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Amoebiasis

Title               

Ñ    Amoebiasis

Definition

Ñ    Infection with Entamoeba histolytica

Ñ    Asymptomatic or symptomatic

Aetiology

Ñ    Entamoeba histolytica:

Protozoan parasite

Pathogenesis

Spread

Ñ    Contaminated food and water

Ñ    Directly from person to person

Ñ    Sexually transmitted disease in male homosexuals

Pathological Process

Ñ    Cysts enter the small intestine

Ñ    Trophozoites emerge from the cysts, pass into the colon

Ñ    Trophozoites invade the colonic epithelium

Ñ    Multiply and penetrate into the submucosa

Ñ    Ulceration of the colonic mucosa occurs

Ñ    Trophozoites may also enter blood vessels, migrate to the liver and cause intra-hepatic abscesses

Clinical Features

Incubation period

Ñ    Few days to several months

Infection with amoebae may cause

Ñ    Asymptomatic infection

Ñ    Amoebic dysentery

Ñ    Chronic infection

Ñ    Metastatic disease

Asymptomatic infection

Ñ    No symptoms but pass cysts in their stools

Amoebic Dysentery

GIT

Ñ    Frequent semi-liquid stools with blood and mucous

Ñ    Abdominal pain

Ñ    Tenderness over liver and colon

E&M

Ñ    Fever

Chronic Infection

GIT

Ñ    Intermittent non-dysenteric diarrhoea with mucous

Ñ    Abdominal pain

Ñ    Flatulence

Ñ    Tender, palpable masses (amoeboma) most common in the caecum and rectosigmoid region          

E&M

Ñ    Weight loss

Metastatic Disease

Originates in the colon and spreads most commonly to the liver

GIT

Ñ    Pain or discomfort over the liver aggravated by movement and occasionally referred to the right shoulder

Ñ    Nausea

Ñ    Vomiting

Ñ    Jaundice:

Unusual, low grade

Ñ    Hepatomegaly

Ñ    Intercostal tenderness

E&M

Ñ    Fever:

High, swinging

Ñ    Weight loss

Ñ    Weakness

IS

Ñ    Skin lesions caused by direct implantation are occasionally seen around the perineum and buttocks or around traumatic or operative wounds

RS

Ñ    Right lower lobe pneumonia or effusion:

Secondary to liver abscess

Investigations

Fluids

Stools

Ñ    Trophozoites in stool

Blood

Immunology

Ñ    Serology (amoebic fluorescent antibody test):

Positive in almost all patients with liver abscess

80% of patients with amoebic dysentery

Imaging

Chest x-ray

Ñ    Elevation of the right hemidiaphragm in liver abscess

Ñ    Right lower lobe pneumonia or effusion

CT scan

Ñ    Shows extent of liver abscess

Ultrasound

Ñ    Liver abscess:

Shows fluid filled cavity

Endoscopy

Lower GI endoscopy

Ñ    Flask shaped ulcers

Surgery

Aspiration of liver abscess:

Ñ    Chocolate brown fluid

Ñ    Motile amoebae not easily seen

Management

Cure               

Drugs

Asymptomatic carriage

Ñ    Diloxanide furoate

Ñ    Iodoquinol

Dysentery

Ñ    Metronidazole

Ñ    Tinidazole

Ñ    Iodoquinol or diloxanide to prevent relapse

Severe symptoms

Ñ    Emetine

Ñ    Dehydroemetine

Metastatic disease

Ñ    Metronidazole

Ñ    Tinidazole

Ñ    Emetine or dehydroemetine combined with chloroquine

Emetine

Ñ    Emetine is toxic and the patient should be kept in bed during treatment with this drug and monitored by ECG

Ñ    Toxicity causes hypotension, muscular weakness, gastrointestinal symptoms, dermatoses

Ñ    Contraindications to treatment with emetine are pregnancy, renal disease, cardiac disease

Surgery

Ñ    Aspiration of abscess

Prevention

Lifestyle Adjustments

Ñ    Prevent contamination of food and water:

Boil drinking water

Ñ    To prevent relapse examine stools in 1,3 and 6 months

 

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