Anal sac problems are fairly common in domestic dogs. Fortunately, they are not particularly difficult to diagnose. Owners usually bring their affected dogs to the veterinary clinic because they have been licking at their rear end and scooting their butts across the floor. They may also complain about a nasty smell coming from their dog’s rear and bad breath. The veterinarian will take a history from the owner about the dog’s general health, including when the current symptoms showed up and whether they have gotten worse or stayed about the same over time. The veterinarian will also perform a thorough physical examination. She will inspect the anal area visually and digitally (by hand). The digital rectal examination involves inserting a finger into the dog’s anus and physically expressing, or squeezing out, the contents of both anal sacs for further evaluation. This procedure can be painful, depending on the severity of the dog’s condition. Sedation or general anesthesia may be needed to complete the rectal examination. Normal anal sac secretions are clear to pale yellowish or grayish brown. Impacted anal sacs become plugged with a thick, pasty material; inflamed sacs often contain a creamy yellow or thin greenish secretion. Abscessed anal sacs typically discharge a reddish-brown material containing pus and blood, accompanied by a fever and obvious swelling and redness around the anal area. The veterinarian’s initial evaluation of the perianal area and the anal sac secretions will give her a good idea about the dog’s condition.
Most veterinarians will draw blood and urine samples. The results of routine blood work (a complete blood count and serum chemistry panel) and a urinalysis are usually normal in dogs with anal sac disorders, unless the sacs are infected. Some dogs will anal sac tumors will have elevated blood levels of parathyroid hormone-related protein and calcium. The veterinarian may recommend radiographs (X-rays) of the chest and pelvis, and possibly an abdominal ultrasound, to look for evidence of metastasis (spread of cancerous cells), especially to the lymph nodes. Samples of the anal sac contents will be examined microscopically through a process called “cytology.” Anal saccular secretions can be cultured to look for infectious microorganisms. However, culture results can be difficult to interpret, due to the normal presence of a so many different bacteria (“normal flora”) in that region. If a mass is found, it can be sampled by a fine needle aspirate or, more diagnostically, by a tissue biopsy. The sample will be sent to a laboratory for detailed evaluation, to confirm or rule out cancer.
Most anal sac disorders in companion dogs are not especially serious and are not hard to diagnose, especially since the area involved is so isolated and accessible. Nonetheless, it is important for owners to take these problems seriously and to seek veterinary assessment and advice when they notice that something is amiss in their dog’s perianal region.