Hydrophilic Polymer Embolization-A Scoping Review of the Available Literature with Focus on Organ Involvement and Outcomes

Background: Hydrophilic polymer embolization (HPE) is a scarcely reported complication associated with endovascular procedures where the hydrophilic coating dislodges and disseminates to more distal vascular beds, leading to ischemic complications. The aim of this study is to assess the clinical outcomes associated with HPE in the literature and try to quantify it in a scoping manner. Methods: All reports with regard to HPE in the PubMed database where clinical data were available were included. Reports were excluded if no clinical data were available and only histopathological descriptions are available, if the language of the report was not in English, and if access could not be obtained to that specific report. Results: A total of 60 publications containing 111 patients were identified. The majority (N = 45, 75%) of the publications were "single-patient" case reports. An overwhelming minority of the reports reported underlying hypertension (N = 27, 45.0%) and ischemic heart disease (N = 28, 46.7%). The most common implicated procedures for HPE occurence were cardiac procedures (N = 28, 46.7%), intracranial procedures (N = 13, 21.7%) and aortic procedures (N = 10, 16.7%). Steroids were trialled in nine (15%) of the reports, mainly for HPE to the CNS (7/9), with no mortality in that specific group. However, HPE-related mortality, identified in 48/111 patients, was largely due to HPE with pulmonary and cardiac involvement (combined 36/48 of all deaths). Conclusions: HPE seems to be a rare occurrence, although low-quality evidence (mainly case reports) comprises most of the research on the subject. Fatal outcomes seem relatively common, and steroid therapy may be trialled in select cases. Further research, potentially through prospective registry studies may aid in providing more knowledge on HPE.