The Malabsorption Syndrome and Its Causes and Consequences

The indication for a small intestinal biopsy is usually the work-up of malabsorption, a clinicopathologic picture caused by a number of infectious and noninfectious inflammatory conditions. The biopsy is generally taken through an endoscope, by either forceps or suction, from the duodenum or proximal jejunum. Depending upon the underlying condition, morphological abnormalities are seen in malabsorption range from normal mucosa with increased intraepithelial lymphocytes (gluten-sensitive enteropathy, viral gastroenteritis, food allergies, etc.), villous shortening with crypt hyperplasia (celiac disease (CD), treated CD, tropical sprue, and bacterial overgrowth), to completely flat mucosa (CD, refractory sprue, enteropathy-induced T-cell lymphoma, and autoimmune enteropathy). Infectious agents that affect gastrointestinal tract can be grouped as food-borne and water-borne bacteria, opportunistic infections (bacterial, fungal, and viral), viral infections (extremely rarely biopsied), and parasitic and helminthic infections. The majority of these infections are, however, self-limited. Although biopsy is more invasive, the use of this procedure allows detection of other causes, including Whipple's disease, other protozoan forms of diarrhea (e.g., cryptosporidiosis, isosporiasis, or cyclosporiasis), Crohn's disease, or lymphoma that may also present as diarrhea and malabsorption.