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Type II Endoleak after Endoaortic Graft Implantation: Diagnosis with Helical CT Arteriography¹

¹ From the Departments of Radiology (V.C., A.M.R., J.C., Z.J.R., M.P.L.) and Surgery (F.J.V.), Albert Einstein College of Medicine and Montefiore Medical Center, 111 E 210th St, Bronx, NY 10467; and Department of Radiology, Hamilton General Hospital, East Hamilton, Ontario, Canada (M.P.). Received June 16, 2005; revision requested August 18; revision received September 9; accepted October 14; final version accepted December 15. Address correspondence to V.C. (e-mail: vichka17{at}hotmail.com).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 
Purpose: To retrospectively assess endoleak shapes and locations within aneurysms to differentiate type II from type I and type III endoleaks.

Materials and Methods: The institutional review board granted an exemption for this HIPAA-compliant study; patient informed consent was not required. A retrospective review of arterial phase helical computed tomographic (CT) studies and medical records was performed for 39 patients (29 men, 10 women; age range, 60–89 years; mean, 78.5 years) who had an endoleak after endoaortic graft implantation for treatment of abdominal aortic aneurysm and who subsequently underwent angiography (n = 25), surgery (n = 8), or long-term follow-up (n = 6) to classify their endoleak into a specific type. At CT, endoleak shape (tubular or nontubular) and location (central or peripheral) were recorded. An endoleak was classified as type II if it contained a peripheral tubular component (PTC) near the aortic wall, with or without an identifiable feeding vessel. Endoleaks without these features were classified as type I or III. The Fisher exact test was used to assess associations between CT findings and endoleak type.

Results: There were 22 type II and 17 type I or III endoleaks. CT enabled correct identification of 22 (100%) of 22 type II endoleaks, all of which contained a PTC. Of 17 type I or III endoleaks, only two (12%) contained a PTC and were misclassified as type II endoleaks; the remaining 15 (88%) were correctly classified. Overall, CT enabled correct identification of endoleaks as type II or type I or III in 37 (95%) of 39 patients. PTCs were significantly more common (P < .001) in type II than in type I or III endoleaks, with a sensitivity, specificity, accuracy, negative predictive value, and positive predictive value of 100%, 88.2%, 94.9%, 100%, and 91.7%, respectively.

Conclusion: A PTC is a statistically significant predictor of type II endoleak in most patients.

© RSNA, 2006

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 
Endoleak frequently complicates endovascular repair of abdominal aortic aneurysm, occurring in 15%–37% of patients (1–4). Detection of endoleaks is performed with contrast material–enhanced helical computed tomography (CT), which is routinely used to follow up patients treated with endovascular grafts (EVGs) and is considered to be an effective method (1,5–8). After an endoleak is detected, further patient care often depends on the specific type of the leak.

Four types of endoleaks are recognized by the Society for Vascular Surgery and the American Association for Vascular Surgery (9). Type I endoleaks originate at the ends of the graft, type III endoleaks result from disruption of the body of the graft or detachment of its components, and type IV endoleaks result from graft porosity (9). Skillern et al (10) suggest that endotension, which is defined as aneurysm sac enlargement without a definable endoleak on imaging studies, represents a type V endoleak. Considering that type V is not identifiable with current imaging modalities and type IV is exceedingly rare, the majority of endoleaks seen in clinical practice are type I, II, or III, with type II leaks being most common (11).

Type II endoleak differs from other types in both its mechanism and its clinical behavior. It results from retrograde flow into the aneurysm sac via the aortic branches and is believed to be unrelated to the graft itself, although some devices have been reported to have very low rates of endoleaks at 6 months (12). On the other hand, type I and III endoleaks occur due to factors involved in a less than optimal initial placement of the EVG, including graft missizing and structural failure, as well as from subsequently occurring graft migration and attachment zone dilatation (13,14). Type II endoleak is considered more benign and can be treated conservatively when the aneurysm sac is decreasing or stable in size, while graft-related endoleaks (types I and III) usually require expeditious treatment (15). Thus, noninvasive recognition of type II endoleaks, as well as noninvasive differentiation of type II from type I and III endoleaks, is desirable.

