Emergency Radiology (2004) 11: 100–103 DOI 10.1007/s10140-004-0375-y
CASE REPORT
Bruno Coulier Æ Odile Tilquin Æ Pierre-Yves Etienne
Multidetector row CT diagnosis of aortocaval fistula complicating aortic aneurysm: a case report
Received: 4 June 2004 / Accepted: 23 August 2004 / Published online: 29 October 2004 ASER 2004
Abstract Aortocaval fistula is a rare complication of abdominal aortic aneurysm involving less than 1% of all abdominal aortic aneurysms and causing severe hemodynamic derangements from a large left-to-right shunt; early diagnosis and repair results in improved morbidity and lower mortality but the diagnosis is difficult. We report a case of prompt diagnosis obtained with thoracoabdominal aortic multidetector row angio-CT as the first imaging procedure and allowing immediate surgical repair. Our report emphasizes the crucial role played by multidetector row CT as the first procedure in thoracoabdominal vascular emergencies. Keywords Aortocaval fistula Æ Aortic abdominal aneurysm Æ Aorta,CT
Introduction Aortocaval fistula is a rare but life-threatening complication of abdominal aortic aneurysm, the diagnosis of which is difficult but essential because early diagnosis and repair result in improved morbidity and lower mortality. We report a case of prompt and convincing diagnosis obtained with thoracoabdominal multidetector row angio-CT (MDCT) as the first imaging procedure. This case emphasizes the new crucial role currently
B. Coulier (&) Department of Diagnostic Radiology, Clinique St Luc, Rue St Luc 8, 5004 Bouge (Namur), Belgium E-mail:
[email protected] Tel.: +32-81-209741 Fax: +32-81-209765 O. Tilquin Department of Emergency, Clinique St Luc, Rue St Luc 8, 5004 Bouge (Namur), Belgium P.-Y. Etienne Department of Thoracic Vascular Surgery, Clinique St Luc, Rue St Luc 8, 5004 Bouge (Namur), Belgium
played by MDCT as the preferred method for imaging in most acute thoracoabdominal vascular conditions.
Case report A 73-year-old patient presented in the emergency room with complaints of shortness of breath and pain radiating into the left arm, mandible, and upper lumbar spine; these symptoms developed half an hour before admission and were accompanied by vertigo, nausea, and intense sweating. The patient also reported pain in his legs that had developed and increased during the previous few days. One month before, the patient had experienced transient ischemic cerebral attack with reversible paresis of the left arm and speech disturbances. Hypertension, hypercholesterolemia, and chronic active smoking were also present. At physical examination the patient had marbled bluish-mottled lower extremities. Iliac pulsations were present but peripheral ankle and feet pulsations were attenuated. Sinus tachycardia was present at 110 beats/ min; tensional asymmetry was measurable with 9/4 on the left and 12/5 on the right. ECG showed ST depression in leads to V3 to V6. Abdominal examination revealed a pulsatile mass accompanied by an audible systolodiastolic murmur. The patient was immediately sent to the department of medical imaging for thoracoabdominal MRCT with high suspicion of aortic dissection or aneurysm rupture. A complete thoracoabdominal MRCT was immediately performed with a 16-row multisclice CT (Lightspeed Ultra, General Electric, Wis.); data were obtained during a single breath-hold of 22 s duration extending from the base of the neck to the inguinal areas; the scan parameters were: 16·1.25 mm collimation, pitch 1.35:1, speed 13.5 mm/rot, tube rotation 0.5 s, 120 kV, 410 mA, reconstruction time about 0.15 s/slice. A total of 120 ml of nonionic contrast material (Ultravist 350, Schering, Berlin, Germany) was injected with a flow rate of 4 ml/s through an 18-G access in the cubital vein and
