This site has some info that may be of some help.
I hope your pup gets well...
http://www.vetinfo.com/doganal.html
This might be a little long please stay with me on this...(this was from another thread where I posted on anal gland issues.)
Let's talk about trouble making a bowel movement (causes of constipation)...which can lead to impacted anal glands.
It happens with middle-aged and older dogs and it is usually because they do not drink enough water, so make sure you provide plenty of clean fresh water (which you probably do.) Even with mild dehydration, water is withdrawn from the colon and that dehydrates the feces and it makes it difficult to make a bowel movement.
Keep an eye on what your dog eats, ingesting foreign materials such as bone chips, hair, grass, cellulose, cloth, paper, raw hides, and other substances can be a cause of acute and chronic constipation. Indigestible materials mixes with feces mixed with mild dehydration can form rock-like masses (poo) in the colon making it very difficult to pass.
If the constipation of recent is due to the anal glands expression, and your dog has been eating, drinking and exercising (as normal) and not going poo, you need to discuss this with your vet immediately, because it is normal for a dog to poo once or twice a day.
Treating Constipation:
Eliminate or control predisposing causes. Again, make sure your dog has plenty of access to clean water. Plenty of regular exercise, walking, playing, etc. Older dogs with reduced bowel activity can be helped along by soaking their kibble (if feeding only dry) with equal parts of water and letting the mixture soak for 20 minutes.
Provide frequent opportunities for your dog to do it's business. If it's still not giving it up, talk with your vet about the possibility of a blockage and perhaps a mild laxative? There are over the counter drugs you can talk with your vet about using such as Metamucil, Milk of Magnesia, Mylanta, Maalox, or Mineral oil (I prefer Olive Oil - personally). They can tell you the dosage and frequency of administration. I would prefer you get the "where" and "why-fore" from your vet.
Anal Sac Disease
The anal sacs (as) are located at five and seven o'clock in reference to the circumference of the anus. They can be seen by drawing down on the skin of the lower part of the anus and looking in those locations.
The (as) are emptied by the pressure of stool passing through the anus. They can also be emptied by forcful contraction of the of the anal sphincter such as when the dog barks, running, is frightened or upset. Anal sac disease is a cycle that begins with impaction and progresses through infection to abscess and rupture. Dogs with anal problems may develop tonsillitis from licking at the rear area.
Anal Sac Impaction
Impaction is the accumulation of pasty secretions in the anal sacs. The sacs become distended and mildly tender. (Which is why your dog is still licking the area, or has become so use to licking it has OCD). The expressed secretions are thick and dark brown or grayish brown. They become impacted when they don't empty completely. They may be due to insufficient pressure on the sacs during defecation because of small, soft stools; inadequate sphincter pressure; or blockage of the opening by thick dry secretions. Impaction tend to occur most often in small-breed dogs and in overweight dogs.
Treatment: Impaction is treated by manually expressing the secretions. Dogs with recurrent (as) impaction should have their sacs emptied at regular intervals. (Discuss the intervals with your vet and if you need a second opinion, get one!) Place the dog on a high-fiber diet or a bulk laxative to increase the size of the stools. Discuss these options with your vet, too!!!
How to Empty the Anal Sacs
Here are step by step instructions. You can also have your vet or groomer show you, if you feel more comfortable before you step in and do it yourself (unless you feel more comfortable having them do it and can afford to have them do it.)
Manually emptying the (as) is called expressing them, it is not necessary to express the (as) unless the dog has an anal sac disease, or when frequent malodor poses a problem. Begin by putting on a disposable latex or plastic surgical glove. Raise the dog's tail and locate the openings (again, the sac are located at five and seven o'clock.) Raise the dogs tail and if they are full, the anal sacs can be felt as small, firm lumps in the perianal area.
Grasp the skin surrounding the sacs between your thumb and forefinger and squeeze. When an anal sac is impacted (blocked), it usually is best to empty the sacs with a finger in the anal canal and a thumb on the outside. (For the comfort of the dog, use a small amount of vaseline (or KY) on the finger before inserting in the anal canal.)
As the sac empties, you may smell a strong odor. (You can avoid this by using Vic's Vapor Rub on / slightly inside of each of your nostrils. Do this prior to putting on the plastic or latex gloves. Makes sure after putting the vapor rub on your nostrils, you wash your hands well. You
do NOT want to touch the dogs anus with the vapor rub as it will burn! I cannot stress that sentence enough!!!) Wipe the secretions with a damp cloth or gently hose the dog's rectal area. Normal secretions are liquid and brown. If the discharge is yellow, bloody, or pus-like, the sac is infected and you should seek veterinary attention.
Please understand I am not a vet. I just want you to have additional information at your fingertips.
I hope this helps!
Reference: Dog Owner's Home Vet Handbook and personal experience