In many practices, angiographic evaluation is required to clarify the nature of an endoleak. To our knowledge, to this date there are no reliable CT criteria for the specific endoleak types except for direct visualization of a feeding artery, which is indicative of a type II endoleak. In our daily practice, we noticed that a number of patients have a channel-like endoleak that is often located near the aortic wall. Thus, the purpose of our study was to retrospectively assess endoleak shapes and locations within aortic aneurysms to differentiate type II from type I or III endoleaks.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 
Patients
For this retrospective review, we used a data set that had been created for an original investigation of aortic EVGs and that was approved by the institutional review board of Albert Einstein College of Medicine and Montefiore Medical Center. All patients in the study had already signed an informed consent form that allowed future retrospective review of their medical records. The institutional review board granted us an exemption for our retrospective study; additional patient informed consent was not required. Our study was in compliance with the Health Insurance Portability and Accountability Act.

Between 1993 and 2004, 381 patients had undergone endovascular repair of abdominal aortic aneurysm at Montefiore Medical Center. Of these patients, 65 (17.1%) had been given a diagnosis of endoleak that was detected with angiography, CT, or a combination of these modalities. Twenty-two of these patients were excluded from this study because of the following reasons: lack of contrast-enhanced CT examination (n = 8), lack of both confirmatory reference-standard evidence (from angiography or surgery) and long-term follow up (n = 4), endoleak detected but type not classified at angiography (n = 3), and negative angiogram (n = 7). In addition, we excluded patients with endoleaks that were demonstrated only on delayed CT images (n = 4) because these leaks were presumed to represent low-flow type II endoleaks (16).

Our study included 39 patients who had an endoleak that was demonstrated at CT. For these 39 patients, the type of endoleak was definitively diagnosed at angiography in 25, at surgery in eight, and after results of long-term clinical and of CT follow-up of at least 12 months showed either resolution of endoleak or persistent endoleak with stability or reduction in size of the aneurysm sac in six. In the latter group, a confirmatory reference-standard examination was not performed because of interval improvement or stability of the CT findings, a situation not expected with type I or type III endoleaks (4,17); therefore, these patients were presumed to have a type II endoleak.

The study group consisted of 29 men and 10 women between 60 and 89 years of age (mean, 78.5 years). Preoperatively, the aneurysms ranged from 4.6 to 9.0 cm in diameter (mean, 6.0 cm). The EVGs used in these patients included tube grafts (n = 5), aortounifemoral grafts (ie, grafts that extend from the aorta into one of the femoral arteries) (n = 8), and bifurcated grafts (n = 26) (Table 1).

In the six of 22 patients with type II endoleak who were followed up clinically, the length of follow-up ranged from 12 to 54 months (mean, 36.7 months). Four of these six patients (67%) had an early endoleak that was detected within 1 month of repair. Two endoleaks (33%) developed 5 and 9 months after repair. Resolution of the endoleak was seen in four of these six patients (67%). The time between endoleak emergence and resolution ranged from 1.5 to 40 months (mean, 14.4 months). The patient whose endoleak resolved in 40 months demonstrated a stable sac size over this time; the sac remained stable in size over a subsequent 14 months of follow-up. In the two patients who had persistent endoleak, the excluded aneurysm sac was stable over a period of 23 and 16 months.

CT Imaging
CT of the abdomen and pelvis was performed with a single–detector row scanner (HiSpeed Advantage; GE Medical Systems, Milwaukee, Wis) in 23 patients and with a four–detector row scanner (LightSpeed Advantage; GE Medical Systems) in 16 patients. Unenhanced helical CT was performed through the entire endovascular device by using a collimation of 5–7 mm and a pitch of 1.0–1.5 reconstructed to 5-mm intervals or by using incremental CT with 10-mm collimation and 10-mm intervals. Then, iohexol 300 (Omnipaque 300; Sanofi-Winthrop, New York, NY) was administered with a single uniphasic power injection at a rate of 3–4 mL/sec to a total of 100–150 mL, with a scan delay of 25–45 seconds.

Early in our experience (between 1993 and 1996), an injection-to-scan delay was calculated by using a time-attenuation curve that was derived from a test scan obtained after intravenous administration of a 20-mL bolus of contrast material. Later, this technique was reserved for patients with cardiomegaly and known congestive heart failure. In the majority of patients between 1996 and 1999, an empiric estimate of the scan delay of 25–30 seconds was used. Since 2000, we have employed an automated bolus-tracking technique.

