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Understanding Swollen Anus in Dogs: Causes, Symptoms, and Treatments

Have you noticed that your dog's anus is swollen? If you notice that the appearance of your dog's anal area is not the usual one and you are worried about his health, the first thing we recommend is to take him to the vet for a check-up and help.

This part of the dog's body is one of the most sensitive, as it is prone to injuries and infections, as well as other problems related to the mucous membrane and anal glands.

At Dogalyo, we want to help you provide the best care for your faithful companion and keep you better informed about aspects of his health. For this reason, we have prepared this article to explain the causes that answer your question "Why does my dog have a swollen anus?", as well as the possible treatments for each cause and some tips.

Dog swollen anus treatment


Symptoms of swollen anus in dogs


Among the main symptoms of anal inflammation in dogs and related problems, we highlight the following:

  • Swelling of the anal and/or perianal area.
  • Irritated anus
  • Itching and scratching at the bottom
  • Clear discharge
  • Pink or red discharge or bleeding
  • Yellow or green discharge
  • Lumps in the perianal or anal area
  • Soreness in the anal area

These are the main signs that something is wrong with this sensitive part of a dog's body, but other symptoms that often accompany these include nervousness, irritability, fever, increased sensitivity to touch in that area as well as the tail and thighs, listlessness, and so on. 


Why is my dog's anus swollen and what should I do? Understanding Causes and Treatments

If you suspect, or your veterinarian has confirmed, that your pet has anal inflammation based on the symptoms you've observed, it's important to understand the possible causes. In the following sections, we'll discuss the most common causes of anal inflammation in dogs. Your veterinarian will need to consider these possibilities and perform the necessary tests to determine the cause and prescribe appropriate treatment. For each potential cause, we'll also discuss possible treatments for a dog's inflamed anus: 

Swollen anal glands in dogs

Dogs have glands on both sides of the rectum and anus called anal glands or anal sacs. These glands secrete a fluid that helps lubricate the stool and serves as each dog's distinctive scent. Sometimes these glands can malfunction, become inflamed, infected, or collapse as the fluid builds up and thickens. Some dogs are more prone to inflammation or collapse than others, and we can help them by emptying their anal sacs. This is a task that can be learned at home, but is best done by a veterinarian.

If the anal glands are swollen, there may be swelling in the anus. If these glands become blocked, anal or perianal fistulas, lumps, and abscesses can develop. Of course, all of these conditions include swelling as a symptom. If these potential problems are not addressed, an anal infection can develop and become complicated in a short period of time.

If the swelling is severe or there is a collapse, the veterinarian will need to provide treatment. Typically, they will perform a lavage and administer an anti-inflammatory. However, if the collapse is severe, surgery may be required. In the event of surgery, the specialist will likely prescribe a series of treatments, as well as the use of an antibiotic ointment for the dog's anal glands to prevent infection. 


The difficulty in passing stool can cause the lining and other tissues of the digestive tract, between the intestines and the anus, to become overstressed. As a result, it's common for the anal area and abdomen to become inflamed in dogs with constipation, especially in chronic or severe cases.

In addition to following the veterinarian-prescribed treatment for dog constipation, discuss with them the compatibility of this treatment with some of the best home remedies for dog constipation. If you're wondering how to treat an irritated anus in dogs, which is one of the main problems associated with this condition, we recommend following the vet's advice, regulating your dog's diet, using the same remedies, and using a special ointment or moisturizing cream for dogs.

Perianal fistula

A perianal fistula is an opening or communication that opens between a body cavity, in this case the rectum, and the surface of the skin or outside, and is an abnormal tunnel-shaped opening, so it has occurred because something is not right in that area, as an escape route for secretions. In this area it can be caused by abscesses, lumps of fluid with or without infection, and problems with the anal glands, although this is not the usual cause. When dogs suffer from this, they will try to bite the area while circling or chasing their tails, and when they get there, they will usually nibble at the base of the tail and drag the butt on the ground where a wound can be seen.

Treatment for perianal fistula in dogs requires surgery and antibiotics after surgery. 

Anal sores

In addition to swelling, you may see some open or crusty sores. Injuries in the anal or perianal area of dogs can be caused by excessive scratching, which can occur for various reasons, as well as constipation, a blow or a fight. Such an injury in this area can easily lead to inflammation in the anus.

Treatment of anal and perianal wounds in dogs includes saline and iodine baths, the use of antibiotics in the form of ointments, creams, pills or injections, and even anti-inflammatory drugs, depending on the case. 


If your furry friend has been hit in this area some time before you see this swelling, it is likely that he will have inflammation for at least a while. This can happen if he has been running and jumping a lot, if he has fallen from a low place, or if he has been hit in any way, such as in a fight with another dog. Any trauma, no matter how minor, to any part of the body can cause swelling, redness, itching, and bruising, as well as localized and more intense pain when the area is touched.

