Volume 32, Issue 5 , Pages 542-544, November 2006
Intra Vascular Ultra Sound: One More Tool to Diagnose Aorto-duodenal Fistula
Article Outline
The incidence of aorto-enteric fistula in the first 5 years after abdominal aortic replacement ranges from 0.3 to 2%. We present a clinical case in which all conventional diagnostic tools failed to demonstrate the aorto-enteric fistula. A 73 year-old male suffering intermittent episodes of melena without signs and symptoms of infection was repeatedly admitted at our institution. All conventional diagnostic tools failed to show the bleeding source. Precise diagnosis was obtained using intra vascular ultrasound (IVUS). IVUS allowed prompt diagnosis of the aorto-duodenal fistula and opened the way to its endovascular treatment.
Keywords: Aortic aneurysm, Aorto-enteric-fistula, Intra vascular ultrasound, Stent
Introduction
Aorto-duodenal fistula (ADF) represents the most important cause of gastrointestinal bleeding in patients after synthetic graft replacement of the abdominal aorta.1, 2
Conventional diagnostic tools include gastroscopy, colonosocopy, selective angiography, radionuclide scanning, and recently an upper endoscopy with push enteroscopy and a wireless capsule endoscopy.3
However, because the bleeding can be intermittent and occasionally of small volume, in some patients it can be very difficult to clearly define the source of intestinal bleeding. Diagnosis is often made in the theatre with the patient in haemorrhagic shock. This approach dramatically increases patient mortality and morbidity.
We present a clinical case in which all conventional diagnostic tools failed to demonstrate the aorto-enteric fistula.
The only diagnostic instrument that allowed precise diagnosis of the origin of intestinal haemorrhage was the intra vascular ultra sound (IVUS).
Case Report
A 73 year-old male suffering intermittent episodes of melena without signs and symptoms of infection was repeatedly admitted at our institution. 15 years previously he had undergone synthetic graft replacement of the abdominal aorta. Over a period of nine months, we performed several investigations including gastroscopy, colonoscopy, angio MRI and wireless capsule endoscopy (Pillcam™ Capsule Endoscopy, Given imaging Ltd, Yoqneam, Israel) which all failed to show the bleeding source.
The recurrence of his symptoms warranted several further hospitalisations.
Finally, after 9 months, the presence of an aorto-duodenal fistula at the level of the proximal anastomosis of the aorto-bifemoral artery graft was suspected on abdominal CT (Fig. 1). However, this finding was not supported by further investigations like a red cell scintigraphy and abdominal angiography.
Fig. 1.
Suspicion of a aorto-duodenal fistula at the level of the proximal anastomosis of the aorto-bifemoral artery graft (arrow).
Suddenly the patient became hemodynamically unstable and we decided to take him to the operating room to perform an IVUS of the abdominal aorta under general anesthesia.
A 9 F introducer sheath was placed into the right femoral artery after systemic heparinization (Heparin 100
UI/kg).
An IVUS (Sonicath® Ultra™ 6 Fr/12MHz Imaging Catheter, Boston Scientific Corporation, MA, USA) of the abdominal aorta was performed and a lesion of the aortic wall, 8×6mm in length, 20mm distal to the left renal artery was identified. In this area, the classical 3 layers of the aortic wall disappeared, replaced by a single, thin layer of hyperechogenic tissue. Periaortic tissue was not clearly visualised, excepted for the presence of small amount of air, a few millimetres proximal to the lesion. This area was in continuity with the anastomotic line.
Matching clinical history with IVUS findings, we concluded that the aortic lesion was an AEF.
Renal arteries origin and graft bifurcation were identified and marked under fluoroscopic control. Vessel diameters were measured (24mm diameter) in order to select an appropriate endograft.
A Gore Aortic Extender® 28mm×3cm (PXA 280300, © 2006 W. L. Gore & Associates, Inc., Medical Products Division, Flagstaff, Arizona, USA) graft was deployed in such a way that the bare stent partially overlapped the origin of renal arteries and the covered part extended to 15mm distal to the anastomosis (Fig. 2).
Fig. 2.
Upper panel: IVUS clearly showed an aorto-duodenal fistula at the level of the proximal anastomosis, 8 by 6
mm diameter, 3cm distal to renal arteries (arrow). Lower panel: A Gore Excluder graft was deployed in such a way that the bare stent overlap renal arteries origin and the covered part extended to 15mm distal to the anastomosis (arrow).
Following the intervention, the patient recovered uneventfully without any evidence of infection of the endovascular graft and without any recurrence of bleeding.
