When a dog's anal sacs are irritated or infected, blood flow to the area increases. The anal area becomes hot, swollen, and painful. This inflammation causes the tiny ducts that empty the anal sacs to swell shut. With the ducts swollen shut, the material within the sac dries out and hardens, first into a paste, then into a hard, gritty material. If the sac is not expressed manually or opened surgically, it bursts, creating an open, draining tract through the skin. All dogs have two anal sacs just under the skin below the anus. Anal sacs are round little pouches approximately pea-sized in small pets and grape-sized in large pets.
Anal Sac Problems & Scooting in Dogs
Anal Sac Problems & Scooting in Dogs - PetMeds®
When a dog's anal sacs are swollen and inflamed they are treated by draining. Draining is done manually or surgically with a scalpel and under anesthetic. When done manually, the procedure is called anal sac expression. Dog anal sacs are emptied manually either by external or internal expression.
Anal Sac Disorders in Dogs
However, the likely culprit is anal glands that need to be expressed. Over time and with domestication, particularly in small dogs, this glandular material is sometimes not expressed. It continues to accumulate, causing swelling that creates sometimes intense pain. The area on one or both sides of the anus may be tender and swollen, or you may notice your dog chewing and licking the anal area, scooting, hiding away as if in distress, or having difficulty in passing stool.
So, what are these things in the first place? They contain a strong smelling, yellow-brown fluid which is released through small ducts when your pet has a bowel movement. Although some dogs may never experience any problems with their anal glands, in some dogs and some breeds in particular the anal gland fluid can become thickened, which causes the gland to become abnormally large, and then the wall of the anal gland itself can become inflamed, causing one or both anal glands to become uncomfortably impacted. Abscesses like these usually need to be treated with a course of antibiotics and pain medication. More rarely, anal glands can also develop cancerous tumours called adenocarcinomas.