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the scan was started using the Smart Prep bolus technique for monitoring peak arrival of the contrast in the aortic crossa (delay ±20 s). A complete diagnosis was obtained almost ‘‘in real time’’ and the patient was immediately sent to the department of thoracic vascular surgery to be operated on only about 30 min later. Data were reviewed on a workstation (Advantage Workstation 4.1, General Electric, Wis.) with multiplanar reformatting (MPR), maximum intensity projection (MIP) and volume rendering (VR). The patient was found to have a 7-cm-diameter infrarenal calcified aortic aneurysm immediately followed by another 7-cm-diameter calcified aneurysm of the right primitive iliac artery. The aortic aneurysm had spontaneously and directly fistulized into the inferior vena cava through a well-identifiable 1-cm right posterolateral hole situated in the distal part of the aneurysm about 1 cm into the transitional zone between the aortic and iliac aneurysms (Figs. 1b,c, 2). The early synchronous and equivalent enhancement of the inferior vena cava and aorta accompanied by the dilatation of the vena cava were the cardinal diagnosis signs (Fig. 1a). Accessory signs were the attenuated nephrography (Fig. 1a) and the delayed opacification of the femoral veins, which were probably due to venous congestion. These signs were corroborated by the patient’s bluish-mottled cyanotic legs and renal insufficiency with creatinine level of 3.6 mg/100 ml. The patient underwent emergency laparotomy. The aortic aneurysm was surgically dissected and a plicature of the aortic wall was used to shut the aortocaval fistula. The arterial continuity was reestablished with aortobifemoral synthetic graft. The postoperative complications were dominated by perioperative myocardial ischemia (with elevation of troponine at 25 ng/ml, creatine phosphokinase at 11 mU/ml, and creatine kinase-MB at 71 ng/ml) and persistent renal insufficiency with creatinine levels varying from 3.5 to 5.4 mg/100 ml. The patient was discharged from the intensive care unit after 6 days.
Discussion Fistulas between the abdominal aorta and the inferior vena cava are rare. This complication is observed in less than 1% of all abdominal aortic aneurysms and 3–4% of ruptured aneurysms [1, 2]. Most abdominal aortic aneurysms rupture either into the retroperitoneum or into the peritoneal cavity. Rupture into the vena cava, the duodenum, the iliac vein, or the left renal vein is very rare [2]. In 80% of cases the rupture is spontaneous and most of the fistulizing aneurysms are atherosclerotic in nature; several cases have also been reported in association with syphilitic, mycotic, and other aneurysm-forming conditions such as Marfan’s syndrome, Elhers–Danlos disease, and Takayasu’s arteritis; neoplastic erosions
Fig. 1 a Axial MIP view at the level of the renal arteries: during the arterial phase the vena cava appears simultaneously isodense with the adjacent aorta and the renal cortical nephrography is considerably reduced. b Coronal MIP reconstruction showing a 7-cm-diameter infrarenal calcified aortic aneurysm (AO) immediately followed by another 7-cm-diameter calcified aneurysm of the right primitive iliac artery (RPI). The aortic aneurysm directly fistulizes into the inferior vena cava through a well-identifiable 1-cm right posterolateral communication situated in the distal part of the aneurysm (arrow). c Axial MIP at the level of the direct aortocaval communication (arrow)
from adjacent malignancy have also been reported. The great majority of affected patients are men in their seventh and eighth decades of life [2]. The remaining 20% of cases are traumatic resulting from stab or gunshot wounds or, rarely, from blunt trauma. Occasional cases may be iatrogenic resulting from disk surgery or cardiac catheterization [1, 3].
