Parasitic Infections

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Introduction

• Caused by Entamoeba histolytica• Common in the Indian subcontinent, Africa, parts

of South America (> 50% population affected)• Mode of infection: faeco – oral• Substandard hygiene and sanitation • Amoebic liver abscess (MC extra intestinal

manifestation): 10% of infected population• Immunocompromised and alcoholic: susceptible

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Pathogenesis

• Organism gut (through food/water contaminated with the cyst)cysts hatch trophozoites carried to colon FLASK SHAPED ULCERS (in the submucosa)

• Trophozoites multiply cysts

Portal circulation Passed in faeces

Infects others

PathogenesisPortal circulation

Trophozoites are filtered and trapped in the interlobular veins of the liver

Multiply in the portal triads; local infarction & liquefactive necrosis (proteolytic enzymes)

Areas ofnecrosis – coalesce to form Amoebic Liver Abscess Cavity

Pathogenesis –Amoebic Liver Abscess• Right lobe> Left lobe (80% > 10%); remaining 10% are

multiple• Right lobe: blood from the superior mesenteric artery

runs n a straighter course through the portal vein into the larger lobe

• More common in the diaphragmatic surface pulmonary complications

• Abscess cavity chocolate coloured, odourless, ‘anchovy – sauce’ like fluid (mixture of necrotic liver tissue and blood)

• Secondary infection in the cavity may occur pus• Untreated abscess likely to rupture

Pathogenesis…

Chronic infection in the large bowel

granulomatous lesion along the large bowel; most commonly seen in the caecum

Amoeboma

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Clinical Features: Symptoms

• Young adult male• h/o pain, fever, insidious onset of non specific

symptoms (anorexia, night sweats, cough, weight loss) gradually progresses to more specific symptoms: pain in the rt upper abdomen, shoulder tp pain, hiccoughs, non productive cough

• Past h/o bloody diarrhoea and travel to an endemic area

Clinical Features: signs

• Toxic, Anemic patient• Upper abdomen rigidity• Tender hepatomealy• Tender and bulging intercostal spaces, overlying

skin edema, pleural effusion and basal pneumonitis

• Occasionally – trace of jaundice, ascites• Rarely – emergency due to rupture into the

peritoneal, pleural or pericardial activiy

Amoeboma

• Chronic granuloma • Arising in the large bowel, most commonly seen

in the caecum• Prone to occur in longstanding amoebic infection

that has been treated intermittently with drugs without completion of a full course

• Suspected when a patient from an endemic area with generalized ill health, pyrexia, mass in the rt iliac fossa with a h/o blood stained mucoid diarrhoea

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Investigations

• Haematological & Biochemical investigations: anemia, leucocytosis, raised ESR, raised CRP, hypoalbuminemia, deranged LFT (particularly raised ALP)

• Serological tests: more specific; tests for complement fixation, indirect haemagglutination, indirect immunofluorescence and ELISA.

• Especially useful in non endemic areas

Investigations

• Rigid sigmoidoscopy– Most ulcers occur in the rectosigmoid & therefore

within reach of the sigmoidoscope– Shallow, flask shaped or collar stud, undermined

ulcers– Biopsy/ scrapings can be taken for microscopic

examination

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Imaging Techniques

• Ultrasound: abscess cavity in the liver is seen as a hypo/ anechoic leson with ill defined borders; accurate; used for aspiration (diagnostic and therapeutic)

• CT may be helpful if doubt in diagnosis• Barium enema• Colonoscopy & biopsy (to differentiate from

carcinoma)

Amoebiasis

• Introduction• Pathogenesis• Clinical Features• Investigations• Imaging techniques• Treatment

Treatment

• Medical– Effective– First choice – Surgery reserved for complications– Metronidazole and tinidazole: effective drugs– After treatment with metro/tinidazole; diloxanide

furoate which is not effective against hepatic infestation, is used for 10 days to destroy any intestinal infestation

Management…

• Aspiration– When imminent rupture of an abscess is expected– Helps in the penetration of metronidazole; hence

reduces the morbidity– Theshold for aspirating an abscess in the left lobe

is lower because of its predilection for rupturing into the pericardium

Management…• Surgical– Reserved for complications of rupture into the pleural

(usually the rt side), peritoneal or pericardial cavities– Resuscitation, drainage and appropriate lavage with

vigorous medical treatment – key principles– Large bowel – severe h’age, toxic megacolon are rare

complications• General principles of a surgical emergency apply• Resuscitation followed by resection of the bowel with

exteriorisation• Vigorous supportive therapy• ICU care