Causes of secondary malabsorption that are most common in the tropics include (1) progressive wasting in people infected with HIV, which is known as ‘slim disease’; (2) various infections—protozoal (e.g. Giardia lamblia, Cryptosporidium parvum), helminthic (e.g. Capillaria philippinensis, Strongyloides stercoralis), and bacterial (Mycobacterium tuberculosis); (3) immunoproliferative small intestinal disease; and (4) hypolactasia. Coeliac disease and Crohn’s disease also occur. When patients with conditions that can cause secondary malabsorption are excluded, a group remains who have chronic diarrhoea, malabsorption, and its nutritional sequelae. This primary or idiopathic malabsorption syndrome is called ‘tropical sprue’, which occurs against the background of tropical enteropathy (describing the fact that the morphology of the mucosa of normal gut is different in tropical preindustrialized countries from that in temperate-zone industrialized countries). The aetiology of tropical sprue is not known: epidemiological data suggests an infective cause, but no causal agent has been identified. Presentation is typically with loose or watery stools lasting for several weeks or months, and with symptoms and signs of nutritional deficiency. Management involves symptomatic relief from diarrhoea, and correction of fluid and electrolyte abnormalities and nutritional deficiencies. Attempts at specific curative measures—folic acid and tetracyclines—are usually given for up to 6 months.
A practical approach to the patient with chronic diarrhoea