Investigations
A colonoscopy three weeks prior to admission, due to weight loss and
diarrhoea, showed a 4cm malignant-looking lesion in the sigmoid colon,
which was tattooed, and several diverticula but no obvious fistulas were
seen (Figure 1 ). Histopathological analysis of the sigmoid
lesion showed high-grade dysplasia.
An
urgent triple-phase computed tomography angiogram (CTA) showed a
ruptured pseudoaneurysm at the anastomotic junction of right aortoiliac
graft limb and common iliac artery, which appeared to fistulate into the
adjacent sigmoid colon. There was no obvious colonic metastatic disease
(Figure 2 A-C ).
Treatment
The patient was fluid
resuscitated according to our hospital’s massive transfusion protocol of
3000 units of Prothrombin Complex Concentrate (due to prolonged
prothrombin time), 2 units of packed red cells, 1 unit of fresh frozen
plasma, 1g tranexamic acid and 10mg of Vitamin K. Prophylactic
intravenous Piperacillin-tazobactam was administered, given the
likelihood of abdominal gut flora spreading onto the prosthetic
material. His Rivaroxaban and Methotrexate were withheld.
Following initial
stabilisation steps, and an urgent multidisciplinary team (MDT) meeting,
it was decided that he would benefit from a temporising endovascular
procedure to prevent further exsanguination, as a bridge to definitive
surgical management.
Ultrasound-guided, percutaneous retrograde Right Common Femoral Artery
access was secured, and an 8Fr sheath placed. The right internal iliac
artery (IIA) was embolised with Concerto coils (Medtronic, Watford, UK).
A 11x79mm balloon-mounted endoprosthesis (Viabahn VBX, Gore®, USA) was
then deployed across the pseudoaneurysm, spanning from Iliac limb graft
into the External Iliac Artery (Figure 3 ). After a period of
in-hospital stabilisation, the patient was discharged home as per his
wishes over the Christmas period, with a view to convalescence and
work-up for definitive surgery. He was prescribed oral Co-Amoxiclav
625mg TDS as a suppressive regime given the likely infected prosthetic
material. His Rivaroxaban and Methotrexate were withheld.
Colorectal MDT gave a
predictive staging of T4b, N0, M0 sigmoid cancer, and the colorectal
team advocated for an anterior resection with an end colostomy to
mitigate any life-threatening risks that might arise from an anastomotic
leak. The vascular surgery team proposed explantation of the aortoiliac
Y graft and reconstruction using autologous deep vein. Alternative
“fallback” options were discussed, including full or partial
explantation with extra-anatomical bypass (femoro-femoral or
axillo-femoral) or a more conservative approach with long-term
suppressive antibiotics.
Satisfactory performance on Cardiopulmonary Exercise Testing (CPET) and
Echocardiography gave objective support to the patient’s
cardiorespiratory fitness to proceed with complex major abdominal
surgery. Venous duplex ultrasound examination confirmed sufficient
superficial femoral vein (SFV) as potential autologous conduit for
arterial reconstruction. It was agreed that both the colorectal and
vascular components of surgery should happen simultaneously.
Soon after the New Year, the patient was reviewed in the vascular
surgery and colorectal outpatient Clinics, where the proposed operative
procedure, alternatives, risks and benefits were explained to the
patient and his wife. He expressed his wish to proceed, and a date for
surgery was fixed.
The patient underwent a joint procedure between the colorectal and
vascular teams, via midline laparotomy. The finding of a fistula between
right iliac limb anastomosis and the sigmoid colon was confirmed. The
colonic tattoo appeared remote from the area of corruption. There was
macroscopic impression of entire aortic graft involvement in an
infective/inflammatory process. The procedure entailed: i) sigmoid
colectomy with end colostomy, ii) right SFV harvesting and fashioning of
Pantaloon bifurcated graft, iii) AAA Y-graft explantation, debridement
of aortic sac, removal of Viabahn stent from CFA and arterial
reconstruction with the autologous SFV graft, anastomosed to infrarenal
aorta, the Left CIA origins, and Right EIA origin. iv) Omental coverage
of the graft via a fenestration in the transverse mesocolon.
Microbiological specimens were taken, including the prosthetic graft,
pseudoaneurysm sac and associated thrombus and Viabahn stent graft.
There were no intraoperative
complications during the procedure with an estimated blood loss of 2
litres over the 9-hour operation. The patient was transferred to the
intensive care unit (ICU) and extubated after 24 hours. Microbiology
results of the iliac stent graft demonstrated Citrobacter koseri, E.
coli, enterococcus faecium and bacteroides. The aortic graft material
showed evidence of E. coli and enterococcus faecium. Based on antibiotic
susceptibility, the patient was commenced on teicoplanin, ciprofloxacin,
and metronidazole, which were continued for 6-week course.
Outcome and
follow-up
The patient stayed in the ICU for 4 days before being stepped down to
the vascular ward for post-operative recovery totalling 30 days.
