A lavage catheter for the treatment of a maxillary sinus is described. The catheter comprises a proximal portion and a distal portion. The distal portion comprises an irrigation tip. The irrigation tip has a tip opening through which fluid may be delivered by one handed operation of the catheter. A method for lavaging the maxillary sinus includes inserting the lavage catheter into a patient's anatomy and advancing the irrigation tip into the maxillary sinus using one hand.