All dogs possess two anal sacs, they are positioned at the 4 and 8 o’clock position just inside the anus. They are lined with glandular cells which secrete a brown pungent smelling liquid. As the dog passes faeces, the pressure on the glands causes a release of some of the pungent liquid onto the outside of the faeces, scent marking it.
Anal sacs may become distended for a variety of reasons
- Small opening means any swelling of the perineal area can lead to closure of the duct and an inability to empty
- Soft stools, meaning no pressure on gland to stimulate emptying during defecation
- Obesity, fat around the sacs will interfere with them emptying
- Inflammatory bowel disease
- There may also be genetic influences as there is an increased incidence of anal sac problems seen in chihuahuas, poodles, cavalier king charles spaniels and labradors
The most common problems seen in anal sacs are
The clinical signs of anal sac disease usually relate to discomfort of the perineal area, and demonstrate as scooting, twitching and pain at the tail base. Sometimes a swelling can be seen in the affected area.
Most anal sac impactions and infections respond to repeated manual expression and appropriate antibiotics, along with pain relief, as it is a very uncomfortable condition.
Occasionally for recurrent problems it is advised to have the anal sacs surgically removed. This is usually a straightforward process, however due to the location of the surgery there is a sight increase in wound complications, and a slight risk (2%) of faecal incontinence afterwards.
A rare disease of anal glands is anal sac adenocarcinoma which is a type of cancer. It is often malignant with over half already having spread by the time of diagnosis. Treatment is surgical removal with or without the addition of radiation treatment of chemotherapy. Although therapy is unlikely to result in a cure, survival time can be years.