Treatment for anal trauma in dogs is the use of anti-inflammatory medications, analgesics, and rest. It is also possible to have surgery depending on the case, as well as antibiotics, especially if there is a wound. 

Intestinal parasites

Internal parasites, especially intestinal parasites, produce symptoms such as constant itching in the anal area, which causes the dog to be on its feet all the time, nibbling at the area and dragging the anus along the floor to relieve the discomfort. This can lead to inflammation, sores, and secondary infections, primarily bacterial. Other clear symptoms of intestinal parasites in dogs include weight loss, even if the animal is eating normally; worms and worm eggs in the feces; and diarrhea and even blood in the feces.

The treatment for intestinal parasites in dogs is internal deworming with antiparasitic medications in the dosage prescribed by your veterinarian. 

Rectal prolapse

If you are wondering, "Why is my dog's anus red?" In addition to swelling, it could be irritation from excessive scratching, but if you notice that your dog's anus is swollen and red, and you see it larger or with a lump, another very likely possibility given these symptoms is rectal prolapse. This means that the animal's rectum has come out through the anal opening and part of it has been left outside the body, so the mucosa looks reddish, there may even be blood, you can see a lump which is the displaced rectum itself, and inflammation. The main cause of this problem is chronic constipation.

The treatment of rectal prolapse in dogs is always surgery, more or less complex depending on the case, but always necessary. 

Anal infection

Inflammation of a dog's anal area can be due to infection both internally, near the sphincter and rectum, and externally, in the anal opening and perianal area. These infections are usually bacterial, but can also be fungal. The main causes are: wounds, fistulas, abscesses, parasites, prolapse, and in the case of collapsed anal glands, if left untreated.

Treatment of anal infections in dogs is based on antibiotics, but the primary cause must also be treated to prevent recurrence.

Below are the most common causes of a dog's swollen anus, along with other more specific symptoms that often accompany this swelling. 

My dog's anus is swollen and bleeding

If your dog has a swollen and bleeding anus, the most likely causes of these symptoms are all of the above, since bleeding is another of the most common symptoms of these conditions, especially when they are somewhat advanced or, in the case of swollen or collapsed anal glands, when they are being treated or pressure is being applied to clean them. Therefore, if you see either of these signs in your dog, it is imperative that you see a veterinarian immediately. 


My dog has a swollen anus and cannot defecate

Another common symptom along with the swelling in this area is difficulty defecating. If you notice that your faithful companion has discomfort and swelling in this area, and you see that he has difficulty defecating, and even if you see that he is unable to pass stool in any way, all of the above causes are possible in this case. However, these are the most likely causes of your dog's swollen anus and inability to defecate: 


  • Constipation
  • Rectal prolapse
  • Collapsed anal glands
  • Trauma or a blow

My dog has a swollen anus and is leaking fluid

If your dog's anus is swollen and leaking, it could be due to one of the following causes:

  • Swollen anal glands: Dogs have anal glands on both sides of the anus that can become inflamed and leak fluid.
  • Injury or trauma: Any injury or trauma to the anal area can cause swelling and leakage.
  • Anal fistula: This is an abnormal connection or tunnel between the anal gland and the skin that can cause leakage and swelling.
  • Wounds: Any cuts or abrasions in the anal area can cause swelling and leakage.
  • Intestinal parasites: Certain parasites can cause inflammation and swelling in the anal area.
  • Anal infection: If the fluid is yellow or green and even a little thick, it could indicate an infection.

Each of these conditions requires a different approach to treatment, so it's important to consult a veterinarian for a proper diagnosis and treatment plan.

My dog has swelling between the anus and testicles


If you have a male dog and you notice swelling between the anus and the testicles, it could be due to any of the above conditions.

It could also be related to a testicular problem or recent neutering. If your dog has been neutered and there is swelling between the anus and scrotum or in the scar area, it's normal if the surgery was recent. However, if several days have passed, it's not normal and there could be an infection in the surgical wound.

In a female dog, this area can also become inflamed if she is in heat. If she tends to have significant swelling in the genital area and rubs or nibbles at it, the swelling may spread to the anal or perianal area. However, this reaction is not normal in the anal area after spaying or neutering.
In conclusion, a swollen anus in dogs can be caused by a variety of conditions, including swollen anal glands, trauma, anal fistulas, wounds, intestinal parasites, and anal infections. It's important to consult a veterinarian for a proper diagnosis and treatment plan. In cases of recent spaying or neutering, some swelling may be normal, but if it persists or is accompanied by other symptoms, it could indicate an infection or other complication. Always monitor your pet's health closely and seek veterinary care as needed to ensure your pet's well-being.