Diarrhea in dogs can occur for a number of reasons. Hemorrhagic Gastroenteritis (HGE) is a particularly serious form of diarrhea that causes massive fluid, protein, and electrolyte loss over a very short period of time. Without medical intervention, this condition can quickly result in life-threatening systemic dehydration and death. Vomiting, anorexia (starvation), and depression often accompany HGE. Anything that causes typical diarrhea as a symptom can advance to HGE; although for unknown reasons, some dogs seem to be predisposed. Heat exhaustion is a common contributor. It should be noted that many dogs that develop HGE will have experienced no other preliminary health problems; this disease process can occur in completely healthy pets without warning.
The blood vessels and tissues of the body are designed to carry fluids and cells within them. The normal function of the intestinal tract includes conserving water. In the healthy dog, the ratio of blood cells (solids) to fluid (water) in the blood, or the packed-cell volume (PCV), is about 35 to 55 percent. In HGE, the intestinal wall becomes permeable to water (but not cells), and the PCV will rise to well above 60 percent. Electrolytes and protein, which are important chemical transporters in the blood, are also leaked through the vessels and intestinal walls. Uncontrollable bloody diarrhea ensues, and the dog quickly dehydrates. This can upset kidney function and can even have impacts on heart rhythm and brain function.
There are no specific tests for HGE, but the symptoms combined with an elevated PCV and a decreased total serum protein are sufficient reasons to suspect the condition and begin treatment.
A dog suspected of HGE should be treated aggressively with intravenous replacement fluids. Because vomiting may coincide, injectable medications are preferred over oral. Antiemetics (to stop vomiting and improve intestinal function) and antibiotics are administered. There is often a bacterial overgrowth in the gut that may be responsible for or secondary to the symptoms. Clostridium is one strain of pathogenic (harmful) bacteria that is thought to contribute to HGE.
A major problem with treating HGE is that the rate of fluid loss may exceed the rate of fluid replacement. In this case, dehydration is not resolved despite rapid IV fluid administration. The reason for this is that the IV fluids given also leak through the vessels and intestinal walls. Protein must be replaced as well to correct the vessel permeability. Plasma or artificial colloid (Hetastarch) transfusions may be required to stop the diarrhea. At extremely low serum protein levels, the fluids may even leak into the abdomen and lungs. This effect is called ascites (fluid in the abdomen) and pleural effusion (fluid in the space around the lungs).
The dog with HGE will usually be hospitalized for several days, until the diarrhea is abated and the PCV returns to an acceptable range. Food will be withheld during treatment until vomiting is controlled.
The prognosis for HGE is good for dogs that are recognized early and treated aggressively. A full recovery is expected. Dogs that have survived HGE should be considered at risk for a future episode; therefore, contributing factors must be especially avoided for these individuals.