Sequential dual-dilution N-butyl cyanoacrylate embolisation ("Nitoryu" technique) for controlled distal penetration and proximal occlusion.

BACKGROUND

N-butyl cyanoacrylate (NBCA) embolisation is an effective technique for rapid haemostasis and tumour devascularisation. However, selection of a single glue dilution requires balancing distal penetration against proximal control, often relying heavily on operator experience. Achieving both deep distribution and stable proximal occlusion can be challenging, particularly in complex lesions.

TECHNIQUE AND CASE PRESENTATION: We describe a sequential dual-dilution NBCA embolisation technique ("Nitoryu" technique), in which a dilute NBCA-lipiodol mixture is first administered to achieve flow-directed distal penetration, followed by injection of a more concentrated mixture to achieve rapid proximal occlusion and stabilisation of the embolic cast. The technique was applied in two cases. In a patient with ruptured hepatocellular carcinoma and coagulopathy, multiple small tumour-feeding arteries and a poorly visualised culprit pseudoaneurysm required deep penetration of dilute glue, followed by proximal occlusion to ensure durable haemostasis. In a second case of bronchial artery pseudoaneurysm causing haemoptysis, a tiny tortuous feeder necessitated very dilute glue for distal delivery, while subsequent proximal embolisation with a more concentrated mixture reduced the risk of reflux and non-target embolisation. In both cases, the sequential approach allowed controlled embolisation with effective distal penetration of glue and stable proximal occlusion.

CONCLUSION

The sequential dual-dilution NBCA embolisation (Nitoryu technique) enables controlled distal penetration and proximal stabilisation, and may improve safety and efficacy in selected cases requiring precise glue delivery.