Antibiotics (Metronidazole and Levofloxacinum) will be continued indefinitely.
Discussion
Massive GI bleeding is a known complication of aorto-duodenal fistula.4
The incidence of aorto-enteric fistula after an aneurysm repair is relatively frequent (0.3 to 2%) in the first 5 years,2 and associated with high mortality and morbidity.
This disorder should be suspected in all patients with massive upper gastrointestinal bleeding and a history of prosthetic vascular graft placement.
The initial bleeding is often transient and selflimiting, owing to the formation of thrombus.
Bouts of bleeding recur over a period of hours, days or weeks, eventually culminating in massive hemorhhage and hypovolemic shock.
Endoscopy is the procedure of choice for diagnosis and to exclude other causes of acute upper gastrointestinal bleeding, such as ulcers.
Endoscopic findings include a mucosal defect, a clot over the bleeding point, an extrinsic pulsatile mass in the distal duodenum and visible prosthetic graft wall.4
Abdominal CT scan, aortography, upper endoscopy with push enteroscopy and a wireless capsule endoscopy can be useful in confirming the diagnosis.
In the extremes cases exploratory laparotomy is indicated for patients with high suspicion of aortoenteric fistula and severe ongoing bleeding.
Surgical repair of the aortic fistula is the standard treatment regardless of the cause.
The standard treatment consist of replacing the synthetic graft with homograft or, removing the graft and carrying out an extra anatomic bypass.2, 5
Surgical reconstruction of the intestinal continuity and intravenous antibiotics are a part of the treatment as well. Surgical treatment is thus associated with high morbidity and mortality (25% to 90%) and may not feasible in patients with high risks for conventional surgery.
Endovascular repair of aorto-enteric fistulas seems to be a valid alternative to open surgery, at least to quickly control the intestinal bleeding. Previous studies have consistenly reported that transluminal endovascular grafting successfully obliterates the enteric fistula.7, 8, 9
The major problem with this technique is the high probability of prosthetic infection.
In fact the fistulous communication and the source of infection is not removed as in conventional surgery.
The diagnosis can be very difficult, as in this case, because the bleeding may be intermittent and diagnostic tools often fail to show aorto-duodenal fistula.
In this case report the only investigation that clearly demonstrated the diagnosis was IVUS performed in the operative room.
IVUS has been used to study arterial and vein conduit cross-sections since 1990 and nowadays it is considered the ideal tool to study vessel lumen, atherosclerotic lesions, thrombus, intimal flaps and wall motion. Moreover, its sensitivity and specificity are higher than those of others investigation tools like angiography and magnetic resonance imaging. In the case we presented, IVUS allowed prompt diagnosis of the ADF and opened the way to its endovascular treatment.6, 7, 8, 9 IVUS images we show in this article are not specific of aortic-enteric fistula (AEF) and, as far as we know, no specific criteria have been described in the literature. IVUS gives detailed information on vessel wall giving us the possibility to precisely study the lesion on the aortic wall and its relationship with adjacent tissue and organs.
In conclusion, the use of IVUS can help identify and monitor treatment of AEF.
References
- Secondary aortoenteric fistulae changes from 1973 to 1993. Eur J Vasc Endovasc Surg. 1996;11:425
- Secondary aortoenteric fistula: contemporary outcome with use of extranatomic bypass and infected graft excision. J Vasc Surg. 1995;21:184–196
- . A prospective study comparing video capsule endoscopy with double-balloon enteroscopy in patients with obscure gastrointestinal bleeding. Am J Gastroenterol. 2006;101:52–57
- . Aortoenteric fistulas. Arch Surg. 1992;127:1191–1194
- . Management of infected aortic grafts: development of less invasive surgery using cryopreserved homografts. Ann Thorac Surg. 1999;67:1986–1989
- . Palliative treatment of a secondary aortoduodenal fistula by stent graft placement. Thorac Cardiovasc Surg. 2000 Feb;48(1):41–42
- . Endovascular repair for aorto-enteric fistula: a bridge too far or a bridge to surgery?. Eur J Vasc Endovasc Surg. 2006;32:27–33
- Intravascular ultrasound imaging: in vitro validation and pathologic correlation. J Am Coll Cardiol. 1990;16:145–154
- . Endovascular repair of a presumed aortoduodenal fistula. Ann Thorac Cardiovasc Surg. 2005;11:424–428
PII: S1078-5884(06)00287-5
doi:10.1016/j.ejvs.2006.05.011
© 2006 Elsevier Ltd. All rights reserved.
Volume 32, Issue 5 , Pages 542-544, November 2006
