enteritis

Enteritis is inflammation of the small intestinal mucosa, most frequently due to infection. Viral causes (norovirus, rotavirus in children, adenovirus) are the most common overall and typically cause watery, non-bloody diarrhea via osmotic/secretory mechanisms without significant mucosal invasion. Bacterial causes include Salmonella, Shigella, Campylobacter jejuni, enterotoxigenic/enteroinvasive E. coli, and Vibrio cholerae—these may produce either watery diarrhea (toxin-mediated, e.g., cholera toxin activating adenylate cyclase) or inflammatory/bloody diarrhea (invasive organisms like Shigella, Campylobacter, EIEC). Parasitic causes include Giardia lamblia (malabsorption, foul-smelling fatty stools) and Entamoeba histolytica (can cause bloody diarrhea and liver abscess). Non-infectious causes include radiation enteritis, Crohn's disease (which classically causes transmural inflammation of the terminal ileum with skip lesions, cobblestoning, and granulomas), and ischemic enteritis. Clinically, patients present with diarrhea, crampy abdominal pain, nausea, vomiting, and sometimes fever. Evaluation includes stool studies (culture, ova and parasites, PCR panels), and treatment is largely supportive (oral rehydration) unless a specific bacterial or parasitic pathogen requiring antibiotics/antiparasitics is identified. Key boards associations: Campylobacter with Guillain-Barré syndrome and reactive arthritis; Salmonella with osteomyelitis in sickle cell patients; EHEC O157:H7 with hemolytic uremic syndrome (avoid antibiotics due to increased toxin release risk); Giardia with campers/hikers and biliary-type symptoms.