The term protein losing enteropathy (PLE) refers to a variety of intestinal diseases that are associated with hypoproteinemia (low protein levels) caused by an excessive loss of protein into the gut. It is important to note that the initial step in the diagnosis is to exclude non-intestinal causes of hypoproteinemia, specifically related to the liver or kidneys.
Many different disease processes can cause or are associated with PLE. The clinical signs seen are quite varied, ranging from mild non-specific intermittent signs, to profound weight loss, emaciation, and in some cases, life-threatening respiratory difficulty secondary to fluid accumulation in the chest cavity. Many disorders must be considered initially.
Liver DiseaseSevere hepatic disease must be ruled out as a contributing cause of hypoproteinemia. These include:
Hepatitis (inflammation of the liver)
Cancer
Cirrhosis
Kidney Disease
Protein losing kidney disorders need to be considered in hypoproteinemic patients. These include:
Glomerulonephritis, an type of kidney inflammation involving the glomeruli, which are a mass of capillaries
Amyloidosis, the deposition or collection of a type of protein in organs and tissues that compromises their normal function
Lymphatic Diseases
Disorders of the lymphatic system need to be considered. These include:
Intestinal lymphangiectasia – blockage of the lymphatics of the gastrointestinal tract – is one of the most common causes of PLE.
Cancer of any sort must be ruled out. Lymphosarcoma is a malignant cancer that is the most common cancer causing PLE. It most often takes the form of a microscopic infiltration into the bowel, although it may form mass lesions.
Granuloma, a non-cancerous mass of tissue, of the small intestines or tissue that attaches abdominal organs to the body wall may be associated with profound protein loss.
Congestive heart failure may be associated with hypoproteinemia. Constrictive pericarditis is a condition where the tissue covering the heart cannot expand for a variety of reasons.
Gastrointestinal Diseases
Diseases associated with increased permeability of mucosa commonly cause PLE. These include:
Lymphoplasmacytic enteritis is a form of inflammatory bowel disease characterized by the infiltration of cells into the intestinal wall, causing a disruption of normal intestinal function and protein loss.
Intestinal cancer of any kind may cause or contribute to protein loss in the gut.
An intussusception, especially chronic, will often be associated with protein loss. This is a telescoping of part of the bowel into an immediately adjacent segment of bowel, and is most often associated with the presence of inflammation, foreign bodies, parasites or tumors.
Chronic foreign bodies of the intestinal tract are often associated with a number of gastrointestinal signs including diarrhea, vomiting and weight loss, and occasionally hypoproteinemia.
Ulcerative gastroenteritis is an inflammation of the lining of the gastrointestinal tract and is often associated with hypoproteinemia. It may be secondary to inflammation, drug administration, cancer or foreign bodies.
Small intestinal bacterial overgrowth (SIBO) is characterized by an overgrowth of normal intestinal bacteria usually secondary to various gastrointestinal diseases, but occasionally as a primary entity.
Histoplasmosis is a fungal infection that affects many systems, including the gastrointestinal tract. It has been associated with profound hypoproteinemia.
Intestinal parasitism has been associated with PLE, especially in young puppies that are anemic as well.
Roundworms, hookworms, whipworms, coccidia and giardia.
Hemorrhagic gastroenteritis (HGE) is a dramatic, potentially fatal disorder with no known cause. It has a predilection for small breed dogs, and it is not recognized in cats. HGE is characterized by the sudden onset of profuse bloody diarrhea and occasional vomiting.
Immune-mediated intestinal diseases may cause PLE.
Food allergies and gluten-induced diseases of the intestines, which are a sensitivity to a component of wheat and other grains.
Miscellaneous
Blood loss for any reason will decrease the protein level.
Inadequate protein intake will contribute to hypoproteinemia.
