Low-flow Endoleaks Research Articles

Type 2 Endoleak Detection After Endovascular Aneurysm Repair: Can Low-Flow Endoleaks Also Be Visualized in Silicon-Photomultiplier-Based Positron Emission Tomography/Computed Tomography Scans?

To present a novel clinical application of silicon-photomultiplier-based positron emission tomography (SiPM-based PET)/computed tomography (CT), detecting a type II endoleak 5 years after endovascular aneurysm repair (EVAR). SiPM-based PET/CT scans with a standard whole-body protocol were performed for a 73-year-old man with a past medical history of abdominal aortic aneurysms treated with EVAR and currently under investigation of his duodenal papillary carcinoma. The PET/CT demonstrated 18F-fluorodeoxyglucose (FDG) accumulation outside the stent graft in the native sac of the aneurysm. The site of accumulation corresponded to that of the contrast enhancement depicted in the CT angiography taken 1 month earlier. Another CT scan performed 3 months later revealed enlargement of the aneurysm. SiPM-based PET/CT, with its superior sensitivity and spatial resolution over conventional PET/CT, can detect type II low-flow endoleaks. Abnormal intra-aneurysmal FDG activity incidentally detected on SiPM-based PET/CT is worthy of attention because it may be indicative of endoleaks. Additional imaging using different modalities should be considered so that the patient would not miss the additional treatment opportunity upon observing sac enlargement. For patients with contraindications for iodine CT contrast media, SiPM-based PET/CT would serve as a suitable alternative.

Multicenter Comparative Analysis of Late Open Conversion in Patients With Adherence and Nonadherence to Instructions for Use Endovascular Aneurysm Repair

Purpose: The widespread adoption of endovascular aneurysm repair (EVAR) as preferred treatment modality for abdominal aortic aneurysm (AAA) has enlarged the number of patients needing open surgical conversion (OSC). The relationship between adherence to Instructions For Use (IFU) and EVAR long-term outcomes remains controversial. The aim of this study is to compare preoperative differences and postoperative outcomes between EVAR patients not adjusted to IFU and adjusted to IFU who underwent OSC. Methods: This multicenter retrospective study reviewed 33 explanted EVARs between January 2003 and December 2019 at 14 Vascular Units. Patients were included if OSC occurred >30 days after implantation and excluded if explantation was performed to treat an endograft infection, aortic dissection, or traumatic transections. Variables analyzed included baseline characteristics, adherence to IFU, implant and explant procedural details, secondary reinterventions, and postoperative outcomes. Results: Fifteen explanted patients (15/33, 45.5%) were identified not accomplished to IFU (out-IFU) at initial EVAR vs 18 explanted patients adjusted (in-IFU). During follow-up, a mean of 1.73±1.2 secondary reinterventions were performed, with more type I endoleaks treated in the subgroup out-IFU: 16.7% vs 6.3% in-IFU patients and more type III endoleaks (8.3% vs 0%). Patients out-IFU had shorter mean interval from implant to explant: 47.60±28.8 months vs 71.17±48. Type II endoleak was the most frequent indication for explantation. Low-flow endoleaks (types II, IV, V) account for 44% of indications for OSC in subgroup of patients in-IFU, compared with 13.3% in patients out-IFU and high-flow endoleaks (types I and III) were the main indication for patients out-IFU (33.3% vs 16.7% in-IFU). Total endograft explantation was performed in 57.5% of cases (19/33) and more suprarenal clamping was required in the subgroup out-IFU. Overall, 30-day mortality rate was 12.1% (4/33): 20% for patients out-IFU and 5.6% in-IFU. Conclusions: In our experience, type II endoleak is the most common indication for conversion and differences have been found between patients treated outside IFU with explantation taking place earlier during follow-up, mainly due to high-flow endoleaks and with higher mortality in comparison with patients adjusted to IFU. Ongoing research is required to delve into these differences.

Which mode of color Doppler ultrasound is most suitable for detecting endoleaks in surveillance after endovascular aneurysm repair?