With the single–detector row scanner, images were acquired by using 280–310 mA, 120 kVp, a collimation of 3 mm, and a pitch of 2; images were retrospectively or prospectively reconstructed at 1.5-mm intervals. With the four–detector row scanner, 280–300 mA and 120 kVp were used to acquire 2.5-mm images with pitch of 6 that were prospectively reconstructed to a thickness of 1 mm. Delayed CT scanning was performed 100–130 seconds after the intravenous injection of contrast material, with 5-mm collimation and a pitch of 1.5 for the single–detector row scanner and 6.0 for the four–detector row scanner; images were reconstructed to 5-mm intervals.

Image Analysis
Images were prepared for review by one radiologist with 9 years of experience in interpreting body CT scans (Z.J.R.); this radiologist also recorded the technical quality of each examination as excellent, good, satisfactory, or inferior. A study was graded as excellent when there was maximal vascular enhancement with sharply outlined aortic branches—including lumbar arteries, extraparenchymal renal artery branches, and mesenteric artery branches—as well as no image noise. Maximal enhancement was defined as the highest vascular attenuation that was achievable with our technique, as judged by visual inspection. Good-quality studies had less than maximal vascular enhancement but sharply outlined aortic branches—including lumbar arteries, extraparenchymal renal artery branches, and mesenteric artery branches—and no image noise. Satisfactory studies had less than maximal vascular enhancement but sharply outlined aortic branches—including lumbar arteries, extraparenchymal renal artery branches, and mesenteric artery branches—and had some image noise caused by the patient's large body habitus. A study was graded as inferior when it did not fulfill any of the above criteria.

All CT scans were retrospectively reviewed in consensus at a computer workstation by two of three radiologists (A.M.R. with M.P. or V.C.; A.M.R., M.P., and V.C. have 20, 5, and 3 years of experience, respectively, in interpreting body CT scans) who were blinded to angiographic, surgical, and other follow-up results. The shape and location of endoleaks were recorded. The shape of endoleaks was classified as tubular (when it appeared channel-like) or nontubular. The location of the endoleak was categorized as central, peripheral, or combined (both central and peripheral), depending on the position of its components relative to the EVG and the aortic wall. The location of an endoleak was deemed central if it was abutting or conforming to the graft or was seen within the aneurysm sac at a distance from the wall; it was deemed peripheral when at least a portion of an endoleak was adjacent to the wall without a gap or with a gap that did not exceed 2 mm. In all endoleaks, we searched for a peripheral tubular component (PTC) located near the aortic wall (Figs 1, 2). We also recorded the presence of a feeding vessel, which was defined as a contrast material–filled aortic branch directly contiguous to the abdominal aortic aneurysm sac (Fig 3).

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: Type II endoleak in patient with bifurcated EVG. (a) Transverse CT image shows short tubular contrast material–filled channel (arrow) along posterior aortic wall. (b) Transverse CT image 12 mm caudal to a shows an additional nontubular contrast material collection (arrow) within the sac. (c) Anteroposterior digital subtraction angiogram shows contrast material (arrowhead) entering the aneurysm sac via an iliolumbar collateral vessel (solid arrow). Note catheter in a branch of the right common iliac artery (open arrow).

View larger version (125K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: Type II endoleak in patient with bifurcated EVG. (a) Transverse CT image shows short tubular contrast material–filled channel (arrow) along posterior aortic wall. (b) Transverse CT image 12 mm caudal to a shows an additional nontubular contrast material collection (arrow) within the sac. (c) Anteroposterior digital subtraction angiogram shows contrast material (arrowhead) entering the aneurysm sac via an iliolumbar collateral vessel (solid arrow). Note catheter in a branch of the right common iliac artery (open arrow).

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: Type II endoleak in patient with bifurcated EVG. (a) Transverse CT image shows short tubular contrast material–filled channel (arrow) along posterior aortic wall. (b) Transverse CT image 12 mm caudal to a shows an additional nontubular contrast material collection (arrow) within the sac. (c) Anteroposterior digital subtraction angiogram shows contrast material (arrowhead) entering the aneurysm sac via an iliolumbar collateral vessel (solid arrow). Note catheter in a branch of the right common iliac artery (open arrow).

