Boxer Colitis: Causes, Symptoms And Treatment

“Boxer colitis”, distinct from regular colitis, is a rare but severe form of gastrointestinal disease predominantly affecting young Boxers.

Dogs diagnosed with Boxer colitis can look significantly underweight and, in the past, have had a poor prognosis, but advances in treatment mean they can now recover.

The cause of Boxer colitis is not well understood but the condition has features in common with Crohn’s disease in humans.

It’s thought that an inherited defect in the dog’s immune defenses somehow allows bacterial invasion of the lining of the colon, leading to inflammation.

I am not a vet. This article is intended for general informational and educational purposes. I encourage readers to view my full disclaimer. Boxer Dog Diaries is reader powered. I may receive a small commission, at no extra cost to you, if you make a purchase via links I share. Thank you for your support.

What Is “Boxer Colitis”?

Colitis refers to any inflammation of the colon, or large bowel, which is the last part of the digestive tract.

There are many different forms of colitis, which can be acute, episodic or chronic.

“Boxer colitis” is one type of chronic colitis, also known as histiocytic ulcerative colitis (HUC) or granulomatous colitis of Boxer dogs (GCB)

This disorder of the large bowel typically affects young Boxers, with symptoms developing before two to four years of age.

Males and females appear to be equally affected.

Though seen primarily in Boxers, there have been sporadic cases in other breeds including:

  • French Bulldogs
  • Mastiffs
  • Alaskan Malamutes
  • Doberman Pinschers

What Causes Boxer Colitis?

Understandings of what causes a Boxer to develop histiocytic ulcerative colitis have changed over the years since the first case was reported in 1965.

It was originally thought to be a breed-specific form of inflammatory bowel disease (IBD) triggered by a dysfunction of the immune system i.e. “immune-mediated”.

But they still didn’t know what caused the dysfunction.

More recent research has linked the condition to an invasive infection of the lining of the colon by E. coli bacteria, similar to what happens in some forms of Crohn’s disease in humans.

Vets still don’t know what causes the bacteria to invade the mucosa or why it seems to happen mostly in Boxers.

More research is needed to identify the genetic basis for the condition, but it appears the breed may have a heritable defect in the immune system that makes the intestines susceptible to bacterial invasion.

(Several genetic defects have been found in people with Crohn’s.)

In terms of colitis more broadly, the causes are many and varied:

  • Stress can contribute to irritable bowel syndrome which is a common cause of colitis in dogs (Sources of stress for Boxers include changes to the routine e.g. moving house or being kennelled)
  • Infectious causes include salmonella, giardia, E. coli and internal parasites
  • Injury due to ingesting a foreign body
  • Antibiotics and other drugs that upset the normal gut microbiome
  • Ingestion of toxins
  • Bacterial overgrowth
  • Fungal infections or toxic blue-green algae (These are much less common causes)

Symptoms Of Boxer Colitis

Colitis, in all its forms, presents as:

  • Watery diarrhea possibly containing fresh red blood and mucus
  • Urgency to get outside to poop
  • Pain on defecation
  • Gas
  • Painful abdominal cramping
  • Increased frequency and urge to poop
  • Nausea and vomiting
  • Redness of tissues around the anus
  • Soft, slimy and greasy loose poops

Once the condition becomes chronic, symptoms can include:

  • Loss of appetite
  • Substantial weight loss with an emaciated appearance (Beyond the usual Boxer skinny phase)
  • Dehydration (If you gently pinch your Boxer’s skin and it doesn’t snap back into shape, this is a sign of dehydration)
  • Cachexia (pronounced kuh-KEK-see-uh) or muscle wasting where the body overzealously breaks down skeletal muscle and fat tissue
  • Extreme pain on rectal palpation and rectal mucosa may feel thickened and produce blood
  • Behavioral changes like lethargy, lack of sociability
  • Poor coat and body condition
  • Black tarry stools (If small intestine also inflamed)
  • Blood tests may reveal anemia (lack of red blood cells to carry oxygen to tissues) and hypoalbuminemia (deficit of the protein albumin in the blood)

Another feature of Boxer colitis is that it’s often unresponsive to treatment with immunosuppressants.

Endoscopy (Insertion of a tube with a camera into the digestive tract) will show an inflamed and ulcerated colonic mucosa (inner lining of the colon).

Diagnosis Of Boxer Colitis

It’s important to distinguish between a bout of acute, regular colitis and the more severe, chronic form that is Boxer colitis.

Acute colitis will typically resolve within a few days with minimal treatment.

A short fast of 24-48 hours may be all that’s required (withhold all food but make sure water is always available).

Chronic colitis, however, will recur and worsen over time.

Definitive diagnosis of histiocytic ulcerative colitis in a Boxer usually involves a colonoscopy, a procedure whereby a tube with a camera is inserted via the anus into the lower digestive tract.

Colonoscopy will typically reveal:

  • Ulcers
  • Bleeding
  • Irregularities in the mucosal surface

During the procedure, biopsies will be taken.

The classic finding when the tissue is examined is the presence of large macrophages (a type of white blood cell) that stain in a certain way under the microscope.

