Transcatheter arterial embolization for small bowel bleeding: N-butyl cyanoacrylate-lipiodol mixture as the first choice for minimizing ischemic complications

To the Editor,

We read with great interest the article by Kim et al. (1) recently published in Acta Radiologica and evaluating the safety and efficacy of superselective transcatheter arterial embolization (TAE) for small bowel bleeding. We have several comments. First of all, we would like to congratulate the authors for their study, which represents the largest one reporting outcomes and prognostic factors associated with ischemic complications in such a setting. Second, whereas most of interventional radiologists are afraid of using glue for gastrointestinal (GI) bleeding, the authors showed by univariate analysis that superselective embolization (odds ratio [OR] = 0.099; 95% confidence interval [CI] = 0.027–0.368; P < 0.001) and the use of N-butyl cyanoacrylate (NBCA) (OR = 0.257; 95% CI = 0.077–0.859; P = 0.027) were associated with lower rates of major complications. Furthermore, results from multivariate analysis showed that superselective embolization had a negative association with major complications (OR = 0.069; 95% CI = 0.012–0.406; P = 0.003) (1). This later result may be explained by the fact that it is usually technically easier to perform superselective embolization with liquid embolic agents such as cyanoacrylate glue than with other embolic agents (2). Indeed, 10 of the 71 patients in the present study developed transmural infarction and underwent subsequent surgery (n = 7) or died (n = 3) within 30 days, but glue was a prognostic factor of lower rates of ischemic complications.

Cyanoacrylate glue embolization continues to be viewed with some circumspection due to reported risks of glue migration into non-target arteries and of microcatheter blockage by the glue. But bowel infarction is only a theoretical concern. Indeed, as previously reported in the only available meta-analysis regarding the use of NBCA for GI bleeding, NBCA has been reported as an effective embolic material with favorable outcome for lower GI bleeding. In particular, NBCA showed a lower complication rate than other embolic materials in patients with lower GI bleeding (3). This can be explained by the characteristics of NBCA. The glue/lipiodol ratio affects the viscosity of the liquid and the polymerization time of the glue. It is recommended to adjust the ratio to the length of the segment to be occluded, as performed in the present study (1). Thus, the mixture has sufficient low viscosity to allow distal embolization of the feeding artery but at the same time it is viscous enough to prevent the embolic agent from propagating too far into the capillary bed, preserving circulation in the distal post-embolic tissue via collateral channels in the intramural microcirculation (4,5). NBCA/lipiodol has several other advantages. Lipiodol makes the NBCA/lipiodol mixture radio-opaque, allowing for easier control under fluoroscopy, compared with other embolic materials that are not directly visualized such as particles (2). In addition, cyanoacrylate glue is a liquid and can therefore be used to occlude vessels in which the microcatheter cannot be advanced (4). This situation is particularly frequent in small bowel bleedings. The shorter procedural time with cyanoacrylate glue compared to microcoil embolization is also particularly valuable in patients with life-threatening bleeding. Last, glue can be more efficient than other embolic agents in patients with coagulopathy, the polymerization of glue in contact with blood not being dependent of the coagulation status of the patient (5). Of course, it is important to take a number of precautions designed to minimize the complication rate. Flushing the microcatheter with dextrose to remove all ionic solutions before the injection and promptly pulling the catheter back after the injection to avoid adhesion to the vessel and trapping of glue are important (2). Wedging the catheter and injecting contrast alone before the glue to calculate the volume needed have also been recommended (4,5).

In conclusion, the use of NBCA as an embolic agent for TAE of small bowel bleeding should probably be the first choice in well-trained hands to minimize the risk of major bowel ischemic complications contrary to what most interventional radiologists think.