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Gastrointestinal & Hepatic System

Amoebiasis

Infection caused by the protozoan parasite Entamoeba histolytica, transmitted via the faecal-oral route. Can cause intestinal disease (dysentery) or extraintestinal disease (most commonly liver abscess).

Also known as: Amoebic Dysentery, Amoebic Liver Abscess

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Referral and warning signs

When to refer

Refer to hospital (H/RR) for: Severe dysentery with dehydration. Suspected complications (toxic megacolon, perforation, peritonitis). Suspected amoebic liver abscess for confirmation and management. Failure to respond to appropriate treatment.

Red flags

  • Signs of toxic megacolon (high fever, tachycardia, abdominal distension, worsening pain)
  • Signs of peritonitis
  • Severe dehydration / Shock
  • High fever with RUQ pain (suggests liver abscess)
  • Altered mental status (possible brain abscess)

Signs and symptoms

  • Asymptomatic carriage (most common).
  • Intestinal Amoebiasis (Amoebic Colitis/Dysentery):
  • - Gradual onset.
  • - Diarrhoea, often with visible blood and mucus.
  • - Abdominal pain/cramping.
  • - Tenesmus (straining to defecate).
  • - Low-grade fever (less common than in bacterial dysentery).
  • - Weight loss (chronic cases).
  • Extraintestinal Amoebiasis:
  • - Amoebic Liver Abscess: Fever, chills, sweating, weight loss, right upper quadrant (RUQ) abdominal pain/tenderness, hepatomegaly. Jaundice uncommon unless large/multiple abscesses.
  • - Less common: Lung abscess (cough, chest pain, rupture into bronchus), Brain abscess (headache, seizures, focal deficits), Amoeboma (granulomatous mass in colon), Perianal ulceration.

Risk factors

  • Poor sanitation and hygiene.
  • Consumption of contaminated food or water.
  • Travel to or residence in endemic areas.
  • Institutionalization.
  • Men who have sex with men.
  • Immunosuppression (may increase severity).

Diagnosis

Clinical assessment

Suspect amoebic dysentery with subacute onset bloody/mucoid diarrhoea, abdominal pain, often without high fever. Suspect liver abscess with fever, RUQ pain, hepatomegaly. Differentiate dysentery from Shigellosis (more acute, higher fever). Differentiate liver abscess from pyogenic liver abscess, hydatid cyst, hepatoma.

Investigations

  • Stool Microscopy: Identification of E. histolytica trophozoites (containing ingested red blood cells is pathognomonic) or cysts. Multiple samples needed. Cannot distinguish E. histolytica from non-pathogenic E. dispar based on morphology alone.
  • Stool Antigen Detection Tests: More sensitive and specific than microscopy, can differentiate E. histolytica from E. dispar.
  • Stool PCR: High sensitivity/specificity (reference labs).
  • Serology (Antibody tests): Useful for diagnosing extraintestinal amoebiasis (e.g., liver abscess), as stool exams often negative. Remain positive after infection.
  • Liver Imaging (Ultrasound or CT scan): For suspected liver abscess - shows characteristic round/oval hypoechoic lesion.
  • Abscess Aspiration: Diagnostic aspiration may show 'anchovy paste' material (typically sterile on bacterial culture). Therapeutic aspiration rarely needed unless rupture imminent or diagnosis uncertain.
  • Colonoscopy: May show flask-shaped ulcers in amoebic colitis (risk of perforation).
  • CBC: Leucocytosis often present, eosinophilia uncommon.

Diagnostic criteria

Identification of E. histolytica (trophozoites/cysts/antigen/PCR) in stool OR characteristic liver abscess on imaging + positive serology.

Management

Non-pharmacological management

  • Rehydration (ORS or IV fluids) if dehydrated.
  • Supportive care.

Pharmacological treatment

  • Tissue Amoebicide (Treats invasive disease - colitis and abscess):
  • - Metronidazole 800mg PO TID for 10 days (Adult); 10-15 mg/kg/dose TID (Child).
  • - OR Tinidazole 2g PO daily for 3 days (colitis) or 5 days (abscess) (Adult); 50-60 mg/kg/day (Child).
  • Luminal Amoebicide (To eradicate cysts in the gut lumen after tissue agent - essential to prevent relapse/transmission):
  • - Diloxanide furoate 500mg PO TID for 10 days (Adult); 20mg/kg/day divided TID (Child).
  • - OR Paromomycin 25-35 mg/kg/day divided TID for 7 days.
  • Asymptomatic Cyst Passers: Treat with luminal agent ONLY (Diloxanide or Paromomycin).

Monitoring

  • Monitor clinical response (resolution of diarrhoea, fever, pain).
  • Follow-up imaging for liver abscess resolution (may take months).
  • Follow-up stool exam (optional) to confirm cyst eradication after treatment.

Complications

  • Intestinal: Toxic megacolon, Bowel perforation, Peritonitis, Amoeboma formation, Stricture formation, Severe haemorrhage.
  • Liver Abscess: Rupture (into peritoneum, pleura, pericardium), Secondary bacterial infection, Extension to adjacent structures.
  • Rare: Lung abscess, Brain abscess, Cutaneous amoebiasis.

Prevention

  • Improve sanitation and access to safe water.
  • Proper food handling and hygiene.
  • Handwashing.
  • Avoid consuming potentially contaminated food/water in endemic areas.
  • Treat asymptomatic cyst passers (food handlers).

Patient education

  • Explain the infection and mode of transmission.
  • Importance of completing both tissue and luminal amoebicide courses.
  • Metronidazole/Tinidazole: Avoid alcohol during and 48h after treatment, take with food.
  • Hygiene measures to prevent spread.
  • Follow-up requirements.
  • Symptoms of relapse or complications.

Uganda-specific notes

Amoebiasis is endemic. Differentiate from bacillary dysentery. Metronidazole is widely available; ensure luminal agent (Diloxanide/Paromomycin) is also given to prevent relapse. Consider in patients with liver abscess.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 6, Section 6.2.1

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