There has been a recent spate of dogs being diagnosed with hemorrhagic gastroenteritis at our practice. While bloody diarrhoea may be a sign of parvovirus, a highly contagious and potentially fatal disease, this is not always the case. Haemorrhagic Gastroenteritis (HGE) is a distinct clinical condition which generally has a far better outcome than parvovirus, especially when treated appropriately. But there are many causes of bloody diarrhoea and all must be investigated to ensure your pet gets appropriate care in a timely manner
HGE is a disease that tends to occur unexpectedly in healthy dogs. The cause is often unknown, though stress may play a role as may dietary allergens and bacterial toxins. Signs may be vague initially and your dog may be off its food, lethargic, potentially nauseous and/or vomiting, and may be passing bloody diarrhoea. Sometimes they are sick enough to warrant veterinary attention before the diarrhoea has shown itself.
Examination of your pet may alert the vet to the possibility of HGE. Your dog’s gums may be dry, the heart rate may be elevated and there may be blood on the thermometer. Lot’s of “may”s I know, but the main diagnostic indicator is found through a simple blood test. Your vet will take a small amount of blood to assess the dog’s PCV (packed cell volume) and TP (total protein or total solids). The PCV is the percentage of red blood cells in the peripheral blood as compared to total blood volume. It is measured by spinning blood in a centrifuge. The TP is measured with an instrument called a refractometer, which assesses the protein content of the serum separated from the red blood cells when the blood is spun.
How is this diagnostic for haemorrhagic gastroenteritis I hear you ask? The majority of dogs with HGE will have a very high PCV, often >60%, with a low or low normal protein level. This may be surprising given that when owners see the diarrhoea, a first concern may be the potential for the dog to become anaemic. HGE dogs rarely become anaemic, even with aggressive intravenous fluid therapy. The reason for the high PCV in the face of bloody diarrhoea is that there is a comparatively small number of red blood cells being lost in the diarrhoea compared to the amount of fluid that is exuded. The extent of dehydration may not be obvious on examination because the fluid loss is rapid. I could insert a whole lecture in here on fluid dynamics but this would be a big distraction from the topic at hand. Maybe this could be reserved for a future post if anyone is interested!
Diarrhoea occurs because the intestine becomes leaky. The leaks are thought to occur due to a type of allergic reaction affecting the intestinal lining. You may have seen your dog’s face swell as a result of a bee sting? Well this same type of swelling would be occurring if the intestine was a closed organ. Being a tube, the fluid pours into the centre (the lumen) and is high in water and small molecules like protein. Hence the low TP. The red blood cells may be too large to pass through the leaks, but enough are lost to give the diarrhoea its classic appearance.
Sometimes the PCV is not that high, especially in the early stages. Other tests may be performed to rule out other potential causes of bloody diarrhoea. These may include a parvovirus test, especially if vaccination history is questionable, a faecal smear or float to rule out intestinal parasitism, and other blood tests to assess for certain diseases and blood clotting disorders.
In the majority of cases, treatment is straightforward and the outcome is generally good. Without treatment, death may occur if dehydration is rapidly progressing, which it can. Bloody diarrhoea is not something that should be left unseen – a “wait and see” approach is definitely not recommended. Treatment involves administering large volumes of a balanced electrolyte solution intravenously to restore tissue hydration and vascular volume. Intravenous antibiotics are often administered to help prevent infections caused by the presence of bacteria in the compromised bowel. Pain relief may be provided if your dog has abdominal pain and possibly drugs for gut protection and nausea if present.
The course of disease is fairly short lived in the milder cases, and many dogs are home within 24-48hrs of commencing intravenous fluids. Discharge will occur when the vets are happy that fluid loss is easing and the dog is eating and drinking happily. More complicated cases may require several days in hospital. They may need additional fluids such as plasma or artificial colloids, which are a manufactured fluid that aims to replace lost protein temporarily until the body can make more of its own. Other times, there may be a secondary (or sometimes another primary) disease process which also needs to be addressed.
So while HGE is often simple and straightforward to treat, complications can occur. Unfortunately, there is not a lot that you can do at home for your dog once the disease takes hold. We can never force our dogs to drink enough water to replace the intestinal losses that occur, and it is not worth risking more serious disease issues by holding off to see if they will get better on their own.