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: Type II endoleak in patient with tube EVG. (a) Transverse CT image shows long contrast material–filled channel (arrow) near aortic wall. (b) Anteroposterior digital substraction angiogram shows the endoleak (arrowhead) in continuity with the lumbar artery (arrow).

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: Type II endoleak in patient with tube EVG. (a) Transverse CT image shows long contrast material–filled channel (arrow) near aortic wall. (b) Anteroposterior digital substraction angiogram shows the endoleak (arrowhead) in continuity with the lumbar artery (arrow).

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 3a: Type II endoleak directly contiguous to inferior mesenteric artery. (a) Transverse oblique reformatted CT image shows continuity of inferior mesenteric artery (arrowhead) with a tubular component (white arrow) of the endoleak. A nontubular component (black arrow) of the endoleak is seen in posterior aspect of the sac. g = EVG limb. (b) Anteroposterior angiogram obtained with superselective catheterization through superior mesenteric artery (arrowhead) shows collateral filling of inferior mesenteric artery with retrograde flow (arrow) into the aneurysm sac.

View larger version (145K): [in this window] [in a new window] [Download PPT slide]   Figure 3b: Type II endoleak directly contiguous to inferior mesenteric artery. (a) Transverse oblique reformatted CT image shows continuity of inferior mesenteric artery (arrowhead) with a tubular component (white arrow) of the endoleak. A nontubular component (black arrow) of the endoleak is seen in posterior aspect of the sac. g = EVG limb. (b) Anteroposterior angiogram obtained with superselective catheterization through superior mesenteric artery (arrowhead) shows collateral filling of inferior mesenteric artery with retrograde flow (arrow) into the aneurysm sac.

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 4a: Type I endoleak in patient with tube EVG. (a) Transverse and (b) coronal reformatted CT images show large collection of contrast material (solid arrow) abutting the distal end of the tube EVG (arrowhead) and extending to the aortic wall (open arrow) without a tubular component. (c) Anteroposterior digital subtraction angiogram confirms presence of type I endoleak (arrow) at distal end of the EVG (arrowhead).

View larger version (96K): [in this window] [in a new window] [Download PPT slide]   Figure 4b: Type I endoleak in patient with tube EVG. (a) Transverse and (b) coronal reformatted CT images show large collection of contrast material (solid arrow) abutting the distal end of the tube EVG (arrowhead) and extending to the aortic wall (open arrow) without a tubular component. (c) Anteroposterior digital subtraction angiogram confirms presence of type I endoleak (arrow) at distal end of the EVG (arrowhead).

View larger version (94K): [in this window] [in a new window] [Download PPT slide]   Figure 4c: Type I endoleak in patient with tube EVG. (a) Transverse and (b) coronal reformatted CT images show large collection of contrast material (solid arrow) abutting the distal end of the tube EVG (arrowhead) and extending to the aortic wall (open arrow) without a tubular component. (c) Anteroposterior digital subtraction angiogram confirms presence of type I endoleak (arrow) at distal end of the EVG (arrowhead).

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 5a: Type III endoleak in patient with bifurcated EVG. (a) Transverse CT image shows large central contrast material collection (arrow) surrounding right limb of the EVG and extending to right posterolateral aortic wall. This is consistent with type I or III endoleak, according to CT criteria. (b) Anteroposterior digital subtraction aortogram shows large endoleak (arrow) surrounding right EVG limb. (c) Anteroposterior selective digital subtraction angiogram with catheter tip in left limb of the EVG shows origin of the endoleak from the left limb EVG defect (arrow). Arrowheads = unenhanced right limb.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 5b: Type III endoleak in patient with bifurcated EVG. (a) Transverse CT image shows large central contrast material collection (arrow) surrounding right limb of the EVG and extending to right posterolateral aortic wall. This is consistent with type I or III endoleak, according to CT criteria. (b) Anteroposterior digital subtraction aortogram shows large endoleak (arrow) surrounding right EVG limb. (c) Anteroposterior selective digital subtraction angiogram with catheter tip in left limb of the EVG shows origin of the endoleak from the left limb EVG defect (arrow). Arrowheads = unenhanced right limb.