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Fig. 2 a Craniocaudal virtual vascular endoscopic view of the ectatic distal aorta showing the fistulous communication between the aorta and the vena cava (arrow). b Caudocranial virtual vascular endoscopy of the vena cava showing the penetrating aortic fistula (arrow)
The typical clinical triad for abdominal aneurysm with aortocaval fistula consists of severe low back or abdominal pain, pulsatile abdominal mass, and machinery-like abdominal bruit. This triad is complete in only 50–80% of patients; the first symptom was lacking in our patient and the abdominal bruit was detected only retrospectively after MRCT diagnosis [1]. Other clinical signs are various and essentially represent consequences of the physiologic derangements of the fistula and the left-to-right shunt [1, 3, 4]: a largevolume left-to-right shunt causes increased venous return leading to venous hypertension and then to passive venous congestion, hepatomegaly, ascites, or severe induced portal hypertension resulting in upper gastronintestinal bleeding [1, 2]. When arterial aneurysm proximally compresses the caval venous return, marked regional venous hypertension may occur, including in 60–70% of patients marked lower-extremity edema with cyanosis and pulsatile venous dilatation and scrotal edema [2]; other manifestations of regional venous
engorgement in various organs may include priapism, rectal bleeding, and vesical bleeding (40–50%). Renal failure is not uncommon and is thought to be due to diminished renal perfusion from decreased diastolic arterial pressure associated with increased venous pressure in the renal veins [1, 5]. This renal insufficiency generally normalizes after successful surgery [5]. Another important hemodynamic consequence is the decreased peripheral resistance (causing diastolic hypotension) that induces a sharp secondary increased cardiac output, a situation that can rapidly lead to left ventricular high-output cardiac failure, especially if there is underlying cardiac disease [4]. Finally, paradoxical pulmonary embolus is another rare complication, during which the embolus originating within the aneurysmal sac migrates in the vena cava. Our patient presented with mixed symptoms combining signs of cardiac failure resulting from increased cardiac output, symptoms of peripheral venous hypertension (marbled painfull legs), and renal failure. Preoperative diagnosis of an aortocaval fistula complicating an aneurysm is difficult because the classical clinical triad—severe abdominal/flank pain, abdominal bruit, and pulsatile abdominal mass—may be absent in up to 50% of cases and may be masked by less specific additional symptoms such as dyspnea, cardiac failure, pain and edema of the legs, or various hemorrhagic complications [1, 3, 6]. A large spectrum of acute thoracoabdominal conditions may be evoked: pulmonary embolism, primary cardiac failure, aortic aneurysm rupture, aortic dissection, and various other acute abdominal conditions. A quick diagnosis is nevertheless of prime importance because prompt surgical treatment is critical and contributes to decreased morbidity and mortality [1]; the operative mortality is about 30% and appears to be no greater than that seen with ruptured abdominal aortic aneurysms in general [2]. The surgical outcome is also heavily influenced by the extent and the duration of the preoperative hemodynamic alterations—acute blood loss, myocardial infarction, coagulopathy, and renal failure. The most common causes of death include myocardial infarction, pulmonary emboli, and pneumonia [1]. In the past decade, great strides have been made in the development of helical CT that have led to shorter scanning time and higher spatial resolution. Higherquality CT examinations result from decreased respiratory misregistration, enhanced intravenous contrast material opacification of vascular structures and parenchymal organs, a greater flexibility in image reconstruction, and improved multiplanar and three-dimensional reformations [7, 8]. Today many traditional emergency imaging procedures have been supplanted by these newer helical CT techniques that can be performed in less time and with greater accuracy, less patient discomfort, and decreased cost [7]. The speed of MRCT now permits CT examination of seriously ill patients in the emergency department, and a
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wide range of traumatic and nontraumatic emergent conditions may be quickly and accurately diagnosed. MRCT angiography has become the preferred method for imaging in emergent abdominal vascular conditions because it enables the acquisition of high-spatial-resolution volumetric image data during a single breathhold, not only depicting the vessels but also allowing assessment of perfusion in adjacent organs [8]; moreover, the delay between imaging and diagnosis is considerably reduced by avoiding the transfer of patients for catheter angiography. CT findings of aortocaval fistula typically include the early detection of the contrast medium in the dilated vena cava, which appears simultaneously isodense with the adjacent aorta, an associated aortic aneurysm, loss of the normal anatomic space between the aorta and the vena cava, and occasionally direct visualization of the abnormal communication between the two vessels [2, 4, 5, 6, 9]. In our patient an additional sign was the delayed opacification of the renal cortex, probably due to the association of reduced renal perfusion owing to decreased diastolic arterial pressure associated with increased venous pressure in the renal veins. Delayed opacification of the femoral veins was also present, probably due to venous congestion.
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