Dogs and cats have two anal sacs located just under the skin on either side of the anus and are connected to it by small ducts. Glands lining the inside of the anal sacs produce a dark, foul-smelling scent which is stored by the sacs. The anal sacs are normally emptied during a bowel movement, extreme excitement or distress. The function of the fluid produced by the anal sacs is as a scent marker.
Signs of Anal Sac Disease
Anal sac disease may occur in animals of any age breed or sex, but is most common in small and toy breed dogs and rare in cats. In some animals the disease may be associated with dermatitis. Many patients may have recently had diarrhoea, soft stool or have been in season.
There are usually signs of anal irritation such as scooting or dragging the anus along the ground, excessive licking under or around the tail, or a bloody or sticky discharge on either side of the anus. Occasionally, a patient may be reluctant to pass stool, become constipated, have reduced appetite or stop eating.
Some dogs are born with anal duct canals that do not close well and they constantly drain anal sac fluid and leave foul-smelling drops behind them. These dogs do not outgrow this problem and anal sac removal is the treatment.
Diseases of the Anal Sacs
- Anal Sac Impaction: an abnormal accumulation of anal sac secretion as a result of inflammation, infection or blockage of the ducts.
- Infection: bacteria grow in this material producing yellow or bloody pus.
- Abscessation: infected material builds up within an impacted sac, leading to rupture of the sac creating a hot, tender abscess under the skin around the sac and anus. The abscess may then rupture and discharge blood and pus onto the skin. This is a very painful condition; some patients can be fevered and very ill.
The treatment for impaction is to express or empty the solidified material from the sacs. In some cases flushing the anal sacs and filling them with an anti-inflammatory and antibiotic treatment is needed and is done under general anaesthesia. Changing to a high fibre diet such as Hill’s Prescription Diet r/d or w/d may increase the bulk of the stool improving the natural emptying of the sacs.
Antibiotics and pain relief are necessary to treat an anal sac abscess and in some cases surgical drainage is necessary.
Removal of Anal Sacs
Despite treatment many patients have recurring or persisting anal sac disease. This can be painful and repeated treatment is distressing for the patient and upsetting for the owner. Most of these patients are best managed by surgical removal of the anal sacs.
The surgery is carried out in sterile manner under general anaesthesia. There is an increased risk of infection because it is done in a dirty area. The sacs are emptied and filled with a plastic material which defines the sacs and makes removal easier. Sutures are placed under the skin and in the skin.
The patient is discharged with antibiotics and a Buster collar to prevent licking or biting at the incision or sutures. Care must be taken to ensure the patient cannot rub the anus along the ground. Pain relief may be necessary, and sutures are removed 10 – 14 days after the surgery.
Most patients have uneventful recoveries from surgery. Possible complications include infection, damage to the surgical wound by the patient. Rarely, inadvertent nerve damage during surgery can cause faecal incontinence. This is usually short lived with most patients usually returning to normal over a short period of time.
An occasional patient may continue to rub the anus along the ground after surgery although there are no signs of disease. It is possible that the patient has found a way of attracting the owner’s attention and continues to do despite the removal of the anal sacs. If there is a suspicion that this is the case, please discuss the problem with your veterinary surgeon.