Prior to doing the colonoscopy, your vet will usually perform:

  • Poop test to look for worms and other parasites
  • Blood tests to rule out other causes of colitis
  • Abdominal scans to check for masses or tumors, fecal impaction or abnormalities like thickening of tissues in the large intestine

If E. coli is detected, a diagnosis of Boxer colitis is likely.

A culture is is recommended prior to commencing treatment, to identify the particular strain of E. coli and to confirm which antibiotics will work against it.

Boxer colitis is distinct from two other common digestive disorders:

  • Acid reflux or GERD (Gastroesophageal Reflux Disease)
  • Pancreatitis

There is a third condition every Boxer owner should know about:

  • Bloat

Bloat, or GDV (gastric dilatation-volvulus), is different again, and a true emergency requiring urgent veterinary — often surgical — intervention, without which dogs can die within a few hours.

One simple way to lower the risk in deep-chested breeds like the Boxer is to always use a slow feeder such as the Outward Hound Slo Bowl, and make sure it’s positioned at ground level (not raised).

Enrofloxacin Treatment For Colitis In Boxer Dogs

As mentioned above, acute colitis can typically be resolved by fasting for 24 hours or until symptoms resolve.

These days, the standard treatment for histiocytic ulcerative colitis involves antibiotics for four to eight weeks, namely enrofloxacin (Baytril), which is a gram-negative, broad spectrum antibiotic of the quinolone class, dosed at 5mg/kg once a day.

(In the past, treatment with novel protein diets, anti-inflammatories like sulfasalazine and immunosuppressants like prednisone and azathioprine had little effect.)

Dogs with GI issues should not have further:

  • Vaccines
  • Drugs including chemical wormers and flea/tick preventives

To quote the prominent integrative veterinarian Dr Karen Becker, “Any chemical that goes into your pet’s body has the potential to contribute to unaddressed sources of inflammation.”

Note: before accepting a diagnosis of colitis, it’s important to make sure you are feeding a fresh, natural canine diet i.e. a raw meaty bone-based diet.

Kibble and other highly processed dog food is not an optimal diet for Boxers and can, it itself, cause an array of gastrointestinal disturbances that may look very much like colitis.

Owners who switch their Boxers to a properly composed raw diet often see all symptoms resolve.

What Is The Best Food For A Boxer Dog With Colitis?

Dr Karen Becker says she has seen “a substantial amount of colitis in pets fed diets that aren’t compatible within their physiology, including prescription diets supposedly designed to address GI issues.”

As mentioned above, it’s imperative to feed a biologically-appropriate diet to your Boxer.

This means a fresh, raw diet consisting of edible bone, lean muscle meat and a little offal (organ meat).

Boxers experience various stomach problems when fed highly processed diets like kibble, and may appear to be picky eaters, until they are offered their natural diet.

Prognosis For Boxer Colitis

The outlook for dogs with Boxer colitis was previously considered to be poor, with relapses common and owners even resorting to euthanasia.

Textbook treatments for HUC used to include combinations of dietary modification, anti-inflammatory and immunosuppressive drugs plus antibiotics including chloramphenicol, metronidazole and tylosin … all of which gave poor results.

Since the treatment has changed to be enrofloxacin alone, or sometimes enrofloxacin combined with metronidazole and amoxicillin, most dogs respond within three to 12 days.

Some dogs appear cured after one course.

Others require longer, or even drugs for the rest of their lives to manage the condition.

A lack of response may be due to an enrofloxacin-resistant strain of E. coli.


The large bowel disorder known as Boxer colitis is a much more severe and chronic condition than regular colitis.

Boxers suffering from the condition can develop an emaciated appearance.

The current thinking is that Boxer colitis is due to infection of the bowel wall with E. coli bacteria.

Treatment with the antibiotic enrofloxacin has much better success than previous approaches.

Researchers are trying to identify genes that may predispose Boxers to an immune defect that makes their intestines susceptible to bacterial infiltration.

Diet is key in promoting gastrointestinal health and a fresh, natural canine diet is advisable.


Becker, Karen, DVM, Makes Your Pet Feel Rotten, If Only for a Fleeting Moment, Mercola Healthy Pets, 2016

Rosey, Bess, DVM, Antibiotics for “Boxer Colitis”! Internal Medicine, Clinician’s brief, 2005

Cornell University College of Veterinary Medicine, FAQs, Cornell University, retrieved from website August 2021

Hostutler, RA et al, Antibiotic-responsive histiocytic ulcerative colitis in 9 dogs, Journal of Veterinary Internal Medicine, 2004

KuKanich, Kate, DVM, what’s new with boxer colitis and other large bowel disorders? (Proceedings), DVM 360, 2011

Mansfield, CS et al, Remission of histiocytic ulcerative colitis in Boxer dogs correlates with eradication of invasive intramucosal Escherichia coli, Journal of Veterinary Internal Medicine, 2009

Simpson, Kenny W et al, Adherent and Invasive Escherichia coli is Associated with Granulomatous Colitis in Boxer Dogs, Infection and Immunity, 2006