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Disorders of the Rectum and Anus in Dogs

By Dana G. Allen, DVM, MSc, DACVIM, Professor and Chair, Department of Clinical Studies, Ontario Veterinary College, University of Guelph ; Lisa E. Moore, DVM, DACVIM ; Carlton L. Gyles, DVM, PhD, Professor Emeritus, Department of Pathobiology, Ontario Veterinary College, University of Guelph ; Sharon Patton, MS, PhD, Professor of Parasitology, Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee ; Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM, Associate Professor, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada ; Thomas W. Swerczek, DVM, PhD, Professor, Department of Veterinary Science, University of Kentucky ; Ben H. Colmery, DVM, DAVDC ; James G. Fox, DVM, MS, DACLAM, Professor and Director, Division of Comparative Medicine, Massachusetts Institute of Technology ; H. Carolien Rutgers, DVM, MS, DACVIM, DECVIM-CA, DSAM, MRCVS, Senior Lecturer, The Royal Veterinary College, University of London ; Jörg M. Steiner, DrMedVet, PhD, DACVIM, DECVIM-CA, AGAF, Associate Professor and Director, Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A & M University ; Sofie Muylle, DVM, PhD, Faculty of Veterinary Medicine, Department of Morphology, Ghent University ; Walter Ingwersen, DVM, DVSc, DACVIM, Specialist, Companion Animals, Boehringer Ingelheim (Canada) Ltd, Vetmedica ; Stanley I. Rubin, DVM, MS, DACVIM, Clinical Professor, Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign ; Sharon Campbell, DVM, MS, DACVIM, Manager, Pharmacovigilance Regulatory Affairs, Veterinary Medicine Research and Development, Pfizer Inc.

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Diseases of the rectum and anus can be congenital (inherited) or occur later in life (Veterinary.heading on page Congenital and Inherited Disorders of the Digestive System of Dogs).

Anal Sac Disease

Anal sac disease is caused by clogging or infection of glands called anal sacs located on each side of the anus. It is the most common disease of the anal region in dogs. The anal sacs are related to the scent glands in skunks and produce a small amount of dark, foul-smelling liquid. The liquid is normally squeezed out during defecation. Small breeds are predisposed to anal sac disease; large or giant breeds are rarely affected.

Anal sacs may become clogged (impacted), infected, abscessed, or cancerous. There are several common causes of clogged anal sacs, including failure of the sacs to be squeezed out during defecation, poor muscle tone in obese dogs, and excessive secretion of the gland. When the gland contents are not periodically squeezed out, this can make the glands susceptible to bacterial overgrowth, infection, and inflammation.

The anal sacs of a dog.

The signs of anal sac disease are related to pain and discomfort associated with sitting. The dog may scoot its buttocks on the ground, lick or bite at the anal area, and have painful defecation with straining. If the glands are impacted, hard masses can be felt in the area of the sacs. When the sacs are infected or abscessed, severe pain and discoloration of the area are often present. Open tracts of tissue can lead from abscessed sacs and rupture through the skin, causing a wound. Tumors involving the anal sacs are sometimes present. A rectal examination by a veterinarian will usually be done to diagnose anal sac disease. Additional tests may be needed if infection or a tumor is suspected.

Your veterinarian can often squeeze out impacted anal sacs by hand. If the material in the sacs is too hard or dry, the veterinarian may inject a softening agent into the sac. If infection is present, antibiotics might be prescribed. Your veterinarian might recommend applying hot compresses if an abscess (infection) is present. Supplemental fiber may be recommended to increase fecal bulk, which facilitates anal sac compression and emptying. If treatment is ineffective or the condition keeps coming back, the anal sac can be surgically removed. A common complication from this surgery is fecal incontinence; however, the incontinence is usually temporary.

Perianal Fistula

Perianal fistula is characterized by chronic, foul-smelling wounds in the tissues surrounding the anus. The cause is unknown. It is most common in German Shepherds but is also seen in setters and retrievers. Dogs more than 7 years old are at higher risk.

Contamination of the hair follicles and glands of the anal area by fecal material and anal sac secretions may result in tissue damage and longterm inflammation of the skin and tissues surrounding the anus. Dogs that are susceptible to skin problems may be affected more often. Low thyroid hormone levels or an immune system defect may also contribute to susceptibility. The likelihood of contamination is greater in dogs with a broad-based tail; deep anal folds may cause feces to be retained within rectal glands and play a major role. Prompt treatment is necessary to keep infection from spreading deeper into the body.

Signs in dogs include attitude change, straining and painful defecation, loss of appetite, lethargy, diarrhea, and attempts to bite and lick the anal area.

