Anal Sac Disease in Dogs

Dogs

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The anal sacs are glands located near the anus (rectum) that produce secretions that are normally expressed during defecation. The secretions from these glands are normally pungent (in fact, very smelly) and straw-colored with brown flecks. Anal sac contents may also be expressed in times of fright (producing a terrible odor in the area).

Dogs are more commonly affected with anal sac disease than cats, and small breed dogs are more commonly affected with anal sac impaction than large breed dogs. Older female dogs are more commonly affected with anal sac tumors.

Types of anal sac disease include:

  • Impaction, which can lead to inflammation or infection of the anal sacs
  • Inflammation
  • Infection or abscess formation
  • Tumors of the sac or related glandular tissues

    What to Watch For

  • Scooting or dragging the anus on the ground or carpet
  • Frequent licking of the anus or tail base
  • Reluctance to sit or sitting asymmetrically to avoid pressure on the painful anal sac
  • Straining to defecate, difficulty defecating, production of ribbon-like stools
  • Painful swelling at the 4 o'clock or 8 o'clock locations around the anus

    Similar signs can be seen in dogs with a different disease called perianal fistula, a severe condition that causes draining tracts around the anus. The breeds that most commonly develop perianal fistulae are German shepherd dogs and Irish setters.

    • Abscesses of the anal sacs are lanced and flushed, and then treated with oral antibiotics.

    • Anal sac tumors are usually not painful and do not have redness on the overlying skin. They occur most often in older female dogs.

    • Anal sacculitis is inflammation of the anal sac, which can be caused by impacted anal sac secretions or bacterial infections of the anal sacs.

    • To prevent licking of the area, pets may be required to use an Elizabethan collar.

    Diagnosis

    Diagnostic tests may be required to confirm the diagnosis and exclude other diseases causing similar signs. Tests may include:

  • A complete history and physical exam

  • Rectal examination, including an attempt to manually express (empty) the anal sacs – this could require sedation.

  • Blood tests (anal sac tumors can cause an increase in blood calcium levels)

  • If a tumor is found, chest and abdominal X-rays to check for tumor spread to other organs (lungs, lymph nodes) and an abdominal ultrasound to check lymph nodes for tumor spread

    Treatment

    For simple impactions and cases of inflammation, expressing the anal sacs may be all that is necessary. If the anal sacs cannot be expressed while your pet is awake, then anesthesia may be necessary to express and flush the anal sacs. Other treatments may include:

  • Antibiotics or anti-inflammatory drugs may be given orally or infused into the sacs if necessary.

  • Chronic cases of impaction or inflammation may require surgical removal of the anal sacs.

  • Abscesses of the anal sacs are lanced and flushed, and then treated with oral antibiotics.

  • Tumors of the anal sacs are treated by complete removal of the affected sac. Affected lymph nodes can also be removed, although this is more difficult.

  • Related Diseases

    The anal sacs are located at the 4:00 and 8:00 positions around the anus, embedded in the muscle of the anal sphincter (the muscle that closes the anus). Related glands produce a pungent yellowish secretion during defecation.

  • Anal Sac Impaction. This disease is more commonly seen in small breed dogs and is the result of large amounts of thick anal sac secretions that cannot be expressed by the dog during defecation. The secretions build up and cause discomfort as the sac becomes distended or even infected. The only symptoms you may notice are "scooting" or rubbing the anus on the carpet or ground, and excessive licking of the anus or tail base.

  • Anal Sacculitis. This is inflammation of the anal sac, which can be caused by impacted anal sac secretions or bacterial infections of the anal sacs. Anal sacculitis is more painful than anal sac impaction. In addition to "scooting" and excessive licking, you may notice your pet straining to defecate, being reluctant to sit, or sitting asymmetrically.

  • Anal Sac Abscess. This pus-filled anal sac results from a bacterial infection. Anal sac abscesses are more painful than anal sac impactions. In addition to "scooting," excessive licking, and straining to defecate, you may also notice a red swelling near the anus, or pus dripping from an open wound near the anus if the abscess has already ruptured.

  • Anal Sac Tumors("apocrine gland adenocarcinomas"). These are not often painful and do not usually have redness on the overlying skin or any open wounds. They occur mostly in older female dogs (spayed as well as unspayed). They can cause an increase in blood calcium levels, which can cause clinical signs such as increased drinking and urination. They most often spread to the sublumbar lymph nodes, which are located in the abdomen right below the lumbar (lower back) vertebrae. If the lymph nodes become enlarged due to spread of the cancer, they can obstruct flow of feces by putting pressure on the colon. This may show itself as difficulty defecating or producing ribbon-like stools. Dogs with anal sac tumors can also have symptoms associated with other types of anal sac disease ("scooting," excessive licking, straining to defecate, reluctance to sit, or sitting asymmetrically).

