When dogs have bloody diarrhea, it can be difficult to determine the cause — here’s what to know
By Kim Campbell Thornton
Andrews McMeel Syndication
Diarrhea. It’s bad enough when a pet has stinky loose stools, but when they’re mixed with bright red blood — or a pet strains to defecate and produces blood only — even the most sanguine pet owner becomes concerned.
Causes of bloody diarrhea can include small, harmless masses; major tumors; toxic substances; or simply emotional upset. Fortunately, it’s rarely an emergency unless the dog is losing enough blood to cause significant anemia or if the dog is bleeding out of the gastrointestinal tract because of a toxin such as rat poison or a systemic disease, says Craig B. Webb, DVM, professor of small animal medicine at Colorado State University’s Veterinary Teaching Hospital in Fort Collins.
Sometimes the cause is never clear. That has been the case with my dog Keeper, whose digestive system is sensitive, to say the least. Usually his veterinarian prescribes antibiotics and a few days of a bland diet. But recent studies show that in some cases, symptomatic treatment — a bland diet to soothe the digestive tract — is all that’s needed.
Approximately 50% to 60% of dogs with acute onset of bloody diarrhea have fecal samples that are positive for a toxin called netF, produced by Clostridium perfringens bacteria. While many healthy dogs have C. perfringens as a normal part of their gut microbiome, in dogs with bloody diarrhea, C. perfringens bacteria are producing the netF toxin gene. The trigger may be something the dog has eaten, infection from another organism or some other cause.
“What makes a strong case that it might be causative is that only dogs with hemorrhagic diarrhea are positive for this toxin,” says Texas A&M researcher Jan S. Suchodolski, DVM, Ph.D., one of the authors of a study on the association of C. perfringens and netF toxin genes with acute hemorrhagic diarrhea published last November in the Journal of Veterinary Internal Medicine. “We don’t typically see it in dogs with acute non-hemorrhagic diarrhea or with chronic diarrhea.”
Dogs who are positive for the toxin, which can be identified through a molecular test, usually eliminate it quickly, independent of treatment with antibiotics, Dr. Suchodolski says.
Why no antibiotics?
They can have a significant effect on intestinal microbiota — the “good bugs” that populate the intestine and play an important role in physiology, metabolism, nutrition and immune function. Broad-spectrum antibiotics disrupt the gut’s microbiome, killing beneficial bacteria.
“We’re discovering more and more that these effects are long-lasting,” Dr. Suchodolski says. “And dogs don’t recover quicker compared to not getting antibiotics for acute diarrhea.”
That doesn’t mean you don’t need to be concerned if your dog is pooping out blood. Small dogs with what is now called acute hemorrhagic diarrhea syndrome (AHDS) — formerly known as hemorrhagic gastroenteritis — can quickly become dehydrated, especially if diarrhea is accompanied by vomiting. A small fraction of dogs may go into shock or sepsis from dehydration and infection, and this may require hospitalization or antibiotics.
Signs that your dog should see the veterinarian as soon as possible include vomiting, lack of appetite, dehydration, increased heart rate and respiration and collapse.
If your dog has bloody diarrhea but is otherwise normal and alert, withhold food for 12 to 24 hours and then feed a bland diet for a few days. Ensuring that the dog is drinking water is more critical than getting him to eat, Dr. Webb says.
“At some point, probiotic therapy should be considered, as changing the gut microbiota may help long term,” says Joseph W. Bartges, DVM, professor of internal medicine and nutrition at the University of Georgia’s College of Veterinary Medicine.
Don’t hesitate to call your veterinarian if you’re worried. “If there are any concerns, especially if your pet feels bad and is not him- or herself, you should take them to a veterinarian,” Dr. Bartges says. “It is better to be safe than sorry.”
PHOTO CAPTION: Young adult smaller-breed dogs are more prone to episodes of acute hemorrhagic diarrhea syndrome, but any dog can experience it