CLASSIFICATION

Malabsorption syndrome includes chronic enter­opathies that cause a generalized failure of diges­tion and absorption, resulting in diarrhea and weight loss. Some common causes include diffuse chronic inflammatory bowel disease (IBD) (lymphocytic-plasmacytic enteritis, eosinophilic enteritis, granulomatous enteritis), lymphangiecta­sia, lymphosarcoma, idiopathic villous atrophy, and histoplasmosis.

Protein-losing enteropathy refers to a group of disorders characterized by excessive loss of serum proteins into the intestinal tract. Blood chemistry profiles reveal proportionately equal depressions of albumin and globulin concentrations, often with a total protein of less than 5.5 g/dl.Hypoproteinemia results from either decreased production or increased loss of protein. Hypoproteinemia due to chronic liver disease is characterized by primary hypoalbu- minemia, resulting from decreased production of albumin. In protein-losing nephropathies there is a primary hypoalbuminemia, due to increased loss of albumin. Macroglobulins are generally not lost until disease is severe and glomerular membranes become porous. In contrast, protein loss from the GI tract generally involves loss of all fractions at an equal rate, regardless of molecular size.

The most common causes of protein-losing enteropathy (PLE) in the dog include moderate to severe lymphocytic-plasmacytic enteritis, lym­phangiectasia, diffuse intestinal lymphosarcoma, and histoplasmosis. Pythiosis causes severe intestinal inflammation and protein loss and is generally seen in dogs living in the Gulf Coast states, although it has been recognized in other southern states as well (see later discussion on pythiosis). Chronic parasitism, including giardiasis, can also result in intestinal protein loss. Subnormal protein levels in cats due to GI disease are not commonly recog­nized. Among this group, lymphosarcoma and severe IBD are the most common causes.

This chapter presents diagnostic and detailed treatment information for some of the most important and challenging chronic small intestinal disorders seen in clinical practice. These include chronic giardiasis, IBD, intestinal bacterial over­growth, lymphangiectasia, pythiosis, short bowel syndrome, and intestinal neoplasia. The diagnostic approach to the problem of chronic diarrhea was reviewed in Chapter 1. The diagnosis and treat­ment of each individual disorder are presented here.