## Diagnosis: Entamoeba histolytica Intestinal Amoebiasis ### Clinical Presentation **Key Point:** The combination of bloody diarrhoea with mucus, afebrile status, and trophozoites containing ingested RBCs on stool microscopy is pathognomonic for *Entamoeba histolytica* infection. ### Diagnostic Features | Feature | E. histolytica | Shigella | Salmonella | V. cholerae | |---------|---|---|---|---| | **Fever** | Absent or mild | Present (often high) | Present | Absent | | **Stool character** | Bloody mucoid, few stools/day | Bloody, tenesmus | Greenish, may be bloody | Watery, rice-water | | **RBCs in trophozoites** | Yes (pathognomonic) | N/A | N/A | N/A | | **Blood culture** | Negative | May be positive | Positive | Negative | | **Duration** | Subacute (weeks) | Acute (days) | Acute to subacute | Acute (hours) | ### Pathophysiology 1. Ingestion of cysts from faecal-contaminated food/water 2. Excystation in terminal ileum and colon 3. Trophozoites invade colonic mucosa → ulceration 4. Trophozoites phagocytose RBCs and WBCs → bloody stools 5. Amoebic colitis results; systemic infection rare without liver involvement **High-Yield:** Trophozoites with ingested RBCs are diagnostic for invasive amoebiasis and distinguish it from non-invasive colonization (cyst-passers). ### Microscopy Findings **Clinical Pearl:** In acute dysentery: - Trophozoites (10–20 µm) with pseudopodia - Ingested RBCs and WBCs within cytoplasm - Nucleus with central karyosome - Found in fresh, warm stool samples (die quickly) ### Treatment Approach For invasive intestinal amoebiasis: - **Tissue amebicide:** Metronidazole 750 mg TDS × 10 days - **Luminal agent:** Paromomycin 25–35 mg/kg/day × 7 days (to eliminate cysts and prevent relapse) **Mnemonic:** METRO-PARA — **Metro**nidazole for tissue invasion, **Para**momycin for luminal cysts.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.