Objectives: The aim of this study was to evaluate the best mode of Doppler ultrasound, blood flow imaging (BFI) versus color Doppler ultrasound (CDUS), in detecting endoleaks diagnosed using computed tomography angiography (CTA). Patients and methods: A total of 70 consecutive patients (60 males, 10 females; mean age: 68.5±7.8 years; range, 48 to 82 years) undergoing standard EVAR procedure were retrospectively evaluated in the outpatient clinic following CTA between January 2018 and December 2019. Ten (13.9%) patients in which endoleaks were detected were also evaluated using CDUS which was performed by two radiologists specializing in Doppler ultrasound. The radiologists were blind to CTA reports. A reporting protocol was developed for endoleak detection using different modes of CDUS (BFI vs. CDUS). Results: Of all cases, 10 (13.9%) endoleaks were detected using CTA. All five type I and III endoleaks requiring an intervention were detected by both modes of CDUS, while four of the five type II endoleaks were not. The single case of type II endoleak was suspected following the visualization of fresh thrombus formation. There was an inadequacy in detecting low flow endoleaks both using BFI and standard color Doppler mode. There was a strong correlation between the aneurysmal sac diameters measured using CTA and CDUS. Conclusion: The CDU and BFI are capable of detecting type I and III endoleaks with similar sensitivity and specificity. These modes should be used in combination as confirmatory tests. For surveillance, CDUS promises accurate results without missing any potential complication requiring an intervention. Lack of detecting type II endoleaks may be negligible, as sac enlargement is the key for reintervention in this case.

Evolution of type II endoleaks based on different ultrasound-identified patterns

ObjectiveThe objective of this study was to delineate the specific types of waveforms that exist in type II endoleaks (T2ELs) and their effect on aneurysm sac size. MethodsPatients who underwent an endovascular aneurysm repair and were diagnosed with a T2EL were included in the study. The flow velocity characteristics of the T2ELs were evaluated in detail with duplex ultrasound. Four different flow patterns were identified: high resistance, low flow; low resistance, low flow; low resistance, high flow; and to-fro flow. The type and number of vessels involved, time at detection, evolution, and need for treatment were recorded. The aneurysm sac diameter was monitored with duplex ultrasound. A computed tomography scan was always performed at baseline within 1 month of the procedure and repeated only when symptoms developed or there were changes in the ultrasound examination findings, such as sac enlargement. ResultsOf 382 patients who underwent endovascular aneurysm repair in our institution, 56 (14.65%) were found to have a T2EL. There were 52 male and four female patients with a mean age of 74 years (61-86 years). The T2EL was diagnosed within the first month in 32 patients; 9 patients were diagnosed at 3 months, 5 patients at 6 months, 3 patients at 9 months, and 7 patients at 1 year or later. There were 43 patients who had a T2EL involving one vessel; two vessels were involved in 11 patients and three vessels were involved in two patients. During follow-up, several changes were observed for the different types of T2EL. High-resistance, low-flow endoleak was detected in 14 patients; of those, 13 were occluded and 1 converted to high flow. Low-resistance, low-flow endoleak was detected in seven patients; of those, 5 were occluded, 1 remained stable, and 1 converted to high flow with sac enlargement requiring treatment. Low-resistance, high-flow endoleak was found in 13 patients; of those, 8 were occluded, 3 remained stable, and 2 had sac enlargement requiring treatment; 1 patient presented with rupture. Finally, to-fro flow was identified in the majority of the patients (22); of those, 14 occluded, 3 remained stable, and 5 had sac enlargement requiring treatment; 2 patients presented with rupture. No deaths due to T2EL were encountered. ConclusionsMost of the T2ELs resulted in spontaneous occlusion and were not associated with sac enlargement. A low-resistance, high-flow or to-fro flow T2EL has higher chances of sac enlargement, rupture, and requiring reintervention.

Intraoperative Gutter Leaks That Merit Our Attention.

