Bump on Your Dog's Anus: Causes and When to See a Vet

Name: Bump on Your Dog's Anus: Causes and When to See a Vet
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

A dog bump on the anus is usually an anal gland problem, such as an impaction, infection, or abscess, but it can also be a perianal tumor or another type of lump. The location, color, size, and how fast it appeared all help point to the cause. Some lumps need same-day care, while others can wait for a routine visit.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Anal sac disease is the most common disease of the anal region in dogs, and small breeds are predisposed [1].
A red, painful, swollen bump near the anus is often an infected or abscessed anal sac, which needs prompt veterinary care.
A firm lump that does not hurt, grows slowly, or sits right at the anal opening may be a tumor and should be checked.
Never squeeze, poke, or try to drain a lump at home. You can cause more pain, bleeding, or infection.
Call your vet the same day for swelling, redness, pain, or drainage. Go to an emergency clinic now if your dog is straining to urinate, cannot pass stool, or seems very ill.

What a Bump on the Anus Looks Like and What Is Normal

The anus is the opening where stool leaves the body. On each side of it, just under the skin, sit two small glands called anal sacs. They make a small amount of foul-smelling liquid that is normally squeezed out during defecation [1]. In a normal dog, you should not see or feel a distinct lump in this area. The skin around the anus may look slightly darker or have a small amount of hair, and that is normal.

A bump can look like many things. It may be a soft swelling on one side of the anus, a red or purple pimple-like spot, a firm pea-sized nodule, or a broad raised area. It may be painful when touched, or your dog may not seem to notice it at all. Some bumps leak blood, pus, or a brownish fluid. Others stay covered by skin.

Where the bump sits matters. Lumps within about 1.5 cm of the anus are often anal canal tumors, while tumors farther inside tend to be rectal tumors [2]. That is one reason your veterinarian will do a rectal exam instead of just looking at the outside.

Main Causes of a Dog Bump on the Anus

Anal sac disease is the most common problem in this region [1]. The sacs can become clogged (impacted), infected, abscessed, or cancerous [1]. Clogging happens when the sacs do not empty during defecation, when an obese dog has poor muscle tone, or when the gland makes too much fluid [1]. When the contents sit there, bacteria can overgrow and cause infection and inflammation [1].

Non-neoplastic anal sac disease was estimated at 15.7% in dogs in one survey of veterinarians [3]. Predisposing factors included diarrhea, skin problems, certain breeds, small breed dogs, and obesity in dogs [3]. Diagnosis is based on clinical signs and rectal examination [3].

Other causes include perianal tumors, which can be benign or malignant, and less common problems such as a fistula between the urinary and rectal tracts. One report described a young dog with persistent anal sac leakage that turned out to be a urethrorectal fistula, which shows why a thorough exam matters when a dog does not respond to standard treatment [4].

Cause	Typical clues	How urgent
Anal sac impaction	Soft or firm swelling on one or both sides of the anus, scooting, licking, straining to defecate	Routine visit within a few days
Anal sac infection	Red, tender swelling, pain when sitting, possible discharge, bad odor	Same-day call to your vet
Anal gland abscess	Hot, red, very painful lump, may rupture and drain pus or blood, fever, lethargy	Same day, or emergency if your dog is very ill
Perianal tumor	Firm lump near the anus, may grow slowly, may ulcerate or bleed, often no pain early on	Routine visit soon, sooner if growing fast
Anal gland tumor	Firm mass in the anal sac area, may cause straining or blood in stool	Prompt visit, often same week
Skin lump (cyst, wart, pimple, rash)	Small raised spot on the skin surface, may be red or itchy	Routine visit unless it grows, bleeds, or hurts
Urethrorectal fistula	Leakage from the anus, urinating from the anus, chronic drainage that does not improve	Prompt specialty evaluation

If your dog also has itchy or irritated skin elsewhere, that can be related to the same underlying allergy or skin problem. See Dog Itchy Skin: When to See the Vet and How to Help and Dog Skin Rash: When to See a Vet and When to Wait for more on those signs.

