Dacryocystitis describes inflammation of the nasolacrimal drainage structures, which comprise the eyelid puncta, lacrimal canaliculi, lacrimal cavern and the sino-nasal ducts that exit to the external nares. Inflammation of the nasolacrimal system may be the result of bacterial infection, extension of inflammation from adjacent structures, neoplasia or entrapment foreign material. Primary aplasia or hypoplasia of any part of this system may also occur, typically manifesting in young animals. Post-inflammatory scarring & fibrosis is a common cause of nasolacrimal non-patency, particularly in cats previously affected by herpesviral-associated inflammation. Chronic inflammation or obstruction of the nasolacrimal ducts may also result in cystic dilation. Clinical symptoms of dacryocystitis may include conjunctivitis, fornix-based mucoid to purulent discharge and localized swelling and/or discomfort over any part of the nasolacrimal duct system, particularly around the medial canthal region. Symptoms are typically unilateral. Both canine and feline species of any breed or mixed breed may be affected.