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(Radiology. 2001;218:477-480.)
© RSNA, 2001

Vascular and Interventional Radiology

Endoleaks after Endovascular Repair of Aortic Aneurysm: Are They Predictable?—Initial Results1

Johannes Görich, MD, Norbert Rilinger, MD, Roman Sokiranski, MD, Joachim Söldner, MD, Werner Kaiser, MD, Stefan Krämer, MD, Cengiz Ermis, MD, Ansgar Schütz, MD, Ludger Sunder-Plassmann, MD and Reinhard Pamler, MD

1 From the Departments of Radiology (J.G., N.R., R.S., S.K., C.E., A.S.) and Thoracic and Vascular Surgery (L.S.P., R.P.), University of Ulm, Steinhoevelstrasse 9, 89075 Ulm, Germany; and the Department of Diagnostic and Interventional Radiology, University of Jena, Germany (J.S., W.K.). Received June 26, 1998; revision requested August 18; final revision received July 28, 2000; accepted August 15. Address correspondence to J.G. (e-mail: johannes.gorich@medizin.uni-ulm.de).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
PURPOSE: To evaluate the predictability of endoleak.

MATERIALS AND METHODS: Thirteen women and 60 men (mean age, 69.8 years) underwent transfemoral insertion of endoluminal stent-grafts for treatment of aortic aneurysms. Follow-up included helical computed tomography (CT) at 3-month intervals. In the cases of endoleak, angiography also was performed to document the number of leak sites, their size and position, the feeding artery, the size of the aneurysm, the amount of thrombus, and the visualization of the lumbar arteries and inferior mesenteric artery. These data were correlated (Student t test) with the probability of endoleak.

RESULTS: A total of seven (10%) endoleaks were identified at CT in 68 patients. The feeding vessels were lumbar arteries in three cases, the inferior mesenteric artery in three cases, and the median sacral artery in one case. Of all factors, only the number of lumbar arteries visualized preoperatively (P < .005) had a significant correlation with probability of endoleak. In 71% (five of seven patients) of the cases of lumbar endoleak, four lumbar arteries were patent, whereas among the 61 patients with successfully repaired aneurysm, only eight (13%) had four patent lumbar arteries. Endoleaks were never found in the primarily thrombosed sections of an aneurysm.

CONCLUSION: Prediction of endoleaks with absolute certainty remains elusive. The single correlating risk factor identified from the data was patency of four or more lumbar arteries visualized preoperatively at CT.

Index terms: Aneurysm, aortic, 981.73 • Aneurysm, CT, 958.12911, 958.12912, 958.12914, 958.12915, 988.12911, 988.12912, 988.12914, 988.12915 • Aorta, grafts and prostheses, 981.1268 • Aorta, stenosis or obstruction, 981.721, 981.73


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Leaks following endovascular repair of aortic aneurysms have been generally termed "endoleaks" and have been reported with frequencies of up to 45% in the international literature (1). Attachment site—that is, type 1—endoleaks result from incomplete sealing at the proximal or distal ends of the prosthesis and are due to problems with technique or anatomy. Retrograde filling of the aneurysm sac—that is, type 2 endoleak—results from backflow by normal arterial branches, for example, the lumbar arteries or inferior mesenteric artery, and are usually unavoidable if these vessels are left patent (2–4).

The objective of the present study was to determine whether the evaluation of angiographic and computed tomographic (CT) studies prior to endovascular treatment could point to possible risk factors for the development of endoleak.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Between October 1995 and March 1998, 68 patients (11 women, 57 men; mean age, 68.7 years; age range, 26–82 years) underwent transfemoral insertion of endoluminal stent-grafts (approved for use in Germany) for treatment of aortic aneurysms (Table 1) at the University Hospitals of Ulm and Jena after written informed consent was obtained. All aneurysms were infrarenal. All procedures were performed jointly by a radiologist and a vascular surgeon (J.G., R.P.) in the surgical suite. A Siremobil 2000 fluoroscopic imaging unit (Siemens, Erlangen, Germany) was used for radiologic monitoring. Details about the stent-graft devices and implantation technique have been described elsewhere (1). The duration of the implantation procedure was 81 minutes ± 14 (± SD).