Anal Gland Problems

A dog red bump on anus is often an inflamed or infected anal sac. The sac may be impacted first, then infected, then form an abscess. An anal gland abscess dog is in real pain. The area is hot, swollen, and tender, and your dog may cry when sitting or passing stool. Abscesses can rupture through the skin and drain pus and blood. That drainage can look alarming, but it often means pressure is being released. Even so, your dog needs veterinary care to clear the infection and manage pain.

Small breeds are predisposed to anal sac disease, while large or giant breeds are rarely affected [1]. Obesity is a risk factor because poor muscle tone makes it harder for the sacs to empty [1][3]. Diarrhea and skin problems are also predisposing factors [3].

Perianal Tumors and Other Lumps

A dog lump on anus that is firm, painless, and slow growing may be a tumor. Tumors in this area can come from the skin, the anal sacs, or the lining of the anal canal and rectum. In one review of 111 cases of epithelial tumors in the rectum and anal canal of dogs, anal gland adenomas and signet-ring cell carcinomas were located within 1.5 cm of the anus, while several adenocarcinoma types were mostly rectal tumors [2]. That study also found that tumors from different locations had different protein patterns on testing, which supports the idea that where the lump sits helps identify what it is [2].

Not every lump is cancer. Cysts, warts, skin tags, and pimples can all appear near the anus. A dog pimple on anus may be a small infected hair follicle or a blocked skin gland. It may look like a tiny red bump and may come and go. If it persists, grows, or bleeds, have it checked.

Less Common Causes

A urethrorectal fistula is a rare connection between the urinary tract and the rectum. In one case, a young dog had ongoing anal sac leakage that did not respond to treatment, and the true problem was found only after surgery and testing [4]. This is uncommon, but it shows that a lump or drainage that does not improve with standard care needs a closer look.

Red Flags That Make It an Emergency

Go to an emergency clinic now if you see any of these:

Your dog cannot pass urine or is straining to urinate with little or no output.
Your dog cannot pass stool and is repeatedly straining with nothing coming out.
The lump is bleeding heavily or will not stop oozing.
Your dog has a high fever, is collapsing, or seems disoriented.
The area looks black, dead, or severely swollen.
Your dog is vomiting, has a swollen belly, or is in obvious severe pain.

Call your veterinarian the same day if you see:

A red, hot, painful swelling near the anus.
Pus, blood, or foul discharge from the area.
Your dog scooting, licking, or biting at the rear end constantly.
A lump that appeared suddenly or is growing quickly.
Your dog seems uncomfortable when sitting or passing stool.

Safe Things You Can Do at Home While You Wait

You cannot diagnose or treat this at home, but you can keep your dog comfortable and avoid making things worse.

Do not squeeze, lance, or drain the lump. You can cause bleeding, spread infection, and create more pain.
Do not apply human creams, ointments, or essential oils to the area. Your dog can lick them off and swallow them.
Keep the area clean and dry. A gentle wipe with a warm damp cloth is fine if your dog tolerates it.
Use a soft, flat bed or cushion so your dog is not putting direct pressure on a painful spot.
Prevent licking with an Elizabethan collar or a soft recovery cone if your dog keeps going after the area.
Offer water and normal meals. If your dog will not eat or seems painful, call your vet.
Note the size, color, and texture of the lump, plus when you first saw it. That information helps your veterinarian.

If your dog also has diarrhea, that can be related to anal sac problems and can make the area sorer. See Dog Diarrhea: When to See a Vet and When to Wait for guidance on that sign.

What Your Veterinarian Will Check and Test

Your veterinarian will start with a full physical exam and a rectal exam. A rectal exam lets them feel both anal sacs, check their size and symmetry, and feel for masses inside the canal and rectum. Diagnosis of anal sac disease is based on clinical signs and rectal examination, because checking the sac contents alone is not enough [3].

Your vet may also:

Express the anal sacs to see what comes out and whether it is thick, bloody, or pus-like.
Use ultrasound to look at the anal sacs. On ultrasound, normal anal sacs in dogs are usually oval and similar on both sides, and most have a hypoechoic appearance with scattered bright spots or unformed echogenic material [5]. Ultrasound can help tell normal from abnormal [5].
Take a sample of cells or a tissue biopsy if a tumor is suspected.
Run blood work or imaging if your dog is ill or if surgery may be needed.

