A perianal fistula is a painful opening in the skin around the anus of a dog. The condition affects German Shepherds most commonly, although other breeds can develop the problem. There are several possible contributing factors, including genetics, allergic skin disease, and alterations in immune system functioning. If your dog strains to defecate, has pain and bleeding around his rear end, seems constipated, licks his bottom excessively, or has a smelly discharge from the area, a perianal fistula is possible. Treatments range from medication to surgery, though for many dogs the problem is persistent.


Perianal fistulae are draining openings in the skin around the anus that do not heal. The word fistulae is the plural of fistula, which is an abnormal tract or passageway from an abscess, organ, or body cavity to the body surface. The term perianal describes the area around the anus.

An affected dog may have a single fistula, or many fistulae that can encircle the anal opening. Although a hereditary component is presumed due to certain breed predilections, the cause of the condition is multifactorial. Allergic skin disease, conformation-related issues (as when dogs hold their tails close to their anuses), and abnormal functioning of the immune system are among the factors thought to play a role in the disease process.

Middle-aged to older dogs (usually seven or older) are most often affected.

Symptoms and Identification

Straining to defecate, perianal pain and bleeding, constipation, licking of the area, and a smelly discharge are typical.

Diagnosis involves evaluating age, breed, clinical signs, and physical exam findings. Rectal examination (under anesthesia, if necessary) is required in most cases. Sometimes, a biopsy may be recommended to rule out tumors or other conditions that can similarly affect the anal area.

Affected Breeds

German Shepherds are most notoriously affected, although Irish Setters and Labrador Retrievers are among the breeds that seem over-represented.


Perianal fistula is a frustrating, difficult-to-treat disease. Though medical and surgical treatments have both been described, these approaches can be insufficiently helpful for some affected dogs. Dogs that do respond to medical treatment may require many months to recover, and relapses can occur.

Medical management typically involves the use of drugs that interfere with the inflammatory response. Cyclosporine and tacrolimus have both been employed successfully. Antimicrobials and antiseptics are often administered as well by way of treating the secondary infections almost always present in this especially bacteria-rich location.

The surgical approach to perianal fistula management relies on the removal of the tracts. More than one procedure is sometimes required. Tail amputation has also been described as potentially helpful for dogs whose tail conformation has been deemed a major contributing cause of the disease.

This article has been reviewed by a Veterinarian.