View larger version (75K): [in this window] [in a new window] [Download PPT slide]   Figure 5c: Type III endoleak in patient with bifurcated EVG. (a) Transverse CT image shows large central contrast material collection (arrow) surrounding right limb of the EVG and extending to right posterolateral aortic wall. This is consistent with type I or III endoleak, according to CT criteria. (b) Anteroposterior digital subtraction aortogram shows large endoleak (arrow) surrounding right EVG limb. (c) Anteroposterior selective digital subtraction angiogram with catheter tip in left limb of the EVG shows origin of the endoleak from the left limb EVG defect (arrow). Arrowheads = unenhanced right limb.

Statistical Analysis
Sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for each CT finding were calculated manually by using standard statistical formulas. The association between individual CT findings and the type I or III and type II endoleak groups was assessed for significance by using software (SAS, version 9.1.2; SAS Institute, Cary, NC). The Fisher exact test was applied because for each comparison at least one expected cell frequency was less than five. A P value of less than .05 was considered to indicate a significant difference.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 
Technical Quality
Technical quality of the examination was graded as excellent, good, satisfactory, and inferior for 13 (33%), 20 (51%), six (15%), and zero (0%) patients, respectively.

Endoleak Type
On the basis of angiographic, surgical, and medical records data, there were 22 (56%) type II and 17 (44%) type I or III endoleaks. CT correctly revealed all 22 (100%) type II endoleaks, all of which contained a PTC. A tubular component of an endoleak (Table 2) was associated with additional nontubular contrast material collections in seven (32%) of the 22 patients with type II endoleaks. Type II endoleaks were purely peripheral in location in 12 (55%) patients, and all of these leaks were small. In the remaining 10 (45%) patients, there was an additional central collection of contrast material, which was small, medium, and large in eight, one, and one endoleak, respectively. Overall, of 22 type II endoleaks, 20 (91%) were small. A feeding vessel was demonstrated in four (18%) type II endoleaks.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 
Any endoleak indicates continued perfusion of the aneurysm and therefore may lead to its progressive expansion. However, type I or III endoleaks are more commonly associated with enlargement of the aneurysm sac than are type II endoleaks (4,17) because the former result in persistent exposure of the aneurysm sac to high systemic pressure, which predisposes the patient to aneurysm sac rupture (6,18). Van Marrewijk et al (4) found that type I or III endoleaks correlate with a higher risk of aneurysmal rupture than do type II endoleaks or the absence of endoleaks.

Because of the associated risk of rupture, patients with type I or III endoleak are treated promptly, usually with reintervention or, less frequently, with open surgical conversion (3,6,19,20). Although in type II endoleaks, retrograde flow produces a smaller degree of pressure within the aneurysm sac, elevated sac pressures have been documented with all endoleak types, and persistent type II endoleaks may occasionally lead to aneurysm rupture (1,6,19,21). The presence of high pressure within the sac is usually associated with sac enlargement (3,4,15). Therefore, patients with a type II endoleak and a stable sac size can be observed, while intervention is reserved for cases of aneurysm enlargement (3,4,15).

Localization of the source of the endoleak is essential for successful treatment (13). Angiography, color duplex ultrasonography (US), magnetic resonance (MR) imaging, and helical CT are modalities utilized in the detection of endoleaks. Angiography is considered the "gold standard," but it is an invasive procedure with limited ability to depict small endoleaks (22). Sensitivity of helical CT in the detection of an endoleak surpasses that of conventional angiography (23). Color duplex US is a cost-effective and noninvasive technique, but it is operator dependent, may be limited by patient body habitus, and is reported to have lower specificity, positive predictive value, and overall accuracy than CT (6,22,24). Although MR imaging is considered to be more sensitive than helical CT for the detection of endoleaks, with comparable specificity and positive predictive values, its use is limited to cases where the EVG has low magnetic susceptibility (8,25). In addition, the limited availability and high cost of MR imaging precludes its widespread use for routine follow-up (7). Helical CT has become the most commonly employed follow-up modality after endovascular abdominal aortic aneurysm repair owing to its high sensitivity for endoleak detection, noninvasiveness, high availability, and good patient acceptance (1,5–7,22,24,26).