Postoperative complications included: i) ileus requiring total
parenteral nutrition for a period of 21 days, ii) hospital acquired
pneumonia, iii) wound dehiscence of the midline laparotomy 9 days
post-operatively requiring an emergency relook laparotomy and primary
closure, iv) right cerebellar embolic-type infarction 25 days
post-operatively; patient continued on Rivaroxaban and did not require
any further interventions given no focal neurological abnormalities and,
v) seroma in patient’s right thigh secondary to vein harvesting which
was treated conservatively with compression stocking.
Histopathology results of the sigmoid colectomy diagnosed a moderately
differentiated adenocarcinoma pT3, pN0, pMx, R0, with clear resection
margins. Interestingly it also showed that diverticular disease was the
most likely cause for the focal fistula, and was therefore completely
unrelated to the tumour.
The patient went on to make a full recovery and was discharged home to
complete the antibiotic regime. His methotrexate was eventually changed
to an IL-23 inhibitor given the association between methotrexate and
malignancy. On follow up 3- and 6- months, the patient has made a full
recovery and remains clinically well. Surveillance colonoscopy, serum
carcinoembryonic antigen (CEA) levels and CT scans were arranged as an
outpatient according to NICE guidelines for follow up of colorectal
cancer.
Discussion
This case report is the first case in literature describing an Iliac
Artery Graft-Enteric fistula on the background of sigmoid cancer and
diverticular disease. The acute endovascular ‘bridging’ procedure
followed by planned definitive surgical intervention proved to be
successful in the management of such complex and potentially
life-threatening pathology.
Primary ArEFs are rarer than secondary ArEF, with an incidence of only
0.04-0.07%, compared to the 0.36-1.6% risk of developing a secondary
ArEF after surgical treatment of aortic disease [7,10,11].
Encountering iliac artery-sigmoid fistulas in literature is rare,
however the majority involve patients with a history of atherosclerotic
aneurysm, pelvic malignancy or radiation [8,12]. An interesting
feature of this particular case is the potential culprits that could
have played a role in the development of a fistula; including
diverticular disease, colorectal cancer and a difficult colonoscopy.
It is the authors’ hypothesis that the patient developed tethering of a
diverticular segment of sigmoid colon onto the graft- Right CIA.
Colonoscopic investigation of the Red-Flag colonic cancer symptoms may
have precipitated fistulation and pseudoaneurysmal degeneration, but
this is difficult to be certain of, and may have happened in any case.
Histopathological analysis provided evidence of a diverticula being
directly involved in fistula formation, and therefore was definitely a
catalyst in the pathological process. Colorectal tumours are also
associated with the development of fistulas [13], allowing us to
assume that the adenocarcinoma may have influenced its formation via
direct forces and inflammatory mechanisms. Colonoscopies don’t have any
direct correlating evidence in the pathophysiological development of
ArEF, however khalaf et al. outlined a case report of a patient
with an AEF into the sigmoid colon, which interestingly presented with
lower GI bleeding during a colonoscopy procedure [14]. In fact,
colonoscopies have been associated with increased risk of rectocutaneous
fistulas, which involves a similar pathophysiological process as ArEF
[15]. The presentation of ArEF is associated with a triad of
gastrointestinal bleeding, abdominal pain and a palpable abdominal mass
- however studies have shown that this is seen in only 11% of cases
[16].
CTA is the gold standard for
initial assessment, with a reported sensitivity of 94% and specificity
of 85% in recognising ArEFs. After initial resuscitation with fluids
and oxygen, this patient was able to tolerate the investigation in order
to aid diagnosis and formulate a strategy in management. The results of
said investigation proved a high risk of death by exsanguination from
the bleeding right CIA, and thus required immediate action to exclude
the fistulous tract. Over the last few years, we have seen an emergence
of endovascular techniques used for haemodynamic stabilisation, control
of sepsis, bridge to definitive surgical repair and palliation for those
at risk of major surgery. Danneel et al. have suggested using
this ‘bridging’ procedure for all those with IEF who are considered
high-risk for open repair [17]. We adopted this approach in the
acute setting given that the CIA was a good target for endovascular
stenting and that the patient would benefit from a period of
stabilistion and planning for major complex definitive procedure to
treat both the graft infection and sigmoid tumour. As a result, this
time-saving approach has allowed for the patient to recover from the
haemodynamic compromise, undergo preoperative investigations and have
reduced risks from both local and systemic infection [17-19]. Given
the assumption that the aorto bi-iliac graft was infected due to contact
with the gut microbiota, the “gold-standard” of complete explantation
and reconstruction with autologous venous conduit was considered the
preferred approach [20, 21]. Numerous studies have found better
outcomes when using autologous vein grafts rather than further synthetic
graft material during reconstruction. Cryopreserved allografts, silver
coated grafts, rifampicin bonded polyester grafts, or bovine pericardium
are alternative options, but considered inferior to autologous deep vein
in this case [22- 28].