The natural history and potential morbidity of gutter endoleaks are unclear. We present our experience with intraoperative gutter endoleaks and strategies to determine which of these require intervention. This is a retrospective review of all patients treated with parallel stent grafts from January 2010 to September 2015. We reviewed all operative records and intraoperative angiograms as well as all postoperative imaging and secondary interventions. All gutter leaks were classified as low-flow/nonsac-enhancing gutter endoleaks or high-flow/sac-enhancing gutter endoleaks. Adjunctive interventions to manage the gutter leaks were noted, as were all subsequent interventions for gutter leak and endoleak management. Seventy-eight patients had 144 parallel stents placed over a 5-year period with an average of 1.8 stents per patient. Twenty-eight patients (36%) had gutter endoleaks diagnosed intraoperatively. Seventeen patients had adjunctive procedures to reduce gutter leaks prior to leaving the operating room (OR). Patients selected for treatment had gutters filling early during completion angiography and/or contrast enhancement of the aneurysm sac. Twenty-two patients (28%) left the OR with low-flow/delayed/nonsac-enhancing gutter endoleaks. At 30 days, a total of 6 persistent gutter endoleaks were diagnosed on computed tomographic angiography. This gives a 73% rate of resolution for low-flow/nonaneurysm sac-enhancing endoleaks. There were 2 de novo endoleaks not detected at the index procedure diagnosed at 6-month follow-up. Of the 8 total postoperative endoleaks, 5 required additional intervention with a 100% success rate. Multivariate analysis revealed that the only significant predictor of having a postoperative endoleak is leaving the OR with an endoleak. Intraoperative treatment of gutter endoleaks has an acceptable rate of resolution. It does have a high rate of converting high-flow endoleaks to low-flow endoleaks. Low-flow/nonsac-enhancing gutter endoleaks have a high rate of spontaneous resolution. Intraoperative gutter endoleaks are not predictive of future aneurysm sac growth.

Evolution of Type II Endoleaks Based on Different Ultrasound-Identified Patterns

The objective of this study was to delineate the specific types of waveforms that exist in type II endoleaks (T2ELs) and their effect on the aneurysmal sac size. Patients who underwent endovascular aneurysm repair and were diagnosed with a T2EL were included in the study. The flow velocity characteristics of the T2ELs were evaluated in detail with duplex ultrasound. Four different flow patterns were identified: high resistance, low flow; low resistance, low flow; low resistance, high flow; and to-fro flow. The type and number of vessels involved, time of detection, evolution, and need for treatment were recorded. The aneurysm sac diameter was monitored with duplex ultrasound. A baseline computed tomography scan was performed within 1 month of the procedure and repeated only when the patient developed symptoms or there were changes in the ultrasound examination findings. Of 382 patients who underwent endovascular aneurysm repair in our institution, 56 were diagnosed with a T2EL (14.65%). There were 52 male and 4 female patients with a mean age of 74 years (61-86). The T2EL was diagnosed within the first month for the majority of the patients (32/56). Nine patients were diagnosed at 3 months, five patients at 6 months, three patients at 9 months, and seven patients at 1 year or later. There were 43 patients who had a T2EL involving one vessel; two vessels were involved in 11 patients, and three vessels were involved in 2 patients. High-resistance, low-flow endoleak was detected in 14 patients; of those, 13 were occluded and 1 was converted to high flow. Low-resistance, low-flow endoleak was detected in seven patients; of those, five were occluded, one remained stable, and one converted to high flow with sac enlargement requiring treatment. Low-resistance, high-flow endoleak was found in 13 patients; of those, 8 were occluded, 3 remained stable, and 2 had sac enlargement requiring treatment; 1 patient presented with rupture. Finally, to-fro flow was identified in the majority of the patients (22); of those, 14 occluded, 3 remained stable, and 5 had sac enlargement requiring treatment; 2 patients presented with rupture. No deaths due to T2EL were encountered. Most of the T2ELs result in spontaneous occlusion and are not associated with sac enlargement. A high-flow or to-fro flow T2EL has higher chances of resulting in sac enlargement and rupture.

