Anal Sac Disease in Dogs: An Overview
Dog Breeds
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.
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Definition of Anal Sac Problems
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 fearful. Anal sac disease is not a single “disease” per se, but refers to a number of conditions that occur when a dog’s anal sacs become infected, inflamed, impacted, abscessed or affected by tumors. When these problems are present, the glands lining the anal sacs cannot eliminate the material that they normally produce or, in cases of infection, the sacs become filled with abnormal substances such as pus or blood. The result is that material builds up inside the anal sacs much like a balloon filling with water or air, causing discomfort, pain and possible anal sac rupture.
Causes of Anal Sac Problems
The underlying causes of anal sac problems are largely unknown. Several predisposing factors 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 the overgrowth of bacteria that normally is present within the anal sacs, thereby increasing the chances of inflammation, infection, impaction and formation of pus-filled abscesses. The reason that tumors develop in the perianal area, like the reason for tumor development elsewhere in the body of dogs or other mammals, is not well understood. However, both benign and malignant tumors can occur in or around the anal sacs, causing symptoms similar if not identical to those caused by more temporary and treatable problems such as bacterial infection or physical impaction by a removable source.
Prevention of Anal Sac Problems
One of the best ways to prevent anal sac problems is to feed dogs a high quality diet that is low in saturated fats and has enough dietary fiber to increase stool bulk and reduce the occurrence of loose or sloppy stools. The material normally found inside the anal sacs cannot be evacuated naturally unless there is a sufficient amount of appropriately firm feces passing through the dog’s rectum. Overweight dogs should be put on a weight loss regimen, as obesity can contribute to anal sac problems as well. Routine manual expression of the anal sacs by veterinarians or by owners should not be necessary in normal dogs but may become appropriate in certain situations, which the treating veterinarian is best suited to assess. Of course, good routine hygiene can help prevent abnormal accumulation of bacteria and other microorganisms around the anal area. Unfortunately, there is no way given the current state of medical knowledge to prevent perianal tumors. Research into the causes and treatment of cancer remains in the forefront of both human and veterinary medicine.
Special Notes
The prognosis for dogs with non-cancerous anal sac problems is quite good. However, if surgical removal of the anal sacs becomes necessary for any reason, the prognosis worsens. If cancer is diagnosed, the prognosis is mixed to guarded, depending upon the tumor type, malignancy and the stage of the disease.
Symptoms and Types