, Machleder HI, Gupta R, Moore WS. Perigraft seroma:
clinical, histologic, and serologic correlates. Am J
Surg 1987;154:173
-178[Medline]
-
Blumenberg RM, Gelfand ML, Dale WA. Perigraft seromas complicating
arterial grafts. Surgery
1985;97:194
-204[Medline]
-
Auffermann W, Olofsson PA, Rabahie GN, Tavares NJ, Stoney RJ,
Higgins CB. Incorporation versus infection of retroperitoneal aortic grafts:
MR imaging features. Radiology
1989;172:359
-362[Abstract/Free Full Text]
-
Kaupp HA, Matulewicz TJ, Lattimer GL, Kremen JF, Celani VJ. Graft
infection or graft reaction? Arch Surg
1979;114:1419
-1422[Medline]
-
Bhuta I, Dorrough R. Noninfectious fluid collection around velour
Dacron graft: possible allergic reaction. South Med J
1981;74:870
-872[Medline]
-
White GH, May J, Petrasek P, Waugh R, Stephen M, Harris J.
Endotension: an explanation for continued AAA growth after successful
endoluminal repair. J Endovasc Surg
1999;6:308
-315[Medline]
-
Williams GM. The management of massive ultrafiltration distending
the aneurysm sac after abdominal aortic aneurysm repair with a
polytetrafluoroethylene aortobiliac graft. J Vasc Surg
1998;28:551
-555[Medline]
-
Fillinger MF. Postoperative imaging after endovascular AAA repair.
Semin Vasc Surg
1999;12:327
-338[Medline]
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Introduction
Case Reports