Imaging Follow-up of Endovascular Repair of Type B Aortic Dissection with Dual-Source, Dual-Energy CT and Late Delayed-Phase Scans

PurposeTo evaluate the diagnostic performance of dual-energy (DE) computed tomography (CT) after thoracic endovascular aortic repair (TEVAR) of type B dissection, and to investigate the value of late delayed (LD) acquisition in endoleak detection and false lumen patency assessment. Materials and MethodsTwenty-four patients with TEVAR for type B dissection underwent 53 tripe-phase CT examinations. Single-source unenhanced acquisition was followed by single-source arterial-phase and DE LD phase (300-s delay) imaging. Virtual noncontrast images were generated from DE acquisition. Two blinded radiologists retrospectively evaluated the cases in three reading sessions: session A (triphasic protocol), session B (virtual noncontrast and arterial phase), and session C (virtual noncontrast and arterial and LD phases). Endoleak detection accuracy during sessions B and C compared with session A (reference standard) was investigated. False lumen patency was assessed. Effective radiation dose was calculated. ResultsSession A revealed 37 endoleaks in 30 of 53 studies (56.6%). Session B revealed 31 of the 37 endoleaks, with one false-positive case, 83.8% sensitivity, 95.8% specificity, 79.3% negative predictive value, and 96.9% positive predictive value. Session C correctly depicted all 37 endoleaks, with one false-positive case, 100% sensitivity, 95.8% specificity, 100% negative predictive value, and 97.4% positive predictive value. Underestimation of false lumen patency was found in session B (P = .013). Virtual noncontrast imaging resulted in 17% radiation exposure reduction. ConclusionsVirtual noncontrast imaging can replace standard unenhanced images in follow-up after TEVAR of type B dissection, thus reducing radiation dose. Delayed-phase imaging is valuable in low-flow endoleaks detection and false lumen patency assessment.

Role of multidetector CT angiography and contrast-enhanced ultrasound in redefining follow-up protocols after endovascular abdominal aortic aneurysm repair

Contrast-enhanced ultrasonography (CEUS) is an appealing alternative to computed tomography angiography (CTA) for the follow-up of patients who underwent endovascular abdominal aortic aneurysm repair (EVAR). We sought to evaluate the accuracy of CEUS compared with a particularly tailored protocol of CTA performed with a 64-row multidetector CT. The study prospectively enrolled 88 consecutive patients for CEUS and CTA imaging during follow-up after EVAR, yielding 142 paired examinations. The outcome is represented by three main goals: identification and characterisation of endoleaks, evaluation of graft patency and measurement of aneurysm diameter. Triple-phase CTA was the gold standard. Sensitivity and specificity of CEUS compared with CTA in endoleak and graft patency evaluation were 91.89% and 100% and 72% and 100%, respectively. A very high correlation between CTA and CEUS diameter measurements was established. CEUS did not appear superior to CTA in endoleak detection, probably because a tailored CTA protocol with a delayed phase (180 s) allows detection of low-flow endoleaks. Patient management was not different following CEUS and CTA results. CTA cannot yet be completely replaced, but several limitations (radiation exposure, contrast agent) encourage redefining the routine follow-up imaging modality. We suggest an algorithm of surveillance alternating CTA and CEUS.

