There are two ways to recognize anal sac problems in dogs—your dog's behavior and the appearance of the anal area. Behaviors, such as scooting (rubbing bottom on the floor or carpet), chewing, and licking the rear end indicate anal sac problems. Some dogs chase their tails. Some resting dogs suddenly jump up as if stung. These dogs are experiencing pain or itching.
The appearance of the anal area that signals anal sac problems includes redness and swelling. If anal sacs are swollen to the point of bursting, the area changes from red to purple. Purple indicates the blood has become congested and carries more carbon dioxide than normal. Dogs with chronic anal sac inflammation have hardened (lichenoid) skin under the tail due to the licking and trauma.
In addition to signs and symptoms directly due to the anal sacs, anal sac inflammation can lead to symptoms elsewhere in the body. For example, if your dog licks his or her bottom frequently and swallows bacteria and anal sac material, it can develop infections in the tonsils, the stomach, and the upper airway (trachea). These pets may exhibit sore throats, vomiting, and chronic coughing that resembles kennel cough (tracheobronchitis). When the anal sac problems are resolved, the other health issues resolve.
Anal sac problems in dogs are diagnosed by examining the perineal area. Your veterinarian will wear disposable gloves and massage your dog's anal sacs to determine whether they are soft and easily compressed or swollen and difficult to compress. As anal sac material is expressed, it is evaluated for color and consistency. Normal secretions are thin and a pale yellow-brown. Dry secretions from impacted anal sacs are thick and pasty brown. If the sac is infected with bacteria, secretions become darker brown with yellow or green-yellow pus. Chronic infections and abscesses cause red-brown secretions. Infected anal sac secretions have a foul odor.
If anal sac material is abnormal, your veterinarian will send it to a laboratory to determine what is causing the infection. Among the common causes are bacteria, such as E. coli, clostridium, proteus, and staphylococcus, yeast (candida), andringworm (malassezia).
Several different cancers can form masses (tumors) in your dog's perineal area. Tumors develop in male and female dogs, especially in Beagles, English Cocker Spaniels, English Bulldogs, Springer Spaniels, Dachshunds, Alaskan Malamutes, German Shepherds, and Samoyeds.
Apocrine (sebaceous) gland tumors (also called perianal adenomas) are common in male dogs because they are stimulated, in part, by testosterone. These tumors may spread through the pelvic area to the lymph nodes. A different type of cancer, an anal sac tumor (anal sac apocrine gland adenocarcinoma), occurs in females and may also infiltrate and spread through the area.
If your dog has a mass (tumor) in the perineal area, your veterinarian will insert a needle and remove cells that can be sent for laboratory identification. X-rays and ultrasound exams help determine the extent of your dog's problem and whether the tumor has spread to another area (metastatic cancer). Some cancers first found in the perineal area have actually come from other areas of the body, and the laboratory tests and X-rays help find the origin of these cancer cells. Because some perineal tumors, especially anal sac tumors, increase the amount of calcium in the blood to a level that damages the kidneys, your veterinarian will include blood tests to fully evaluate your dog's health.