The anal glands, technically called anal sacs, are two small sacs located on either side of a dog's anus within the anal sphincter. Anal glands collect oily secretions from sebaceous glands inside the sacs. When full, anal glands usually range in size from that of a pea to that of a small grape. The size will vary based on the size of the dog and the fullness of the anal glands. When anal glands are full, it's uncomfortable for the dog.
That's usually why dogs scoot their butts.
The fluid inside the anal glands is oily and foul-smelling. Anal glands are not a necessary part of the modern dog's anatomy, but they do act as scent glands, similar to that of a skunk. They may be emptied by the dog during times of distress. The fluid in anal glands is routinely released during defecation, and may aid in lubrication. However, the material in anal glands is not always naturally released as it should be. This may be due to soft stool, or simply because of the specific dog's anatomy. For this reason, it is sometimes necessary for a dog's anal glands to be manually expressed by a human.
How to Express Anal Glands
Manually expressing anal glands is best taught in person. Any dog owner can learn to do this at home, though many choose to leave it to the professionals due to its unpleasantness. There are two ways to express the anal sacs: externally and internally.
External expression is done by using a tissue or cloth to gently squeeze the anal glands and massage out the fluid. Internal expression is done by inserting a gloved index finger into the anus and gently squeezing each anal sac (one at a time) between the index finger and thumb. The internal method is more effective, especially if the material in the anal sacs is thick.
Remember, before attempting to express anal sacs, it is best to have a professional show you how (like a vet tech). Improper expression can be very uncomfortable for your dog.
How do I know if my dog's anal glands need to be expressed?
In general, a dog's anal glands do not need to be manually expressed unless there is a problem. Many dogs are able to release the fluid regularly during bowel movements. One noticeable sign that your dog needs the anal glands expressed is if he is scooting his rear. Though many people think this is a sign of worms, a dog scooting his rear on the ground is typically doing it because his anal glands are bothering him. He may scoot if he has skin problems in this area.
Complications of the Anal Sacs
In some cases, anal glands can become compacted and/or infected (abscessed). This is usually due to a long-term inability to empty the anal sacs during normal defecation. If the anal area becomes reddened or a wound is seen around the anus, it may be a problem with the anal sacs. See your veterinarian right away. Other potential but less common anal gland complications include tumors, both benign and malignant.