Until recently, management of perianal fistulas usually involved surgery to remove the anal sacs and the diseased tissues. Because of complications such as incontinence and rectal narrowing, surgery is now recommended only for dogs that do not improve with medical treatment. Several medications have been shown to provide effective treatment. Your pet may also be prescribed stool softeners to reduce painful defecation. Antibiotics (if prescribed) and cleansing the anal area may reduce inflammation. For your pet’s comfort, follow all treatment instructions carefully.

Perineal Hernia

Perineal hernia is a type of hernia that occurs near the anus. It occurs most often in unneutered 6- to 8-year-old male dogs. Welsh Corgis, Boston Terriers, Boxers, Collies, Kelpies and Kelpie mixes, Dachshunds and Dachshund mixes, Old English Sheepdogs, and Pekingese are at higher risk than other breeds. Many factors are involved in the development of this condition, including breed predisposition, hormonal imbalance, prostate disease, chronic constipation, and pelvic muscle weakness.

Common signs include constipation, straining, and painful defecation. Urinary obstruction may develop if the bladder and/or prostate gland become displaced into the hernia. A swelling below and to the side of the anus may be evident. Hernias may occur on both sides, but two-thirds of cases occur on one side only and more than 80% of these are on the right side. Diagnosis is done by rectal examination to determine what organs and tissues are involved.

Perineal hernia is rarely an emergency, except when the dog is unable to urinate. If this occurs, the veterinarian will attempt to insert a catheter into the bladder or remove the urine using a needle. This is followed by an attempt to correct the hernia surgically. If your pet is an unneutered male, neutering may be recommended to reduce the chance of recurrence. In up to half of affected dogs, perianal hernias will happen again. Postoperative complications such as infection, nerve damage, and other anal or rectal problems can occur.

Rectal and Anorectal Narrowing (Strictures)

Rectal and anorectal strictures are narrowings caused by scar tissue. The scarring may be the result of injury from foreign objects or trauma (such as bite wounds or accidents) or may be a complication of inflammation. In dogs, strictures usually involve both the rectum and the anus, but they are not common. Strictures are more frequent in German Shepherds, Beagles, and Poodles than in other breeds.

Rectal Tumors

Signs of rectal tumors can include straining, painful defecation, blood in the feces, or diarrhea. Surgery is the treatment of choice for rectal tumors, but it may not be effective because the disease may have spread beyond the rectum before any signs are visible.

Rectal Polyps

The growths called rectal polyps occur infrequently in dogs. The polyps are usually benign and do not spread to other tissues. The larger the polyp, the greater the probability that it is malignant (cancerous). Signs include straining to defecate, blood in the feces, and diarrhea. The polyp can be felt by a veterinarian during a rectal examination, and its surface tends to bleed easily. Periodically, the polyp may protrude from the anus. Surgical removal is usually followed by rapid recovery and lengthy survival time. New polyps may develop after surgery. Your veterinarian may submit a tissue sample from the polyp for microscopic analysis to confirm the diagnosis.

Rectal Prolapse

Rectal prolapse is a condition in which one or more layers of the rectum protrude through the anus. Prolapse may be classified as incomplete (only the innermost rectal layer is protruding) or complete (all rectal layers are protruding).

The condition commonly occurs in young dogs that have severe diarrhea or that routinely strain to defecate. Prolapse can be caused by a number of intestinal, anorectal, or urinary diseases. Perineal hernia (see Disorders of the Rectum and Anus in Dogs : Perineal Hernia) or other conditions that affect the nerves of the anal sphincter may also produce prolapse.

An elongated, cylinder-shaped mass protruding through the anal opening is usually a sign of rectal prolapse. However, prolapses involving other parts of the intestine can have a similar appearance. No matter what type of prolapse is present, any tissue mass protruding from the anal opening should be promptly examined by a veterinarian.

Identifying and eliminating the cause of prolapse is a key part of treatment. Small or incomplete prolapses can often be manually replaced by the veterinarian while the dog is anesthetized. This is usually followed by partial closure of the anus with stitches for 5 to 7 days to prevent the prolapse from happening again. The dog may be given a topical anesthetic or epidural injection before or after the procedure to reduce straining. In some cases, surgery to repair the prolapse may be required. After treatment, a moist diet and a stool softener are likely to be recommended. Diarrhea occurring shortly after surgery may require additional treatment and should be discussed with your veterinarian.

Rectal Tears

A tear in the rectum or anus can be caused by a dog swallowing a sharp object (such as a sharp bone, needle, or other rough material) or from injury such as a bite. The tear may involve only the surface layers of the rectum (partial tear) or penetrate all layers (complete tear). Signs may include constipation, straining, rectal bleeding, and reluctance to defecate. A diagnosis is based on these signs and inspection of the rectum and anus. Swelling may be present when the injury has been present for some time.

Treatment to avoid infection and close the wound will be started immediately. The tear will be cleansed and stitched closed. Depending on the location, the wound may be accessible through the anus or may require abdominal surgery. Antibiotics and stool softeners will probably be prescribed after surgery.

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