Pathological conditions in the intestines that are characterized by the gastrointestinal loss of serum proteins, including serum albumin; immunoglobulins; and at times lymphocytes. Severe condition can result in hypogammaglobulinemia or lymphopenia. Protein-losing enteropathies are associated with a number of diseases including intestinal lymphangiectasis; whipple'S disease; and neoplasms of the small intestine.