Diagnosis and Treatment of Anal Sacculitis and Perianal Fistula in Dogs

Just like weasels (yellow weasels) and skunks, dogs also have a pair of anal sacs, which open on both sides of the anus. They are secretory glands that emit a foul odor, and their secretions are discharged along with feces during defecation. The perianal area is frequently contaminated by feces and dirt, making it prone to disease. Anal sacculitis is inflammation caused by obstruction of the anal sac duct for some reason, causing the glandular secretions within the anal sac to accumulate inside the sac and irritate the mucosa, after which the purulent lesion spreads to the perianal area. Hair follicles, sweat glands, and sebaceous glands are distributed around the anus, and these tissues can produce superficial and deep purulent lesions, forming many fistulas to discharge pus; this condition is called perianal fistula.

Among the diseases around the anus in dogs, anal sacculitis has the highest incidence. The occurrence of this disease is unrelated to age or sex, and it mostly occurs in small breeds such as Miniature Poodles, Toy Poodles, and Chihuahuas.

I. Etiology

The anal sacs of dogs are located on the ventral side between the internal and external anal sphincters, one on each side, and are spherical. In neutered dogs, the anal sacs are about 1 cm in diameter. The anal sac opens through a 2-4 mm long duct at the junction of the anal mucosa and the skin. When the dog's tail is lifted upward, the opening protrudes from the anus and is easy to see. The wall of the anal sac is lined with glands that secrete a gray or brown sebum-like secretion containing small particles. When the drainage duct of the anal sac becomes blocked for some reason, or the dog has a seborrheic constitution with hyperactive sebaceous gland secretion, the sac becomes filled with glandular secretions, and bacterial infection can cause this disease.

Anal sacculitis is associated with pyogenic bacteria. In dogs with chronic soft stool or diarrhea, small breeds, and obese dogs, the decreased tension of muscles such as the anal sphincter makes this condition more likely to occur.

II. Symptoms

This disease presents with various symptoms, most of which are caused by inflammation of the anal sacs, retention of secretions, and discomfort around the anus. The diseased dog's anus shows inflammatory swelling. One can often see tail chasing, licking and attempting to bite the anus, rubbing the anus on the ground or floor, a distinctive gait, and constantly spinning after its own tail. Defecation is difficult, and the dog refuses to be patted on the hindquarters. A foul odor can be detected near the dog's body. When the inflammation is severe, the anal sac ruptures, discharging a large amount of yellow, thin secretory fluid mixed with pus. On anal palpation, a fistula can be seen forming at the anus, with an aggravated pain response, and perianal fistula appears. In dogs with perianal fistula, purulent secretions with a putrid odor can be seen around the perineum centered on the anus; defecation is difficult, causing constipation; the tail rubs against the ground, and the area around the anus is filthy and unclean. As the condition worsens, symptoms such as fever, fecal incontinence, obstructed defecation, diarrhea, loss of appetite, and weight loss appear.

III. Diagnosis

A preliminary diagnosis can be made based on clinical symptoms, and a definitive diagnosis can be made through rectal palpation or proctoscopy.

IV. Treatment

1. In early-stage affected dogs, squeeze the opening of the anal sac with the thumb and index finger, or insert the index finger into the anus and squeeze in coordination with the thumb outside to remove the contents of the anal sac. If helium-neon laser therapy can be used in conjunction, the effect will be even more pronounced. Then, inject anti-inflammatory ointment or the like into the sac. Apply 0.3% basic fuchsin solution to the ruptured area of the anal sac after debridement, or after an enema to induce defecation, dip a bandage roll in fuchsin solution and insert it into the rectum; 2-3 times can be effective.

2. For dogs with more severe symptoms accompanied by systemic symptoms, systemic anti-infection treatment should be given.

3. When the anal sac has already ulcerated or a fistula has formed, the anal sac should be surgically removed, taking care not to damage the anal sphincter and levator ani muscle. After trimming into a fresh wound, perform routine suturing. Within 4 days after surgery, fast the dog or feed a liquid diet to reduce defecation, prevent the dog from sitting down and biting the affected area, and take the dog for a walk 2 times a day.