Infection bowel disease
SCOPE AND CAUSES
Infectious bowel disease is inflammation of the small or large intestine caused by bacteria, viruses, parasites or toxins. Transmission is usually faecal–oral through contaminated food/water or person-to-person spread. Important pathogens include norovirus, rotavirus, Campylobacter, Salmonella, Shigella, diarrhoeagenic E. coli, Yersinia, Clostridioides difficile, Giardia and Entamoeba histolytica. The pattern may be watery secretory diarrhoea or inflammatory diarrhoea with blood, mucus, fever and tenesmus.
PATHOPHYSIOLOGY AND CLINICAL FEATURES
Enterotoxins increase intestinal secretion, producing watery diarrhoea; mucosal invasion/cytotoxins cause inflammation, ulceration, blood and systemic features. Symptoms include diarrhoea, abdominal cramps, nausea, vomiting and fever. Severe disease causes dehydration, electrolyte disturbance, acute kidney injury, sepsis or toxic megacolon. Bloody diarrhoea with severe cramps may occur with Shiga-toxin-producing E. coli; antibiotics and antimotility drugs may increase risk of haemolytic uraemic syndrome and should be avoided when suspected.
ASSESSMENT AND INVESTIGATIONS
Assess hydration, perfusion, urine output, mental state, abdominal signs, fever and sepsis. Ask about travel, food, water, sick contacts, recent antibiotics/hospitalisation, immunosuppression and outbreak exposure. Mild short-lived illness usually needs no microbiology. Stool culture/PCR is indicated for bloody diarrhoea, severe illness, prolonged symptoms, immunocompromise, outbreak or public-health concern. Test for C. difficile after relevant antibiotic/healthcare exposure. Blood tests assess electrolytes, renal function, FBC and inflammatory markers in severe disease; blood cultures if sepsis/enteric fever suspected.
MANAGEMENT
Oral rehydration solution is first-line for mild–moderate dehydration; IV isotonic fluids are used for shock, severe dehydration or inability to tolerate oral fluids. Continue feeding as tolerated. Antibiotics are not routinely indicated for uncomplicated acute gastroenteritis. Use pathogen-directed treatment for selected severe/invasive infections, cholera, enteric fever, giardiasis or amoebiasis, guided by local protocols and resistance. Avoid antibiotics in suspected STEC. Avoid antimotility agents in bloody diarrhoea, high fever, suspected C. difficile or ileus. C. difficile requires infection-control measures and specific therapy (e.g. fidaxomicin or oral vancomycin according to local guidance); severe/fulminant disease needs urgent specialist/surgical review.
SURGICAL COMPLICATIONS AND PREVENTION
Surgical review is urgent for peritonitis, perforation, toxic megacolon, uncontrolled bleeding, ischaemia or suspected appendicitis/other surgical abdomen. Complications include dehydration, electrolyte imbalance, HUS, reactive arthritis, Guillain–Barré syndrome, post-infectious IBS and toxic megacolon. Prevention includes hand hygiene, safe water, food hygiene, vaccination where available, isolation/contact precautions and appropriate public-health notification.