What Are Those Sacs by a Dog's Rear That Can Become Clogged?

Undrained anal sacs can be painful.
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Your dog has two anal glands under his skin on either side of his anus. They naturally express themselves when your dog has a bowel movement, but in some cases, fluid may build up due to impaction, abscess or infection, and need to be manually expressed. A vet or a trained grooming professional can do it, or you can get one to teach you how to do it at home.

Anal Glands

Wild dogs used their anal sacs or anal glands, for marking territory or even spraying in self-defense. Domesticated dogs, though, don’t have the ability to release the musky fluid of their anal sacs at will. Sometimes they need the help of their human companions to do the job. Sacs that don’t drain can become uncomfortable for your pup.


A number of things can cause problems with anal sacs, though a primary cause is a low-fiber diet. Anal sacs that don't drain can become infected or the fluid inside can become thick, leading to swelling. Abscesses can form if the problem goes untreated. This condition presents as rectal bleeding and must be treated by a vet, often with antibiotics.

Signs of Anal Gland Problems

The most common indication that your dog needs his anal sacs expressed is when you find him scooting his rear along the ground. You may also see noticeable swelling and redness in the area, or impacted feces. Your pup may chew and bite at the spot, shiver or hold his tail between his legs.

Draining Anal Sacs

Most people allow their vet or groomer to express their dog’s anal sacs, as it’s a messy and smelly endeavor. A handler can express them manually from the outside by gently squeezing the glands on either side of the anus, or internally, using a gloved finger inserted into the anus to squeeze the glands. Sacs may require draining more than once to fully evacuate them.

Preventing Future Problems

Some dogs are predisposed to anal sac problems, especially small dogs. Regular expressing during grooming or vet appointments may be enough to keep the problem under control. If sacs need to be expressed more regularly, your vet may recommend surgically removing the glands to prevent future problems. This is called an anal sacculectomy and is a relatively simple surgical procedure. Your vet may also recommend dietary changes to ward off problems.