Abstract: The present invention provides a method to treat sinusitis comprising (a) inserting a portion of an irrigation catheter having an expandable material in a non-expanded state endoscopically into a sinus of a patient through ostium of a sinus; (b) expand the expandable material under endoscopic visualization until it has expanded and filled some portion of the sinus without directly contacting and compressing mucosal surfaces of the sinus; (c) introducing irrigation fluid into the sinus through an irrigation lumen of the catheter to create a circumferential irrigation flow in space between the expanded material and the mucosal surface in order to dislodge and express sinus contents.