anal sacs

A pair of sacs between the internal and external anal sphincter on either side at the mucocutaneous junction of the anus in carnivores. The walls are lined with large sebaceous glands and in dogs also apocrine glands. The combined secretions are malodorous, gray-brown, granular material that is expelled in small quantities with each defecation, as a form of territorial marking, or in larger amounts from vigorous struggling or due to fear and may occur during treatment by a veterinarian. These sacs are subject to hypersecretion, ductal blockage, impaction and abscess formation which may necessitate surgical removal. Discomfort associated with disease may give rise to ‘scooting’, rubbing or licking of the anal area in dogs.

• a. s. abscess — infection, aided by impaction of secretions, of anal sacs can lead to abscess formation which may rupture and drain to perianal skin or into deep tissues surrounding the rectum. See also perianal fistula.
• a. s. tumor — the most common tumors of the anal sacs are apocrine adenocarcinomas, occurring most often in aged bitches. These tumors are sometimes associated with the paraneoplastic syndrome of pseudohyperparathyroidism.