If medical treatment does not control the problem, surgery to remove the anal sacs may be an option. In one review of 50 dogs having bilateral anal sacculectomy for non-neoplastic anal sac disease, intraoperative anal sac perforation happened in 10% of dogs, and among 43 dogs with two-week follow-up, grade 1 complications occurred in 32%, grade 2 in 5%, and grade 3B in 5% [6]. Most grade 1 complications had resolved by two weeks [6]. Your veterinarian will discuss whether surgery is right for your dog and what to expect.

Prevention and Monitoring

You cannot prevent every lump, but you can lower the risk of anal sac problems and catch changes early.

Keep your dog at a healthy weight. Obesity is a predisposing factor for anal sac disease [3].
Manage diarrhea and skin problems promptly, since both are predisposing factors [3].
Check your dog's rear end during routine grooming or petting. Look for swelling, redness, or discharge.
Note any scooting, licking, or straining to defecate. These are common early signs.
Keep routine wellness visits. Your vet can check the anal sacs during a physical exam.
If your dog has had anal sac disease before, ask your vet how often the sacs should be checked. Impaction is the most recurrent form of anal sac disease [3].

If your dog has other skin lumps, see Dog Skin Bumps and Lumps: When to See the Vet for a broader look at when a lump needs attention. If the skin around the rear end is red and itchy, Dog Skin Rash on Back: Causes and When to See a Vet may also help you sort out what you are seeing.

Limitations and When to Contact a Veterinarian

This article cannot tell you what your dog's lump is. Only a veterinarian can examine the area, feel the tissue, and run the right tests. Individual cases need a veterinarian.

Contact your veterinarian the same day for a red, hot, painful swelling, pus or blood, or a lump that appeared suddenly. Go to an emergency clinic now if your dog cannot urinate or pass stool, is bleeding heavily, has a high fever, or is in severe pain. Schedule a routine visit soon for a firm lump that is not painful but has been there for more than a week, or any lump that is growing, changing color, or bleeding. When in doubt, call your vet's office and describe what you see. They can tell you whether to come in now or wait.

Frequently Asked Questions

Can I pop a bump on my dog's anus at home?

No. Never squeeze or pop a lump near the anus. You can cause bleeding, spread infection, and create severe pain. If the lump is an abscess, it needs veterinary care to drain safely and to treat the infection.

Is a bump on the anus always cancer?

No. Most bumps in this area are anal sac problems, not cancer. Anal sac disease is the most common disease of the anal region in dogs [1]. Still, any firm or persistent lump should be checked so a tumor is not missed.

Why is my dog scooting and licking the area?

Scooting and licking are common signs of anal sac discomfort. The sacs may be impacted, infected, or inflamed. Your dog may also have a skin problem or an allergy in that area. A vet visit can sort out the cause.

Will my dog need surgery?

Not always. Many anal sac problems improve with manual expression and treatment of any underlying disease [3]. Surgery is usually reserved for cases that do not respond or for certain tumors. Your veterinarian will recommend the least invasive option that fits your dog.

How long can I wait before seeing a vet?

If the area is red, swollen, or painful, call the same day. If your dog cannot urinate or pass stool, go now. For a small, painless lump that is not changing, a routine visit within a week or two is reasonable.

References

Disorders of the Rectum and Anus in Dogs - Dog Owners. Merck Veterinary Manual.
Retrospective and histopathological study on epithelial tumors in the rectum and anal canal of dogs. Journal of toxicologic pathology, 2026.
A Cross-Sectional Study on Canine and Feline Anal Sac Disease. Animals : an open access journal from MDPI, 2021.
Urethrorectal fistula ligation and transection in a dog with a history of unilateral abdominal cryptorchidism and misdiagnosed anal gland disease. The Canadian veterinary journal = La revue veterinaire canadienne, 2023.
Ultrasound Morphology of Presumed Normal Anal Sacs in Dogs and Cats. Animals : an open access journal from MDPI, 2024.
Modified closed sacculectomy in 50 dogs with non-neoplastic anal sac disease. Veterinary surgery : VS, 2025.