Despite the high sensitivity of CT, reliable criteria for differentiation between endoleak types are lacking. The difference in prognosis and treatment between type I or III and type II endoleaks necessitates differentiation between the two groups. CT-based classification of endoleaks may reduce the need for extensive angiographic studies (22). Tillich et al (27) have noted type II endoleaks in the periphery of the aneurysm sac. Gorich et al (22) proposed a classification system for endoleaks on the basis of findings at CT, digital subtraction angiography, and radiography. According to this classification, four configurations of endoleak are observed: (a) Broad-based collections directly adjacent to the prosthesis result from leakage at the terminal ends of the stent-graft, (b) ventral collections without direct connection to the endoprosthesis are supplied by the inferior mesenteric artery, (c) dorsolateral endoleaks are supplied by the lumbar arteries or the median sacral artery, and (d) large circumferential perigraft collections are indicative of dislocation of the stent-graft or insufficient length of a tube endoprosthesis (22). This classification system, although applicable in some cases, is often difficult to implement due to the presence of multiple endoleak components. In addition, it is based primarily on the location of an endoleak and does not take its shape into account.

We suggest that the shape of an endoleak is important for its characterization. We hypothesize that when backflow enters the sac, it assumes a channel-like tubular shape that insinuates between the aortic wall and luminal thrombus at some distance from the graft. Away from its origin, an endoleak may then acquire a different configuration, which possibly depends on several factors, such as the pressure gradient and the presence and number of outflow vessels. Therefore, we postulated that a tubular contrast material collection located at or near the aortic wall provides indirect evidence of a type II endoleak.

Our data have substantiated the above hypothesis. A PTC was significantly more common in type II than in type I or III endoleaks, and it had the highest sensitivity, specificity, and accuracy of the studied CT findings. PTC was demonstrated in 100% of patients with type II endoleak. Slightly less than half of these patients had additional central contrast material collections near the graft, which were small in 80% of the patients. In type II endoleaks associated with central collections, accurate categorization as suggested by Gorich et al (22) is not applicable. Like Gorich et al, we saw large centrally located contrast material collections in the majority of patients with type I or III endoleaks. However, this finding had a low specificity of 63.6%. Specificity of PTC for type II endoleak was 88.2%, with two false-positive results. In these two patients with small type I endoleak, there was associated thrombosis of one of the graft limbs. Direct evidence of type II endoleak is definite visualization of a feeding vessel, a finding that has a specificity of 100% but low sensitivity, which is a limiting factor. The lack of statistical significance in the frequency of this finding between the two groups probably is a result of the small sample size and low prevalence of the finding in our series, because only four patients with type II endoleak (18%) had a directly visualized feeding vessel.

The majority of type II endoleaks that were diagnosed with CT in our institution could not be used for this study owing to lack of long-term follow-up or verification with other imaging studies. This resulted in a large proportion of type I or III endoleaks in our study group. Most type I or III endoleaks were encountered in the early period of EVG placement, when surgical techniques were evolving and the number of available devices was limited. Currently, the most common endoleaks diagnosed in our center are type II.

Our study had limitations. A large proportion of CT scans were obtained with single-section scanners, and our multisection equipment was limited to four–detector row scanners. Perhaps with widespread use of multisection CT scans obtained with a higher number of detector rows, more accurate detection of the feeding vessel can be achieved in patients with type II endoleaks. Another limitation of our study was its retrospective nature. In addition, our study included only a subset of patients with endoleaks, excluding those whose endoleaks were not confirmed or classified with surgery or angiography. Last, in six patients, the endoleak type was not confirmed by using another diagnostic modality. Rather, the diagnosis was supported by clinical behavior that was consistent with the known natural history of type II endoleaks (28).

In summary, our study results indicate that a tubular component of an endoleak located at or near the aortic wall at helical CT arteriography is a statistically significant predictor of type II endoleak in the majority of patients, although false-positive results for small type I endoleaks may occur.

	ADVANCE IN KNOWLEDGE

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 

• The presence of a peripheral tubular component of an endoleak is a statistically significant predictor of type II endoleak at CT arteriography.
  

	FOOTNOTES

 

Abbreviations: EVG = endovascular graft • PTC = peripheral tubular component

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, V.C., A.M.R.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, V.C., A.M.R., M.P.; clinical studies, all authors; statistical analysis, V.C.; and manuscript editing, V.C., A.M.R., Z.J.R., M.P.L.

	References

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCE IN KNOWLEDGE References

 

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