Summary
Infectious diseases that do not primarily affect the gastrointestinal tract can cause severe diarrhea. The pathogenesis of this kind of diarrhea includes cytokine action, intestinal inflammation, sequestration of red blood cells, apoptosis and increased permeability of endothelial cells in the gut microvasculature, and direct invasion of gut epithelial cells by various infectious agents. Of the travel-associated systemic infections presenting with fever, diarrhea occurs in patients with malaria, dengue fever and SARS. Diarrhea also occurs in patients with community-acquired pneumonia, when it is suggestive of legionellosis. Diarrhea can also occur in patients with systemic bacterial infections. In addition, although diarrhea is rare in patients with early Lyme borreliosis, the incidence is higher in those with other tick-borne infections, such as ehrlichiosis, tick-borne relapsing fever and Rocky Mountain spotted fever. Unfortunately, it is often not established whether diarrhea is an initial symptom or develops during the course of the disease. The real incidence of diarrhea in some infectious diseases must also be questioned because it could represent an adverse reaction to antibiotics.
Introduction
Diagnostic algorithms classify diarrhea as either infectious or non-infectious. Infectious diarrhea is caused by direct infection of the gastrointestinal tract by such organisms as rotavirus or salmonella. Very little consideration is usually given to diarrhea in patients with infectious diseases that do not primarily affect the gastrointestinal tract but are systemic or affect other organ systems.
In one report, of 594 patients diagnosed with gastroenteritis, 71% had gastrointestinal infections, 15% had non-infectious gastrointestinal diseases, 8% had systemic infections, including urinary tract infections (19 patients), respiratory tract infections (8 patients), septicemia (6 patients), pelvic inflammatory disease (5 patients), malaria (2 patients) and others, and 6% had systemic non-infectious diseases. Although the urinary tract infections detected in this study might be a consequence of diarrhea, other systemic infections are directly or indirectly responsible for diarrhea.
Unfortunately, in many cases the definition of diarrhea remains unclear and it is not established whether the diarrhea is an initial symptom or has developed during the course of the disease, or whether it occurred before or after the initiation of antibiotic treatment. The reported incidence of diarrhea in extraintestinal infections can be questioned, because many cases of diarrhea are adverse events associated with antibiotics and most reports lack controls.
This review focuses on the wide spectrum of clinically relevant infectious diseases that do not primarily affect the gastrointestinal tract, but in which diarrhea is common ( Table 1 ).