• 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)
• 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)
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
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)
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Author & Educational Disclaimer
Author:
Dr Phillip Cockrell BM FRCP DipClinEd
Dr Phillip Cockrell is a UK Consultant Physician in Internal Medicine, currently working at Queen Alexandra Hospital, Portsmouth University Hospitals NHS Trust. He has previously worked as a registrar across Intensive Care Medicine, Gastroenterology, Cardiology, Stroke Medicine, Acute Medicine, and Respiratory Medicine.
He has held senior leadership roles including Associate Clinical Director of the Acute Medical Unit, Clinical Director of Internal Medicine, and Chief of Medicine. Dr Cockrell has over 15 years’ experience in postgraduate medical education, having lectured extensively across the MRCP syllabus and contributed to MRCP revision teaching and course development.
Dr Cockrell holds a Bachelor of Medicine (BM), Fellowship of the Royal College of Physicians (FRCP), and a Diploma in Clinical Education (DipClinEd). His teaching approach is based on structured consolidation of complex medical topics to support efficient and effective revision for postgraduate examinations.
Purpose of this content:
The material on this page is intended solely for educational purposes to support revision for the MRCP (UK) Part 1 examination. It reflects examination-relevant principles of internal medicine and is designed to aid learning and pattern recognition.
Medical disclaimer:
This content is designed for postgraduate medical examination revision and does not constitute medical advice, diagnosis, or treatment guidance and must not be used as a substitute for professional clinical judgement, local guidelines, or specialist consultation. Clinical decisions should always be made in the context of individual patient circumstances and current national guidance.