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  		TABLE 1. Characteristics of 68 Aortic Infrarenal Endoprostheses
 
To determine the dimensions of the aneurysm, including the patent lumen and any thrombosed portion, for stent-graft sizing and treatment follow-up, three-phase helical CT of the abdomen and thorax was performed before and within 7 days after the endovascular procedure. The following CT protocol was used prior to treatment: nonenhanced imaging with a pitch of 1.5, section thickness of 8.8 mm (effective), and 10-mm increments; and contrast material–enhanced imaging (with iopamidol [Solutrast 300; Byk Gulden, Constance, Germany]) with a pitch of 1.0, section thickness of 5.5 mm, 2.5-mm increments, contrast material volume of 150 mL, flow rate of 2.5 mL/sec, and scanning delay of 45 seconds (determined from test bolus scanning in the first patient). After treatment, the same protocol was used with an additional scanning delay of 100 seconds, pitch of 1.5, section thickness of 5.5 mm, and 2.5-mm increments. Patients underwent CT scanning with an Elscint Twin (Elscint, Haifa, Israel) or Somatom Plus S (Siemens, Erlangen, Germany: pitch of 1.6, 120 KV, 210 mAS, three increments) unit.

In addition, before the endovascular procedure and per our routine, angiography of the abdominal aorta and pelvic vasculature was performed by using a 5-F pigtail catheter (Cook, Mönchengladbach, Germany) with radiopaque markings at 1-cm intervals. The pigtail catheter was placed at the level of the renal arteries, and 30 mL of nonionic contrast material (iopamidol) was injected at a flow rate of 12 mL/sec. Images were acquired at a rate of one image per second. Structures were visualized in at least three planes.

Angiographic follow-up was routinely performed during the 1st postoperative week in the first 40 patients. Thereafter, because of concerns about radiation exposure, angiography was performed only in cases of abnormal CT findings, in which case, angiography was performed within the 1st 2 postoperative days. The angiographic technique included use of a Cobra or Sidewinder catheter (Cook) to inject contrast material at the proximal end of the prosthesis, as well as selective catheterization of the internal iliac arteries bilaterally (with manual injection of 10 mL of contrast material) and the superior mesenteric artery (with administration of 25 mL of contrast material at a flow rate of 5 mL/sec). If the contralateral internal iliac artery could not be catheterized by using a crossover technique, angiographic visualization was attempted from the contralateral side the next day.

Only the retrograde endoleaks that remained unchanged at CT over the course of two 3-month follow-up periods were included in the study. Patients with perigraft leaks—that is, leaks due to inadequate sealing of the ends of the prosthesis—were excluded. Patients in whom leaks appeared immediately following implantation of the prosthesis and were thrombosed by the first 3-month follow-up examination also were excluded. Evaluation was based on comparison of pre- and postoperative imaging findings, including number, size, and localization of leaks; feeding artery; size of the aneurysm; thickness and localization of the thrombus (Figure); and preoperative visualization of the lumbar arteries (including the number of arteries visualized) and inferior mesenteric artery. Statistical analysis of data was performed by using the Student t test. Evaluation of the CT scans and angiograms was performed by two endovascular specialists (J.G., N.R.) in consensus.



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  		Figure a. (a) Calculation of the relative differences in aneurysm size: maximum length of the aneurysm (A) times maximum diameter of the aneurysm (B). (b) Calculation of the size of the thrombosed sections of the aneurysm: [(A1 + A2) x (B1 + B2)] x 0.3, where A1 and A2 are the two lengths of the thrombus on the x axis and B1 and B2 are the two lengths of the thrombus on the y axis. The center of the circle represents the patent lumen, and the periphery surrounding the center represents different sections of the thrombosed aneurysm.

 


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  		Figure b. (a) Calculation of the relative differences in aneurysm size: maximum length of the aneurysm (A) times maximum diameter of the aneurysm (B). (b) Calculation of the size of the thrombosed sections of the aneurysm: [(A1 + A2) x (B1 + B2)] x 0.3, where A1 and A2 are the two lengths of the thrombus on the x axis and B1 and B2 are the two lengths of the thrombus on the y axis. The center of the circle represents the patent lumen, and the periphery surrounding the center represents different sections of the thrombosed aneurysm.

