The symptoms of hemorrhagic gastroenteritis (HGE) begin like any other gastrointestinal illness—soft brown stool, not eating, and perhaps some vomiting. But over a 24-hour period, that soft stool will progress to a watery, bloody, and explosive diarrhea. Dogs with HGE feel nauseous and may not drink enough water to keep up with the fluid loss associated with their diarrhea. This leads to dehydration that may become severe and life-threatening.
Most dogs with HGE will need to be hospitalized and treated with aggressive intravenous fluid therapy to resolve their dehydration. Antiemetic medications—such as Cerenia and ondansetron—are administered to alleviate the nausea associated with HGE. Probiotics to promote healthy gut flora and fiber to provide nutrition to cells lining the colon are started.
Some dogs with HGE have such profound losses of protein and fluid from their diarrhea that they require one or more transfusions of blood products. Blood products used to treat HGE include albumin (a protein found in blood) and fresh frozen plasma (the fluid portion of blood).
Eating a high quality, easily digestible diet provides nutrition to the cells that line the gastrointestinal tract and helps them heal. But dogs with HGE are unlikely to begin eating right away during the acute part of their illness. Your veterinarian may recommend placing a nasogastric tube to deliver a liquid recovery diet to your dog until he starts eating on his own.
A nasogastric tube is a thin feeding tube that is inserted into one of your dog’s nostrils. The tube passes down the back of his throat, through the esophagus, and into the stomach. The nasogastric tube does not interfere with your dog’s ability to eat or swallow. Most dogs do not seem to mind having a nasogastric tube in place.
Dogs with HGE require close monitoring of their electrolytes, blood pressure, hydration status, and vital signs. This is best accomplished in the intensive care unit (ICU) of a 24/7 emergency and specialty hospital. A veterinary technician that specializes in caring for ICU patients will be dedicated to monitoring your dog’s vital signs and providing treatments to your dog. A board-certified veterinary criticalist or an emergency veterinarian trained to care for critical patients will help your dog recover from HGE.
Dogs that are hospitalized for treatment of HGE spend an average of two to three days in the hospital. They are discharged from the hospital once they are eating, no longer vomiting, and have returned to having soft or semi-formed stool.
What Causes HGE in Dogs
HGE is caused by an overgrowth of a bacteria called Clostridium perfringens. Clostridium perfringens is a part of the normal gut flora of the dog’s colon. The normal gut flora has a system of checks and balances that keeps any one species of bacteria from growing out of control.
It is not currently known why this system of checks and balances suddenly allows Clostridium perfringens to begin proliferating uncontrollably. There is speculation that dietary indiscretion (such as eating a toy or getting into the garbage), a change in diet without an appropriate transition period, intestinal parasites, food poisoning, or stress may be contributing factors.
There are five types of Clostridium perfringens. These include types A, B, C, D, and E. Clostridium perfringens type A produces a toxin called NetF. The NetF toxin creates pores, or openings, in cells that line the inside of the colon. This causes the cells to swell with fluid and burst like a balloon, destroying the cells.
The cells that line the inside of the colon act like a permeable barrier. This permeable barrier allows a controlled amount of fluid and electrolytes to move back and forth between the lumen of the colon and the blood vessels in the colon wall. The NetF toxin damages that permeable barrier, allowing some blood and massive amounts of fluid to enter the colon lumen. The result is a profuse watery, bloody diarrhea.
As the disease progresses, the population of Clostridium perfringens type A migrates from the colon to the small intestine. The NetF toxin produced by this bacterial species damages the mucosal lining of the small intestine. This worsens the diarrhea that is produced by the large intestine.
The damage done by the NetF toxin is confined to the small and large intestines. The NetF toxin does not affect the stomach. The term gastroenteritis refers to inflammation of the stomach and the small and large intestines. Since HGE does not affect the stomach, this condition was recently renamed acute hemorrhagic diarrhea syndrome (AHDS). This reflects the damage that occurs to just the intestines rather than the entire gastrointestinal system.
Diagnosis
There is no specific test for AHDS. Diagnosis is based on the acute onset of watery, bloody diarrhea, severe dehydration, and the exclusion of other causes of your dog’s symptoms. Your dog may be suspected of having AHDS if he meets the following criteria:
- One or more episodes of vomiting that start about 10-12 hours before the onset of diarrhea
- Sudden onset of watery, bloody diarrhea that looks like straight blood. Sometimes this can look like raspberry jam if there is mucus mixed in with the diarrhea.
- Young age (median age is 5 years)
- Small breed dog (median weight is 25 pounds)
- A packed cell volume (PCV) of 57% or greater. This is a blood test that examines the ratio of red blood cells to plasma (also known as the fluid component of blood).
- Relatively low total protein level in the blood
Your veterinarian may recommend additional diagnostic tests to rule out other causes of bloody diarrhea. These tests may include a complete blood count (CBC) and chemistry panel, a coagulation panel, abdominal radiographs (x-rays), and abdominal ultrasound. If your dog is not vaccinated for parvovirus or is a puppy in the middle of his parvovirus vaccination series, your veterinarian may recommend testing your dog for parvovirus.
Prognosis
Most dogs that receive timely and appropriate intervention for AHDS will make a complete recovery. However, serious complications can occur if appropriate treatment for AHDS is not started early in the disease process.
Dogs with AHDS may continue to have soft stool for 7-10 days following resolution of diarrhea. Their stool quality should improve a little each day during their recovery period.
Some dogs will develop chronic diarrhea following their recovery from AHDS. Diarrhea may be ongoing or intermittent. It may resolve with a change in diet or addition of a probiotic. Some cases may require treatment with medication to resolve the diarrhea.
You may have noticed something missing from the discussion of treating AHDS—antibiotics. At one time, antibiotics such as metronidazole and ampicillin or amoxicillin were routinely administered to dogs suspected of having AHDS. It has since been discovered that using antibiotics to treat AHDS may do more harm than good.
Antibiotics can have a negative impact on the normal bacterial flora of the small and large intestine. Antibiotics will promote the growth of some bacterial species while inhibiting the growth of others. Simplistically, this could be looked at as the inhibition of good bacteria and the growth of bad bacteria. But in reality, it is much more complex than this.
AHDS is caused by the overgrowth of Clostridium perfringens—one of many bacterial species in the gut. While antibiotics will decrease the population of Clostridium perfringens, they will also cause the other bacterial species in the gut flora to become unbalanced. This may worsen the already altered permeability of the intestines. Healing of the intestines is delayed and chronic diarrhea can develop even after recovery from AHDS.
Probiotics and fiber are now part of the treatment for AHDS. Probiotics can help restore the correct bacterial balance in the gut flora. Fiber provides nutrition to the cells that line the colon and helps these cells heal.
There are circumstances in which the use of antibiotics in treating AHDS is warranted. Dogs that have developed sepsis (a blood infection that causes multi-organ failure), have an abnormally low white blood cell count, or that are not responding to the typical treatment protocol for AHDS may need one or more antibiotics added to their treatment plan. But most dogs with uncomplicated AHDS do not require antibiotics to recover from their illness.