10 Years of Emergency Endovascular Aneurysm Repair for Ruptured Abdominal Aortoiliac Aneurysms: Lessons Learned

To evaluate a single center's 10-year experience with emergency endovascular aneurysm repair (eEVAR) in 102 patients with ruptured abdominal aortoiliac aneurysms (RAAA). Data from 102 patients (mean age, 73 +/- 9 years) with RAAA treated by eEVAR from January 1998 to April 2008 were retrospectively reviewed. From January 2000, all patients were treated according to an intention-to-treat protocol. The only exclusion criterion was unsuitable anatomy. 31/102 patients had moderate shock and 14/102 patients had severe shock with a systolic blood pressure <70 mm Hg or <50 mm Hg, respectively. 71/102 procedures were carried out under local anesthesia. Endograft types used were mainly bifurcated (92/102). Open abdomen treatment (OAT) because of abdominal compartment syndrome (ACS) was used when signs of organ failure occurred and/or bladder pressure rose >20 mm Hg. The 30-day mortality for eEVAR was 13% (13/102). Technical success (defined as successful deployment of the endograft, absence of extravasation in the postprocedural contrast enhanced CT scan and hemodynamic stabilization) was 99% (101/102). Nineteen unstable patients (19%) required transfemoral supraceliac aortic balloon occlusion. ACS was detected and treated by OAT in 20 patients (20%). 16 type I, 26 type II and 1 type III endoleaks were detected on postoperative CT examination. Two patients had a combined type I and II endoleak. 11 patients were retreated for immediate correction of 10 type I and 2 type II endoleaks. 6 type I and 1 type III low-flow endoleaks were observed and resolved spontaneously within 30 days. Major 30-day morbidity was 35%. In this 102 patient contemporary series of eEVAR for RAAA, endografting proved to be safe with a 30-day mortality of 13%. Key components of this favorable outcome result were adequate preoperative diagnostic imaging, hypotensive hemostasis, selective transfemoral supraceliac aortic balloon occlusion, predominantly local anesthesia, detection and treatment of ACS, and attention to logistics. Widespread adoption of these treatment components is recommended.

Intérêt de l’échographie de contraste dans la surveillance des endoprothèses aortiques

Endovascular aortic aneurysm repair (EVAR) is a widely accepted treatment for anatomically fitted abdominal aortic aneurysms. The increasing use of this procedure has prompted the need for close surveillance and reliable post-operative imaging. The current tool for assessing EVAR technical success is to perform computed tomography angiography (CTA) in order to exclude endoleaks and to confirm the exclusion of the aneurysm sac. Contrast enhanced ultrasound with low mechanical index is a promising method for follow-up of patients after EVAR. It seems to allow better identification and characterization of endoleaks than unenhanced ultrasound and even than CTA for very low flow endoleaks.

Multidetector-Row Computed Tomography Angiography in Abdominal Aortic Aneurysm Treated With Endovascular Repair

To evaluate the optimal timing of delayed phase imaging for detecting low-flow endoleaks. Fifty-eight patients with unruptured abdominal aortic aneurysm treated with endovascular repair underwent 1- and 6-month follow-up multidetector row computed tomography (CT) performed during unenhanced, arterial, and delayed phase. At 6-month follow-up, delayed phase imaging, focused on stent graft, was performed with a delay of 60 (early delayed enhanced phase) and 300 seconds (late delayed enhanced phase) after intravenous injection of 120 mL of iodinated nonionic contrast medium (iomeprol 300 mgI/mL, Iomeron), at a flow rate of 3 mL/s via an antecubital vein, with a detector-row configuration of 4 x 1-mm, a 1.25-mm slice width, and a pitch of 6. Six-month follow-up CT images were independently evaluated by 2 readers during 2 different reading sessions: sets A (unenhanced, arterial, and early delayed phase images) and B (unenhanced, arterial, and late delayed phase images). Sensitivity and diagnostic accuracy of both reading sessions were compared. The standard of reference was represented by the combined evaluation of 1- and 6-month CT scans. At standard of reference, 24 of 58 patients had an endoleak classified as type 1 in 2 cases, type 2 in 21 cases, and type 3 in the last 1 case. Seven of 21 type 2 endoleaks were classified as low-flow endoleaks. Set A reading session, including early delayed enhanced phase, allowed the detection of 19 of 24 endoleaks (5 false-negative cases represented by low-flow endoleaks), whereas all endoleaks were detected during set B reading session, including late delayed enhanced phase. Differences between sets A and B in terms of sensitivity and diagnostic accuracy were statistically significant (P < 0.05). For optimal multidetector CT detection of low-flow endoleaks in patients who underwent endovascular repair, delayed phase should be acquired 300 seconds after injection of contrast medium.

