Limb Stent Occlusion from Intraoperative Nellix Stent Migration and Prolapse

Incidence of Nellix stent migration is uncommon despite the absence of a proximal fixation mechanism. We present a case of intraoperative Nellix stent migration to highlight the potential complications. Our patient had renal artery occlusion and threatened limb stent perfusion as a result of intraoperative stent migration, with resultant prolapse of the Nellix endobag. We also present a successful salvage procedure to deploy an additional stent to restore limb stent flow.

A 71-year-old Chinese gentleman with symptomatic concomitant infrarenal abdominal aortic aneurysm and bilateral common iliac aneurysms was discussed at a multidisciplinary meeting and deemed suitable for endovascular sealing of the aneurysms with the Nellix device. Prefilling imaging confirmed satisfactory stent positions bilaterally below the level of renal arteries. Routine filling of endobag was performed with stent-graft molding by standard angioplasty technique. Final check angiogram did not identify any endoleaks and demonstrated adequate sealing of the aneurysm. Unfortunately, patient developed acute kidney injury postoperatively. This was attributed to contrast-induced nephropathy. The creatinine level peaked at 150 μmol/L and stabilized. Ultrasound duplex on the seventh postoperative day however diagnosed absent left renal artery flow. An interval computed tomography aortogram at 3 month also detected threatened limb stent occlusion from the contralateral endobag prolapse. Subsequently, the patient underwent successful extension of the threatened limb stent to restore luminal flow.

Retrospective examination of angiographic images confirmed that the left renal artery flow was preserved on the completion angiogram. The difference in level of limb stents observed postmolding compared to premolding widened from 1 mm to 6 mm due to a degree of stent bowing within the iliac arteries. We postulate the left renal artery occlusion was either caused by further proximal migration of the right limb stent due to the left stent bowing within the curve of the iliac artery or endobag prolapse post molding. Mismatched, unopposed filling of the endobags after the molding process could result in an unexpected behavior of prolapsing into the contralateral limb stent and obstruct luminal flow. This case highlights a significant sequalae of proximal migration after the molding process of Nellix. Augmenting the level of limb stent to the same level may be necessary and easily achieved with additional stent deployment. We recommend close inspection of completion angiogram to check for stent migration, and if required for additional angiograms to be taken perpendicular to each other or use of adjuncts such as intravascular ultrasound post endobag filling to document stent positions in relation to adjacent renal arteries, luminal flow, and detect any early intraoperative migration.