In some aspects, the present disclosure pertains to radiopaque hydrogel compositions that comprise a radiopaque polysaccharide that comprises a plurality of radiopaque moieties that are covalently linked to a carboxylic-acid-containing polysaccharide along a backbone of the carboxylic-acid-containing polysaccharide. In some aspects, the present disclosure pertains to radiopaque hydrogel compositions that comprise a carboxylate-anion-containing polysaccharide that is ionically crosslinked by multivalent cations. In other aspects, the present disclosure pertains to kits that contain such radiopaque hydrogel compositions, to methods of treatment that comprise administering such radiopaque hydrogel compositions to patients, and to methods of making such radiopaque hydrogel compositions.