  • Perianal Fistulas. This is a severe condition of the tissue around the anus, creating fistulas, or draining/oozing tracts, around the anus. It is most commonly seen in German shepherds, and is also seen in Irish setters. The cause of this difficult to control disease is unknown, but is currently thought to have an immune-mediated origin (which means that the dog's immune system is for some unknown reason attacking the tissues around the anus). German shepherds and Irish setters with symptoms of anal sac disease should also be screened for this more serious disease.

  • Diagnosis In-depth

  • History. Your veterinarian will ask specific questions regarding defecation habits (straining, size/shape of stool, frequency, pain), appetite, weight loss, drinking and urination habits, what symptoms (licking, "scooting") you have noticed, and how long they have been going on.

  • Physical exam. Your veterinarian will perform a complete physical exam, including a rectal exam of the anal sacs. The veterinarian will attempt to express the anal sacs and note the quality of the secretions.

  • Blood tests. If your veterinarian suspects an infection or abscess of the anal sacs, he or she may recommend a complete blood count, which will assess the number and type of red and white blood cells and platelets. The white blood cell count will usually increase in an infection. If your veterinarian suspects an anal sac tumor, he or she will recommend a serum chemistry panel. This test checks the major organs to see if they are functioning normally (important if the dog will need anesthesia) and also checks the levels of the major electrolytes in the body. Anal sac tumors can cause an increase in serum calcium levels.

  • Chest and abdominal X-rays. Anal sac tumors can spread to lymph nodes and lungs, and rarely to other organs or bones of the body. X-rays are used to check for obvious spread of the cancer, although microscopic spread cannot be ruled out. Chest X-rays are also important in older dogs that will be undergoing anesthesia, to make sure that there is no heart or lung disease that would make anesthesia risky.

  • Abdominal ultrasound. The most common location for anal sac tumors to spread is the sublumbar lymph nodes. These lymph nodes can become extremely large, and may be able to be palpated rectally. If not, they can be seen using an ultrasound. If the lymph nodes become very large, they can push on the colon and obstruct the flow of feces. This can make defecation difficult and may alter the shape or size of the stool.

    Treatment In-depth

  • Anal sac expression. The veterinarian rectally palpates the anal sacs and squeezes them to empty the sacs of the secretions. If the dog is too painful or if the secretions are too firm, then the patient may need to be heavily sedated or anesthetized to have this procedure done. Anal sac expression is often all that needs to be done for simple cases of anal sac impaction or mild cases of anal sacculitis.

  • Anal sac irrigation. This involves anesthetizing the patient and flushing saline into the opening of the anal sac to break up firm anal sac secretions so that the sacs can be emptied. This procedure is indicated when the anal sacs cannot be manually expressed. More severe cases of anal sacculitis often require subsequent irrigation with a topical steroid to help decrease the inflammation.

  • Abscess lancing. An anal sac abscess, unless it has already ruptured on its own, needs to be opened up, or lanced and drained. The dog may be briefly anesthetized, and the abscess is opened up and flushed with saline. Antibiotics are indicated to treat the underlying infection. Warm compresses applied to the area are also helpful.

  • Anal sacculectomy. This is the technical term for surgical removal of the anal sac. This can be done to one or both sides. It is often recommended for recurrent cases of anal sac infection or anal sac impaction, and is necessary for treatment of anal sac tumors. The possible risks of surgery, besides the risks of general anesthesia, are fecal incontinence, chronic draining tracts from residual infection or secretory tissue, recurrence of the tumor, and straining to defecate from postoperative anal scar formation.

  • Sublumbar lymph node removal. If a tumor of the anal sac has spread to the sublumbar lymph nodes, then removal of the lymph nodes can be considered. This is a technically challenging procedure that can result in significant bleeding during surgery and could also result in temporary or permanent urinary incontinence since the nerves controlling urination are close to the lymph nodes. It is not curative, however it may alleviate some of the problems associated with the enlarged lymph nodes, such as difficulty defecating.

  • Chemotherapy and radiation therapy. Both of these treatment types have been used with mixed results in dogs that have anal sac cancer. There is unfortunately no cure for this disease, but adding these therapies to surgical removal of the tumors can help prolong the dog's life.

  • Be familiar with your dog's defecation habits. This may sound strange, but it can be very helpful if you notice subtle changes in your dog's fecal size or shape, frequency of defecation, and manner of defecation. The more you are aware of what is "normal" for your dog, the quicker you will be able to notice something going wrong. As with most diseases, early detection and intervention is best.

  • Be familiar with your dog's body. Look under the tail and feel your dog's body. You should be able to detect lumps or weight loss.

  • Bring your dog to your veterinarian for an annual complete physical exam. Develop a relationship with one doctor so that he or she will get to know your dog's body and habits. This will help your veterinarian notice subtle changes from year to year.

  • If your veterinarian prescribes medications or instructions for treatment of one of these diseases, follow their instructions carefully to get the best results.

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