Blockage, or obstruction of the ureter can occur. A blockage of the gallbladder or cystic duct may cause cholecystitis. Preventive treatment of severe dryness with measures such as nasolacrimal duct blockage is important. Medical imaging such as ultrasound is useful for detecting bile duct blockage. Barker underwent carotid endarterectomy to remove the blockage. Ursodiol may be useful if the disease is due to blockage of the bile ducts. The increased pressure is caused by trabecular meshwork blockage. Inflammation associated with blockage of the duct is sometimes termed "obstructive sialadenitis". He originally had a urinary tract blockage but refused surgery or medication. Gregarines infect the gut and may cause blockage and secondary infection. Pipes must be carefully sloped to prevent trapped condensate blockage. The lump may be accompanied by symptoms of duct blockage (e.g. xerostomia). Syringomyelia is a disease caused by the blockage of the central canal. Topotecan cannot be used in people with an intestinal blockage. This is an extremely serious condition regardless of the cause of blockage.