the diagnosis of gastroenteritis in the ED is essentially one of exclusion and generally requires both vomiting and diarrhoeal illness.
in Australia, it is the treating doctor's legal responsibility to notify the government of 2 or more cases of suspected food or water-borne diseases, this is particularly important when those cases arise in Residential Aged Care Facilities
in general, children should NOT be given anti-emetics (although ondansetron wafers may be considered but may increase amount of diarrhoea) nor anti-diarrhoeal (antimotility) agents - see The child with gastroenteritis
most cases do NOT need antibiotic Rx, even if they are bacterial.
increasingly, antibiotic-related Clostridium difficile enteritis is becoming a major problem and can be life threatening.
gastroenteritis can reduce the absorption of some medications, and patients should be warned of a potential decrease in efficacy (eg the combined oral contraceptive pill)
acute gastroenteritis is usually caused by serotypes 40 and 41, and mainly affects infants and young children
astrovirus
similar to rotaviral infection but less severe
mainly affects day care and school children
incubation period 3-4 days
additionally, in the immunocompromised, reactivation of cytomegalovirus (CMV) can cause serious gastroenteritis
bacterial infections
Campylobacter, Salmonella and E. coli are the most common causes of bacterial enteritis in developed countries and generally do not require antibiotic Rx
Campylobacter infections may require antibiotic Rx if severe or prolonged illness, or in immunocompromised, infants, elderly, or perhaps 3rd trimester pregnancy.
antibiotic Rx of Salmonella enteritis is not generally advisable as it is usually not clinically beneficial and it may prolong excretion of pathogenic organisms, however, antibiotic Rx is indicated in infants and in patients who are severely ill (eg requiring hospital admission), septicaemic or have prosthetic vascular grafts
severe disease from Salmonella is more likely to occur in infants who are malnourished or less than 3 months old, or people who are immunosuppressed, achlorhydric or elderly.
Clostridium difficile is the most important bacterial cause of healthcare-associated enteritis
Yersinia enterocolitica causes a spectrum of disease including acute enterocolitis, mesenteric adenitis and pharyngitis with or without diarrhoea. Postinfectious complications such as reactive arthritis and erythema nodosum may occur. Antibiotics generally not indicated unless immunocompromised or persistent or extra-intestinal disease.
overseas travellers are potentially at risk of the following:
if fever for > 7 days or wish to start iv Rx anyway, Rx with iv ceftriaxone, otherwise Rx with azithromycin (or perhaps ciprofloxacin if not contracted from SE Asia).
some patients with enteric fever become long-term carriers—seek expert advice.