 

   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Follow-up ranged from 1 to 33 months (mean, 6.9 months). Of 73 patients treated, seven (10%) had evidence of endoleaks at CT. Six of these were primary endoleaks, that is, they occurred within 30 days after implantation. In one patient, a small late leak fed by a lumbar artery occurred after primary aneurysm repair. The size of the endoleaks ranged from 1 to 9 cm3. In all cases of retrograde endoleak supplied by a lumbar artery, CT was successful in depicting the feeding vessel. These leaks occurred exclusively in the dorsolateral position, whereas the retrograde endoleaks fed by the inferior mesenteric artery were always found ventral to the prosthesis. In no case were endoleaks found in a section of the aneurysm that had previously thrombosed.

Scout aortography performed with adequate catheter position at the level of the renal arteries depicted endoleaks in four (57%) of the seven patients. Use of selective or superselective angiography, however, helped to confirm CT findings in each case.

In two patients, there was more than one leak source. In the first patient, endoleak persisted owing to filling by the inferior mesenteric artery after a perigraft leak initially had been successfully embolized. In the second patient, there was spontaneous occlusion of the entry from the inferior mesenteric artery, although the flow into the aneurysm sac was maintained by flow from the median sacral artery.

There were no differences between the groups with and those without leak with regard to aneurysm size and thrombus thickness. There was, however, a significant correlation between the number of lumbar arteries visualized preoperatively and the incidence of endoleak (P < .005) (Table 2). Although five (71%) of seven patients with lumbar endoleaks had four lumbar arteries at preoperative work-up, only eight (13%) of 61 patients with successfully repaired aneurysms showed four lumbar arteries.


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  		TABLE 2. Data on Patients with Endoleaks following Endovascular Repair of Aortic Aneurysm
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
According to reports in the literature (2–6), endoleak as a complication of endovascular repair of abdominal aortic aneurysm occurs in 2.4%–45.5% of cases. Reperfusion of the aneurysmal sac may occurs through the lumbar, sacral, gonadal, or accessory renal arteries or the inferior mesenteric artery. Of these leakages, 40%–67% thrombose spontaneously, whereas some of them lead to rupture of the aorta (5). Spontaneous closure of a leak after more than 6 months is rare (7). Retrograde endoleaks are unavoidable with current endovascular techniques. In our collective series, nearly 10% of patients had this leak type, which remained unchanged for several months. Experience in three cases showed that endoleaks may be a combination of perigraft and retrograde flow.

Because the reduction in the size of the aneurysm following endovascular therapy is limited, even in the absence of leaks, the hemodynamic significance of an endoleak cannot be immediately determined from findings at CT. Blum et al (1) suggest that in the first 12 months postoperatively, a size reduction of only 2–4 mm is to be expected, whereas in the next 24 months, a more pronounced reduction of 5–15 mm may be observed. Malina et al (4) observed that even minor leakage or collateral perfusion inhibited the reduction of aneurysm diameter in patients with endovascular repair of abdominal aortic aneurysms.

In 1996, Resnikoff et al (8) examined 831 patients who underwent nonresective treatment of an infrarenal abdominal aortic aneurysm. The technique involved proximal and distal ligation of the aneurysm sac combined with aortic bypass. In that series, retrograde endoleaks fed by the lumbar or hypogastric arteries or the inferior mesenteric artery were observed in only 17 (2%) cases. However, a large proportion of those patients experienced rupture during the follow-up period. These numbers underscore the importance of an adequate screening protocol for detection of endoleaks.

Because, to our knowledge, no confirmed results contraindicate the protocol, it has been the practice of our department to recommend treatment of all endoleaks that do not spontaneously occlude within 3 months, regardless of their cause. Percutaneous intervention is possible in nearly all cases. As a rule, embolization with metal coils is attempted first. This procedure, as confirmed by reports in the literature (5,9,10–13), is also safe and effective in treating proximal perigraft endoleaks, in which the goal is not so much closure of the perfused lumen of the aneurysmal sac but rather elimination of the source of blood flow to prevent the pressure of blood from acting against the aneurysm wall (10). The use of gelatin sponge particles has been associated with damage to nerve and muscle tissue (13). Liquid embolic agents are potentially dangerous as well (14).

