Gastroenteritis

•    Viral causes (most common):

o    Norovirus: outbreaks in care homes, cruise ships

o    Rotavirus: most common in children (vaccine-preventable)

•    Bacterial causes:

o    Salmonella: diarrhoea ± systemic symptoms; poultry/eggs

o    Shigella: bloody diarrhoea, seizures (esp. in children)

o    E. coli:

    ETEC: traveller’s diarrhoea

    EHEC (O157:H7): bloody diarrhoea, risk of HUS (avoid antibiotics)

o    Campylobacter: diarrhoea ± bloody, associated with Guillain–Barré syndrome

•    Management: supportive (rehydration); antibiotics only for specific indications (e.g. severe dysentery, immunocompromised)

Gastrointestinal Tuberculosis

•    Most commonly affects the ileocaecal region

•    Features: chronic abdominal pain, diarrhoea, weight loss, fever, night sweats

•    Complications: strictures, obstruction, perforation

•    Diagnosis: colonoscopy with biopsy (caseating granulomas), culture, PCR

•    Treatment: standard anti-TB therapy (e.g. RIPE)

Parasitic Infections

Amoebiasis

•    Caused by Entamoeba histolytica

•    Transmission: faeco-oral (contaminated food/water)

•    Features:

o    Dysentery, abdominal pain

o    "Flask-shaped" ulcers on colonoscopy

•    Can lead to amoebic liver abscess

•    Treatment: metronidazole, followed by luminal agent (e.g. paromomycin)

Giardiasis

•    Caused by Giardia lamblia

•    Features: steatorrhoea, bloating, weight loss, often post-travel

•    Diagnosis: stool microscopy or antigen testing

•    Treatment: metronidazole

Hepatic Abscesses

Pyogenic Abscess

•    Typically polymicrobial (from biliary tract, diverticulitis, portal vein)

•    Features: fever, RUQ pain, raised inflammatory markers

•    Diagnosis: USS/CT liver

•    Treatment: IV antibiotics ± drainage

Amoebic Abscess

•    Usually due to Entamoeba histolytica

•    Features: similar to pyogenic, often in young travellers

•    No pus on aspiration ("anchovy paste")

•    Treatment: metronidazole (drainage rarely needed)

Hydatid Cyst

•    Caused by Echinococcus granulosus (tapeworm)

•    Transmission: contact with dogs/sheep

•    Most common site: liver

•    Features: usually asymptomatic; may cause cyst rupture → anaphylaxis

•    Imaging: "hydatid sand" on USS/CT

•    Treatment:

o    Albendazole

o    Surgical excision or PAIR (puncture–aspiration–injection–reaspiration)