the present invention comprises compositions and methods for forming an endovascular occlusion to treat conditions such as aneurysms , arterio - venous malformations , excessive blood supply to tumors , massive vascular hemorrhaging , and other conditions which require an embolization to alleviate the condition . embodiments of the present invention comprise compositions and methods that use calcium alginate , without or without endovascular coils or similar devices , to form occlusions at a site within the mammalian body targeted for occlusion .