In summary, prediction of endoleaks with certainty remains elusive. The only correlating risk factor that we were able to identify was the number of patent lumbar arteries. Serious consideration should be given to preoperative embolization when four or more patent lumbar arteries are visualized, since postoperative embolization may be even more technically challenging because of constraints imposed by the presence of an endoluminal prosthesis. Prophylactic embolization of the inferior mesenteric artery in this setting also may be indicated, although our study data did not show a statistical correlation owing to the small sample size. Endoleaks were not seen in previously thrombosed sections of aneurysms.


   FOOTNOTES
 
Author contributions: Guarantors of integrity of entire study, J.G., N.R.; study concepts, J.G., R.P.; study design, S.K.; definition of intellectual content, J.G.; literature research, J.S., W.K.; clinical studies, C.E., A.S.; data acquisition, C.E., A.S.; data analysis, W.K.; statistical analysis, J.S.; manuscript preparation, J.G., R.S.; manuscript editing, J.G., S.K.; manuscript review, L.S.P., R.P.; final manuscript approval, all authors.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Blum U, Voshage G, Lammer J, et al. Endoluminal stent-grafts for infrarenal abdominal aortic aneurysms. N Engl J Med 1997; 336:13-20.[Abstract/Free Full Text]
  2. White GH, Yu W, May J, et al. Three-year experience with the White-Yu endovascular GAD graft for transluminal repair of aortic and iliac aneurysms. J Endovasc Surg 1997; 4:124-136.[Medline]
  3. White GH, Yu W, May J, Chaufour X, Stephen MS. Endoleak as a complication of endoluminal grafting of abdominal aortic aneurysms: classification, incidence, diagnosis, and management. J Endovasc Surg 1997; 4:152-168.[Medline]
  4. Malina M, Ivancev K, Chuter TAM, et al. Changing aneurysmal morphology after endovascular grafting: relation to leakage or persistent perfusion. J Endovasc Surg 1997; 4:23-30.[Medline]
  5. Kato N, Semba CP, Dake MD. Embolization of perigraft leaks after endovascular stent-graft treatment of aortic aneurysms. J Vasc Interv Radiol 1996; 7:805-811.[Medline]
  6. Heilberger P, Schunn C, Ritter W, Weber S, Raithel D. Postoperative color flow duplex scanning in aortic endografting. J Endovasc Surg 1997; 4:262-271.[Medline]
  7. Broeders AMJ, Blankensteijn JD, Gvakharia A, et al. The efficacy of transfemoral endovascular aneurysm management: a study on size changes of the abdominal aorta during mid-term follow-up. Eur J Vasc Endovasc Surg 1997; 14:84-90.
  8. Resnikoff M, Darlin RC, Chang BB, et al. Fate of the excluded abdominal aortic aneurysm sac: long-term follow-up of 831 patients. J Vasc Surg 1996; 24:851-855.[Medline]
  9. van Schie G, Sieunarine K, Holt M, et al. Successful embolization of persistent endoleak from a patent inferior mesenteric artery. J Endovasc Surg 1997; 4:312-315.[Medline]
  10. Stelter WJ, Umscheid T, Ziegler P. Schwierigkeiten und komplikationen der transfemoralen implantation von stent-prothesen beim infrarenalen bauchaortenaneurysma (BAA). Zentralbl Chir 1996; 121:734-743.[Medline]
  11. Ivancev K, Chuter T, Lindh M, Lindbladt B, Brunkwall J, Risberg B. Options for treatment of persistent aneurysm perfusion after endovascular repair. World J Surg 1996; 20:673-678.[Medline]
  12. Khilnani NM, Sos TA, Trost DW, et al. Embolization of backbleeding lumbar arteries filling an aortic aneurysm sac after endovascular stent-graft placement. J Vasc Interv Radiol 1996; 7:813-817.[Medline]
  13. Golzarian J, Struyven J, Abada HT, et al. Endovascular aortic stent-grafts: transcatheter embolization of persistent perigraft leaks. Radiology 1997; 202:731-734.[Abstract/Free Full Text]
  14. Yamaguchi T, Maeda M, Abe H, et al. Embolization of perigraft leaks after endovascular stent-graft treatment of distal arch anastomotic pseudoaneurysm with coil and n-butyl 2-cyanoacrylate. J Vasc Interv Radiol 1998; 9:61-64.[Medline]



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