The main pathogen of amoebiasis is Entamoeba histolytica. This protozoan most commonly invades the colon in humans, causing amoebic dysentery. When it invades organs such as the liver, lungs, or brain, it can also cause corresponding organ lesions, with liver involvement being the most common.

bubble_chart Clinical Manifestations

1. Most patients have an insidious onset. The frequency of bowel movements may increase, reaching more than 10 times a day, or remain normal, with alternating constipation and diarrhea. The stool contains blood and mucus. There is no tenesmus, but there may be tenderness in the lower abdomen. The body temperature is normal, systemic symptoms are mild, and the total white blood cell count is slightly elevated.
2. A small number of patients with acute onset have severe conditions, mostly due to weakened body resistance or concurrent bacterial infection. The onset is sudden, with aversion to cold and high fever, which can reach 39°C. Bowel movements are frequent, appearing as bloody water with a foul, fishy odor. It is accompanied by vomiting, dehydration, collapse, delirium, and other toxic symptoms. The white blood cell count is significantly increased. Complications such as intestinal bleeding and perforation are likely.
3. Chronic patients have a prolonged course, with symptoms persisting for a long time or recurring frequently. Anemia and emaciation are common. During remission periods, only constipation, abdominal pain, and abdominal distension and fullness are present.
4. When complicated by amebic hepatitis or liver abscess, there is irregular fever, night sweating, liver pain, hepatomegaly, and tenderness. If amebic liver disease is suspected, a history of amebic dysentery should be investigated. When suffering from amebic lung abscess or brain abscess, the symptoms are similar to those of suppurative lung abscess or suppurative brain abscess, but both are relatively rare.

bubble_chart Auxiliary Examination

1. Stool Examination Fresh stool is smeared and examined under a microscope. Trophozoites of Entamoeba histolytica can be found in the acute phase, while cysts may be detected in the chronic phase. Typical amoebic dysentery stools appear dark red, contain more fecal matter, blood, and mucus, and sometimes exhibit slender, spindle-shaped Charcot-Leyden crystals. A negative result once or twice does not rule out the diagnosis, and repeated examinations should be conducted.
2. Sigmoidoscopy For patients with repeatedly negative stool tests, sigmoidoscopy can be performed. However, only about !)% of cases reveal scattered ulcers of varying sizes in the rectum and sigmoid colon, with well-defined edges and mostly normal mucosa between the ulcers. Microscopic examination of material scraped from the ulcer surface often reveals the pathogen. 3. Serological Tests For patients with repeatedly negative stool tests but high suspicion of infection or those with extraintestinal amoebiasis, indirect fluorescent antibody tests or enzyme-linked immunosorbent assays (ELISA) may be used. 4. Other Examinations For suspected amoebic liver disease, liver ultrasound or liver puncture may be performed, and liver function tests often show abnormalities. For suspected lung abscess, chest X-rays can be conducted, while brain abscess may require electroencephalography (EEG) and cranial CT scans.

bubble_chart Diagnosis

Epidemiological history includes consumption of unclean food in endemic areas or close contact with patients affected by the disease.

bubble_chart Treatment Measures

Treatment

(1) General Management For dehydration and acidosis, fluid therapy should be administered for correction. During the acute phase, a residue-free diet is recommended, while in the chronic phase, attention should be paid to nutritional supplementation and anemia correction. (2) Pathogenic Treatment Anti-amoebic therapy should be timely and thorough. After completing the course, stool tests should be conducted, and if necessary, 1–2 additional courses should be repeated to prevent relapse. The following medications are available for selection. 1. **Metronidazole** Effective against all types of amoebic protozoa. Dose: 50 mg/(kg·d), divided into 3 doses, with a maximum daily dose not exceeding 1 g. The treatment course lasts 7 days. Side effects such as nausea, abdominal pain, or dizziness generally require no special intervention; however, if ataxia or similar symptoms occur, the medication should be discontinued immediately. 2. **Tinidazole** Effective against all types and locations of amoebiasis. Dose: 50 mg/(kg·d), administered in a single dose. The treatment course lasts 5 days. 3. **Chiniofon (Yatren)** Used for acute and chronic amoebic dysentery but ineffective for extraintestinal amoebiasis. Dose: 40–45 mg/(kg·d), divided into 3 doses, with a treatment course of 8–10 days. Alternatively, a 1% solution can be prepared with saline for retention enemas (100–200 ml per session). Oral administration and enemas can be alternated every other day, with a total course of 8–10 days. 4. **Iodochlorhydroxyquin (Vioform)** Similar in action to chiniofon. Dose: 15–30 mg/(kg·d), divided into 3 oral doses, with a treatment course of 10 days. 5. **Phanguone (Entobex)** Used for acute and chronic amoebic dysentery. For older children: 100 mg per dose, 3 times daily, with a 10-day course. Dosage should be reduced for younger children. 6. **Emetine HCl** Kills amoebic trophozoites. Dose: 0.5–1 mg/(kg·d), administered via deep subcutaneous or intramuscular injection, divided into 2 doses daily. The treatment course lasts 4–5 days. Before injection, patients should rest in bed, and blood pressure and pulse should be monitored. If abdominal pain, weakness, arrhythmia, or hypotension occurs, the medication should be discontinued immediately. Contraindicated in young children. If a repeat course is needed, an interval of at least 6 weeks is required. Due to high toxicity, it is now rarely used. 7. **Carbarsone** Effective against both amoebic trophozoites and cysts, used for acute/chronic amoebic dysentery and relapse prevention. Primarily for older children. Dose: 8 mg/(kg·d), divided into 2–3 oral doses, with a 10-day course. 8. **Paromomycin** Used for acute and chronic amoebic dysentery. Dose: 20–30 mg/(kg·d), divided into 4 oral doses, with a 7–10 day course. This drug has limited efficacy when used alone and is best combined with other anti-amoebic agents. **Prevention** (1) Maintain personal and dietary hygiene, improve environmental sanitation, eliminate flies and cockroaches, and strengthen water source management. (2) Isolate patients until stool tests are negative three times. Chronic cases working in the food industry should receive thorough treatment and be temporarily reassigned during therapy.

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The main differentiation should be made from bacterial dysentery. The latter usually has an acute onset, with fever or even high fever, obvious toxic symptoms, and stools primarily consisting of mucus, pus, and blood.