Definition of Anal Sacs and Anal Sac Disorders
Canines, like other carnivores, have a pair of sacs on either side of the anus, between the internal and external anal sphincter muscles. The walls of these paired structures are lined with large glands that secrete a foul-smelling, yellow-gray or brownish liquid or pasty material. Normally, small amounts of this material are expelled from the anal sacs when the dog defecates and also when it is startled or suddenly becomes very fearful. Anal sac disease is not a single “disease” per se, but rather refers to a condition in dogs that occurs when the anal sacs become infected, inflamed, impacted, abscessed or affected by tumors.
How Anal Sac Disease Affects Dogs
Dogs with anal sac disorders usually show signs of physical discomfort that include tail-chasing, licking and biting at the area around their anus (called the perianal or perineal area) and straining to defecate. They commonly “scoot” their hind end along the ground and sometimes are reluctant to sit. These behaviors are caused by the pain, itchiness and general discomfort that accompany anal sac disorders. Owners often report a foul, "fishy" odor around their dog’s perianal region and possible around its mouth (from the dog’s licking). Small breed dogs more commonly have this condition and overweight animals are at a higher risk of developing anal sac disease.
Causes of Anal Sac Disease
The underlying causes of anal sac disease are largely unknown. Several predisposing causes have been suggested, including obesity, recent diarrhea, poor perianal muscle tone, chronically soft feces and excessive or retained anal glandular secretions. These conditions are thought to promote bacterial overgrowth and increase the chances of inflammation, infection, impaction and abscess formation. The reason for tumor development in the perianal area, like the reason for tumor development elsewhere in the body, is not known.
Prevention of Anal Sac Disease
One of the best ways to prevent anal sac disorders is to ensure that dogs are fed a high quality diet with adequate dietary fiber and low in saturated fats, to increase stool bulk and reduce the occurrence of abnormally loose stools. A sufficient volume of appropriately firm feces is necessary to help evacuate the anal sacs normally. Overweight dogs should be put on a weight loss regimen, as obesity can contribute to anal sac problems. Routine manual expression of the anal sacs should not be necessary in normal dogs. Of course, good routine hygiene will help prevent abnormal accumulation of bacteria and other microorganisms.
Special Notes
The prognosis for dogs with non-neoplastic anal sac disease is quite good. However, if surgical removal of the anal sacs becomes necessary, the prognosis worsens. If cancer is diagnosed, the prognosis is mixed to guarded, depending upon the tumor type and stage of the disease.