Contrast ultrasound imaging: the best method to detect type II endoleak during endovascular aneurysm repair follow-up☆

Type II endoleak is the most common complication after endovascular aneurysm repair and require close surveillance. Hence, the need to validate new techniques as alternative to helical CT-scan, the reference standard. The aim of this study is to evaluate the efficacy of Cadence Contrast Pulse Sequencing ultrasound technique with second generation contrast agents in detecting endoleaks, and to compare the results with data obtained from CTA. 30 patients with endovascular stent grafts, during their regular follow-up consisting in serial CT and ultrasound exams performed at discharge, at one and six months and at one year thereafter, previous informed consent, were enrolled in a prospectic double blind study design in order to compare triphasic helical CT-scan to another adjunctive ultrasound investigation (Cadence CPS technique with Sono Vue). No more than 15 days occurred between the two examinations. In the study were evaluated only data obtained from the comparison of the two concomitant investigations, independently from the follow-up. Variables analysed were changes in the maximum diameter of the aneurysmal sac, presence and type of endoleak, if detected. In the case of disagreement between the two diagnostic tools angiography was performed. One patient dropped out because of violation of the study protocol (a stroke occurred in the time interval between the two investigations). Both exams visualised patency and proper graft placement in all the remaining patients. Aneurysmal diameters with both investigations overlapped (r(s):0.98). In 21 patients no endoleak was detected with a significant aneurysmal sac shrinkage (P<0.001). In seven patients both methods confirmed presence of endoleak. Ultrasonography detected all type of endoleaks, while CT-scan was uncertain in one. Moreover, in one patient CT-angiography showed an increased aneurysmal diameter without other evidence, while a contrast ultrasound investigation disclosed a type II low-flow endoleak, confirmed by angiography. The Cadence Contrast Pulse Sequencing with echo contrast agent is an ultrasound technique that substantially improves the ultrasound diagnostic reliability.

Multidetector CT in Abdominal Aortic Aneurysm Treated with Endovascular Repair: Are Unenhanced and Delayed Phase Enhanced Images Effective for Endoleak Detection?

To retrospectively determine the sensitivity and specificity of unenhanced, delayed enhanced phase (DEP), and arterial enhanced phase (AEP) multi-detector row computed tomography (CT) for depicting endoleaks during follow-up of endovascular aneurysm repair. Fifty patients (two women, 48 men; mean age, 72 years) underwent follow-up multi-detector row CT 1, 6, and 12 months after endovascular aneurysm repair. Unenhanced CT was performed with 2.5-mm collimation; 1-mm collimation was used with AEP and DEP examinations. Two independent readers assessed the presence of endoleak in three reading sessions: AEP (session A), unenhanced and AEP (session B), and AEP and DEP (session C). At 6- and 12-month follow-up, a fourth set was included: 1-month unenhanced and AEP (session D). Sensitivity, specificity, and positive predictive value of each session were calculated. Triple-phase multi-detector row CT was the reference standard. At 1 month, sensitivity, specificity, and positive predictive value, respectively, were 79%, 75%, and 55% for session A; 93%, 97%, and 93% for session B; and 93%, 78%, and 62% for session C. At 6 months, sensitivity, specificity, and positive predictive value, respectively, were 92%, 68%, and 48% for session A; 92%, 100%, and 100% for session B; and 100%, 84%, and 67% for session C. At 12 months, sensitivity, specificity, and positive predictive value, respectively, were 80%, 80%, and 50% for session A; 90%, 98%, and 90% for session B; and 100%, 80%, and 56% for session C. Sensitivity did not significantly differ (P > .05) among reading sessions A, B, and C, whereas specificity and positive predictive values in session B were significantly higher (P < .001). For 6- and 12-month follow-up, no significant differences (P > .05) were found between sessions D and B. The combination of AEP and unenhanced imaging performed at 1-month follow-up offers improved specificity and positive predictive values compared with AEP alone. DEP imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low-flow endoleaks not seen at AEP.

