Anal sac disorder in dogs

What is anal sac disorder?

The anal sacs, also called ‘anal glands’, are two small pouches located on either side of, and slightly below, the dog’s anus. Each sac is connected by a tiny duct to an opening just inside the anus.

The walls of the anal sacs are lined with numerous specialised sebaceous (sweat) glands that secrete a smelly, oily, brown fluid that is stored in the anal sacs. Some of these smelly yellow-brown secretions are released through the ducts when the dog defecates. The pungent smell is unique to every dog, male and female, and is used to mark the animal’s territory. It also explains why dogs are interested in smelling one another’s anuses and faeces. In addition to their role as scent glands, the anal sacs assist with the regulation of stool consistency and the elimination of toxins.

Anal sac disease is the most common disorder of the anal region in dogs. The anal sacs may become impacted, infected, abscessed or in rare cases, neoplastic (cancerous). Small breeds such as Miniature Poodles, Toy Poodles and Chihuahuas are predisposed to these conditions, while the large or giant breeds are seldomly affected.

Impaction of the anal sacs

The anal sacs frequently become impacted, or blocked, usually as a result of inflammation of the ducts. Within the impacted sacs, the secretion will thicken into a pasty, brown substance and the sacs will become hard, swollen and distended, making defecation painful.

Infection and abscess of the anal sacs

The thickened secretions within the anal sacs are an ideal medium for bacterial growth, resulting in infection and the formation of abscesses. An abscess will appear as a painful, red, hot swelling on one or both sides of the anus. If the abscess ruptures, it will release greenish-yellow or bloody pus. If left untreated, the infection can quickly spread and cause serious damage to the anus and rectum.

Other problems relating to the anal sacs

Some dogs typically release the contents of their anal sacs when frightened. Some dogs appear to lack control of the anus or anal sac ducts so that small quantities of fluid will drain out when they are resting, leaving an unpleasant lingering odour in the home.

Cost of anal sac treatment for dogs

Anal sac disorder was one of the most common health issues experienced by dogs in 2022, according to PetSure claims data. They were most prevalent in smaller dog breeds.

Because it is difficult to predict the costs of veterinary care, it can help to have measures in place to help prepare for the unexpected. Pet insurance can help by covering a portion of the eligible vet bill if the unexpected does happen.

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Symptoms of anal sac disorder in dogs

The first sign of an anal sac disorder is often scooting or dragging the bottom along the ground. In some cases, the dog has an episode of diarrhoea or digestive upset a week or two before the clinical signs of anal sac disease became evident. Anal sac disease is very painful, and even normally gentle dogs may snap or growl if you touch the tail or anus.

Signs of an anal sac disorder are:

• Sliding or scooting the bottom on the floor to relieve itchiness
• Constant licking and biting of the anus or base of the tail
• An unpleasant, musky odour
• Straining to defecate
• Tail chasing
• Discharge of pus
• If the anal sac ruptures, blood or pus draining from the rectum
• Obvious constipation

Causes of anal sac disorder in dogs

It is often difficult to determine why some dogs develop an anal sac disorder. Failure of the sacs to expel the fluids during defecation, poor muscle tone in the anal region, and over-secretion by the glands can all lead to retention of fluids within the anal sacs. This retention may predispose the dog to inflammation, bacterial overgrowth and infection. Each impaction may cause further scarring and narrowing of the ducts, leading to more frequent recurrences.

Overweight and obese dogs tend to have chronic anal sac problems because their anal sacs do not empty properly, possibly because the extra body fat they carry in the anal region reduces the pressure that passing faeces applies to the anal sacs. Some dogs may be born with very narrow ducts that drain the anal sacs.

While any breed can suffer an anal sac disorder, smaller breeds, such as Miniature Poodles, Toy Poodles, Miniature Schnauzers, Lhasa Apsos and Chihuahuas appear to have an increased risk. It does not appear to occur as frequently in large and giant breeds. There is no age or sex predisposition.

Possible predisposing factors for anal sac disorders may include:

• Chronically soft faeces
• Recent bout of diarrhoea
• Excessive glandular secretions
• Poor anal muscle tone
• Retained secretions
• Chronically loose stools, which may be caused by a poor diet
• Lack of exercise
• Obesity
• Over-feeding
• Liver problems

How is anal sac disorder in dogs diagnosed?

Diagnosis of an anal sac disorder usually entails a complete physical examination and an account of the dog’s history, symptoms and factors that might have precipitated the condition. The veterinarian will probably order a blood chemical profile, a complete blood count, an electrolyte panel and a urinalysis to rule out other causes of disease.

A digital rectal examination is usually performed by the veterinarian to determine if the glands are impacted or infected. If so, the normally clear or pale yellow-brown secretion will present as a thick, pasty brown substance. Abscessed anal sacs will contain a red-brown fluid and show signs of swelling and redness. The anal sacs may also be clearly ruptured. A sample of the anal sac contents will be sent to a laboratory for culture and sensitivity testing.

Prognosis

Most anal sac disorders in are not especially serious and are not hard to diagnose, especially since the area involved is so isolated and accessible.

Some dogs will have recurrent anal sac impactions or abscesses. For dogs suffering from chronic or recurrent anal sac infection or impaction, surgical removal of the anal sacs may be the only way, and last resort, to relieve the dog’s pain.

Treatment for anal sac disorder in dogs

Treatment for impacted anal sacs depends on the severity of the condition and whether or not there is an identifiable underlying cause.

Impacted anal sacs can be relieved by manually expressing or emptying the sacs by squeezing the glands. If the impaction is severe or if there is an infection, it may be necessary to flush out the affected sac to remove the solidified material. Abscessed anal sacs will be lanced and drained. The anal sacs will then be cleaned and flushed, and antibiotics will be infused into them. Since these procedures are painful, a sedative or an anaesthetic may be required.

Oral or topical antibiotics are usually prescribed and sometimes may need to be infused into the sacs over a period of several days Most dogs require pain relief medications for several days until the swelling and inflammation have subsided.

Some dogs will have recurrent anal sac impactions or abscesses. If this condition recurs frequently, causing chronic pain and suffering, and in advanced or severe cases, surgical removal of the sacs may be recommended. Removal of the anal sacs is a delicate and specialised surgery requiring general anaesthesia.

Ongoing management:

• Follow up appointments will be required as necessary.
• An Elizabethan collar may be required to prevent licking at the wound.
• A high fibre diet and increased exercise may be recommended.
• Owners may be shown how to express blocked anal glands at home.

In summary

Dogs have two small pouches on either side of their anus which produce a smelly, oily, brown fluid that they use to identify each other and mark their territory. An anal sac disorder begins as an uncomfortable impaction of the anal sacs and can develop into to a painful infection or abscess. A bad smell, licking or biting at the anal area and scooting are common signs of these conditions.

The vet will perform a rectal examination and cytology testing of the contents of the anal sacs. Treatment entails manually expressing, or emptying, the impacted anal sacs to provide relief. A severe impaction or infection will be flushed out and antibiotics are usually prescribed. Weight loss and a diet high in fibre may be recommended to prevent recurrences. Surgery may be a last resort in severe and chronic cases.

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