A Technique to Improve the Confidence of Color Duplex Ultrasound assessment of Aortic Endografts: The use of Contrast Agents

Introduction Color duplex ultrasound (CDU) is routinely used in the evaluation of aortic endografts in many centers. CDU compliments computed tomography (CT) and selective angiography in the identification of persistent endoleaks in these grafts. Because of the complexity of these procedures and the subtle nature of endoleaks, CDU can be time-consuming and challenging. Contrast agents can improve the ease of imaging by rapidly detecting low flow endoleaks. The application of ultrasound contrast agents has been studied in other specialties, such as cardiac echocardiography. This article describes our technique and early experience using contrast-enhanced CDU in aortic endograft assessment. Methods Nineteen patients being seen for a routine CDU examination after endovascular aortic aneurysm repair were evaluated according to published protocol. An initial CDU examination was completed, thoroughly assessing for the presence of graft patency, limb dysfunction, and endoleak. After patient consent, a focused ultrasound was performed using a Food and Drug Administration–approved contrast agent (Optison). The residual aneurysm sac was closely inspected after a 0.3-ml intravenous injection. A maximum of three injections were given in 10-min intervals, with careful evaluation in transverse and sagittal views of the residual aortic sac. Contrast was used to confirm endoleaks noted on the baseline study and help clarify subtle perigraft flow, especially on suboptimal examinations. Results Of the 19 patients given the contrast agent, none had side effects, and all tolerated contrast well. In 9 of 19 examinations, contrast-enhanced CDU confirmed the baseline results positive for perigraft endoleak. Six of nine studies had improved ease of identification of endoleak with contrast. Six of 19 studies were negative for endoleak before and after contrast. Three of 19 studies were indeterminate for endoleak by CDU only secondary to bowel gas and body habitus. The contrast agent was given and was negative for endoleak in these three cases. One study was initially negative for endoleak by CDU, and contrast revealed a small lumber artery leaking into the aneurysm sac. The contrast was easily identified within the endograft and leak sites in all patients. Conclusions CDU is a valuable modality in the postoperative evaluation of endovascular aortic aneurysm repairs. These examinations can be challenging and subject to limitations including bowel gas and body habitus, even when performed by experienced technologists. Color artifacts within the residual aneurysm sac can be difficult to differentiate from true endoleak. Contrast-enhanced CDU can improve the technologist's confidence in the detection of endoleaks.

Endotension: An Explanation for Continued AAA Growth after Successful Endoluminal Repair

Purpose: To present and analyze several cases that illustrate persistent sac pressurization following endovascular abdominal aortic aneurysm (AAA) repair. Methods and Results: Four patients with successful endovascular AAA exclusion presented in follow-up with an expanding aneurysm. Two had initial sac diameter decrease, but by 18 and 24 months, respectively, the AAA had enlarged and become pulsatile. There was no endoleak evident, but the proximal attachment stents had migrated distally in both cases. One patient developed endoleak with aneurysm expansion at 6 months; contained rupture occurred at 12 months. The last case had slowly evolving aneurysm expansion over 36 months but no endoleak. All endografts were removed and successfully replaced with conventional grafts. Intrasac thrombus was implicated as the means of pressure transmission that precipitated AAA expansion in these cases. Conclusions: Excluded AAAs can increase in size owing to persistent or recurrent pressurization (endotension) of the sac even when there is no evidence of endoleak. One proposed mechanism is pressure transmission via thrombus that lines the attachment site. Endotension may also represent an indiscernible, very low flow endoleak that allows blood to clot at the source of leakage.

Endotension: An Explanation for Continued AAA Growth After Successful Endoluminal Repair

To present and analyze several cases that illustrate persistent sac pressurization following endovascular abdominal aortic aneurysm (AAA) repair. Four patients with successful endovascular AAA exclusion presented in follow-up with an expanding aneurysm. Two had initial sac diameter decrease, but by 18 and 24 months, respectively, the AAA had enlarged and become pulsatile. There was no endoleak evident, but the proximal attachment stents had mig rated distally in both cases. One patient developed endoleak with aneurysm expansion at 6 months; contained rupture occurred at 12 months. The last case had slowly evolving aneurysm expansion over 36 months but no endoleak. All endografts were removed and successfully replaced with conventional grafts. Intrasac thrombus was implicated as the means of pressure transmission that precipitated AAA expansion in these cases. Excluded AAAs can increase in size owing to persistent or recurrent pressurization (endotension) of the sac even when there is no evidence of endoleak. One proposed mechanism is pressure transmission via thrombus that lines the attachment site. Endotension may also represent an indiscernible, very low flow endoleak that allows blood to clot at the source of leakage.